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Sujanthan S, Shmuel A, Mendola JD. Visually driven functional MRI techniques for characterization of optic neuropathy. Front Hum Neurosci 2022; 16:943603. [PMID: 36158617 PMCID: PMC9500431 DOI: 10.3389/fnhum.2022.943603] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/01/2022] [Indexed: 11/16/2022] Open
Abstract
Optic neuropathies are conditions that cause disease to the optic nerve, and can result in loss of visual acuity and/or visual field defects. An improved understanding of how these conditions affect the entire visual system is warranted, to better predict and/or restore the visual loss. In this article, we review visually-driven functional magnetic resonance imaging (fMRI) studies of optic neuropathies, including glaucoma and optic neuritis (ON); we also discuss traumatic optic neuropathy (TON). Optic neuropathy-related vision loss results in fMRI deficit within the visual cortex, and is often strongly correlated with clinical severity measures. Using predominantly flickering checkerboard stimuli, glaucoma studies indicated retinotopic-specific cortical alteration with more prominent deficits in advanced than in early glaucoma. Some glaucoma studies indicate a reorganized visual cortex. ON studies have indicated that the impacted cortical areas are briefly hyperactive. For ON, brain deficits are greater in the acute stages of the disease, followed by (near) normalization of responses of the LGN, visual cortex, and the dorsal visual stream, but not the ventral extrastriate cortex. Visually-driven fMRI is sensitive, at least in ON, in discriminating patients from controls, as well as the affected eye from the fellow eye within patients. The use of a greater variety of stimuli beyond checkerboards (e.g., visual motion and object recognition) in recent ON studies is encouraging, and needs to continue to disentangle the results in terms of change over time. Finally, visually-driven fMRI has not yet been applied in TON, although preliminary efforts suggest it may be feasible. Future fMRI studies of optic neuropathies should consider using more complex visual stimuli, and inter-regional analysis methods including functional connectivity. We suggest that a more systematic longitudinal comparison of optic neuropathies with advanced fMRI would provide improved diagnostic and prognostic information.
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Affiliation(s)
- Sujeevini Sujanthan
- Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC, Canada
- *Correspondence: Sujeevini Sujanthan
| | - Amir Shmuel
- Departments of Neurology, Neurosurgery, Physiology and Biomedical Engineering, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Janine Dale Mendola
- Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC, Canada
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2
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Rocca MA, Schoonheim MM, Valsasina P, Geurts JJG, Filippi M. Task- and resting-state fMRI studies in multiple sclerosis: From regions to systems and time-varying analysis. Current status and future perspective. Neuroimage Clin 2022; 35:103076. [PMID: 35691253 PMCID: PMC9194954 DOI: 10.1016/j.nicl.2022.103076] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 06/01/2022] [Accepted: 06/02/2022] [Indexed: 01/12/2023]
Abstract
Functional MRI is able to detect adaptive and maladaptive abnormalities at different MS stages. Increased fMRI activity is a feature of early MS, while progressive exhaustion of adaptive mechanisms is detected later on in the disease. Collapse of long-range connections and impaired hub integration characterize MS network reorganization. Time-varying connectivity analysis provides useful and complementary pieces of information to static functional connectivity. New perspectives might be the use of multimodal MRI and artificial intelligence.
Multiple sclerosis (MS) is a neurological disorder affecting the central nervous system and features extensive functional brain changes that are poorly understood but relate strongly to clinical impairments. Functional magnetic resonance imaging (fMRI) is a non-invasive, powerful technique able to map activity of brain regions and to assess how such regions interact for an efficient brain network. FMRI has been widely applied to study functional brain changes in MS, allowing to investigate functional plasticity consequent to disease-related structural injury. The first studies in MS using active fMRI tasks mainly aimed to study such plastic changes by identifying abnormal activity in salient brain regions (or systems) involved by the task. In later studies the focus shifted towards resting state (RS) functional connectivity (FC) studies, which aimed to map large-scale functional networks of the brain and to establish how MS pathology impairs functional integration, eventually leading to the hypothesized network collapse as patients clinically progress. This review provides a summary of the main findings from studies using task-based and RS fMRI and illustrates how functional brain alterations relate to clinical disability and cognitive deficits in this condition. We also give an overview of longitudinal studies that used task-based and RS fMRI to monitor disease evolution and effects of motor and cognitive rehabilitation. In addition, we discuss the results of studies using newer technologies involving time-varying FC to investigate abnormal dynamism and flexibility of network configurations in MS. Finally, we show some preliminary results from two recent topics (i.e., multimodal MRI analysis and artificial intelligence) that are receiving increasing attention. Together, these functional studies could provide new (conceptual) insights into disease stage-specific mechanisms underlying progression in MS, with recommendations for future research.
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Affiliation(s)
- Maria A Rocca
- Neuroimaging Research Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy; Neurology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.
| | - Menno M Schoonheim
- Department of Anatomy and Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Paola Valsasina
- Neuroimaging Research Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Jeroen J G Geurts
- Department of Anatomy and Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Massimo Filippi
- Neuroimaging Research Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy; Neurology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy; Neurorehabilitation Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy; Neurophysiology Service, IRCCS San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy
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3
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Chard DT, Alahmadi AAS, Audoin B, Charalambous T, Enzinger C, Hulst HE, Rocca MA, Rovira À, Sastre-Garriga J, Schoonheim MM, Tijms B, Tur C, Gandini Wheeler-Kingshott CAM, Wink AM, Ciccarelli O, Barkhof F. Mind the gap: from neurons to networks to outcomes in multiple sclerosis. Nat Rev Neurol 2021; 17:173-184. [PMID: 33437067 DOI: 10.1038/s41582-020-00439-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2020] [Indexed: 12/21/2022]
Abstract
MRI studies have provided valuable insights into the structure and function of neural networks, particularly in health and in classical neurodegenerative conditions such as Alzheimer disease. However, such work is also highly relevant in other diseases of the CNS, including multiple sclerosis (MS). In this Review, we consider the effects of MS pathology on brain networks, as assessed using MRI, and how these changes to brain networks translate into clinical impairments. We also discuss how this knowledge can inform the targeting of MS treatments and the potential future directions for research in this area. Studying MS is challenging as its pathology involves neurodegenerative and focal inflammatory elements, both of which could disrupt neural networks. The disruption of white matter tracts in MS is reflected in changes in network efficiency, an increasingly random grey matter network topology, relative cortical disconnection, and both increases and decreases in connectivity centred around hubs such as the thalamus and the default mode network. The results of initial longitudinal studies suggest that these changes evolve rather than simply increase over time and are linked with clinical features. Studies have also identified a potential role for treatments that functionally modify neural networks as opposed to altering their structure.
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Affiliation(s)
- Declan T Chard
- NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK. .,National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre, London, UK.
