Functional magnetic resonance imaging and cognition at the very early stage of MS

Cognitive impairment in multiple sclerosis - a review of current knowledge and recent research

Multiple sclerosis (MS) is a chronic, progressive disease of the central nervous system that is characterised by inflammatory damage to the myelin sheath. Though often neglected, cognitive impairment is a common feature of MS that affects 43-70% of patients. It has a sophisticated neuroanatomic and pathophysiologic background and disturbs such vital cognitive domains as speed of information processing, memory, attention, executive functions and visual perceptual functions. In recent years there has been growing interest in neuroimaging findings with regard to cognitive impairment in MS. The possible options of managing cognitive dysfunction in MS are pharmacologic interventions, cognitive rehabilitation and exercise training; however, not enough evidence has been presented in this field. The aim of our article is to provide current knowledge on cognitive impairment in MS based on the most recent scientific results and conclusions with regard to affected cognitive domains, neuropsychological assessment, underlying mechanisms of this disturbance, neuroimaging findings and therapeutic options.

Ocular motor signatures of cognitive dysfunction in multiple sclerosis

The anatomical and functional overlap between ocular motor command circuitry and the higher-order networks that form the scaffolding for cognition makes for a compelling hypothesis that measures of ocular motility could provide a means to sensitively interrogate cognitive dysfunction in people with multiple sclerosis (MS). Such an approach may ultimately provide objective and reproducible measures of cognitive dysfunction that offer an innovative capability to refine diagnosis, improve prognostication, and more accurately codify disease burden. A further dividend may be the validation and application of biomarkers that can be used in studies aimed at identifying and monitoring preventative, protective and even restorative properties of novel neurotherapeutics in MS. This Review discusses the utility of ocular motor measures in patients with MS to characterize disruption to wide-ranging networks that support cognitive function.

The effect of a therapeutic regimen of Traditional Chinese Medicine rehabilitation for post-stroke cognitive impairment: study protocol for a randomized controlled trial

BACKGROUND

Post-stroke cognitive impairment (PSCI) lessens quality of life, restricts the rehabilitation of stroke, and increases the social and economic burden stroke imposes on patients and their families. Therefore effective treatment is of paramount importance. However, the treatment of PSCI is very limited. The primary aim of this protocol is to propose a lower cost and more effective therapy, and to confirm the long-term effectiveness of a therapeutic regimen of Traditional Chinese Medicine (TCM) rehabilitation for PSCI.

METHODS/DESIGN

A prospective, multicenter, large sample, randomized controlled trial will be conducted. A total of 416 eligible patients will be recruited from seven inpatient and outpatient stroke rehabilitation units and randomly allocated into a therapeutic regimen of TCM rehabilitation group or cognitive training (CT) control group. The intervention period of both groups will last 12 weeks (30 minutes per day, five days per week). Primary and secondary outcomes will be measured at baseline, 12 weeks (at the end of the intervention), and 36 weeks (after the 24-week follow-up period).

DISCUSSION

This protocol presents an objective design of a multicenter, large sample, randomized controlled trial that aims to put forward a lower cost and more effective therapy, and confirm the long-term effectiveness of a therapeutic regimen of TCM rehabilitation for PSCI through subjective and objective assessments, as well as highlight its economic advantages.

TRIAL REGISTRATION

This trial was registered with the Chinese Clinical Trial Registry (identifier: ChiCTR-TRC-14004872 ) on 23 June 2014.

Three approaches to investigating functional compromise to the default mode network after traumatic axonal injury

The default mode network (DMN) is a reliably elicited functional neural network with potential clinical implications. Its discriminant and prognostic utility following traumatic axonal injury (TAI) have not been previously investigated. The present study used three approaches to analyze DMN functional connectedness, including a whole-brain analysis [A1], network-specific analysis [A2], and between-node (edge) analysis [A3]. The purpose was to identify the utility of each method in distinguishing between healthy and brain-injured individuals, and determine whether observed differences have clinical significance. Resting-state fMRI was acquired from 25 patients with TAI and 17 healthy controls. Patients were scanned 6-11 months post-injury, and functional and neurocognitive outcomes were assessed the same day. Using all three approaches, TAI subjects revealed significantly weaker functional connectivity (FC) than controls, and binary logistic regressions demonstrated all three approaches have discriminant value. Clinical outcomes were not correlated with FC using any approach. Results suggest that compromise to the functional connectedness of the DMN after TAI can be identified using resting-state FC; however, the degree of functional compromise to this network, as measured in this study, may not have clinical implications in chronic TAI.

