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

Age-related decline in cerebral oxygen consumption in multiple sclerosis

Cerebral oxygen metabolism is altered in relapsing-remitting multiple sclerosis (RRMS), possibly a result of disease related cerebral atrophy with subsequent decreased oxygen demand. However, MS inflammation can also inhibit brain metabolism. Therefore, we measured cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) using MRI phase contrast mapping and susceptibility-based oximetry in 44 patients with early RRMS and 36 healthy controls. Cerebral atrophy and white matter lesion load were assessed from high-resolution structural MRI. Expanded Disability Status Scale (EDSS) scores were collected from medical records. The CMRO2 was significantly lower in patients (-15%, p = 0.002) and decreased significantly with age in patients relative to the controls (-1.35 µmol/100 g/min/year, p = 0.036). The lower CMRO2 in RRMS was primarily driven by a higher venous oxygen saturation in the sagittal sinus (p = 0.007) and not a reduction in CBF (p = 0.69). There was no difference in cerebral atrophy between the groups, and no correlation between CMRO2 and MS lesion volume or EDSS score. Therefore, the progressive CMRO2 decline observed before the occurrence of significant cerebral atrophy and despite adequate CBF supports emerging evidence of dysfunctional cellular respiration as a potential pathogenic mechanism and therapeutic target in RRMS.

Measuring Pathology in Patients with Multiple Sclerosis Using Positron Emission Tomography

PURPOSE OF REVIEW

Multiple sclerosis is characterized by a diverse and complex pathology. Clinical relapses, the hallmark of the disease, are accompanied by focal white matter lesions with intense inflammatory and demyelinating activity. Prevention of these relapses has been the major focus of pharmaceutical development, and it is now possible to dramatically reduce this inflammatory activity. Unfortunately, disability accumulation persists for many people living with multiple sclerosis owing to ongoing damage within existing lesions, pathology outside of discrete lesions, and other yet unknown factors. Understanding this complex pathological cascade will be critical to stopping progressive multiple sclerosis. Positron emission tomography uses biochemically specific radioligands to quantitatively measure pathological processes with molecular specificity. This review examines recent advances in the understanding of multiple sclerosis facilitated by positron emission tomography and identifies future avenues to expand understanding and treatment options.

RECENT FINDINGS

An increasing number of radiotracers allow for the quantitative measurement of inflammatory abnormalities, de- and re-myelination, and metabolic disruption associated with multiple sclerosis. The studies have identified contributions of ongoing, smoldering inflammation to accumulating tissue injury and clinical worsening. Myelin studies have quantified the dynamics of myelin loss and recovery. Lastly, metabolic changes have been found to contribute to symptom worsening. The molecular specificity facilitated by positron emission tomography in people living with multiple sclerosis will critically inform efforts to modulate the pathology leading to progressive disability accumulation. Existing studies show the power of this approach applied to multiple sclerosis. This armamentarium of radioligands allows for new understanding of how the brain and spinal cord of people is impacted by multiple sclerosis.

N-acetyl Cysteine Administration Is Associated With Increased Cerebral Glucose Metabolism in Patients With Multiple Sclerosis: An Exploratory Study

Background: Multiple Sclerosis (MS) is an autoimmune disease marked by progressive neurocognitive injury. Treatment options affording neuroprotective effects remain largely experimental. The purpose of this proof of concept study was to explore the effects of N-acetyl-cysteine (NAC) on cerebral glucose metabolism (CMRGlu) and symptoms in patients with multiple sclerosis (MS).

Methods: Twenty-four patients with MS were randomized to either NAC plus standard of care, or standard of care only (waitlist control). The experimental group received NAC intravenously once per week and orally the other 6 days. Patients in both groups were evaluated at baseline and after 2 months (of receiving the NAC or waitlist control period) with an integrated Position Emission Tomography (PET)/ Magnetic Resonance Imaging (MRI) scanner, using 18F Fluorodeoxyglucose (FDG) to measure cerebral glucose metabolism. Following imaging evaluation at 2 months, subjects initially attributed to the standard of care arm were eligible for treatment with NAC. Clinical and symptom questionnaires were also completed initially and after 2 months.