| | - Adnan A S Alahmadi
- Department of Diagnostic Radiology, Faculty of Applied Medical Science, King Abdulaziz University (KAU), Jeddah, Saudi Arabia
| | - Bertrand Audoin
- Aix-Marseille University, CNRS, CRMBM, Marseille, France.,AP-HM, University Hospital Timone, Department of Neurology, Marseille, France
| | - Thalis Charalambous
- NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK
| | - Christian Enzinger
- Department of Neurology, Research Unit for Neuronal Repair and Plasticity, Medical University of Graz, Graz, Austria.,Department of Radiology, Division of Neuroradiology, Vascular and Interventional Radiology, Medical University of Graz, Graz, Austria
| | - Hanneke E Hulst
- Department of Anatomy and Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Maria A Rocca
- Neuroimaging Research Unit, Institute of Experimental Neurology, Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Àlex Rovira
- Section of Neuroradiology, Department of Radiology Hospital Universitari Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Jaume Sastre-Garriga
- Servei de Neurologia/Neuroimmunologia, Multiple Sclerosis Centre of Catalonia (Cemcat), Hospital Universitari Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Menno M Schoonheim
- Department of Anatomy and Neurosciences, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Betty Tijms
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Carmen Tur
- NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK.,Department of Neurology, Luton and Dunstable University Hospital, Luton, UK
| | - Claudia A M Gandini Wheeler-Kingshott
- NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK.,Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy.,Brain MRI 3T Research Center, IRCCS Mondino Foundation, Pavia, Italy
| | - Alle Meije Wink
- Department of Radiology & Nuclear Medicine, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Olga Ciccarelli
- NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, Faculty of Brain Sciences, University College London, London, UK.,National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre, London, UK
| | - Frederik Barkhof
- National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre, London, UK.,Department of Radiology & Nuclear Medicine, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.,Institutes of Neurology and Healthcare Engineering, University College London, London, UK
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4
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Finke C, Zimmermann H, Pache F, Oertel FC, Chavarro VS, Kramarenko Y, Bellmann-Strobl J, Ruprecht K, Brandt AU, Paul F. Association of Visual Impairment in Neuromyelitis Optica Spectrum Disorder With Visual Network Reorganization. JAMA Neurol 2019; 75:296-303. [PMID: 29297041 DOI: 10.1001/jamaneurol.2017.3890] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Importance Severe visual impairment is one of the major symptoms in neuromyelitis optica spectrum disorder (NMOSD), but functional network reorganization induced by the diminished sensory input has not been investigated thus far. Objective To examine adaptive visual network connectivity changes in NMOSD. Design, Setting, and Participants In this cross-sectional study, data were collected from May 1, 2013, through February 31, 2016, from 31 patients with aquaporin-4 antibody-positive NMOSD and 31 age- and sex-matched healthy control individuals at the Department of Neurology and NeuroCure Clinical Research Center at Charité-Universitätsmedizin Berlin, Berlin, Germany. Main Outcomes and Measures Visual function (high-contrast visual acuity and contrast sensitivity), optical coherence tomography (peripapillary retinal nerve fiber layer and ganglion cell layer thickness), and resting-state functional magnetic resonance imaging (functional connectivity of large-scale brain networks). Results Thirty-one patients with NMOSD (mean [SD] age, 48.2 [13.9] years; 28 women and 3 men) and 31 healthy controls (mean [SD] age, 47.2 [15.3] years; 28 women and 3 men) participated in the study. Patients had a selective and pronounced increase of functional connectivity in the primary and secondary visual networks. Increased primary visual network connectivity correlated with reduced high-contrast visual acuity (r = -0.39, P = .006), reduced low-contrast sensitivity (r = -0.33, P = .03), and more severe retinal damage measured by optical coherence tomography (r = -0.4, P = .01). Furthermore, visual functional connectivity was significantly higher in patients with a history of optic neuritis compared with patients without optic neuritis (mean [SD] regression coefficients, 50.0 [4.3] vs 34.6 [5.6]; P = .04). Conclusions and Relevance Impaired visual function and retinal damage are associated with selective reorganization of the visual network in NMOSD. These findings advance the understanding of visual system dysfunction in NMOSD and, more generally, provide insight into pathophysiologic responses of the visual system to impaired visual input.
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Affiliation(s)
- Carsten Finke
- Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Hanna Zimmermann
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Florence Pache
- Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Frederike C Oertel
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | | | | | - Judith Bellmann-Strobl
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Experimental and Clinical Research Center, Max Delbrueck Center for Molecular Medicine and Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Klemens Ruprecht
- Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Alexander U Brandt
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Friedemann Paul
- Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Experimental and Clinical Research Center, Max Delbrueck Center for Molecular Medicine and Charité-Universitätsmedizin Berlin, Berlin, Germany
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5
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Huang J, Duan Y, Liu S, Liang P, Ren Z, Gao Y, Liu Y, Zhang X, Lu J, Li K. Altered Brain Structure and Functional Connectivity of Primary Visual Cortex in Optic Neuritis. Front Hum Neurosci 2018; 12:473. [PMID: 30618673 PMCID: PMC6306625 DOI: 10.3389/fnhum.2018.00473] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Accepted: 11/12/2018] [Indexed: 01/25/2023] Open
Abstract
Previous studies have revealed brain adaptations to injury that occurs in optic neuritis (ON); however, the mechanisms underlying the functional connectivity (FC) and gray matter volume (GMV) changes in ON have not been clarified. Here, 51 single attack ON patients and 45 recurrent attacks ON patients were examined using structural MRI and resting-state functional MRI (RS-fMRI), and compared to 49 age- and gender-matched healthy controls (HC). FC analysis with a seed in primary visual cortex (V1 area) was used to assess the differences among three groups. Whole brain GMV was assessed using voxel-based morphometry (VBM). Correlation analyses were performed between FC results, structural MRI and clinical variables. We found positive correlations between the Paced Auditory Serial Addition Test (PASAT) score and FC in V1 area with bilateral middle frontal gyrus. Disease duration is significantly negatively related to FC in V1 area with the left inferior parietal lobule. Compared to the HC, single attack ON patients were found to have decreased FC values in the frontal, temporal lobes, right inferior occipital gyrus, right insula, right inferior parietal lobule, and significant increased FC values in the left thalamus. Recurrent attacks ON patients had the same pattern with single attack ON. No significant differences were found in brain GMV among three groups. This study provides the imaging evidence that impairment and compensation of V1 area connectivity coexist in ON patients, and provides important insights into the underlying neural mechanisms of ON.
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Affiliation(s)
- Jing Huang
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Capital Medical University, Beijing, China
| | - Yunyun Duan
- Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Sidong Liu
- Brain and Mind Centre, Sydney Medical School Nepean, The University of Sydney, Sydney, NSW, Australia
| | - Peipeng Liang
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Capital Medical University, Beijing, China
| | - Zhuoqiong Ren
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Capital Medical University, Beijing, China
| | - Yang Gao
- School of Instrumentation Science and Opto-electronics Engineering, Beihang University, Beijing, China
| | - Yaou Liu
- Department of Radiology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Xiaojun Zhang
- Department of Neurology, Tongren Hospital, Capital Medical University, Beijing, China
| | - Jie Lu
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Capital Medical University, Beijing, China.,Department of Nuclear Medicine, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Kuncheng Li
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Capital Medical University, Beijing, China
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6
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Lemos J, Pereira D, Castelo-Branco M. Visual Cortex Plasticity Following Peripheral Damage To The Visual System: fMRI Evidence. Curr Neurol Neurosci Rep 2016; 16:89. [DOI: 10.1007/s11910-016-0691-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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7
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Gallo A, Bisecco A, Bonavita S, Tedeschi G. Functional plasticity of the visual system in multiple sclerosis. Front Neurol 2015; 6:79. [PMID: 25904894 PMCID: PMC4389402 DOI: 10.3389/fneur.2015.00079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 03/23/2015] [Indexed: 11/13/2022] Open
Affiliation(s)
- Antonio Gallo
- Department of Medical, Surgical, Neurological, Metabolic and Aging Sciences, Second University of Naples , Naples , Italy ; MRI Center SUN-FISM, Neurological Institute for Diagnosis and Care "Hermitage Capodimonte" , Naples , Italy
| | - Alvino Bisecco
- Department of Medical, Surgical, Neurological, Metabolic and Aging Sciences, Second University of Naples , Naples , Italy ; MRI Center SUN-FISM, Neurological Institute for Diagnosis and Care "Hermitage Capodimonte" , Naples , Italy
| | - Simona Bonavita
- Department of Medical, Surgical, Neurological, Metabolic and Aging Sciences, Second University of Naples , Naples , Italy ; MRI Center SUN-FISM, Neurological Institute for Diagnosis and Care "Hermitage Capodimonte" , Naples , Italy
| | - Gioacchino Tedeschi
- Department of Medical, Surgical, Neurological, Metabolic and Aging Sciences, Second University of Naples , Naples , Italy ; MRI Center SUN-FISM, Neurological Institute for Diagnosis and Care "Hermitage Capodimonte" , Naples , Italy
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8
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Tomassini V, Matthews PM, Thompson AJ, Fuglø D, Geurts JJ, Johansen-Berg H, Jones DK, Rocca MA, Wise RG, Barkhof F, Palace J. Neuroplasticity and functional recovery in multiple sclerosis. Nat Rev Neurol 2012; 8:635-46. [PMID: 22986429 PMCID: PMC3770511 DOI: 10.1038/nrneurol.2012.179] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The development of therapeutic strategies that promote functional recovery is a major goal of multiple sclerosis (MS) research. Neuroscientific and methodological advances have improved our understanding of the brain's recovery from damage, generating novel hypotheses about potential targets and modes of intervention, and laying the foundation for development of scientifically informed recovery-promoting strategies in interventional studies. This Review aims to encourage the transition from characterization of recovery mechanisms to development of strategies that promote recovery in MS. We discuss current evidence for functional reorganization that underlies recovery and its implications for development of new recovery-oriented strategies in MS. Promotion of functional recovery requires an improved understanding of recovery mechanisms that can be modulated by interventions and the development of robust measurements of therapeutic effects. As imaging methods can be used to measure functional and structural alterations associated with recovery, this Review discusses their use to obtain reliable markers of the effects of interventions.
