Functional basis of memory impairment in multiple sclerosis: a[18F]FDG PET study

Left thalamomegaly in a patient with partial epilepsy

Temporal lobe epilepsy (TLE) is associated with modification in thalamic structure and function. In particular, thalamic atrophy and hypometabolism can occur, affecting ipsilateral, contralateral thalami or both. We describe a 28-year-old epileptic woman, who presented peculiar neuroimaging findings, with enlargement of the thalamus contralateral to the epileptic focus. The patient was born from dystocic delivery, she presented partial motor seizures in the left side of the body, followed by generalisation, and the EEG showed a right temporal epileptic focus. Serial CT and MRI scan, performed along 11 years, showed a non-evolutive left thalamomegaly. 18-FDG PET showed reduced metabolic activity in the upper right temporal gyrus and in the ipsilateral thalamus. Thalamic asymmetry in our patient could be an occasional finding.

Perfusion magnetic resonance imaging correlates of neuropsychological impairment in multiple sclerosis

Although cognitive impairment is common in multiple sclerosis (MS), its pathophysiology is still poorly understood. Abnormalities of cerebral blood flow (CBF) have long been acknowledged in MS and advances in perfusion magnetic resonance imaging (MRI) allow for their assessment in vivo. We investigated the relationship between regional perfusion changes and neuropsychological (NP) dysfunctions in patients with relapsing-remitting and primary-progressive MS. Absolute CBF, cerebral blood volume (CBV) and mean transit time were measured in 32 MS patients and 11 healthy controls using dynamic susceptibility contrast-enhanced T2(*)-weighted MRI. A comprehensive NP test battery was administered to all patients. A mixed model analysis of covariance was performed for group comparisons in terms of perfusion measures in normal-appearing white matter (NAWM) and deep gray matter (GM). Pearson's correlations were used to describe the association of perfusion metrics with NP Z-scores. CBF and CBV values were significantly decreased in both NAWM and deep GM in MS patients compared with controls (P=0.01). In all patients, deep GM CBF was significantly associated with Rey Complex Figure Test (RCFT)-Copy (r=0.5; P=0.001) and deep GM CBV and NAWM CBV were significantly associated with Color-Word Interference Inhibition Switching test (D-KEFSIS) (r=0.4; P=0.008 and r=0.4; P=0.02). However, the only associations that remained significant after Bonferroni correction were between deep GM CBF and RCFT-Copy (P=0.006), and deep GM CBV and D-KEFSIS (P=0.04). Our results suggest a role for tissue perfusion impairment in NP dysfunction in MS. Large-scale studies are needed to characterize better this association.

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.

CD4+CD25- effector T-cells inhibit hippocampal long-term potentiation in vitro

During neuroinflammation T-cells invade the CNS, and may lead to the development and progression of several pathologies, of which multiple sclerosis is the most common. In these pathologies neuroinflammation is often associated with cognitive dysfunction. Using mouse hippocampal slices, we show here that CD4(+)CD25(-) T-cells inhibit long-term potentiation (LTP) induced by high-frequency stimulation. The T-cell-mediated inhibition of LTP can be prevented by blockade of gamma-aminobutyric acid (GABA)(A) receptors. These findings provide additional insight into the multiple functions of T-cells in CNS pathologies.

Extensive Hippocampal Demyelination in Multiple Sclerosis

Memory impairment is especially prominent within the spectrum of cognitive deficits in multiple sclerosis (MS), and a crucial role for hippocampal pathology may therefore be expected in this disease. This study is the first to systematically assess hippocampal demyelination in MS. Hippocampal tissue samples of 19 chronic MS cases and 7 controls with non-neurologic disease were stained immunohistochemically for myelin proteolipid protein. Subsequently, number, location, and size of demyelinated lesions were assessed. Furthermore, the specimens were stained for HLA-DR to investigate microglia/macrophage activity. An unexpectedly high number of lesions (n = 37) was found in 15 of the 19 MS cases. Mixed intrahippocampal-perihippocampal lesions, which were more often found in cases with cognitive decline, were large and did not respect anatomical borders. Moderate microglial activation was frequently observed at the edges of these mixed lesions. Isolated intrahippocampal lesions were also frequently found. These were smaller than the mixed lesions and had a specific anatomical predilection: the cornu ammonis 2 subregion and the hilus of the dentate gyrus were consistently spared. Microglial activation was rare in isolated intrahippocampal lesions. Our results indicate that hippocampal demyelination is frequent and extensive in MS and that anatomical localization, size, and inflammatory activity vary for different lesion types.