Ocular motor measures of cognitive dysfunction in multiple sclerosis II: working memory

Our companion paper documents pervasive inhibitory deficits in multiple sclerosis (MS) using ocular motor (OM) measures. Here we investigated the utility of an OM working memory (WMem) task in characterising WMem deficits in these patients as a function of disease status and disease duration. 22 patients with CIS, 22 early clinically definite MS patients (CDMS: <7 years of diagnosis), 22 late CDMS patients (>7 years from diagnosis), and 22 healthy controls participated. All participants completed the ocular motor WMem task, the paced auditory serial addition test (PASAT), and the symbol digit modalities test (SDMT). Clinical disability was characterised in CDMS patients using the Expanded Disability Severity Scale (EDSS). WMem performance was measured as proportion of errors (WMem errors), saccade latency, and relative sensitivity to WMem loading (WMem effect), an indicator of WMem capacity. All patient groups performed more WMem errors than controls with proportion of WMem errors, and degree of WMem effect increasing with increasing disease duration. A larger WMem effect, reflecting poorer WMem capacity, corresponded to poorer performance on neuropsychological measures, and a higher disability score for CDMS patients with the longest disease duration; an observation that suggests wider implication of WMem executive processes with advancing disease. Conspicuously, performance decrements on standard neuropsychological testing did not similarly increase commensurate with disease duration. The ocular motor WMem task appears to meaningfully dissociate WMem deficit from healthy individuals as well as a function of increasing disease duration. Potentially, this task represents a highly informative and objective method by which to ascertain progressive WMem changes from the earliest inception of MS.

Gray matter atrophy is associated with functional connectivity reorganization during the Paced Auditory Serial Addition Test (PASAT) execution in Multiple Sclerosis (MS)

BACKGROUND AND PURPOSE

We explored the relationship between gray matter atrophy and reorganization of functional connectivity in multiple sclerosis patients during execution of the Paced Auditory Serial Addition Test (PASAT).

MATERIALS AND METHODS

Seventeen patients and 15 healthy controls were selected for the study. Atrophy was determined using voxel-based morphometry, and atrophy-related connectivity changes were assessed using psychophysiological interaction analysis. Group differences, and correlations with PASAT performance and radiological variables were also examined.

RESULTS

Gray matter atrophy in MS patients was circumscribed to the bilateral posterior cingulate gyrus/precuneus. Compared with controls, patients showed stronger connectivity between the left posterior cingulate gyrus/precuneus, and the left middle temporal gyrus and left cerebellum. A regression analysis in controls showed a negative correlation between PASAT scores and functional connectivity between: (1) the left posterior cingulate gyrus/precuneus, and left pre/postcentral gyri and left occipital gyrus, and (2) the right posterior cingulate gyrus/precuneus, and bilateral cerebellum and left pre/postcentral gyri. Patients showed a negative correlation between brain parenchymal fraction and functional connectivity between the left posterior cingulate gyrus/precuneus and left cerebellum.

CONCLUSION

Patients with early MS and little brain damage presented more connectivity during PASAT execution, which may be interpreted as compensatory processes that help preserve cognitive functions.

Altered inter-subregion connectivity of the default mode network in relapsing remitting multiple sclerosis: a functional and structural connectivity study

Background and Purpose

Little is known about the interactions between the default mode network (DMN) subregions in relapsing-remitting multiple sclerosis (RRMS). This study used diffusion tensor imaging (DTI) and resting-state functional MRI (rs-fMRI) to examine alterations of long white matter tracts in paired DMN subregions and their functional connectivity in RRMS patients.

Methods

Twenty-four RRMS patients and 24 healthy subjects participated in this study. The fiber connections derived from DTI tractography and the temporal correlation coefficient derived from rs-fMRI were combined to examine the inter-subregion structural-functional connectivity (SC-FC) within the DMN and its correlations with clinical markers.

Results

Compared with healthy subjects, the RRMS patients showed the following: 1) significantly decreased SC and increased FC in the pair-wise subregions; 2) two significant correlations in SC-FC coupling patterns, including the positive correlation between slightly increased FC value and long white matter tract damage in the PCC/PCUN-MPFC connection, and the negative correlations between significantly increased FC values and long white matter tract damage in the PCC/PCUN-bilateral mTL connections; 3) SC alterations [log(N track) of the PCC/PCUN-left IPL, RD value of the MPFC-left IPL, FA value of the PCC/PCUN-left mTL connections] correlated with EDSS, increases in the RD value of MPFC-left IPL connection was positively correlated to the MFIS; and decreases in the FA value of PCC/PCUN-right IPL connection was negatively correlated with the PASAT; 4) decreased SC (FA value of the MPFC-left IPL, track volume of the PCC/PCUN-MPFC, and log(N track) of PCC/PCUN-left mTL connections) was positively correlated with brain atrophy.