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Colorado RA, Shukla K, Zhou Y, Wolinsky JS, Narayana PA. Multi-task functional MRI in multiple sclerosis patients without clinical disability. Neuroimage 2011; 59:573-81. [PMID: 21840409 DOI: 10.1016/j.neuroimage.2011.07.065] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/09/2011] [Accepted: 07/22/2011] [Indexed: 12/28/2022] Open
Abstract
While the majority of individuals with multiple sclerosis (MS) develop significant clinical disability, a subset experiences a disease course with minimal impairment even in the presence of significant apparent tissue damage on magnetic resonance imaging (MRI). Functional magnetic resonance imaging (fMRI) in MS patients with low disability suggests that increased use of the cognitive control system may limit the clinical manifestation of the disease. The current fMRI studies tested the hypothesis that nondisabled MS patients show increased recruitment of cognitive control regions while performing sensory, motor and cognitive tasks. Twenty two patients with relapsing-remitting MS and an Expanded Disability Status Scale (EDSS) score of ≤1.5 and 23 matched healthy controls were recruited. Subjects underwent fMRI while observing flashing checkerboards, performing right or left hand movements, or executing the 2-back working memory task. Compared to control subjects, patients demonstrated increased activation of the right dorsolateral prefrontal cortex and anterior cingulate cortex during the performance of the working memory task. This pattern of functional recruitment also was observed during the performance of non-dominant hand movements. These results support the mounting evidence of increased functional recruitment of cognitive control regions in the working memory system of MS patients with low disability and provide new evidence for the role of increased cognitive control recruitment in the motor system.
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Affiliation(s)
- René A Colorado
- Department of Diagnostic and Interventional Imaging, University of Texas Medical School at Houston, Houston, Texas 77030, USA.
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10
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Barb SM, Rodriguez-Galindo C, Wilson MW, Phillips NS, Zou P, Scoggins MA, Li Y, Qaddoumi I, Helton KJ, Bikhazi G, Haik BG, Ogg RJ. Functional neuroimaging to characterize visual system development in children with retinoblastoma. Invest Ophthalmol Vis Sci 2011; 52:2619-26. [PMID: 21245407 DOI: 10.1167/iovs.10-5600] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
PURPOSE To use functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to investigate visual system development in children being treated for retinoblastoma. METHODS Informed consent was obtained for all participants (N = 42) in this institutional review board-approved study. Participants were imaged with a 1.5-T scanner while under propofol sedation. Diagnostic brain and orbital imaging was followed by investigational functional neuroimaging, which included fMRI during photic stimulation through closed eyelids, to measure functional activation in the visual cortex, and DTI, to evaluate diffusion parameters of white matter tracts in the corpus callosum and the periventricular optic radiations. Analysis included 115 examinations of 39 patients with a median age of 16.4 months and age range from 1.5 to 101.5 months at first evaluation. RESULTS The blood oxygen level-dependent signal was predominantly negative and located in the anterior visual cortex. Activation was affected by tumor lateralization (unilateral or bilateral), macular involvement, and retinal detachment. Patients who had undergone unilateral enucleation showed cortical dominance corresponding to the projection from the nasal hemiretina in the unaffected eye. Diffusion parameters followed a normal developmental trajectory in the optic radiations and corpus callosum, but variability was greater in the splenium than in the genu of the corpus callosum. CONCLUSIONS Longitudinal functional neuroimaging demonstrated important effects of disease and treatment. Therefore, fMRI and DTI may be useful for characterizing the impact of retinoblastoma on the developing visual system and improving the prediction of visual outcome in survivors.
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Affiliation(s)
- Scott M Barb
- Department of Radiological Sciences, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-2794, USA
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11
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Sastre-Garriga J, Alonso J, Renom M, Arévalo MJ, González I, Galán I, Montalban X, Rovira A. A functional magnetic resonance proof of concept pilot trial of cognitive rehabilitation in multiple sclerosis. Mult Scler 2010; 17:457-67. [PMID: 21177323 DOI: 10.1177/1352458510389219] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Cognitive impairment is frequent in multiple sclerosis (MS) and lacks effective treatment. Cognitive rehabilitation is widely applied in neurorehabilitation settings. Functional magnetic resonance imaging (fMRI) may help in investigating changes in brain activity and provide a tool to assess the efficacy of rehabilitation. AIM To investigate the effect on brain activity as measured by fMRI of a cognitive rehabilitation programme in patients with MS and cognitive impairment. METHOD Fifteen patients with MS and cognitive impairment and five healthy subjects were recruited. Neuropsychological assessments were performed in patients with MS at study entry and after rehabilitation to assess cognitive changes. fMRI scans were performed at week -5 (baseline), week 0 (immediately before rehabilitation) and week 5 (immediately after rehabilitation). The fMRI paradigm was the Paced Auditory Serial Addition Test (PASAT). The cognitive rehabilitation programme was composed of 15 computer-aided drill and practice sessions and five non-computer-aided cognitive stimulation group sessions (over 5 weeks). Strict guidelines ensured comparability of all rehabilitation interventions. RESULTS Patients had increased brain fMRI activity after rehabilitation in several cerebellar areas when compared with healthy subjects. After rehabilitation, patients had significantly improved their performance on the backward version of the Digit Span Test (p = 0.007) and on a composite score of neuropsychological outcomes (p = 0.009). CONCLUSION The results of the present study indicate that this cognitive rehabilitation programme increases brain activity in the cerebellum of cognitively impaired patients with MS. The role of fMRI in the assessment of neurorehabilitation schemes warrants further investigation.
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Affiliation(s)
- J Sastre-Garriga
- Hospital de Dia de Barcelona, Multiple Sclerosis Centre of Catalonia, Barcelona, Spain.
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12
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Palmer HS, Garzon B, Xu J, Berntsen EM, Skandsen T, Håberg AK. Reduced fractional anisotropy does not change the shape of the hemodynamic response in survivors of severe traumatic brain injury. J Neurotrauma 2010; 27:853-62. [PMID: 20199173 DOI: 10.1089/neu.2009.1225] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The hemodynamic response (HDR) function is the basis for standard functional magnetic resonance imaging (fMRI) analysis. HDR is influenced by white matter inflammation. Traumatic brain injury (TBI) is frequently accompanied by diffuse white matter injury, but the effect of this on the HDR has not been investigated. The aims of the present study were to describe the HDR in visual cortex and examine its relationship with the microstructure of the optic radiation in severe TBI survivors and controls. Ten severe TBI survivors without visual impairments, but with known diffuse axonal injury, and 9 matched controls underwent diffusion tensor imaging (DTI) and fMRI. From the fMRI time series obtained during brief randomized visual stimuli, blood oxygenation level-dependent (BOLD) signal changes for each subject were estimated in V1, and group HDR curves were produced. Standard between-group analysis of BOLD activation in V1 + V2 was performed. For each individual the optic radiations were identified and fractional anisotropy (FA) plus mean apparent diffusion coefficient (ADC(mean)) values for these tracts were calculated. Group HDR curves from the visual cortex were fully transposable between TBI survivors and controls, despite a significant reduction in FA in the optic radiation in TBI survivors. A significant correlation between BOLD signal in the visual cortex and FA values in the optical tract was present in controls, but not in TBI survivors. Between-group comparisons showed that TBI survivors had increased areas of activation in V1 and V2. The HDR appears to be intact in traumatic white matter damage, supporting the validity of using standard fMRI methodology to study neuroplasticity in TBI.