Alteration of the somatostatinergic system in the striatum of rats with acute experimental autoimmune encephalomyelitis

To date, the neurochemical basis underlying the motor and cognitive deficits described in patients with multiple sclerosis (MS) is unclear. Since the neuropeptide somatostatin (SRIF) and the striatum have been implicated in movement control and implicit memory, the aim of this study was to analyze the striatal somatostatinergic system in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). Female Lewis rats were immunized with an emulsion containing myelin basic protein (MBP) in complete Freund's adjuvant to induce the disease. The animals were decapitated when limp tail (grade 1) or severe hind limb paralysis (grade 3) was observed. Acute EAE in grade 3 did not modify striatal somatostatin-like immunoreactivity (SRIF-LI) content but decreased the overall SRIF receptor density, without affecting the apparent affinity, in the rat striatal membranes. A selective reduction in the protein levels of the SRIF receptor subtype sst2, analyzed by Western blotting, was detected in the EAE rats, which correlated with decreased sst2 mRNA levels. The expression of the receptor subtypes sst1, sst3 or sst4 was unaltered by the disease. The decrease in the SRIF receptor density was accompanied by an attenuated capacity of SRIF to inhibit both basal and forskolin-stimulated adenylyl cyclase activity. No significant changes, however, were found in the protein levels of Gi proteins (G(ialpha1), G(ialpha2) or G(ialpha3)) nor in those of the G-protein-coupled receptor kinase subtypes GRK2, GRK5 or GRK6. Acute EAE in grade 1 did not modify any of the parameters studied. In conclusion, these data demonstrate that acute EAE, in grade 3, disrupts the rat striatal SRIF receptor-effector system. These findings provide new insight into the molecular basis of EAE which might contribute to a better understanding of multiple sclerosis in humans.

Impact of individual cognitive profile on visuo-motor reorganization in relapsing-remitting multiple sclerosis

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.

Positron emission tomography with computed tomography imaging of neuroinflammation in experimental autoimmune encephalomyelitis

2-[(18)F]Fluoro-2-deoxy-d-glucose positron emission tomography ([(18)F]FDG PET) detection of the up-regulated glycolysis associated with malignant transformation is a noninvasive imaging technique used extensively in cancer diagnosis. Although striking similarities exist in glucose transport and metabolism between tumor cells and activated immune cells, the potential use of [(18)F]FDG PET for the diagnosis and evaluation of autoimmune disorders has not been systematically investigated. Here we ask whether [(18)F]FDG PET in conjunction with computed tomography (CT) could be used to monitor a complex autoimmune disorder such as murine experimental autoimmune encephalomyelitis (EAE) and whether this approach is sensitive enough to evaluate therapeutic interventions. We found that (i) coregistration of metabolic (i.e., microPET) and high-resolution anatomical (i.e., CT) images allows serial quantification of glycolysis with [(18)F]FDG in various spinal column segments; (ii) [(18)F]FDG PET/CT can detect the increased glycolysis associated with paralysis-causing inflammatory infiltrates in the spinal cord; and (iii) the [(18)F]FDG measure of glycolysis in the spinal cord is sensitive to systemic immunosuppressive therapy. These results highlight the potential use of serial [(18)F]FDG PET/CT imaging to monitor neuroinflammation in EAE and suggest that similar approaches could be applied to the diagnosis and evaluation of other autoimmune and inflammatory disorders in animal models and in humans.

MRI markers of destructive pathology in multiple sclerosis-related cognitive dysfunction

Studies with conventional magnetic resonance imaging (MRI) indicate that cognitive impairment in multiple sclerosis (MS) patients is not fully explained by the burden of T2-visible lesions in the brain. Other non-conventional MRI techniques with increased specificity to the more destructive aspects of MS pathology, such as magnetization transfer MRI, diffusion-weighted MRI and proton magnetic resonance spectroscopy, have recently been applied to MS cognitive studies. The results suggest that the presence and extent of "occult" MS pathological features in the normal-appearing brain tissue and the location of lesions in eloquent sites play a central role in the pathogenesis of MS neuropsychological impairment.

Cognitive dysfunction and emotional–behavioural changes in MS: The potential of positron emission tomography

Cognitive dysfunction and emotional-behavioral changes are symptoms with increasing clinical relevance during progression of the disease. They cannot be explained by demyelination of white matter alone but clearly indicate cortical dysfunction. Positron emission tomography (PET) provides methods to assess cortical dysfunction quantitatively by measuring cerebral glucose metabolism using the tracer (18)F-2-fluoro-2-deoxy-d-glucose (FDG). The technique has been employed to study fatigue and disease progression. Microglial activation was studied by 11C-PK-11195 PET. It was found not only in active plaques but also in degenerating fibre tracks. Other tracers offer a broad spectrum of measuring local physiological functions and pathophysiological processes, but some of them are still limited to experimental animal research.

Anticholinesterasics in the treatment of cognitive impairment in multiple sclerosis

Neuropsychological impairment is a common manifestation in multiple sclerosis (MS) and is found in 40-60% of patients. The pattern of cognitive impairment in MS is characterized by difficulties in recent memory, sustained attention, executive functions and information processing speed. These cognitive deficits have a significant impact on the patients' daily activities. However, there is no specific treatment available at present for cognitive disorders in MS patients. Treatment with acetylcholinesterase inhibitors (AChEI) has shown a positive effect on cognitive functions of patients with Alzheimer's disease and other conditions such as Lewy Body dementia, subcortical vascular dementia and Parkinson's disease. In this paper we review the results from studies and clinical trials aiming to demonstrate that AChEI could be a potential treatment for cognitive disorders in MS patients. Finally, we discuss future issues to take into consideration for AChEI treatments in the context of MS.