Results: The FDG PET data showed significantly increased cerebral glucose metabolism in several brain regions including the caudate, inferior frontal gyrus, lateral temporal gyrus, and middle temporal gyrus (p < 0.05) in the MS group treated with NAC, as compared to the control group. Self-reported scores related to cognition and attention were also significantly improved in the NAC group as compared to the control group.

Conclusions: The results of this study suggest that NAC positively affects cerebral glucose metabolism in MS patients, which is associated with qualitative, patient reported improvements in cognition and attention. Larger scale studies may help to determine the clinical impact of NAC on measures of functioning over the course of illness, as well as the most effective dosage and dosage regimen.

Relapsing-Remitting Multiple Sclerosis Is Associated With Regional Brain Activity Deficits in Motor- and Cognitive-Related Brain Areas

Objective: To identify the abnormal regional spontaneous brain activity associated with relapsing-remitting multiple sclerosis (RRMS) using fractional amplitude of low-frequency fluctuation (fALFF) analysis and their relationships with clinical features.

Methods: A total of 26 RRMS (11 males, 15 females; age, 36.58 ± 10.82 years) and 27 status-matched healthy group (HGs; 12 males, 15 females; age, 35.85 ± 12.05 years) underwent an Expanded Disability Status Scale (EDSS) examination. fALFF was applied to evaluate the abnormal regional brain activity associated with RRMS. Pearson's correlation analysis was applied to calculate the correlations between the signal values of brain areas that exhibited abnormal fALFF values and clinical features. Receiver operating characteristic (ROC) curve was performed to evaluate the sensitivity and specificity of those altered brain areas to distinguish between RRMS and HGs.

Results: Compared with HGs, RRMS exhibited higher fALFF in the right cerebellum posterior lobe, left orbitofrontal cortex, left dorsolateral prefrontal cortex, bilateral supplementary motor area, and right fusiform gyrus and lower fALFF values in the left hippocampus and right precuneus. ROC revealed that these areas showed two good and five fair AUC values (0.77 ± 0.03, 0.729~0.822). However, four combinations with more than five brain regions received the same best discriminatory power with a sensitivity of 96.3% and a specificity of 88.5%. EDSS revealed a negative correlation with supplementary motor area (r = −0.395, p = 0.046).

Conclusions: RRMS is associated with abnormal regional brain activity deficits of motor- and cognitive-related areas. The fALFF parameter may serve as a potential biological marker to discriminate between the two groups.

Vascular aspects of multiple sclerosis: emphasis on perfusion and cardiovascular comorbidities

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. Over the last two decades, more favorable MS long-term outcomes have contributed toward increase in prevalence of the aged MS population. Emergence of age-associated pathology, such as cardiovascular diseases, may interact with the MS pathophysiology and further contribute to disease progression. Areas covered: This review summarizes the cardiovascular involvement in MS pathology, its disease activity, and progression. The cardiovascular health, the presence of various cardiovascular diseases, and their effect on MS cognitive performance are further explored. In similar fashion, the emerging evidence of a higher incidence of extracranial arterial pathology and its association with brain MS pathology are discussed. Finally, the authors outline the methodologies behind specific perfusion magnetic resonance imaging (MRI) and ultrasound Doppler techniques, which allow measurement of disease-specific and age-specific vascular changes in the aging population and MS patients. Expert opinion: Cardiovascular pathology significantly contributes to worse clinical and MRI-derived disease outcomes in MS. Global and regional cerebral hypoperfusion may be associated with poorer physical and cognitive performance. Prevention, improved detection, and treatment of the cardiovascular-based pathology may improve the overall long-term health of MS patients.

Exploring the heterogeneity of MS lesions using positron emission tomography: a reappraisal of their contribution to disability

The biological mechanisms driving disability worsening in multiple sclerosis (MS) are only partly understood. Monitoring changes in lesion load on MRI has a limited predictive value on the progression of clinical disability, and there is an essential need for novel imaging markers specific for the main candidate mechanisms underlying neurodegeneration which include failing myelin repair, innate immune cell activation and gray matter neuronal damage. Positron Emission Tomography (PET) is an imaging technology based on the injection of radiotracers directed against specific molecular targets, which has recently allowed the selective quantification in-vivo of the key biological mechanisms relevant to MS pathophysiology. Pilot PET studies performed in patients with all forms of MS allowed to revisit the contribution of MS lesions to disability worsening and showed that the evolution of lesions toward chronic activation, together with their remyelination profile were relevant predictors of disability worsening. PET offers the opportunity to bridge a critical gap between neuropathology and in-vivo imaging. This technique provides an original approach to disentangle some of the most relevant pathological components driving MS progression, to follow-up their temporal evolution, to investigate their clinical relevance and to evaluate novel therapeutics aimed to prevent disease progression.