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Affiliation(s)
- Helen S Palmer
- Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
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13
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Jenkins T, Ciccarelli O, Toosy A, Miszkiel K, Wheeler-Kingshott C, Altmann D, Mancini L, Jones S, Plant G, Miller D, Thompson A. Dissecting structure-function interactions in acute optic neuritis to investigate neuroplasticity. Hum Brain Mapp 2010; 31:276-86. [PMID: 19662659 DOI: 10.1002/hbm.20863] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Structural MRI, electrophysiology, and functional MRI (fMRI) elucidate different aspects of damage and repair in demyelinating diseases. We combined them to investigate why patients with optic neuritis (ON) exhibit a wide variation in severity of acute visual loss, with the following objectives: (1) To determine how structural and electrophysiological changes in the anterior and posterior visual pathways contribute to acute visual loss. (2) To combine these data with fMRI, to investigate whether cortical activity modulates visual acuity. The visual system of 28 patients with acute unilateral ON was assessed. Linear regression modeling was used to identify parameters associated with acute visual loss, and to determine whether fMRI activity was associated with vision, after accounting for structural and electrophysiological predictors, age, and gender. Optic nerve lesion length and visual evoked potential (VEP) amplitude were associated with visual loss. Bilateral activation in the extra-striate occipital cortex correlated directly with vision, after adjusting for optic nerve lesion length, VEP amplitude, and demographic characteristics. These data suggest that acute visual loss is associated with the extent of inflammation and conduction block in the optic nerve, but not with pathology in the optic radiations or occipital cortex. The association of better vision with greater fMRI responses, after accounting for factors which reduce afferent input, suggests a role for adaptive neuroplasticity within the association cortex of the dorsal stream of higher visual processing. Longitudinal studies will clarify whether different extra-striate cortical regions play a role in adaptive plasticity in the acute and chronic stages of injury.
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Affiliation(s)
- Thomas Jenkins
- Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, Queen Square, London, United Kingdom.
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14
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Anwar MN, Bonzano L, Sebastiano DR, Roccatagliata L, Gualniera G, Vitali P, Ogliastro C, Spadavecchia L, Rodriguez G, Sanguineti V, Morasso P, Bandini F. Real-time artifact filtering in continuous VEPs/fMRI recording. J Neurosci Methods 2009; 184:213-23. [PMID: 19682492 DOI: 10.1016/j.jneumeth.2009.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 08/04/2009] [Accepted: 08/05/2009] [Indexed: 11/19/2022]
Abstract
Continuous recording of Visual Evoked Potentials (VEPs) and functional Magnetic Resonance Imaging (fMRI) exploits the VEPs high temporal resolution and the fMRI high spatial resolution. In this work, we present a new method of continuous VEPs/fMRI recording to study visual function in seven normal subjects. Our real-time artifact filtering is characterized by a procedure based on an analytical study of echo-planar imaging (EPI) sequence parameters related electro-encephalogram (EEG)-artifact shapes. The magnetic field artifacts were minimized by using a dedicated amagnetic device and by a subtraction algorithm that takes into account the EPI sequence parameters. No significant decrease in signal-to-noise ratio was observed in case of EEG recording simultaneously with MR acquisition; similarly, transient and steady-state VEPs parameters were comparable during fMRI acquisition and in the off-phase of fMRI recording. We also applied this method to one patient with optic neuritis, and, compared with controls, found different results. We suggest that our technique can be reliably used to investigate the function of human visual cortex and properly correlate the electrophysiological and functional neuroimaging related changes.
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Affiliation(s)
- Muhammad Nabeel Anwar
- Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology, G3-50, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
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15
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Assessing structure and function of the afferent visual pathway in multiple sclerosis and associated optic neuritis. J Neurol 2009; 256:305-19. [PMID: 19296047 DOI: 10.1007/s00415-009-0123-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 10/01/2008] [Accepted: 10/07/2008] [Indexed: 12/19/2022]
Abstract
The afferent visual pathway is commonly affected in MS. Assessment of the afferent visual pathway using clinical, imaging and electrophysiological methods not only provides insights into the pathophysiology of MS, but also provides a method of investigating potential therapeutic measures in MS. This review summarises the various assessment methods, in particular imaging techniques of the visual pathway. Retinal nerve fibre layer (RNFL) thickness is usually reduced following an episode of optic neuritis. Techniques such as optical coherence tomography, scanning laser polarimetry, and confocal scanning laser ophthalmoscopy are used to quantify RNFL thickness. MRI of the optic nerve is not routinely used in the diagnosis of MS or optic neuritis, but is valuable in atypical cases and in research. T2- weighted images of the optic nerve usually show the hyperintense lesion in optic neuritis and gadolinium enhancement is seen in the acute attack. Quantifying atrophy of the optic nerve using MRI gives an indication of the degree of axonal loss. Magnetization transfer ratio (MTR) of the optic nerve provides an indication of myelination. Diffusion tensor imaging (DTI) of the optic nerve and optic radiation provide information about the integrity of the visual white matter tracts. Functional MRI following visual stimulation is used to assess the contribution of cortical reorganisation to functional recovery following optic neuritis. Investigations including logMAR visual acuity, Sloan contrast acuity, Farnsworth- Munsell 100-hue colour vision tests and Humphrey perimetry provide detailed quantitative information on different aspects of visual function. Visual evoked potentials identify conduction block or delay reflecting demyelination. These collective investigative methods have advanced knowledge of pathophysiological mechanisms in MS and optic neuritis. Relevant ongoing studies and future directions are discussed.
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16
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17
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Cortical neuroplasticity in patients recovering from acute optic neuritis. Neuroimage 2008; 42:836-44. [DOI: 10.1016/j.neuroimage.2008.05.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 05/14/2008] [Accepted: 05/16/2008] [Indexed: 11/20/2022] Open
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18
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Charil A, Filippi M. Inflammatory demyelination and neurodegeneration in early multiple sclerosis. J Neurol Sci 2007; 259:7-15. [PMID: 17397873 DOI: 10.1016/j.jns.2006.08.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 08/18/2006] [Accepted: 08/31/2006] [Indexed: 11/24/2022]
Abstract
A number of recent magnetic resonance imaging studies have challenged the classical view of multiple sclerosis (MS) as a "two-stage" disease where an early inflammatory demyelinating phase with focal macroscopic lesions formed in the white matter (WM) of the central nervous system is followed by a late neurodegenerative phase, which is believed to be a mere consequence of repeated inflammatory insults and irreversible demyelination. These studies have consistently shown the presence of diffuse normal-appearing WM damage, marked gray matter involvement and significant cortical functional reorganization, as well as the occurrence of the neurodegenerative component of MS from the earliest clinical stages of the disease with only a partial relation to MRI markers of inflammatory demyelination. The present review argues that MS can no longer be viewed as a "two-stage" disease, which suggests that the two pathological components are dissociated in time, but rather as a "simultaneous two-component" disease, where the relative contributions of the various pathological processes of the disease to the development of "fixed" disability, their relationship and their evolution over time need to be clarified. This new view of MS should inform the development of future research protocols to define its actual physiopathology and prompt the institution of early treatment which should ideally target not only inflammatory demyelination, but also the neurodegenerative aspects of the disease, as well as promote neuroprotection and enhance reparative mechanisms and adaptive functional reorganization of the cortex.