Reduced thalamic and cerebellar rest metabolism in relapsing-remitting multiple sclerosis, a positron emission tomography study: correlations to lesion load

Magnetic resonance imaging (MRI) is the main tool for detecting central nervous system lesions in MS. However, classical anatomical MRI is unable to assess exactly disease related injury in normal-appearing brain tissue and to give information about the functional consequences of the disease, explaining weak correlation frequently observed between lesion load and clinical data. Recently, functional brain imaging techniques have provided new insights concerning pathophysiological processes of the disease. Among them Positron Emission Tomography (PET), a sensitive technique to evaluate functional consequences of tissue injury in other neurological diseases, has rarely been used in MS. Seventeen Relapsing-Remitting (RR-) MS patients with low disability at the early stage of the disease underwent measurements of cerebral metabolic rate of glucose (rCMRglu) in resting state by PET using [(18)F] fluorodeoxyglucose (FDG) and assessment of regional cortical and white matter lesion volume (LV), using an in-house-developed semi-automatic method, was done at the same time on MRI. rCMRglu of MS patients was compared with rCMRglu of 18 normal control subjects using univariate SPM99 analysis through Matlab 5 and correlations between rCMRglu and LV were tested using multivariate linear regression using SPM99. Statistical threshold was set at p<0.05 corrected for multiple comparisons and correlations. Compared to controls, reduced rCMRglu was found in the right thalamus (p<0.001), in bilateral cerebellum (p<0.05 for right and p<0.01 for left) and the posterior part of left inferior parietal cortex (p<0.05). In addition, higher rCMRglu in patients compared to controls was observed in left inferior frontal cortex, left (anterior part) and right inferior parietal cortex (p<0.001). rCMRglu in right thalamus correlates negatively with different LV: total LV, total juxtacortical and/or overlapping cortico-subcortical LV, total and frontal deep white matter LV. rCMRglu of the right superior frontal cortex negatively correlated with total and parieto-occipital deep white matter LV. The results of this study, performed in a group of recent RR-MS patients with low disability, suggest that demyelinating lesions in MS mainly have a remote effect on cortical, basal ganglia and cerebellum metabolism and that regional cortical compensatory mechanisms may be observed concurrently.

Clinical characteristics of cortical multiple sclerosis

There are several articles in this special issue in which authors eloquently describe neurobehavioural and cognitive complications of multiple sclerosis with relevant neuropsychological assessments and neuroimaging findings. However behavioural and cognitive presentation of multiple sclerosis remains poorly understood. Two years ago, we reported a series of patients with multiple sclerosis who presented with neurobehavioural symptoms and had neuropsychological deficits consistent with cortical dysfunction. Based on previous case reports, pathological studies of cerebral cortex in multiple sclerosis and advanced neuroimaging studies we suggested that neurobehavioural presentation of multiple sclerosis represents a new variant called "cortical multiple sclerosis". The condition is characterised by predominant or exclusive cortical pathology presenting with neurobehavioural symptoms, such as depression, amnesia or distinct cortical syndromes. Since the publication of our report, there has been further neuroimaging and neuropathological findings that further supported the above concept. In addition, observation of more patients with this condition helped us to formulate a logical approach in the detection of these patients. This article focuses on their clinical characteristics.

Reduced brain functional reserve and altered functional connectivity in patients with multiple sclerosis

Cognitive dysfunction (affecting particularly attention and working memory) occurs early in patients with multiple sclerosis. Previous studies have focused on identifying potentially adaptive functional reorganization through recruitment of new brain regions that could limit expression of these deficits. However, lesion studies remind us that functional specializations in the brain make certain brain regions necessary for a given task. We therefore have asked whether altered functional interactions between regions normally recruited provide an alternative adaptive mechanism with multiple sclerosis pathology. We used a version of the n-back task to probe working memory in patients with early multiple sclerosis. We applied a functional connectivity analysis to test whether relationships between relative activations in different brain regions change in potentially adaptive ways with multiple sclerosis. We studied 21 patients with relapsing-remitting multiple sclerosis and 16 age- and sex-matched healthy controls with 3T functional MRI. The two groups performed equally well on the task. Task-related activations were found in similar regions for patients and controls. However, patients showed relatively reduced activation in the superior frontal and anterior cingulate gyri (P > 0.01). Patients also showed a variable, but generally substantially smaller increase in activation than healthy controls with greater task complexity, depending on the specific brain region assessed (P < 0.001). Functional connectivity analysis defined further differences not apparent from the univariate contrast of the task-associated activation patterns. Control subjects showed significantly greater correlations between right dorsolateral prefrontal and superior frontal/anterior cingulate activations (P < 0.05). Patients showed correlations between activations in the right and left prefrontal cortices, although this relationship was not significant in healthy controls (P < 0.05). We interpret these results as showing that, while cognitive processing in the task appears to be performed using similar brain regions in patients and controls, the patients have reduced functional reserve for cognition relevant to memory. Functional connectivity analysis suggests that altered inter-hemispheric interactions between dorsal and lateral prefrontal regions may provide an adaptive mechanism that could limit clinical expression of the disease distinct from recruitment of novel processing regions. Together, these results suggest that therapeutic enhancement of the coherence of interactions between brain regions normally recruited (functional enhancement), as well as recruitment of alternative areas or use of complementary cognitive strategies (both forms of adaptive functional change), may limit expression of cognitive impairments in multiple sclerosis.