The Role of Advanced Magnetic Resonance Imaging Techniques in Multiple Sclerosis Clinical Trials

Magnetic resonance imaging has been crucial in the development of anti-inflammatory disease-modifying treatments. The current landscape of multiple sclerosis clinical trials is currently expanding to include testing not only of anti-inflammatory agents, but also neuroprotective, remyelinating, neuromodulating, and restorative therapies. This is especially true of therapies targeting progressive forms of the disease where neurodegeneration is a prominent feature. Imaging techniques of the brain and spinal cord have rapidly evolved in the last decade to permit in vivo characterization of tissue microstructural changes, connectivity, metabolic changes, neuronal loss, glial activity, and demyelination. Advanced magnetic resonance imaging techniques hold significant promise for accelerating the development of different treatment modalities targeting a variety of pathways in MS.

Gray Matter Hypoxia in the Brain of the Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis

Background

Multiple sclerosis (MS) has a significant inflammatory component and may have significant gray matter (GM) pathophysiology. Brain oxygenation is a sensitive measurement of the balance between metabolic need and oxygen delivery. There is evidence that inflammation and hypoxia are interdependent. In this paper, we applied novel, implanted PO₂ sensors to measure hypoxia in cortical and cerebellar GM, in an inflammation-induced mouse model of MS.

Objective

Quantify oxygenation in cortical and cerebellar GM in the awake, unrestrained experimental autoimmune encephalomyelitis (EAE) mouse model and to relate the results to symptom level and disease time-course.

Methods

C57BL/6 mice were implanted with a fiber-optic sensor in the cerebellum (n = 13) and cortex (n = 24). Animals were induced with stimulation of the immune response and sensitization to myelin oligodendrocyte glycoprotein (MOG). Controls did not have MOG. We measured PO₂ in awake, unrestrained animals from pre-induction (baseline) up to 36 days post-induction for EAE and controls.

Results

There were more days with hypoxia than hyperoxia (cerebellum: 34/67 vs. 18/67 days; cortex: 85/112 vs. 22/112) compared to time-matched controls. The average decline in PO₂ on days that were significantly lower than time-matched controls was -8.8±6.0 mmHg (mean ± SD) for the cerebellum and -8.0±4.6 for the cortex. Conversely, the average increase in PO₂ on days that were significantly hyperoxic was +3.2±2.8 mmHg (mean ± SD) for the cerebellum and +0.8±2.1 for the cortex. Cortical hypoxia related to increased behavioral deficits. Evidence for hypoxia occurred before measurable behavioral deficits.

Conclusions

A highly inflammatory condition primed to a white matter (WM) autoimmune response correlates with significant hypoxia and increased variation in oxygenation in GM of both cerebellum and cortex in the mouse EAE model of MS.

Differential Impact of Multiple Sclerosis on Cortical and Deep Gray Matter Structures in African Americans and Caucasian Americans

BACKGROUND

African Americans with multiple sclerosis (AAwMS) have different disease phenotypes when compared to Caucasians Americans with MS (CAwMS). The pathologic basis of this difference in disease presentation is unknown.

METHODS

Fifty-Four AAwMS and 54 CAwMS were appropriately matched for age, gender, treatment duration, and disease duration. FreeSurfer was used to segment brain white matter and gray matter from T1 images and compute thalamic volume. Regional cortical thickness was calculated using QDEC.

RESULTS

The 2 matched cohorts differed in disability, with AAwMS demonstrating significantly higher EDSS scores (2.3±2.2 vs. 1.3±1.5, P < .009), yet the 2 populations had similar T2 hyperintense lesion volumes (P = .35). AAwMS had a significantly lower total global cortical thickness when compared to CAwMS (P = .03). Controlling for EDSS, AAwMS showed multiple cortical regions to be significantly thinner than CAwMS; these included areas within the temporal, parietal and occipital lobes, as well as the precentral and postcentral gyrus. Middletemporal cortex was most affected in AAwMS in the left hemisphere (P = .009), while the superiortemporal cortex was most affected in the right hemisphere (P = .0001). In contrast, thalamic volume was significantly reduced in CAwMS when compared to AAwMS (P = .01). In both groups, worse disability was associated with lower total thalamic volume percentage.