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Affiliation(s)
- Arnaud Charil
- Neuroimaging Research Unit, Department of Neurology, Scientific Institute and University Ospedale San Raffaele, Milan, Italy
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19
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Gioia MC, Cerasa A, Liguori M, Passamonti L, Condino F, Vercillo L, Valentino P, Clodomiro A, Quattrone A, Fera F. Impact of individual cognitive profile on visuo-motor reorganization in relapsing-remitting multiple sclerosis. Brain Res 2007; 1167:71-9. [PMID: 17689504 DOI: 10.1016/j.brainres.2007.06.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Revised: 05/31/2007] [Accepted: 06/12/2007] [Indexed: 12/01/2022]
Abstract
BACKGROUND In multiple sclerosis (MS), relationships between disease-related MRI changes, cognitive function and brain responses are complex and still unclear. This study addresses the relative effects of cognitive impairment and brain atrophy on the cortical reorganization associated with a visuo-motor task. METHODS Multivariate analysis was applied to compare functional MRI brain responses of 28 relapsing-remitting (RR) MS patients (16 cognitively preserved and 12 cognitively impaired) to that of 35 matched healthy controls during the execution of visuo-motor integration task. Regression analysis was performed to test for linear effects of structural variables (grey matter (GM) and white matter (WM) volumes) and cognitive profiles--and their combined effect--on the same response. RESULTS Compared to preserved MS patients or normal controls, cognitively impaired MS patients showed significant decreases of brain parenchymal and GM volumes, but only a trend for lower WM volume. Multivariate analysis showed that cognitive profile, GM and WM atrophy independently contributed to the activation of parieto-premotor cortices. Baseline cognition predicted the greatest response of the entire network, whereas WM and GM losses predicted selective responses of parietal and premotor regions. CONCLUSIONS Visuo-motor function in MS is associated with altered patterns of brain activation that vary as a function of cognitive decline. This is confirmed by a larger effect size of the individual cognitive profile compared to the structural damage. Both effects contribute in an additive way to cortical reorganization, which is primarily driven by such a cognitive gradient in RR-MS patients.
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Affiliation(s)
- Maria Cecilia Gioia
- Institute of Neurological Sciences, National Research Council, Piano Lago di Mangone, 87050, Cosenza, Italy
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20
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Abstract
There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not simply depend on the extent of tissue destruction, but rather represents a complex balance among tissue damage, tissue repair, and cortical reorganization. Functional magnetic resonance imaging (fMRI) provides information about the extent and nature of brain plasticity, which follows MS structural injury and might have the potential to limit the clinical manifestations of the disease. An altered recruitment of regions normally devoted to the performance of a given task and/or the recruitment of additional areas, which are not typically activated by healthy people for performing that given task, have been described in patients with MS, independent of their clinical phenotype when investigating the visual, cognitive, and motor systems. These functional changes have been related to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific central nervous system (CNS) structures, including the spinal cord and the optic nerve. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. An increased recruitment of the cerebral networks might represent a first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent "second-order" compensatory areas, and, on the other, contribute to the clinical manifestations of the disease.
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Affiliation(s)
- Maria A Rocca
- Neuroimaging Research Unit, Department of Neurology, Scientific Institute and University Ospedale San Raffaele, Milan, Italy
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21
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Levin N, Orlov T, Dotan S, Zohary E. Normal and abnormal fMRI activation patterns in the visual cortex after recovery from optic neuritis. Neuroimage 2006; 33:1161-8. [PMID: 17011793 DOI: 10.1016/j.neuroimage.2006.07.030] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 06/08/2006] [Accepted: 07/07/2006] [Indexed: 11/20/2022] Open
Abstract
Recovery to normal or near normal visual acuity after an optic neuritis episode is common, despite frequent persistence of conduction abnormalities, evident in prolonged visual evoked potential (VEP) latencies. Improvement of visual function is commonly attributed to peripheral nerve recovery. However, central reorganization processes may also be involved. To assess this, we compared the patterns of fMRI activation, elicited by stimulation of the affected and the normal eye, along the visual cortical hierarchy. Activation was assessed in 8 subjects, which recovered clinically from an episode of optic neuritis but still had prolonged VEP latencies. In all patients, reduced fMRI activation was seen in V1 during stimulation of the affected eye, compared to the normal eye. The fMRI signal difference decreased in magnitude with progression along the visual hierarchy, and in some regions within the lateral occipital complex even showed the opposite preference (for the affected eye). These results may indicate a built-in robustness of the object-related areas to disruption of the visual input. Alternatively, it could reflect an adaptive functional reorganization of the cortical response to an abnormal input.
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Affiliation(s)
- Netta Levin
- Department of Neurobiology, Hebrew University, Jerusalem, Israel.
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22
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Frohman E, Costello F, Zivadinov R, Stuve O, Conger A, Winslow H, Trip A, Frohman T, Balcer L. Optical coherence tomography in multiple sclerosis. Lancet Neurol 2006; 5:853-63. [PMID: 16987732 DOI: 10.1016/s1474-4422(06)70573-7] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We do not have currently satisfactory clinical and anatomical correlates to gauge disability in multiple sclerosis. Structural biomarkers (such as MRI) are hindered because they cannot precisely segregate demyelination from axonal elements of tissue injury within the CNS. Axonal degeneration in multiple sclerosis is related to irreversible disability, which suggests that the confirmation of neuroprotective strategies needs highly quantifiable measures of axon loss that can be correlated with reliable measures of physiological function. The coupling of quantifiable measures of visual function with ocular imaging techniques, such as optical coherence tomography, enables us to begin to understand how structural changes in the visual system influence function in patients with multiple sclerosis. In this review, we consider the usefulness of optical imaging of the retina as a biomarker for neurodegeneration in multiple-sclerosis.
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Affiliation(s)
- Elliot Frohman
- Department of Neurology, University of Texas Southwestern Medical Center at Dallas, 75235, USA.
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23
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Pantano P, Mainero C, Caramia F. Functional brain reorganization in multiple sclerosis: evidence from fMRI studies. J Neuroimaging 2006; 16:104-14. [PMID: 16629730 DOI: 10.1111/j.1552-6569.2006.00029.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
In patients with multiple sclerosis (MS), the severity of clinical signs is not closely related to indices of structural brain damage provided by conventional magnetic resonance MR. Accordingly, patients with MS may show symptom recovery while progressively accumulating tissue damage. Changes in functional organization of the cerebral cortex have been reported in functional magnetic resonance (fMRI) studies that have compared the activation patterns during motor, visual, and cognitive tasks of patients with MS with those of healthy controls. fMRI studies on MS have provided the results that are difficult to compare and may be discrepant because of differences in the criteria used for patient selection, the activation paradigm, the experimental design, and the MR acquisition parameters. Nevertheless, they do provide a new, interesting tool that sheds light on how the brain changes its functional organization in response to MS. In patients with MS, functional brain reorganization mainly consists of an increase in the extent of activation of the brain areas used by healthy subjects, as well as the recruitment of additional brain areas. These findings have been interpreted as adaptive or compensatory mechanisms that allow normal performance despite neural damage or loss. However, brain functional activity may also change in response to clinical disability, though the precise role of brain functional changes in MS has yet to fully understand. Longitudinal studies designed to explore the effects of both rehabilitation and pharmacological agents on brain plasticity might shed light on this issue.
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Affiliation(s)
- Patrizia Pantano
- Department of Neurological Sciences, University La Sapienza, Viale dell'Università 30, 00185 Rome, Italy.
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24
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Abstract
There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not result simply from the extent of tissue destruction, rather it represents a complex balance between tissue damage, tissue repair and cortical reorganization. Functional magnetic resonance imaging provides information regarding the extent and nature of brain plasticity following MS-related structural injury, with the potential to limit the clinical manifestations of the disease. An altered recruitment of regions devoted normally to the performance of a given task and/or the recruitment of additional areas that are not typically activated by healthy people for performing that given task have been described in patients with MS, independent of their clinical phenotype, when investigating visual, cognitive and motor systems. These functional changes have been related not only to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific brain structures, but also to the degree of spinal cord and optic nerve involvement. It has also been suggested that an altered recruitment of specific brain regions might be associated with the appearance of clinical symptoms in MS, such as fatigue. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. More recently, in patients at the earliest clinical stage of the disease, it has been shown that such changes might contribute to predicting the evolution to definite MS, and it has been postulated that dynamic changes of brain cortical activations might occur with the progression of the disease. An increased recruitment of the cerebral networks might represent the first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent second-order compensatory areas, and on the other, contribute to the accumulation of irreversible disability.