Lyme disease of the brainstem

Lyme disease is a multisystem infectious disease caused by the tick-borne spirochete, Borrelia burgdorferi. Central nervous system (CNS) involvement typically causes local inflammation, most commonly meningitis, but rarely parenchymal brain involvement. We describe a patient who presented with clinical findings suggesting a brainstem process. Magnetic resonance imaging (MRI) and positron emission tomography (PET) suggested a brainstem neoplasm. Prior to biopsy, laboratory evaluation led to the diagnosis of Lyme disease. Clinical and imaging abnormalities improved markedly following antimicrobial therapy. We describe Lyme disease involvement of the cerebellar peduncles with hypermetabolism on PET. Although MRI is the primary imaging modality for most suspected CNS pathology, the practical applications of PET continue to expand.

Cerebral activation patterns during working memory performance in multiple sclerosis using FMRI

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.

Imaging of multiple sclerosis: role in neurotherapeutics

Magnetic resonance imaging (MRI) plays an ever-expanding role in the evaluation of multiple sclerosis (MS). This includes its sensitivity for the diagnosis of the disease and its role in identifying patients at high risk for conversion to MS after a first presentation with selected clinically isolated syndromes. In addition, MRI is a key tool in providing primary therapeutic outcome measures for phase I/II trials and secondary outcome measures in phase III trials. The utility of MRI stems from its sensitivity to longitudinal changes including those in overt lesions and, with advanced MRI techniques, in areas affected by diffuse occult disease (the so-called normal-appearing brain tissue). However, all current MRI methodology suffers from limited specificity for the underlying histopathology. Conventional MRI techniques, including lesion detection and measurement of atrophy from T1- or T2-weighted images, have been the mainstay for monitoring disease activity in clinical trials, in which the use of gadolinium with T1-weighted images adds additional sensitivity and specificity for areas of acute inflammation. Advanced imaging methods including magnetization transfer, fluid attenuated inversion recovery, diffusion, magnetic resonance spectroscopy, functional MRI, and nuclear imaging techniques have added to our understanding of the pathogenesis of MS and may provide methods to monitor therapies more sensitively in the future. However, these advanced methods are limited by their cost, availability, complexity, and lack of validation. In this article, we review the role of conventional and advanced imaging techniques with an emphasis on neurotherapeutics.

Abnormalities of cerebral perfusion in multiple sclerosis

BACKGROUND

Measuring perfusion provides a potential indication of metabolic activity in brain tissue. Studies in multiple sclerosis (MS) have identified areas of decreased perfusion in grey matter (GM) and white matter (WM), but the pattern in clinical subgroups is unclear.

OBJECTIVES

This study investigated perfusion changes in differing MS clinical subgroups on or off beta-interferon therapy using a non-invasive MRI technique (continuous arterial spin labelling) to investigate whether different clinical MS subtypes displayed perfusion changes and whether this could give a further insight into the pathological mechanisms involved.

METHODS

Sixty patients (21 relapsing remitting, 14 secondary progressive, 12 primary progressive, 13 benign) and 34 healthy controls were compared. Statistical parametric mapping (SPM '99) was used to investigate regional variations in perfusion in both GM and WM. Global WM perfusion was derived by segmenting WM from images using T(1) relaxation times.

RESULTS

Regions of lower perfusion in predominantly GM were observed in the primary and secondary progressive cohorts, particularly in the thalamus. Increased WM perfusion was seen in relapsing remitting and secondary progressive cohorts.

CONCLUSIONS

Low GM perfusion could reflect decreased metabolism secondary to neuronal and axonal loss or dysfunction with a predilection for progressive forms of MS. Increased WM perfusion may indicate increased metabolic activity possibly due to increased cellularity and inflammation. Improved methodology and longitudinal studies may enable further investigation of regional and temporal changes, and their relationship with physical and cognitive impairment.

fMRI evidence of brain reorganization during attention and memory tasks in multiple sclerosis

Functional magnetic resonance imaging (fMRI) data on motor function have shown adaptive functional changes related to brain injury in multiple sclerosis (MS). We investigated whether patients with MS have altered fMRI activation patterns during attention and memory tasks, and whether functional changes in the brain correlate with the extent of overall tissue damage on conventional MRI. Twenty-two right-handed patients with relapsing-remitting MS (RRMS) and no or only mild deficits at neuropsychological testing and 22 matched healthy subjects were scanned during the Paced Auditory Serial Addition Test (PASAT) and a recall task. fMRI data were analyzed using Statistical Parametric Mapping (SPM99). The relation between fMRI changes during both tasks and T2 lesion load was investigated. During both tasks, patients exhibited significantly greater brain activation than controls and recruited additional brain areas. Task-related functional changes were more significant in patients whose performance matched that of controls than in patients with a lower performance. During the PASAT, brain functional changes involved the right supplementary motor area and cingulate, the bilateral prefrontal, temporal and parietal areas, whereas during the recall task they involved the prefrontal and temporal cortex and basal ganglia bilaterally, and the left thalamus. In patients, activation in specific brain areas during performance of both tasks positively correlated with T2 brain lesions. Patients with RRMS exhibit altered patterns of activation during tasks exploring sustained attention, information processing and memory. During these tasks, fMRI activity is greater in patients with better cognitive function than in those with lower cognitive function. Functional changes in specific brain areas increase with increasing tissue damage suggesting that they may also represent adaptive mechanisms that reflect underlying neural disorganization or disinhibition, possibly associated with MS.