Conclusions

In the connections of paired DMN subregions, we observed decreased SC and increased FC in RRMS patients. The relationship between MS-related structural abnormalities and clinical markers suggests that the disruption of this long-distance “inter-subregion” connectivity (white matter) may significantly impact the integrity of the network's function.

Efficacy and safety of subcutaneous interferon-β-1a in patients with a first demyelinating event and early multiple sclerosis

Introduction: Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS. Evidence suggests that MS should be treated as early as possible in order to maximize the benefit of treatment.

Areas covered: This review details current understanding about the treatment of relapsing–remitting MS (RRMS). The pharmacological and clinical data on the use of subcutaneous (s.c.) interferon β-1a (IFN-β-1a) as a therapeutic option for RRMS are covered, with a focus on the importance of treating patients with MS as early as possible in the course of the disease, in order to delay permanent axonal damage that is responsible for the signs and symptoms of disease progression.

Expert opinion: There is a wealth of data on the treatment of RRMS with s.c. IFN-β-1a indicating that patients treated during the early inflammatory stages of the disease have significantly improved short-term outcomes compared with patients who commence treatment late. It remains to be determined whether the short-term effects of early treatment will translate into long-lasting benefits, although it is hoped that ongoing research will help to answer this question.

Increased thalamic intrinsic oscillation amplitude in relapsing-remitting multiple sclerosis associated with the slowed cognitive processing

OBJECTIVE

To investigate the relationship between the amplitude of thalamic intrinsic neuronal activity, structural imaging indices, and the clinical neurological scales in relapsing-remitting multiple sclerosis (RRMS).

METHODS

Twenty-three patients with RRMS and 23 healthy controls were examined by resting-state fMRI (rs-fMRI) scan. Thalamic intrinsic oscillation amplitude was calculated by amplitude of low frequency fluctuation (ALFF) of rs-fMRI, as well as its correlations with clinical and structural imaging indices.

RESULTS

Compared with the healthy controls, RRMS patients showed significantly increased ALFF values in bilateral thalami (P<.05, corrected). In the patient group, positive correlation was found between bilateral ALFF values and paced auditory serial addition test (left: P=.033; right: P=.016). Significant correlation was detected between the ALFF values and fractional anisotropy (FA) values in the left thalamus (r=0.550, P=.007); only tendency increased correlation was detected between the ALFF values and FA values in the right thalamus (P=.114). No correlation was observed between bilateral thalamic ALFF values and disease duration, expanded disability status scale score, brain parenchymal fraction, or total white matter lesion loads (P>.05).

CONCLUSION

The increased thalamic intrinsic oscillation amplitude as an ineffective reorganization was responded to microstructural damage in the RRMS patients, as well as it was associated with the slowed cognitive processing in relatively minimally disabled stage.

Brain activity changes in cognitive networks in relapsing-remitting multiple sclerosis - insights from a longitudinal FMRI study

Background

Extrapolations from previous cross-sectional fMRI studies suggest cerebral functional changes with progression of Multiple Sclerosis (MS), but longitudinal studies are scarce. We assessed brain activation changes over time in MS patients using a cognitive fMRI paradigm and examined correlations with clinical and cognitive status and brain morphology.

Methods

13 MS patients and 15 healthy controls (HC) underwent MRI including fMRI (go/no-go task), neurological and neuropsychological exams at baseline (BL) and follow-up (FU; minimum 12, median 20 months). We assessed estimates of and changes in fMRI activation, total brain and subcortical grey matter volumes, cortical thickness, and T2-lesion load. Bland-Altman (BA) plots served to assess fMRI signal variability.

Results

Cognitive and disability levels remained largely stable in the patients. With the fMRI task, both at BL and FU, patients compared to HC showed increased activation in the insular cortex, precuneus, cerebellum, posterior cingulate cortex, and occipital cortex. At BL, patients vs. HC also had lower caudate nucleus, thalamus and putamen volumes. Over time, patients (but not HC) demonstrated fMRI activity increments in the left inferior parietal lobule. These correlated with worse single-digit-modality test (SDMT) performance. BA-plots attested to reproducibility of the fMRI task. In the patients, the right caudate nucleus decreased in volume which again correlated with worsening SDMT performance.

Conclusions

Given preserved cognitive performance, the increased activation at BL in the patients may be viewed as largely adaptive. In contrast, the negative correlation with SDMT performance suggests increasing parietal activation over time to be maladaptive. Several areas with purported relevance for cognition showed decreased volumes at BL and right caudate nucleus volume decline correlated with decreasing SDMT performance. This highlights the dynamics of functional changes and the strategic importance of specific brain areas for cognitive processes in MS.