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25
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Rocca MA, Hickman SJ, Bö L, Agosta F, Miller DH, Comi G, Filippi M. Imaging the optic nerve in multiple sclerosis. Mult Scler 2005; 11:537-41. [PMID: 16193891 DOI: 10.1191/1352458505ms1213oa] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Although multiple sclerosis (MS) frequently involves the optic nerves, imaging this structure is not yet performed routinely in clinical practice. The recent improvement of magnetic resonance (MR) technology and the development of new MR strategies, capable of providing an, in vivo, overall assessment of MS pathology has allowed objective metrics to be obtained for monitoring disease evolution, essentially in the brain. However, despite this progress, the correlation between brain MR metrics of the disease and clinical disability are still disappointing. An objective and accurate estimate of the presence and extent of optic nerve involvement might help to overcome this clinical/MRI paradox. This review summarizes the main results obtained from the application of conventional and modern MR-based techniques for the evaluation of optic nerve damage in MS.
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Affiliation(s)
- M A Rocca
- Neuroimaging Research Unit, Scientific Institute and University Ospedale San Raffaele, Milan, Italy
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26
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Filippi M, Rocca MA. MRI evidence for multiple sclerosis as a diffuse disease of the central nervous system. J Neurol 2005; 252 Suppl 5:v16-24. [PMID: 16254697 DOI: 10.1007/s00415-005-5004-5] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The classical view of MS as a chronic inflammatory demyelinating disease leading to the formation of focal central nervous system (CNS) white matter (WM) lesions has been recently challenged by pathological studies and by the extensive application of modern MRI-based techniques. There is now overwhelming evidence supporting the following statements: MS causes widespread tissue damage in the normal-appearing white matter (NAWM) of the brain and spinal cord, whose extent and severity is more strictly associated to the clinical manifestations of the disease than the extent of focal pathology. Discrete, macroscopic lesions are just the tip of the iceberg of MS pathology. Grey matter (GM) damage is a consistent feature of all MS phenotypes, which is progressive from the start of the relapsing-remitting phase of the disease. As is the case for WM, GM damage is also a mixture of focal lesions and diffuse pathology. High-field strength MR scanners are improving our ability to image focal GM lesions and modern MR-based techniques are enabling us to quantify in vivo the extent and severity of GM pathology, which have been shown to correlate only moderately with the amount of WM changes. At least part of GM pathology in MS is not secondary to retrograde degeneration of fibers traversing WM lesions. The neurodegenerative component of the disease is not a late phenomenon and it is not completely driven by inflammatory demyelination. In fact, neurodegeneration occurs very early in the course of MS and the correlation between MRI measures of inflammation and neurodegeneration is weak in all disease phases. The interplay of inflammation and neurodegeneration is a complex and still poorly understood phenomenon. At least part of MS-related neurodegeneration is not directly driven by Wallerian degeneration. Functional cortical changes can be seen in virtually all MS patients and are likely to play a central role in the ability of the MS brain to respond to tissue injury and, hence, limit the functional consequences of structural damage. MS disability is not just the result of tissue destruction but rather a balance between tissue destruction, tissue repair and adaptive cortical reorganization. All of this calls for the concept of MS as a focal, inflammatory demyelinating, WM disease to be reexamined and to start viewing MS as a diffuse CNS disease with an important neurodegenerative component. This is central for identifying novel and effective treatment strategies.
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Affiliation(s)
- Massimo Filippi
- Neuroimaging Research Unit, Dept. of Neurology Scientific Institute and University Ospedale San Raffaele, Via Olgettina 60, 20132, Milan, Italy.
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27
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Toosy AT, Hickman SJ, Miszkiel KA, Jones SJ, Plant GT, Altmann DR, Barker GJ, Miller DH, Thompson AJ. Adaptive cortical plasticity in higher visual areas after acute optic neuritis. Ann Neurol 2005; 57:622-33. [PMID: 15852380 DOI: 10.1002/ana.20448] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The ability to distinguish adaptive cortical reorganization may help to target future therapeutic strategies after neurological insult. We investigated cortical plasticity by prospectively applying visual functional magnetic resonance imaging (fMRI) and optic nerve MRI to 20 patients with acute optic neuritis at baseline, 1, 3, 6, and 12 months. We performed three types of correlation analyses to investigate the relationships between fMRI activity, clinical function, and optic nerve structure. The first analysis directly correlated the fMRI response to clinical function or optic nerve structure and found dynamic relations especially within the first 3 months. The second analysis used a novel technique that modeled the fMRI response and optic nerve structure together with clinical function, to determine the contribution fMRI made to clinical function after accounting for structural factors. Significant effects were found at baseline only, within the right peristriate cortex, and bilaterally in the lateral occipital complexes, which are normally involved in higher order visual processing. The third analysis investigated the relation between the modeled visual recovery rate and fMRI response but found no significant effects. The key findings of this study are from the second analysis and suggest a genuine adaptive role for cortical reorganization within extrastriate visual areas early after optic neuritis.
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Affiliation(s)
- Ahmed T Toosy
- Department of Headache, Brain Injury and Rehabilitation, Institute of Neurology, University College London, London, United Kingdom
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28
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Chiaravalloti N, Hillary F, Ricker J, Christodoulou C, Kalnin A, Liu WC, Steffener J, DeLuca J. Cerebral activation patterns during working memory performance in multiple sclerosis using FMRI. J Clin Exp Neuropsychol 2005; 27:33-54. [PMID: 15814441 DOI: 10.1080/138033990513609] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Working memory deficits are common in Multi Sclerosis (MS) and have been identified behaviourally in numerous studies. Despite recent advance in functional magnetic resonance imaging (fMRI), few published studies have examined cerebral activations associated with working memory dysfunction in MS. The present study examines brain activation patterns during performance of a working memory task in individual with clinically definite MS, compared to healthy controls (HC). fMRI was performed using a 1.5 Tesla GE scanner during a modified Paced Auditory Serial Addition Test (mPA-SAT). Participants were 6 individuals with MS with working memory impairment as evidenced on neuropsychological testing, 5 individuals with MS without working memory impairment, and 5 HC. Groups were demographically equivalent. Data were analyzed using Statistical Parametric Mapping (SPM99) software, with a stringent significance level (alpha < .005, voxel extent > or =8). Both MS groups and the HC group were able to perform the task, with comparable performance in terms of numbers of correct responses. Activation patterns within the HC and MS not-impaired groups were noted in similar brain regions, consistent with published observations in healthy samples That is, activations were lateralized to the left hemisphere, involving predominantly frontal regions. In contrast, the MS impaired group showed greater right frontal and right parietal lobe activation, when compared with the HC group. Thus, it appears that working memory dysfunction in MS is associated with altered patterns of cerebral activation that are related to the presence of cognitive impairement, and not solely a function of MS.
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Affiliation(s)
- Nancy Chiaravalloti
- Kessler Medical Rehabilitation Research and Education Corporation, 1199 Pleasant Valley Way, West Orange, NJ 07052, USA
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29
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Schmitz B, Käsmann-Kellner B, Schäfer T, Krick CM, Grön G, Backens M, Reith W. Monocular visual activation patterns in albinism as revealed by functional magnetic resonance imaging. Hum Brain Mapp 2004; 23:40-52. [PMID: 15281140 PMCID: PMC6871927 DOI: 10.1002/hbm.20046] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Human albinism is characterized by a disturbance of the chiasmatic projection system leading to predominant representation of just one eye in the contralateral hemisphere. Patients show congenital nystagmus without perceiving oscillopsia. The purpose of the present study was to demonstrate the consequences of atypical chiasmatic crossing with monocular visual stimulation using functional magnetic resonance imaging (fMRI). Sixteen patients with albinism and fifteen normally pigmented controls were stimulated with a monocular visual activation paradigm using flickering checkerboards. In patients, we observed contralaterally dominated activation of visual cortices correlating to clinical albinism parameters. This confirms albinism as a continuous range of hypopigmentation disorders. Additionally, albinos showed activation of the superior colliculus and of visual motion areas although the stimulus was stationary. Activation of visual motion areas is due probably to congenital nystagmus without a conscious correlate like oscillopsia.
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Affiliation(s)
- Bernd Schmitz
- Department of Diagnostic Radiology, Ulm University Hospital, Ulm, Germany.