A paced visual serial addition test for fMRI

BACKGROUND AND PURPOSE

The Paced Auditory Serial Attention Task (PASAT) is an attention and information processing task used in patients with diffuse brain disorders, like cerebral trauma and multiple sclerosis (MS). Based on the PASAT we used a adapted version of the test to assess several cognitive functions with fMRI. In this study we investigated the activation pattern on a group and individual level and upon parametric stimulation.

METHODS

Nine young, healthy, right-handed subjects (mean age 24 years) were studied. The test contrasts an adding-and-memory stage with a control stage in a block design, at two different speeds. Group average maps (random effects analysis, p=0.05) were created to identify the brain areas subserving this task. For each area found active in the group map, the percentage of individuals showing activation in that same anatomical area was calculated.

RESULTS

Group activation was localized in the superior and inferior parietal lobe bilaterally, the superior frontal gyrus bilaterally, the left medial frontal gyrus, the left inferior frontal gyrus and adjacent part of the insula, the anterior part of the cingulate gyrus and some cerebellar areas. For the main activated areas, 78-100% of the individual subjects showed activation in that same area. Contrasting the low speed with the high speed condition yielded activation with a considerable individual variation.

CONCLUSION

The group mean activated areas were located mainly in the frontal and parietal lobes and those areas were also activated in the majority of the subjects, indicating limited inter-individual variation, rendering this test suitable for clinical applications in a variety of neurological disorders.

Cognitive presentation of multiple sclerosis: evidence for a cortical variant

BACKGROUND

Although neuropsychiatric complications are well recognised, the presentation of multiple sclerosis with cognitive or neuropsychiatric symptoms has generally been considered a rare occurrence and to reflect subcortical pathology.

OBJECTIVES

To document the clinical, neuropsychological, and radiological features of six cases of cognitive presentation of multiple sclerosis, to review the relevant literature, and to propose a possible cortical basis for this clinical presentation.

SUBJECTS

Six patients (five women; age range 38 to 60 years) presented to the memory and cognitive disorders clinic in Cambridge with an initially undiagnosed cognitive/neuropsychiatric syndrome. All underwent neuropsychological evaluation, brain imaging, and ancillary investigations to establish a diagnosis of multiple sclerosis.

RESULTS

The six cases all had a progressive dementia syndrome with prominent amnesia, often accompanied by classic cortical features including dysphasia, dysgraphia, or dyslexia. Mood disturbance was ubiquitous and in three patients there was a long history of preceding severe depression. All six developed characteristic physical signs on follow up, with marked disabilities. A review of 17 previously reported cases highlighted the prominence of memory impairment and depression in the early stages.

CONCLUSIONS

On clinical, pathological, and radiological grounds, the neuropsychiatric presentation of multiple sclerosis may represent a clinicopathological entity of "cortical multiple sclerosis." Failure to recognise this will delay diagnosis and may expose patients to potentially dangerous and invasive investigation. Because the neuropsychiatric features of cortical multiple sclerosis are a major cause of handicap, their early recognition may be particularly important in view of emerging treatments.

Electrophysiological evidence for a defect in the processing of temporal sound patterns in multiple sclerosis

OBJECTIVES

To assess the processing of spectrotemporal sound patterns in multiple sclerosis by using auditory evoked potentials (AEPs) to complex harmonic tones.

METHODS

22 patients with definite multiple sclerosis but mild disability and no auditory complaints were compared with 15 normal controls. Short latency AEPs were recorded using standard methods. Long latency AEPs were recorded to synthesised musical instrument tones, at onset every two seconds, at abrupt frequency changes every two seconds, and at the end of a two second period of 16/s frequency changes. The subjects were inattentive but awake, reading irrelevant material.

RESULTS

Short latency AEPs were abnormal in only 4 of 22 patients, whereas long latency AEPs were abnormal to one or more stimuli in 17 of 22. No significant latency prolongation was seen in response to onset and infrequent frequency changes (P1, N1, P2) but the potentials at the end of 16/s frequency modulations, particularly the P2 peaking approximately 200 ms after the next expected change, were significantly delayed.

CONCLUSION

The delayed responses appear to be a mild disorder in the processing of change in temporal sound patterns. The delay may be conceived of as extra time taken to compare the incoming sound with the contents of a temporally ordered sensory memory store (the long auditory store or echoic memory), which generates a response when the next expected frequency change fails to occur. The defect cannot be ascribed to lesions of the afferent pathways and so may be due to disseminated brain lesions visible or invisible on magnetic resonance imaging.