Cognitive dysfunction in multiple sclerosis

In Multiple Sclerosis (MS) prevalence studies of community and clinical samples, indicate that 45-60% of patients are cognitively impaired. These cognitive dysfunctions have been traditionally described as heterogeneous, but more recent studies suggest that there is a specific pattern of MS-related cognitive dysfunctions. With the advent of disease-modifying medications for MS and emphasis on early intervention and treatment, detection of cognitive impairment at its earliest stage becomes particularly important. In this review the authors address: the cognitive domains most commonly impaired in MS (memory, attention, executive functions, speed of information processing, and visual-spatial abilities); the pathophysiological mechanism implied in MS cognitive dysfunction and correlated brain MRI features; the importance of neuropsychological assessment of MS patients in different stages of the disease and the influence of its course on cognitive performance; the most used tests and batteries for neuropsychological assessment; therapeutic strategies to improve cognitive abilities.

Longitudinal assessment of antisaccades in patients with multiple sclerosis

We have previously demonstrated that assessment of antisaccades (AS) provides not only measures of motor function in multiple sclerosis (MS), but measures of cognitive control processes in particular, attention and working memory. This study sought to demonstrate the potential for AS measures to sensitively reflect change in functional status in MS. Twenty-four patients with relapsing-remitting MS and 12 age-matched controls were evaluated longitudinally using an AS saccade task. Compared to control subjects, a number of saccade parameters changed significantly over a two year period for MS patients. These included saccade error rates, latencies, and accuracy measures. Further, for MS patients, correlations were retained between OM measures and scores on the PASAT, which is considered the reference task for the cognitive evaluation of MS patients. Notably, EDSS scores for these patients did not change significantly over this period. These results demonstrate that OM measures may reflect disease evolution in MS, in the absence of clinically evident changes as measured using conventional techniques. With replication, these markers could ultimately be developed into a cost-effective, non-invasive, and well tolerated assessment tool to assist in confirming progression early in the disease process, and in measuring and predicting response to therapy.

Physical activity associated with increased resting-state functional connectivity in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system, resulting in physical, cognitive and affective disturbances, with notable declines in the ability to learn and retain new information. In this study, we examined if higher levels of physical activity in MS individuals were associated with an increased resting-state connectivity of the hippocampus and cortex, resulting in better performance on a task of episodic memory. Forty-five individuals with a clinically definite diagnosis of MS were recruited for the study. Consistent with previous reports, hippocampus was functionally connected to the posteromedial cortex, parahippocampal gyrus, superior frontal gyrus, and the medial frontal cortex. Higher levels of physical activity in MS patients were associated with an increased coherence between the hippocampus and the posteromedial cortex (PMC). The increased connectivity between these two regions, in turn, was predictive of better relational memory, such that MS patients who showed an increased coherence between the left (not right) hippocampus and the PMC also showed better relational memory. Results of the study are interpreted in light of the challenge of disentangling effects of physical activity from effects of disease severity and its neuropathological correlates.

Thalamocortical sensorimotor circuit in multiple sclerosis: an integrated structural and electrophysiological assessment

Demyelination and axonal damage are pathologic hallmarks of multiple sclerosis (MS), leading to loss of neuronal synchronization, functional disconnection amongst brain relays, and clinical sequelae. To investigate these properties, the primary component of the sensorimotor network was analyzed in mildly disabled Relapsing-Remitting MS patients without sensory symptoms at the time of the investigation. By magnetoencephalography (MEG), the recruitment pattern within the primary sensory (S1) and motor (M1) areas was estimated through the morphology of the early components of somatosensory evoked magnetic fields (SEFs), after evaluating the S1 responsiveness to sensory inputs from the contralateral arm. In each hemisphere, network recruitment properties were correlated with ispilateral thalamus volume, estimated by morphometric techniques upon high-resolution 3D structural magnetic resonance images (MRI). S1 activation was preserved, whereas SEF morphology was strikingly distorted in MS patients, marking a disruption of primary somatosensory network patterning. An unbalance of S1-M1 dynamic recruitment was documented and correlated with the thalamic volume reduction in the left hemisphere. These findings support the model of MS as a disconnection syndrome, with major susceptibility to damage experienced by nodes belonging to more frequently recruited and highly specialized networks.

New methods for multiple sclerosis drug discovery

INTRODUCTION

MS is a heterogeneous disorder that requires the development of better diagnostics to identify disease subtypes enabling appropriate therapeutic intervention at an early stage of the disease. Accumulating evidence indicates that members of the inhibitor of apoptosis (IAP) family play an important role in the pathogenesis of MS by reducing the apoptotic elimination of autoreactive immune cells.

AREAS COVERED

The authors describe improved animal modeling strategies to identify compounds that have immunomodulatory, neurorestorative and neuroprotective properties. In addition, the authors propose new approaches to better model cognitive dysfunction in MS, which will aid the development of novel therapeutics for this complex disorder. The paper provides the reader with an appreciation for the diagnostic and therapeutic potential of apoptosis-related proteins for MS.