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30
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Filippi M, Rocca MA, Comi G. The use of quantitative magnetic-resonance-based techniques to monitor the evolution of multiple sclerosis. Lancet Neurol 2003; 2:337-46. [PMID: 12849150 DOI: 10.1016/s1474-4422(03)00408-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Conventional MRI can improve accuracy in the diagnosis of multiple sclerosis (MS) and monitor the efficacy of experimental treatments. However, conventional MRI provides only gross estimates of the extent and nature of tissue damage associated with this disease. Other quantitative magnetic-resonance-based techniques have the potential to overcome the limitations of conventional MRI and, as a consequence, to improve our understanding of the natural history of MS. Magnetisation-transfer, diffusion-weighted, and functional MRI--as well as proton magnetic-resonance spectroscopy--are helping us to elucidate the mechanisms that underlie injury, repair, and functional adaptation in patients with MS. These techniques are substantially changing our understanding of how MS causes irreversible disability and should be used more extensively in clinical trials and in studies of disease progression.
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Affiliation(s)
- Massimo Filippi
- Department of Neurology, Scientific Institute and University Ospedale San Raffaele, Milan, Italy.
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31
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Miki A, Haselgrove JC, Liu GT. Functional magnetic resonance imaging and its clinical utility in patients with visual disturbances. Surv Ophthalmol 2002; 47:562-79. [PMID: 12504740 DOI: 10.1016/s0039-6257(02)00356-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Functional magnetic resonance imaging (fMRI) is a powerful, non-invasive technique for mapping human brain function. Because of the robust signal intensity changes associated with visual stimuli, fMRI is particularly useful for studying visual cortex (including both striate and extrastriate cortex). Also, activation of the lateral geniculate nuclei has been successfully demonstrated by fMRI. Therefore, fMRI may be potentially useful in patients with visual deficits by providing a non-invasive method for assessing the afferent visual pathways and higher cortical areas. Although there have been several reviews on fMRI, few have highlighted its clinical applicability in patients with visual disturbances. Our article will review fMRI principles and methodology, then focus on the possible applications and limitations of this technique in clinical ophthalmology.
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Affiliation(s)
- Atsushi Miki
- The Functional MRI Research Unit, Children's Hospital of Philadelphia, Philadelphia, PA, USA
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Russ MO, Cleff U, Lanfermann H, Schalnus R, Enzensberger W, Kleinschmidt A. Functional magnetic resonance imaging in acute unilateral optic neuritis. J Neuroimaging 2002; 12:339-50. [PMID: 12380481 DOI: 10.1111/j.1552-6569.2002.tb00142.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Despite good clinical criteria for diagnosing optic neuritis (ON), only a few techniques can precisely assess its impact on visual brain function. The authors studied whether functional magnetic resonance imaging (fMRI) of visual activation reliably reflects the cerebral consequences of acute unilateral ON, and how fMRI correlates with clinical function and visual evoked potentials (VEPs). Twenty ON patients, before and after steroid treatment, were compared to 20 controls. Each eye was stimulated separately with a checkerboard pattern reversing at 1, 2, 4, and 8 Hz. VEPs were recorded the same day. Initially, affected eye responses differed significantly from those of unaffected counterparts and controls in 12 patients. Post hoc classification by fMRI criteria was correct in approximately 85%. fMRI and VEP response parameters (as well as visual acuity) correlated significantly. The higher stimulation frequencies yielded greater fMRI responses from unaffected eyes, but not from affected eyes, in controls. The fMRI responses were quantifiable in every subject, whereas in 11 ON eyes, no VEPs were obtained during the acute stage. The authors conclude that fMRI is sensitive to the cerebral response alteration during ON and might therefore contribute to evaluating the temporal evolution of the visual functional deficit during recovery or therapy.
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Affiliation(s)
- Michael O Russ
- Department of Neurology, Klinikum der J. W. Goethe-Universität, Schleusenweg 2-16, D-60528 Frankfurt am Main, Germany.
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Langkilde AR, Frederiksen JL, Rostrup E, Larsson HBW. Functional MRI of the visual cortex and visual testing in patients with previous optic neuritis. Eur J Neurol 2002; 9:277-86. [PMID: 11985636 DOI: 10.1046/j.1468-1331.2002.00399.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The volume of cortical activation as detected by functional magnetic resonance imaging (fMRI) in the visual cortex has previously been shown to be reduced following optic neuritis (ON). In order to understand the cause of this change, we studied the cortical activation, both the size of the activated area and the signal change following ON, and compared the results with results of neuroophthalmological testing. We studied nine patients with previous acute ON and 10 healthy persons served as controls using fMRI with visual stimulation. In addition to a reduced activated volume, patients showed a reduced blood oxygenation level dependent (BOLD) signal increase and a greater asymmetry in the visual cortex, compared with controls. The volume of visual cortical activation was significantly correlated to the result of the contrast sensitivity test. The BOLD signal increase correlated significantly to both the results of the contrast sensitivity test and to the Snellen visual acuity. Our results indicate that fMRI is a useful method for the study of ON, even in cases where the visual acuity is severely impaired. The reduction in activated volume could be explained as a reduced neuronal input; however, the greater asymmetry might point to a cortical reorganization as a consequence of neuronal damage. Future fMRI studies in ON will add to the understanding of the neural adaptive behaviour following ON.
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Affiliation(s)
- A R Langkilde
- Danish Research Centre for Magnetic Resonance, Hvidovre University Hospital, Copenhagen, Norway.
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Miki A, Liu GT, Modestino EJ, Liu CS, Bonhomme GR, Dobre CM, Haselgrove JC. Functional magnetic resonance imaging of the visual system. Curr Opin Ophthalmol 2001; 12:423-31. [PMID: 11734682 DOI: 10.1097/00055735-200112000-00007] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Functional magnetic resonance imaging (fMRI), which is a technique useful for non-invasive mapping of brain function, is well suited for studying the visual system. This review highlights current clinical applications and research studies involving patients with visual deficits. Relevant reports regarding the investigation of the brain's role in visual processing and some newer fMRI techniques are also reviewed. Functional magnetic resonance imaging has been used for presurgical mapping of visual cortex in patients with brain lesions and for studying patients with amblyopia, optic neuritis, and residual vision in homonymous hemianopia. Retinotopic borders, motion processing, and visual attention have been the topics of several fMRI studies. These reports suggest that fMRI can be useful in clinical and research studies in patients with visual deficits.
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Affiliation(s)
- A Miki
- Division of Neuro-Ophthalmology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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35
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Toosy AT, Werring DJ, Plant GT, Bullmore ET, Miller DH, Thompson AJ. Asymmetrical activation of human visual cortex demonstrated by functional MRI with monocular stimulation. Neuroimage 2001; 14:632-41. [PMID: 11506536 DOI: 10.1006/nimg.2001.0851] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have demonstrated asymmetric activation patterns in the visual cortices of normal humans who have undergone functional MRI with monocular photic stimulation. The contralateral hemisphere is activated more strongly and to a greater spatial extent than the ipsilateral hemisphere when either eye is stimulated. This asymmetry can be explained by nasotemporal asymmetries which have been described in anatomical studies of the visual system in primates and humans. In part, the representation of the monocular crescent of the temporal hemifield of either eye, which exists only in the crossed projection, may explain this. In addition, within the binocular field, there is a biased crossed projection of nasal retinal ganglion cells which drive the contralateral ocular dominance columns in V1. Finally, the blind spot representation in the ipsilateral visual cortex may also contribute to the observed asymmetries. Our study may in effect provide a functional correlate of the anatomical asymmetries that have been observed in humans and animals.
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Affiliation(s)
- A T Toosy
- NMR Research Unit, Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
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36
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Rovaris M, Comi G, Filippi M. The role of non-conventional MR techniques to study multiple sclerosis patients. J Neurol Sci 2001; 186 Suppl 1:S3-9. [PMID: 11334984 DOI: 10.1016/s0022-510x(01)00485-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Conventional magnetic resonance imaging (MRI) lacks pathological specificity to the heterogeneous substrates of multiple sclerosis (MS) lesions and is not able to detect subtle, disease-related changes in the normal-appearing white matter (NAWM). As a consequence, the correlation between MRI findings and the long-term evolution of MS is moderate at best. To overcome the limitations of conventional MRI, new quantitative magnetic resonance (MR) techniques, such as cell-specific imaging, magnetization transfer imaging (MTI), proton magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI) and functional MR imaging (fMRI) have all been recently applied to the study of MS. These techniques should provide more accurate and pathologically specific estimates of the MS lesion burden than conventional MR and should improve our understanding of the mechanisms leading to MS-related irreversible disability.