CONCLUSION

AAwMS and CAwMS patients differ with regard to global and regional cortical thickness and thalamic volume. This diverging pattern of gray matter volumetrics among otherwise matched patients suggests that racial-specific disease differences may exist.

Thalamus Degeneration and Inflammation in Two Distinct Multiple Sclerosis Animal Models

There is a broad consensus that multiple sclerosis (MS) represents more than an inflammatory disease: it harbors several characteristic aspects of a classical neurodegenerative disorder, i.e., damage to axons, synapses, and nerve cell bodies. While several accepted paraclinical methods exist to monitor the inflammatory-driven aspects of the disease, techniques to monitor progression of early and late neurodegeneration are still in their infancy and have not been convincingly validated. It was speculated that the thalamus with its multiple reciprocal connections is sensitive to inflammatory processes occurring in different brain regions, thus acting as a "barometer" for diffuse brain parenchymal damage in MS. To what extent the thalamus is affected in commonly applied MS animal models is, however, not known. In this article we describe direct and indirect damage to the thalamus in two distinct MS animal models. In the cuprizone model, we observed primary oligodendrocyte stress which is followed by demyelination, microglia/astrocyte activation, and acute axonal damage. These degenerative cuprizone-induced lesions were found to be more severe in the lateral compared to the medial part of the thalamus. In MOG35-55-induced EAE, in contrast, most parts of the forebrain, including the thalamus were not directly involved in the autoimmune attack. However, important thalamic afferent fiber tracts, such as the spinothalamic tract were inflamed and demyelinated on the spinal cord level. Quantitative immunohistochemistry revealed that this spinal cord inflammatory-demyelination is associated with neuronal loss within the target region of the spinothalamic tract, namely the sensory ventral posterolateral nucleus of the thalamus. This study highlights the possibility of trans-neuronal degeneration as one mechanism of secondary neuronal damage in MS. Further studies are now warranted to investigate involved cell types and cellular mechanisms.

Cognitive-Motor Related Brain Activity During Walking: Differences Between Men and Women With Multiple Sclerosis

OBJECTIVE

To determine if sex differences in glucose uptake, a marker of brain activity, are present in brain regions that facilitate walking performance in persons with multiple sclerosis (MS).

DESIGN

Cross-sectional, observational pilot.

SETTING

University laboratory.

PARTICIPANTS

Positron emission tomography with fluorine-18-labeled deoxyglucose (FDG) was performed on persons with MS and healthy controls (4 men and 4 women per group; N=16) after a 15-minute walking test.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

Brain activity was quantified as the mean standardized uptake value (SUV).

RESULTS

The mean SUV was significantly lower in the thalamus (P=.029) and cerebellum (P=.029) for men with MS compared with women with MS, but not for the prefrontal (P=.057) or frontal (P=.057) cortices. Similar nonsignificant trends were found for healthy controls. No mean SUV group × sex interaction effects were found between the MS and healthy control groups (all P>.05).

CONCLUSIONS

To our knowledge, this is the first study of brain activity sex differences based on FDG uptake in persons with MS during walking. Significantly less FDG uptake in the thalamus and cerebellum brain regions important for walking performance was found in men with MS compared with women with MS; however, these comparisons were not significantly different in the healthy control group. No differences in FDG uptake were found between the MS and healthy control groups in any of the brain regions examined. Results from this study provide pilot data for larger studies aimed at identifying underlying mechanisms responsible for accelerated disability in men with MS.

The neurocognitive profile of the cerebellum in multiple sclerosis

In recent years, a high number of studies have demonstrated that neuropsychological functions are altered in multiple sclerosis (MS) patients with cerebellar lesions, mainly including attention, working memory and verbal fluency. Since the present literature is often elusive on this topic, we aim to provide a comprehensive report about the real impact of cerebellar damages (evaluated as volume, lesions or connectivity measures) on cognitive functions. In particular in this review, we report and discuss recent works from 2009 to 2015, which have demonstrated the key role of the cerebellum in cognitive impairment of MS patients.