Magnetic resonance imaging of multiple sclerosis

Although conventional magnetic resonance imaging (cMRI) is widely used for diagnosing multiple sclerosis (MS) and monitoring disease activity and evolution, the correlation between cMRI and clinical findings is far from strict. Among the reasons for this "clinical-MRI paradox," a major role has been attributed to the limited specificity of cMRI to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Modern quantitative MRI techniques have the potential to overcome some of the limitations of cMRI. Metrics derived from magnetization transfer and diffusion-weighted MRI enable one to quantify the extent of structural changes occurring within and outside macroscopic MS lesions with increased pathological specificity over cMRI. Magnetic resonance spectroscopy can add information on the biochemical nature of such changes, with the potential to improve significantly our ability to monitor inflammatory demyelination and axonal injury. Finally, functional MRI might provide new insights into the role of cortical adaptive changes in limiting the clinical consequences of white-matter structural damage. This review outlines the major contributions given by MRI-based techniques to the diagnostic work-up of MS patients, to the understanding of the pathobiology of the disease, and to the assessment of the effects of new experimental treatments.

Cognitive function and fMRI in patients with multiple sclerosis: evidence for compensatory cortical activation during an attention task

Mild cognitive impairment has frequently been reported for patients in the early stages of multiple sclerosis. The aim of the present study was to measure whether altered cortical activation during a sustained attention task occurs along with limited extent of neuropsychological problems. Expanded brain activation of multiple sclerosis patients with normal motor function compared with healthy controls during a finger tapping paradigm has previously been reported. Compensatory brain activation in patients with multiple sclerosis compared with normal controls may also be observed when the subjects are performing cognitive functions. In 21 patients with clinically definite relapsing-remitting multiple sclerosis, a psychometric assessment was performed using the Wechsler Memory Scale (WMS) and the Multiple Sclerosis Functional Composite Score (MSFC). In addition, functional MRI was performed during a Paced Visual Serial Addition Task (PVSAT), a visual analogue of the Paced Auditory Serial Addition Task (PASAT). All patients were within 3 years of diagnosis and were not suffering from a relapse at the time of investigation. The multiple sclerosis patients were compared with a control group of 21 healthy volunteers matched for handedness, age, years of education and sex. With regard to psychometric results, the WMS general memory score showed statistically significant differences between patients and controls. We did not find differences for either the MSFC or the PASAT scores. A group analysis of the functional imaging data during the PVSAT revealed different activation patterns for patients compared with control subjects. In healthy volunteers, the main activation was found in the frontal part of the right gyrus cinguli (Brodmann area 32). In patients, the main activation was detected at the right hemispheric frontal cortex (Brodmann areas 6, 8 and 9). In addition, the left hemispheric Brodmann area 39 was activated. We interpret the different patterns of activation, accompanied with intact performance in a sustained attention task of our multiple sclerosis sample compared with healthy controls, as the consequence of compensatory mechanisms. This is an expression of neuronal plasticity during early stages of a chronic disease.

Diffusion tensor imaging in early relapsing-remitting multiple sclerosis

Diffusion tensor magnetic resonance imaging (DTI) indices are abnormal in patients with established multiple sclerosis (MS). The objective of this study was to examine the diffusion characteristics of MS lesions, normal appearing white matter (NAWM) and normal appearing grey matter (NAGM) in MS patients with early relapsing-remitting disease. A further objective was to investigate the relationship between three DTI parameters (fractional anisotropy (FA), mean diffusivity (MD) and volume ratio (VR)) and clinical outcome measures (Kurtzke expanded disability status scale (EDSS) and MS Functional Composite Measure) in early disease. DTI was performed in 28 patients and 27 controls. Analysis was carried out using a region of interest (ROI) approach. ROIs were placed in 12 NAWM and nine NAGM regions. Significant differences were found in FA, MD and VR between lesions and NAWM (P< 0.001 for all three DTI parameters). No significant differences were found between patients and controls when examining NAWM or NAGM, although there was a trend for abnormal NAWM FA and VR in some regions. No correlation was found between DTI parameters in lesions, NAWM or NAGM and the clinical outcome measures. The lack of significant DTI abnormality in the NAWM and NAGM may reflect a lack of pathological change or a limited sensitivity of DTI using ROI methodology. Previous studies have shown abnormalities in TI relaxation time, magnetisation transfer ratio (MTR) and N-Acetyl aspartate (NM) in this cohort of patients, and as such, DTI using a region of interest (ROI) approach may not be as sensitive as other MR techniques in detecting subtle changes in normal appearing brain

The neuropsychology of multiple sclerosis: contributions of neuroimaging research

Multiple sclerosis (MS) is often associated with cognitive and emotional changes that affect daily activities and quality of life. Deficits in memory, executive function, processing speed, and other cognitive domains are frequently reported. In addition, mood disturbances and fatigue are common. In this article, the authors highlight research on individual differences in the neuropsychology of MS, and emphasize neuroimaging studies that help elucidate the basis of the deficits.

Investigation of MS normal-appearing brain using diffusion tensor MRI with clinical correlations

OBJECTIVE

To quantitatively investigate water diffusion changes in normal-appearing white matter (NAWM) and gray matter in patients with MS, and to evaluate whether these changes are correlated with clinical disability and disease duration.