EXPERT OPINION

Recent evidence suggests that increased resistance of autoreactive immune cells to apoptotic elimination is a contributing factor to both disease susceptibility and progression in MS. This occurs, at least in part, because of elevated levels of the IAP family of anti-apoptotic genes that display distinct expression profiles associated with different subtypes of MS. The authors believe that the detection and targeting of members of the IAP family can provide better drugs for MS. Particularly, the authors feel that the overexpression of IAPs in animal models can provide novel insights into MS for both its pathogenesis and the discovery of new lead compounds.

Disruption of functional connectivity of the default-mode network in alcoholism

The default mode network (DMN) comprises brain structures maximally active at rest. Disturbance of network nodes or their connections occurs with some neuropsychiatric conditions and may underlie associated dysfunction. DMN connectivity has not been examined in alcoholism, which is marked by compromised DMN nodes and impaired spatial working memory. To test whether performance would be related to DMN integrity, we examined DMN functional connectivity using functional magnetic resonance imaging (fMRI) data and graph theory analysis. We assumed that disruption of short paths between network nodes would attenuate processing efficiency. Alcoholics and controls were scanned at rest and during a spatial working memory task. At rest, the spontaneous slow fluctuations of fMRI signals in the posterior cingulate and cerebellar regions in alcoholics were less synchronized than in controls, indicative of compromised functional connectivity. Graph theory analysis indicated that during rest, alcoholics had significantly lower efficiency indices than controls between the posterior cingulate seed and multiple cerebellar sites. Greater efficiency in several connections correlated with longer sobriety in alcoholics. During the task, on which alcoholics performed on par with controls, connectivity between the left posterior cingulate seed and left cerebellar regions was more robust in alcoholics than controls and suggests compensatory networking to achieve normal performance.

Functional brain network changes associated with maintenance of cognitive function in multiple sclerosis

In multiple sclerosis (MS) functional changes in connectivity due to cortical reorganization could lead to cognitive impairment (CI), or reflect a re-adjustment to reduce the clinical effects of widespread tissue damage. Such alterations in connectivity could result in changes in neural activation as assayed by executive function tasks. We examined cognitive function in MS patients with mild to moderate CI and age-matched controls. We evaluated brain activity using functional magnetic resonance imaging (fMRI) during the successful performance of the Wisconsin card sorting (WCS) task by MS patients, showing compensatory maintenance of normal function, as measured by response latency and error rate. To assess changes in functional connectivity throughout the brain, we performed a global functional brain network analysis by computing voxel-by-voxel correlations on the fMRI time series data and carrying out a hierarchical cluster analysis. We found that during the WCS task there is a significant reduction in the number of smaller size brain functional networks, and a change in the brain areas representing the nodes of these networks in MS patients compared to age-matched controls. There is also a concomitant increase in the strength of functional connections between brain loci separated at intermediate-scale distances in these patients. These functional alterations might reflect compensatory neuroplastic reorganization underlying maintenance of relatively normal cognitive function in the face of white matter lesions and cortical atrophy produced by MS.

Differential patterns of interhemispheric functional disconnection in mild and advanced multiple sclerosis

BACKGROUND

Patients with multiple sclerosis may present altered patterns of connectivity between the two brain hemispheres. To date, only transcallosal connectivity between the two primary motor cortices (M1) has been investigated functionally in patients with multiple sclerosis.

OBJECTIVES

The aim of this study was to investigate whether connectivity between the dorsal premotor cortex and the contralateral M1 was altered in patients with multiple sclerosis, and to see whether clinical progression is accompanied by exacerbated dorsal premotor cortex-M1 disconnectivity.

METHODS

A twin-coil transcranial magnetic stimulation approach was used to investigate both excitatory and inhibitory interhemispheric connections between the left dorsal premotor cortex and the contralateral M1 in 18 multiple sclerosis patients without disability, in 18 multiple sclerosis patients with advanced disease and in 12 age-matched healthy subjects. To activate distinct inhibitory and facilitatory transcallosal pathways, the intensity of dorsal premotor cortex stimulation was adjusted to be either suprathreshold (110% of resting motor threshold) or subthreshold (80% of active motor threshold).

RESULTS

Our sample of patients with multiple sclerosis showed altered patterns of interhemispheric dorsal premotor cortex-M1 functional connectivity even in the absence of clinical deficits. Facilitatory connections originating from dorsal premotor cortex were reduced in multiple sclerosis patients with or without disability, while inhibitory dorsal premotor cortex-M1 connections were altered only in disabled patients.