Functional connectivity underlying postural motor adaptation in people with multiple sclerosis

A well-characterized neural network is associated with motor learning, involving several brain regions known to have functional and structural deficits in persons with multiple sclerosis (PwMS). However, it is not known how MS affects postural motor learning or the neural networks involved. The aim of this study was to gain a better understanding of the neural networks underlying adaptation of postural responses within PwMS. Participants stood on a hydraulically driven, servo-controlled platform that translated horizontally forward and backward in a continuous sinusoidal pattern across multiple trials over two consecutive days. Our results show similar postural adaptation between PwMS and age-matched control participants despite overall deficits in postural motor control in PwMS. Moreover, PwMS demonstrated better retention the following day. PwMS had significantly reduced functional connectivity within both the cortico-cerebellar and cortico-striatal motor loops; neural networks that subserve implicit motor learning. In PwMS, greater connectivity strength within the cortico-cerebellar circuit was strongly related to better baseline postural control, but not to postural adaptation as it was in control participants. Further, anti-correlated cortico-striatal connectivity within the right hemisphere was related to improved postural adaptation in both groups. Taken together with previous studies showing a reduced reliance on cerebellar- and proprioceptive-related feedback control in PwMS, we suggest that PwMS may rely on cortico-striatal circuitry to a greater extent than cortico-cerebellar circuitry for the acquisition and retention of motor skills.

Evidence for early, non-lesional cerebellar damage in patients with multiple sclerosis: DTI measures correlate with disability, atrophy, and disease duration

BACKGROUND

Common symptoms of multiple sclerosis (MS) such as gait ataxia, poor coordination of the hands, and intention tremor are usually the result of dysfunctionality in the cerebellum. Magnetic resonance imaging (MRI) has frequently failed to detect cerebellar damage in the form of inflammatory lesions in patients presenting with symptoms of cerebellar dysfunction.

OBJECTIVE

To detect microstructural cerebellar tissue alterations in early MS patients with a "normal appearing" cerebellum using diffusion tensor imaging (DTI).

METHODS

A total of 68 patients with relapsing-remitting MS (RRMS) and without cerebellar lesions and 26 age-matched healthy controls were admitted to high-resolution MRI and DTI to assess microstructure and volume of the cerebellar white matter (CBWM).

RESULTS

We found cerebellar fractional anisotropy (FA) and CBWM volume reductions in the group of 68 patients. Interestingly, a subgroup of these patients that was derived by including only patients with early and mild MS (N=23, median age 30 years, median Expanded Disability Status Scale =1.5, median duration 28 months) showed already cerebellar FA but no CBWM volume reductions. FA reductions were correlated with disability, atrophy, and disease duration.

CONCLUSION

"Normal appearing" cerebellar white matter can be damaged in a very early stage of RRMS. DTI seems to be a sensitive tool for detecting this hidden cerebellar damage.

Thalamus pathology in multiple sclerosis: from biology to clinical application

There is a broad consensus that MS represents more than an inflammatory disease: it harbors several characteristic aspects of a classical neurodegenerative disorder, i.e. damage to axons, synapses and nerve cell bodies. While the clinician is equipped with appropriate tools to dampen peripheral cell recruitment and, thus, is able to prevent immune-cell driven relapses, effective therapeutic options to prevent the simultaneously progressing neurodegeneration are still missing. Furthermore, while several sophisticated paraclinical methods exist to monitor the inflammatory-driven aspects of the disease, techniques to monitor progression of early neurodegeneration are still in their infancy and have not been convincingly validated. In this review article, we aim to elaborate why the thalamus with its multiple reciprocal connections is sensitive to pathological processes occurring in different brain regions, thus acting as a "barometer" for diffuse brain parenchymal damage in MS. The thalamus might be, thus, an ideal region of interest to test the effectiveness of new neuroprotective MS drugs. Especially, we will address underlying pathological mechanisms operant during thalamus degeneration in MS, such as trans-neuronal or Wallerian degeneration. Furthermore, we aim at giving an overview about different paraclinical methods used to estimate the extent of thalamic pathology in MS patients, and we discuss their limitations. Finally, thalamus involvement in different MS animal models will be described, and their relevance for the design of preclinical trials elaborated.