BACKGROUND

Diffusion tensor imaging provides quantitative information about the magnitude and directionality (anisotropy) of water diffusion in vivo and detects pathologic changes in MS brain tissue.

METHODS

Diffusion tensor imaging was performed in 39 patients with MS and in 21 age-matched control subjects. Quantitative indices, including fractional anisotropy, volume ratio, and mean diffusivity, were obtained in 30 regions of interest located in normal-appearing basal ganglia, cerebellar gray matter, and supratentorial and infratentorial NAWM.

RESULTS

Patients with MS showed significantly reduced anisotropy and a trend toward increased diffusivity in the infratentorial and supratentorial NAWM, and significantly increased anisotropy in the basal ganglia. In all patients with MS, both fractional anisotropy and mean diffusivity in the cerebral peduncles were inversely correlated with the Expanded Disability Status Scale and pyramidal functional scores. In patients with relapsing-remitting MS, there was a strong correlation between Expanded Disability Status Scale score and fractional anisotropy in both supratentorial and infratentorial NAWM. In primary and secondary progressive MS, disease duration correlated strongly with mean diffusivity in infratentorial NAWM and fractional anisotropy in the cerebral peduncles, respectively.

CONCLUSION

The most striking finding of decreased fractional anisotropy in supratentorial and infratentorial NAWM and increased fractional anisotropy in basal ganglia may result from axonal degeneration due to fiber transection in remote focal lesions. Diffusion tensor imaging indices, in particular fractional anisotropy, appear sensitive to structural damage in NAWM that is associated with disability and progression in MS.

Magnetization transfer and diffusion tensor MR imaging of basal ganglia from patients with multiple sclerosis

Although post-mortem studies have shown that lesions of multiple sclerosis (MS) can be detected in the basal ganglia, conventional T2-weighted magnetic resonance (MR) imaging is poorly sensitive for detecting such abnormalities. This study was performed to investigate whether magnetization transfer (MT) and diffusion tensor MR imaging are able to detect in vivo basal ganglia changes in patients with MS. After image coregistration, MT ratio (MTR) and mean diffusivity (&Dmacr;) maps were obtained and MTR and &Dmacr; values of the putamen, head of the caudatus and thalamus measured from 31 patients with clinically definite MS and 14 age- and sex-matched healthy volunteers using region of interest analysis. Although we found slightly decreased MTR and increased &Dmacr; in the basal ganglia from patients compared to controls, suggesting increased extra-cellular water and reduced amount of 'barriers' restricting water molecular motion in the basal ganglia of patients with MS, none of the differences was statistically significant. These data suggest that the more sophisticated MR probes of tissue disruption and cellular integrity are no more sensitive than current conventional imaging for detecting basal ganglia abnormalities in patients with MS.

A 12-week, open trial of donepezil hydrochloride in patients with multiple sclerosis and associated cognitive impairments

Cognitive dysfunction occurs in up to 65% of patients with multiple sclerosis (MS), but there is no effective treatment for the symptoms. The authors conducted a 12-week, open-pilot study to assess the efficacy and tolerability of donepezil HCl administered in patients with MS and cognitive impairment. Seventeen patients at a long-term care facility with Mini-Mental State Examination scores of < or = 25 received 5 mg of donepezil HCl for a 4-week period, followed by 8 weeks of 10 mg of donepezil HCl. Cognitive, neurologic, functional, and behavioral assessments were conducted at baseline and at 4 and 12 weeks. Statistically significant improvement was observed in several cognitive domains including attention, memory, and executive functioning, as well as different aspects of behavior. These data suggest that donepezil HCl merits further study as a potentially viable treatment option for patients with cognitive impairment associated with MS.

Changes in the normal appearing brain tissue and cognitive impairment in multiple sclerosis

OBJECTIVES

To assess (a) whether the changes in the normal appearing brain tissue (NABT), as revealed by magnetisation transfer (MT) histogram analysis, correlates with cognitive dysfunction in patients with multiple sclerosis and (b) the relative contribution of these changes by comparison with that of multiple sclerosis lesions visible on conventional MRI.

METHODS

Dual echo, T1 weighted and MT scans of the brain were obtained in 12 patients with multiple sclerosis with cognitive impairment and in seven without cognitive impairment. Lesion loads were assessed from T2 and T1 weighted scans. To create MT histograms of the NABT, multiple sclerosis lesion outlines from dual echo scans were superimposed automatically and nulled out from the coregistered and scalp stripped MTR maps. Average lesion MT ratio (MTR) and brain size were also measured.

RESULTS

T2 and T1 lesion loads were significantly higher and the average lesion MTR and brain size were significantly lower in the group of cognitively impaired patients. Patients with cognitive deficits also had significantly lower average MTR and peak location of the NABT histogram. Logistic regression analysis showed that 68% of the total variance was explained by average NABT-MTR alone. A multivariable regression model showed that NABT-MTR was the only factor that significantly correlated with cognitive impairment in these patients (p=0.001).

CONCLUSIONS

The extent of abnormalities which go undetected when using conventional MRI is relevant in determining cognitive impairment in multiple sclerosis.