CONCLUSIONS

The current study demonstrates that functional excitatory connectivity originating from non-primary motor areas is compromised in multiple sclerosis patients even in the absence of clinical disability. Clinical disease progression leads to an impairment of both excitatory and inhibitory transcallosal connections.

Impaired small-world efficiency in structural cortical networks in multiple sclerosis associated with white matter lesion load

White matter tracts, which play a crucial role in the coordination of information flow between different regions of grey matter, are particularly vulnerable to multiple sclerosis. Many studies have shown that the white matter lesions in multiple sclerosis are associated with focal abnormalities of grey matter, but little is known about the alterations in the coordinated patterns of cortical morphology among regions in the disease. Here, we used cortical thickness measurements from structural magnetic resonance imaging to investigate the relationship between the white matter lesion load and the topological efficiency of structural cortical networks in multiple sclerosis. Network efficiency was defined using a 'small-world' network model that quantifies the effectiveness of information transfer within brain networks. In this study, we first classified patients (n = 330) into six subgroups according to their total white matter lesion loads, and identified structural brain networks for each multiple sclerosis group by thresholding the corresponding inter-regional cortical thickness correlation matrix, followed by a network efficiency analysis with graph theoretical approaches. The structural cortical networks in multiple sclerosis demonstrated efficient small-world architecture regardless of the lesion load, an organization that maximizes the information processing at a relatively low wiring cost. However, we found that the overall small-world network efficiency in multiple sclerosis was significantly disrupted in a manner proportional to the extent of total white matter lesions. Moreover, regional efficiency was also significantly decreased in specific brain regions, including the insula and precentral gyrus as well as regions of prefrontal and temporal association cortices. Finally, we showed that the lesions also altered many cortical thickness correlations in the frontal, temporal and parietal lobes. Our results suggest that the white matter lesions in multiple sclerosis might be associated with aberrant neuronal connectivity among widely distributed brain regions, and provide structural (morphological) evidence for the notion of multiple sclerosis as a disconnection syndrome.

Matrix metalloproteinases, synaptic injury, and multiple sclerosis

Multiple sclerosis (MS) is a disease of the central nervous system in which immune mediated damage to myelin is characteristic. For an overview of this condition and its pathophysiology, please refer to one of many excellent published reviews (Sorensen and Ransohoff, 1998; Weiner, 2009). To follow, is a discussion focused on the possibility that synaptic injury occurs in at least a subset of patients, and that matrix metalloproteinases (MMPs) play a role in such.

Long-term effect of early treatment with interferon beta-1b after a first clinical event suggestive of multiple sclerosis: 5-year active treatment extension of the phase 3 BENEFIT trial

BACKGROUND

The Betaferon/Betaseron in newly emerging multiple sclerosis for initial treatment (BENEFIT) trial investigated the effect of treatment with interferon beta-1b after a clinically isolated syndrome. The 5-year active treatment extension compares the effects of early and delayed treatment with interferon beta-1b on time to clinically definite multiple sclerosis (CDMS) and other disease outcomes, including disability progression.

METHODS

Patients with a first event suggestive of multiple sclerosis and a minimum of two clinically silent lesions in MRI were randomly assigned to receive interferon beta-1b 250 microg (n=292; early treatment) or placebo (n=176; delayed treatment) subcutaneously every other day for 2 years, or until diagnosis of CDMS. All patients were then eligible to enter a prospectively planned follow-up phase with open-label interferon beta-1b up to a maximum of 5 years after randomisation. Patients and study personnel remained unaware of initial treatment allocation throughout the study. Primary endpoints were time to CDMS, time to confirmed disability progression measured with the expanded disability status scale, and the functional assessment of multiple sclerosis trial outcomes index (FAMS-TOI) at 5 years. Analysis of the primary endpoints was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00185211.

FINDINGS

235 (80%) patients from the early treatment and 123 (70%) from the delayed treatment group completed the 5-year study. Early treatment reduced the risk of CDMS by 37% (hazard ratio [HR] 0.63, 95% CI 0.48-0.83; p=0.003) compared with delayed treatment. The risk for confirmed disability progression was not significantly lower in the early treatment group (0.76, 0.52-1.11; p=0.177). At 5 years, median FAMS-TOI scores were 125 in both groups. No significant differences in other disability related outcomes were recorded. Frequency and severity of adverse events remained within the established safety and tolerability profile of interferon beta-1b.

INTERPRETATION

Effects on the rate of conversion to CDMS and the favourable long-term safety and tolerability profile support early initiation of treatment with interferon beta-1b, although a delay in treatment by up to 2 years did not affect long-term disability outcomes.

FUNDING

Bayer Schering Pharma.