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Affiliation(s)
- M Rovaris
- Neuroimaging Research Unit, Department of Neuroscience, Scientific Institute and University Ospedale San Raffaele, via Olgettina 60, 20132 Milan, Italy
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37
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Werring DJ, Bullmore ET, Toosy AT, Miller DH, Barker GJ, MacManus DG, Brammer MJ, Giampietro VP, Brusa A, Brex PA, Moseley IF, Plant GT, McDonald WI, Thompson AJ. Recovery from optic neuritis is associated with a change in the distribution of cerebral response to visual stimulation: a functional magnetic resonance imaging study. J Neurol Neurosurg Psychiatry 2000; 68:441-9. [PMID: 10727479 PMCID: PMC1736877 DOI: 10.1136/jnnp.68.4.441] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES Recovery to normal or near normal visual acuity is usual after acute demyelinating optic neuritis, despite the frequent persistence of conduction abnormalities as evidenced by the visual evoked potential (VEP). This raises the possibility that cortical adaptation to a persistently abnormal input contributes to the recovery process. The objective of this study was to investigate the pattern of cerebral response to a simple visual stimulus in recovered patients in comparison to normal subjects. METHODS Functional magnetic resonance imaging (fMRI) was used to study the brain activation pattern induced by a periodic monocular 8Hz photic stimulus in seven patients who had recovered from a single episode of acute unilateral optic neuritis, and in seven normal controls. VEPs and structural optic nerve MRI were performed on patients. RESULTS Stimulation of either eye in controls activated only the occipital visual cortex. However, in patients, stimulation of the recovered eye also induced extensive activation in other areas including the insula-claustrum, lateral temporal and posterior parietal cortices, and thalamus; stimulation of the clinically unaffected eye activated visual cortex and right insula-claustrum only. The volume of extraoccipital activation in patients was strongly correlated with VEP latency (r = 0.71, p = 0.005). CONCLUSIONS The extraoccipital areas that were activated in patients all have extensive visual connections, and some have been proposed as sites of multimodal sensory integration. The results indicate a functional reorganisation of the cerebral response to simple visual stimuli after optic neuritis that may represent an adaptive response to a persistently abnormal input. Whether this is a necessary part of the recovery process remains to be determined.
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Affiliation(s)
- D J Werring
- NMR Research Unit, Institute of Neurology, Queen Square, London WC1N 3BG, UK
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38
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Rovaris M, Filippi M. The role of magnetic resonance in the assessment of multiple sclerosis. J Neurol Sci 2000; 172 Suppl 1:S3-S12. [PMID: 10606798 DOI: 10.1016/s0022-510x(99)00270-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Although the correlations between magnetic resonance imaging (MRI) findings and long-term disease evolution range from poor to moderate, conventional pre- and post-contrast MRI provides sensitive and reliable measures to monitor multiple sclerosis (MS) activity over time. MRI pulse sequences that have been recently introduced have shorter acquisition times and their use in large-scale studies can significantly decrease their costs in terms of both working load and patients' discomfort. The application of non-conventional techniques can increase the pathological specificity of MRI findings and, as a consequence, improve the relationship with the clinical evolution of the disease. These techniques also enable us to quantify the subtle abnormalities occuring in the so-called normal-appearing white matter, thus allowing a more accurate assessment of MS burden to be achieved. Some of these techniques have already shown their value for assessing MS dynamics, whereas other still need to go through a more complete validation process prior to any extensive clinical application in MS.
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Affiliation(s)
- M Rovaris
- Neuroimaging Research Unit, Department of Neuroscience, Scientific Institute Ospedale San Raffaele, University of Milan, via Olgettina 60, 20132, Milan, Italy
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39
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Simon JH, McDonald WI. Assessment of optic nerve damage in multiple sclerosis using magnetic resonance imaging. J Neurol Sci 2000; 172 Suppl 1:S23-6. [PMID: 10606801 DOI: 10.1016/s0022-510x(99)00273-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The MR imaging-based assessment of the optic nerve in optic neuritis and multiple sclerosis provides information that is complementary to clinical and electrophysiological methods. The standard and more tissue destruction specific methods can be used in strategies to measure treatment efficacy and for understanding the mechanisms of relapse, recovery, and failure of recovery.
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Affiliation(s)
- J H Simon
- Department of Radiology/MRI, University of Colorado Health Sciences Center, 4200 E Ninth Ave, Denver, CO, USA.
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40
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Rovaris M, Filippi M. Magnetic resonance techniques to monitor disease evolution and treatment trial outcomes in multiple sclerosis. Curr Opin Neurol 1999; 12:337-44. [PMID: 10499178 DOI: 10.1097/00019052-199906000-00012] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Although the correlations between magnetic resonance findings and long-term disease evolution range from poor to moderate, conventional precontrast and postcontrast magnetic resonance imaging provides sensitive and reliable measures to monitor multiple sclerosis activity over time. New pulse sequences with shorter acquisition times can be cost effective and reduce patients' discomfort. The application of other techniques that give more accurate estimates of disease burden and have higher pathological specificity might improve our understanding of multiple sclerosis evolution and provide new outcomes for monitoring clinical trials. Work is still needed to obtain optimal imaging of the spinal cord for multiple sclerosis diagnosis and monitoring.
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Affiliation(s)
- M Rovaris
- Department of Neuroscience, Scientific Institute Ospedale San Raffaele, University of Milan, Italy
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41
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Gareau PJ, Gati JS, Menon RS, Lee D, Rice G, Mitchell JR, Mandelfino P, Karlik SJ. Reduced visual evoked responses in multiple sclerosis patients with optic neuritis: comparison of functional magnetic resonance imaging and visual evoked potentials. Mult Scler 1999; 5:161-4. [PMID: 10408715 DOI: 10.1177/135245859900500304] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The limited application of functional magnetic resonance imaging (fMRI) for investigations of multiple sclerosis (MS) patients has already shown that deficits of the motor, cognitive and visual systems may be identified by differences in the patterns of activation in response to a suitable stimulus. In MS patients with unilateral optic neuritis, the area of activation in the primary visual cortex, measured by fMRI techniques, is dramatically reduced in response to stimulation of the affected eye. The latency of the major positive component of the visual evoked potential (VEP) recorded upon stimulation of the affected eye is significantly increased in these patients, as compared to the unaffected eye and normal volunteers. We have found a correlation between the neural response measured using fMRI and the latency of the VEP. fMRI signal responses have the potential to provide more detailed topographic information relating to functional deficits in MS.
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Affiliation(s)
- P J Gareau
- Robarts Research Institute, London Health Sciences Center, Ontario, Canada
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42
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Di Salle F, Formisano E, Linden DE, Goebel R, Bonavita S, Pepino A, Smaltino F, Tedeschi G. Exploring brain function with magnetic resonance imaging. Eur J Radiol 1999; 30:84-94. [PMID: 10401589 DOI: 10.1016/s0720-048x(99)00047-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Since its invention in the early 1990s, functional magnetic resonance imaging (fMRI) has rapidly assumed a leading role among the techniques used to localize brain activity. The spatial and temporal resolution provided by state-of-the-art MR technology and its non-invasive character, which allows multiple studies of the same subject, are some of the main advantages of fMRI over the other functional neuroimaging modalities that are based on changes in blood flow and cortical metabolism. This paper describes the basic principles and methodology of fMRI and some aspects of its application to functional activation studies. Attention is focused on the physiology of the blood oxygenation level-dependent (BOLD) contrast mechanism and on the acquisition of functional time-series with echo planar imaging (EPI). We also provide an introduction to the current strategies for the correction of signal artefacts and other image processing techniques. In order to convey an idea of the numerous applications of fMRI, we will review some of the recent results in the fields of cognitive and sensorimotor psychology and physiology.
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Affiliation(s)
- F Di Salle
- Department of Biomorphological and Functional Sciences, II University of Naples, Italy
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