A multiparametric MRI study of frontal lobe dementia in multiple sclerosis

Previous studies achieved conflicting results when correlating magnetic resonance imaging (MRI) abnormalities and cognitive impairment in multiple sclerosis (MS) patients. Recently, the estimation of MS lesion load on T1-weighted images and the analysis of magnetization transfer ratio (MTR) histograms, increased the degree of the correlation between physical disability and MRI findings in MS. We assessed the relationship of conventional and non-conventional MRI-derived measures with frontal lobe dementia in MS. Dual echo, T1-weighted and MT MRI scans of the brain were obtained in 11 MS patients with and in 11 without frontal lobe dementia, matched for age, sex, education and disability. Total (TLL) and frontal (FLL) lesion loads were assessed from T2- and T1-weighted scans. MTR histogram analysis was performed for the whole brain, the frontal lobe and the cerebellum. Median TLL and FLL were significantly higher in cognitively impaired patients on both T2- and T1-weighted scans. The MRI measure that better discriminated the two groups of patients was T1-weighted TLL (median values were 19.1 ml for demented and 1.9 ml for non-demented patients, P=0.006). Average MTR, peak height and location of overall brain and frontal lobe histograms were significantly lower for cognitively impaired than for cognitively intact patients (P values ranged from 0.0001 to 0.001). Cerebellar MTR histogram metrics did not significantly differ in patients with and without cognitive decline. The presence of cognitive decline in MS is associated with the extent and pathological severity of brain MRI abnormalities.

Multiple sclerosis: the disease and its manifestations

Multiple sclerosis is an immune-mediated inflammatory demyelinating disease of the central nervous system clinically characterized by relapses and remissions of neurological disturbance. A typical relapse, exemplified by optic neuritis, increases in severity over a week or two and after approximately one month begins to remit. Resolution takes place over the course of two to three months. In the early stages, clinical recovery is virtually complete, though persistent abnormalities of conduction can usually be detected by evoked potential techniques and persistent structural abnormalities can be detected by magnetic resonance imaging (MRI). These techniques, together with cerebrospinal fluid examination for oligoclonal IgG, provide supporting evidence for the diagnosis which, in the absence of a specific test, nevertheless remains primarily clinical. The course of the disease is very variable, but after a number of years neurological deficit begins to accumulate after each relapse. In most patients, the relapsing and remitting phase of the disease is followed by a phase of continuous progression of disability. Cognitive disturbances can be detected in many patients even quite early in the course of the illness. Deficits in attention, memory and executive skills may be prominent and tend to become increasingly prominent as neurological deficit increases, although this is not always the case. There is some correlation between the extent of MRI abnormalities in the cerebral white matter and the severity of cognitive deficit. Depression and anxiety are commonly experienced but are poorly correlated to the lesion load seen on MRI. In contrast, the much rarer psychotic symptoms, euphoria and emotional lability are closely linked to the severity of white matter disease.

Rapid assessment of regional cerebral metabolic abnormalities in single subjects with quantitative and nonquantitative [18F]FDG PET: A clinical validation of statistical parametric mapping

The [18F]fluorodeoxyglucose ([18F]FDG) method for measuring brain metabolism has not the wide clinical application that one might expect, partly because of its high cost and the complexity of the quantification procedure, but also because of reporting techniques based on region of interest (ROI) analysis, which are time-consuming and not fully objective. In this paper we report a clinical validation of statistical parametric mapping (SPM) using rCMRglc (quantitative) and radioactivity distribution (nonquantitative) [18F]FDG PET data. We show that a 10-min noninteractive voxel-based SPM analysis on a standard workstation enables objective assessment, including localization in stereotactic space, of regional glucose consumption abnormalities, whose reliability can be assessed on statistical and clinical grounds. Clinical validity was established using a small series of patients with degenerative or developmental disorders, including probable Alzheimer's disease, progressive aphasia, multiple sclerosis, developmental specific language impairment, and epilepsy. Analysis of quantitative and nonquantitative data showed the same pattern of results, suggesting that, for clinical purposes, quantitation and invasive arterial cannulation can be avoided. This should facilitate a wider application of the technique and the extension of SPM clinical analysis to H215O PET or high resolution SPECT perfusion studies.

MRI measures and their relations with clinical disability in relapsing-remitting and secondary progressive multiple sclerosis

To further evaluate the relationship between clinical disability and Magnetic Resonance Imaging (MRI) lesion burden, we examined 85 patients with clinically definite multiple sclerosis (54 relapsing-remitting and 31 secondary progressive). This cross-sectional study reports on the correlations between total and infratentorial lesion volume on both T1 and T2 weighted images, and overall physical disability measured by Expanded Disability Status Scale, ambulation index and individual functional systems. Assessment of the hypointense lesion load on T1 weighted images rather than the hyperintense lesion load on T2 weighted images at brain MRI was shown to be useful for differentiating relapsing-remitting from secondary progressive Multiple Sclerosis. A weak relationship between disability and total lesion volume on both T1 and T2 weighted images was found in relapsing-remitting Multiple Sclerosis. In secondary progressive Multiple Sclerosis, infratentorial lesion volume on T2 weighted images represents the only marker of disability. Finally, the presence of cerebellar, brainstem and mental impairment was significantly associated to a greater total lesion volume on MRI, while no relationship was found with other functional systems.