PET imaging of glucose metabolism, neuroinflammation and demyelination in the lysolecithin rat model for multiple sclerosis

Background:

Injection of lysolecithin in the central nervous system results in demyelination accompanied by local activation of microglia and recruitment of monocytes. Positron-emission tomography (PET) imaging, using specific tracers, may be an adequate technique to monitor these events in vivo and therefore may become a tool for monitoring disease progression in multiple sclerosis (MS) patients.

Objectives:

The objective of this paper is to evaluate the potential of PET imaging in monitoring local lesions, using [11C]MeDAS, [11C]PK11195 and [18F]FDG as PET tracers for myelin density, microglia activation and glucose metabolism, respectively.

Methods:

Sprague-Dawley rats were stereotactically injected with either 1% lysolecithin or saline in the corpus callosum and striatum of the right brain hemisphere. PET imaging was performed three days, one week and four weeks after injection. Animals were terminated after PET imaging and the brains were explanted for (immuno)histochemical analysis.

Results:

PET imaging was able to detect local demyelination induced by lysolecithin in the corpus callosum and striatum with [11C]MeDAS and concomitant microglia activation and monocyte recruitment with [11C]PK11195. [18F]FDG imaging demonstrated that glucose metabolism was maintained in the demyelinated lesions.

Conclusion:

PET imaging with multiple tracers allows simultaneous in vivo monitoring of myelin density, neuroinflammation and brain metabolism in small MS-like lesions, indicating its potential to monitor disease progression in MS patients.

Multiple sclerosis impairs regional functional connectivity in the cerebellum

Resting-state functional magnetic resonance imaging (rs-fMRI) has been used to study changes in long-range functional brain connectivity in multiple sclerosis (MS). Yet little is known about how MS affects functional brain connectivity at the local level. Here we studied 42 patients with MS and 30 matched healthy controls with whole-brain rs-fMRI at 3 T to examine local functional connectivity. Using the Kendall's Coefficient of Concordance, regional homogeneity of blood-oxygen-level-dependent (BOLD)-signal fluctuations was calculated for each voxel and used as a measure of local connectivity. Patients with MS showed a decrease in regional homogeneity in the upper left cerebellar hemisphere in lobules V and VI relative to healthy controls. Similar trend changes in regional homogeneity were present in the right cerebellar hemisphere. The results indicate a disintegration of regional processing in the cerebellum in MS. This might be caused by a functional disruption of cortico-ponto-cerebellar and spino-cerebellar inputs, since patients with higher lesion load in the left cerebellar peduncles showed a stronger reduction in cerebellar homogeneity. In patients, two clusters in the left posterior cerebellum expressed a reduction in regional homogeneity with increasing global disability as reflected by the Expanded Disability Status Scale (EDSS) score or higher ataxia scores. The two clusters were mainly located in Crus I and extended into Crus II and the dentate nucleus but with little spatial overlap. These findings suggest a link between impaired regional integration in the cerebellum and general disability and ataxia.

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Multiple sclerosis (MS) leads to reduced regional cerebellar functional connectivity.

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Reduced cerebellar connectivity correlates with lesion load of cerebellar peduncles.

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Regional cerebellar connectivity is inversely correlated with clinical disability.

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The findings suggest a disintegration of regional cerebellar processing in MS.

Repeated mild traumatic brain injury: mechanisms of cerebral vulnerability

Among the 3.5 million annual new head injury cases is a subpopulation of children and young adults who experience repeated traumatic brain injury (TBI). The duration of vulnerability after a single TBI remains unknown, and biomarkers have yet to be determined. Decreases in glucose metabolism (cerebral metabolic rate of glucose [CMRglc]) are consistently observed after experimental and human TBI. In the current study, it is hypothesized that the duration of vulnerability is related to the duration of decreased CMRglc and that a single mild TBI (mTBI) increases the brain's vulnerability to a second insult for a period, during which a subsequent mTBI will worsen the outcome. Postnatal day 35 rats were given sham, single mTBI, or two mTBI at 24-h or 120-h intervals. (14)C-2-deoxy-D-glucose autoradiography was conducted at 1 or 3 days post-injury to calculate CMRglc. At 24 h after a single mTBI, CMRglc is decreased by 19% in both the parietal cortex and hippocampus, but approached sham levels by 3 days post-injury. When a second mTBI is introduced during the CMRglc depression of the first injury, the consequent CMRglc is depressed (36.5%) at 24 h and remains depressed (25%) at 3 days. In contrast, when the second mTBI is introduced after the metabolic recovery of the first injury, the consequent CMRglc depression is similar to that seen with a single injury. Results suggest that the duration of metabolic depression reflects the time-course of vulnerability to second injury in the juvenile brain and could serve as a valuable biomarker in establishing window of vulnerability guidelines.