Control of visually guided saccades in multiple sclerosis: Disruption to higher-order processes

Ocular motor abnormalities are a common feature of multiple sclerosis (MS), with more salient deficits reflecting tissue damage within brainstem and cerebellar circuits. However, MS may also result in disruption to higher level or cognitive control processes governing eye movement, including attentional processes that enhance the neural processing of behaviourally relevant information. The attentional control of eye movement was investigated in 25 individuals with MS and a comparable number of neurologically healthy individuals matched for age and IQ. This entailed an evaluation of distractor-related effects on the generation of both unpredictable and predictable visually guided saccades, as well as an evaluation of the effects of presenting endogenous cues prior to target onset. For unpredictable saccades, we revealed an exaggerated distractor effect in MS, with saccade latencies prolonged and endpoints less accurate in the presence of a visual distractor. Predictable saccades tended to be hypometric for MS patients, although we found no significant distractor effects. For endogenously cued saccades, we found no group differences in latency following a valid cue, but an exaggerated increase in latency following invalid cues for MS patients. MS patients also generated a significantly greater proportion of erroneous responses to cue stimuli. These ocular motor characteristics demonstrate considerable sensitivity with respect to evaluating attentional deficits in MS, evident even in the absence of clinical signs of disease.

Multiple sclerosis: Cognition and saccadic eye movements

Ocular motor abnormalities are frequently reported in Multiple Sclerosis (MS), the most salient of which are well represented by the commonly used clinical measure, the EDSS. However, cognitive function, which is poorly represented by this scale, may also be ascertained from ocular motor measures, suggesting that an analysis of eye movements has the potential to extend and complement this more conventional measure. The generation of single and triple-step memory-guided saccades was investigated in 25 individuals with MS and a comparable number of neurologically healthy individuals matched for age and IQ. Experimental measures were correlated with a battery of neuropsychological tests evaluating attentional, working memory and executive processes, the cognitive domains most commonly compromised in MS. For single memory-guided saccades, MS patients were less accurate and generated more erroneous responses to non-target stimuli. Saccadic latencies were also prolonged. For triple-step memory-guided saccades, MS patients were less accurate and more variable. A number of significant correlations were revealed between measures of each of these characteristics and scores on the range of neuropsychological assessments. These ocular motor measures demonstrate considerable sensitivity with respect to evaluating cognitive function in MS, particularly working memory and inhibitory control processes. This suggests that they could represent the foundation of a user-friendly surrogate marker of disease severity and progression in MS.

Contributions of Neuroscience to Our Understanding of Cognitive Development

One major contribution of neuroscience to understanding cognitive development has been in demonstrating that biology is not destiny-that is, demonstrating the remarkable role of experience in shaping the mind, brain, and body. Only rarely has neuroscience provided wholly new insights into cognitive development, but often it has provided evidence of mechanisms by which observations of developmental psychologists could be explained. Behavioral findings have often remained controversial until an underlying biological mechanism for them was offered. Neuroscience has demonstrated promise for detecting cognitive problems before they are behaviorally observable-and, hence, promise for early intervention. In this article, we discuss examples drawn from imitation and mirror neurons, phenylketonuria (PKU) and prefrontal dopamine, maternal touch and stress reactivity, and non-genetic (behavioral) intergenerational transmission of biological characteristics.

Relation between functional brain imaging, cognitive impairment and cognitive rehabilitation in patients with multiple sclerosis

Cognitive impairment belongs to the core symptoms in MS affecting quality of life, self-esteem, and social as well as occupational functioning. Due to this high impact on patients' well-being efficient treatment concepts are required. Imaging studies on cognition have shown that functional reorganisation takes place spontaneously to compensate for deficits. In mildly to moderately impaired patients these processes may support coping with emerging deficits. However, these compensatory processes seem to be limited as brain activation of cognitively severely impaired patients is characterised by decreased additional recruitment of brain regions. Cognitive rehabilitation concentrates on the question whether induction of brain plasticity is possible for both the support of the spontaneous processes and the initiation of new ones. Combining cognition, brain imaging and cognitive rehabilitation in MS, an intriguing question is whether fMRI can provide further insights into the mechanisms of induced plasticity and serve as objective outcome measures for efficient cognitive intervention.

Incidental use of ecstasy: no evidence for harmful effects on cognitive brain function in a prospective fMRI study

RATIONALE

Heavy ecstasy use in humans has been associated with cognitive impairments and changes in cognitive brain function supposedly due to damage to the serotonin system. There is concern that even a single dose of 3,4-methylenedioxymethamphetamine may be neurotoxic, but very little is known about the consequences of a low dose of ecstasy for cognitive brain function.

OBJECTIVES

The objective of the study was to assess the effects of a low dose of ecstasy on human cognitive brain function using functional magnetic resonance imaging (fMRI).

MATERIALS AND METHOD

We prospectively studied, as part of the NeXT (Netherlands XTC toxicity) study, sustained effects of a low dose of ecstasy on brain function in 25 subjects before and after their first episode of ecstasy use (mean 2.0 +/- 1.4 ecstasy pills, on average 11.1 +/- 12.9 weeks since last ecstasy use), compared to 24 persistent ecstasy-naive controls, also measured twice and matched with the novice users on age, gender, IQ, and cannabis use. Cognitive brain function was measured in the domains of working memory, selective attention, and associative memory using fMRI.

RESULTS

No significant effects were found of a low dose of ecstasy on working memory, selective attention, or associative memory neither at the behavioral level nor at the neurophysiological level.

CONCLUSIONS

This study yielded no firm evidence for sustained effects of a low dose of ecstasy on human cognitive brain function. The present findings are relevant for the development of prevention and harm reduction strategies. Furthermore, the study is relevant to the discussion concerning potential therapeutic use of ecstasy.

Cognitive impairment in multiple sclerosis: evidence-based analysis and recommendations

Cognitive impairment is common in multiple sclerosis (MS), occurring at all stages of the disease, and can be a major source of vocational disability, social impairment, and impoverished quality of life. Dysfunction in free recall from long-term memory, speed of information processing, working memory, and abstract reasoning are frequently observed in MS. Despite weak correlation with disease duration and physical disability status, the degree of cognitive impairment in MS has been related to the extent of topographically specific neuronal tissue damage and loss. Additional clinical factors including disease course, fatigue, affective disturbance, and medication can impact on the degree of MS-related cognitive impairment. We suggest that the symbol digits modalities test, paced auditory serial addition task, the clock drawing test and the MS neuropsychological screening questionnaire be considered as valid and relevant screening tests for cognitive impairment in MS.

[Future of non conventional MR techniques in MS]

Although conventional magnetic resonance imaging (MRI) is used for diagnosing multiple sclerosis (MS) and monitoring disease activity and course, the correlation between conventional MRI data and clinical findings remains weak. This "clinical-MRI paradox" could be partly due to the lack of MRI specificity related to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Recently, non-conventional MRI techniques, including magnetization transfer MRI, diffusion tensor MRI, and proton MR spectroscopy have been applied to improve our understanding of the pathophysiology of MS. These techniques may provide information about structural and biochemical changes occurring within and outside macroscopic MS lesions (inflammation, demyelination, axonal loss), in particular in the normal-appearing white and grey matter. These techniques could also significantly improve our ability to monitor inflammatory demyelination and axonal injury. In the same way, functional MRI gives us the potential substrate to assess the mechanisms of adaptive cortical reorganization, which may limit the irreversible consequences of MS tissue injury.

Cognitive impairment in multiple sclerosis

PURPOSE OF REVIEW

For a long time, cognitive impairment in multiple sclerosis patients has been considered less important than, for instance, physical disability. This is no longer true because of the crucial role that cognitive deficits play in the good day-to-day adjustment of patients. This review highlights recent progress made in this area. A special focus lies on studies investigating the neural correlates of cognitive impairment in multiple sclerosis patients as detectable by conventional, quantitative and functional magnetic resonance imaging.

RECENT FINDINGS

Measures of information-processing speed appear to be the most robust and sensitive markers of cognitive impairment in multiple sclerosis patients. Recent studies demonstrate that single, predominantly speed-related cognitive tests may be superior to extensive and time-consuming test batteries in screening overall cognitive decline. Quantitative magnetic-resonance-imaging findings suggest the extent of subtle tissue damage in normal-appearing white and grey matter to correlate best with the severity of cognitive impairment in multiple sclerosis patients.

SUMMARY

From neuropsychological test data, and findings from magnetic resonance imaging and functional magnetic resonance imaging it is evident that cognitive impairment in multiple sclerosis is not just the result of tissue destruction, but rather a balance between tissue destruction, tissue repair, and adaptive functional reorganization.

Les troubles cognitifs au cours de la sclérose en plaques

Forty to sixty percent of patients with multiple sclerosis (MS) have cognitive dysfunction. The frequency of cognitive disturbances according to the clinical form is not completely understood and the natural history of these disorders has not been extensively studied. Cognitive deficits can be detected in early stages of the disease. Their frequency increases from clinically isolated syndromes, to relapsing-remitting and secondary progressive MS. Cognitive abnormalities are frequently observed also in primary progressive MS. The most frequently impaired functions are information processing speed, attention and memory. Dementia is uncommon but may disclose the disease. Diffuse cerebral injury, assessed by magnetic resonance imaging, contributes to cognitive dysfunction in MS, probably by interrupting connecting fibers between neuronal networks involved in these cognitive functions. Compensatory mechanisms may occur at early stages but they are limited by extension of brain injury.