Abnormalities of cerebral blood flow in multiple sclerosis: a pseudocontinuous arterial spin labeling MRI study

Arterial spin labeling (ASL) is a noninvasive technique that can measure cerebral blood flow (CBF). To our knowledge, there is no study that examined regional CBF of multiple sclerosis (MS) patients by using this technique. The present study assessed the relationship between clinical presentations and functional imaging data in MS using pseudocontinuous arterial spin labeling (pCASL). Twenty-seven patients with MS and 24 healthy volunteers underwent magnetic resonance imaging and pCASL to assess CBF. Differences in CBF between the two groups and the relationships of CBF values with the T2-hyperintense volume were evaluated. Compared to the healthy volunteers, reduced CBF was found in the bilateral thalami and right frontal region of the MS patients. The volume of the T2-hyperintense lesion was negatively correlated with regional CBF in some areas, such as both thalami. Our results suggest that demyelinated lesions in MS mainly have a remote effect on the thalamus and that the measurement of CBF using ASL could be an objective marker for monitoring disease activity in MS.

Chronic cerebrospinal venous insufficiency and venous stenoses in multiple sclerosis

OBJECTIVES

The traditional view that multiple sclerosis (MS) is an autoimmune disease has recently been challenged by the claim that MS is caused by chronic cerebrospinal venous insufficiency (CCSVI). Although several studies have questioned this vascular theory, the CCSVI controversy is still ongoing. Our aim was to assess the prevalence of CCSVI in Danish MS patients using sonography and compare these findings with MRI measures of venous flow and morphology.

METHODS

We investigated cervical and cerebral veins in 24 patients with relapsing-remitting MS (RRMS) and 15 healthy controls, using extracranial high-resolution ultrasound colour Doppler (US-CD) and transcranial colour Doppler sonography (TCDS), as well as magnetic resonance imaging (MRI) and phase-contrast MR blood flow measurements (PC-MR) of the cervical veins.

RESULTS

US-CD could not identify the left internal jugular vein (IJV) in one MS patient, other ultrasound examinations were normal in patients with MS. There was no difference in mean cross-sectional area of the IJV in MS patients compared with controls. Only one patient with MS and two healthy controls fulfilled one CCSVI criterion, and none fulfilled more than one CCSVI criterion. MR venography showed insignificant IJV stenosis (1-49%) in two patients with MS, whereas 50-69% IJV stenosis was detected in two healthy controls. There was no difference in PC-MR measurements of mean IJV blood flow between patients with MS and controls.

CONCLUSION

Our results do not corroborate the presence of vascular pathology in RRMS and we found no evidence supporting the CCSVI hypothesis.

Multimodal quantitative magnetic resonance imaging of thalamic development and aging across the human lifespan: implications to neurodegeneration in multiple sclerosis

The human brain thalami play essential roles in integrating cognitive, sensory, and motor functions. In multiple sclerosis (MS), quantitative magnetic resonance imaging (qMRI) measurements of the thalami provide important biomarkers of disease progression, but late development and aging confound the interpretation of data collected from patients over a wide age range. Thalamic tissue volume loss due to natural aging and its interplay with lesion-driven pathology has not been investigated previously. In this work, we used standardized thalamic volumetry combined with diffusion tensor imaging, T2 relaxometry, and lesion mapping on large cohorts of controls (N = 255, age range = 6.2-69.1 years) and MS patients (N = 109, age range = 20.8-68.5 years) to demonstrate early age- and lesion-independent thalamic neurodegeneration.

Human brain atlas-based multimodal MRI analysis of volumetry, diffusimetry, relaxometry and lesion distribution in multiple sclerosis patients and healthy adult controls: implications for understanding the pathogenesis of multiple sclerosis and consolidation of quantitative MRI results in MS

Multiple sclerosis (MS) is the most common immune-mediated disabling neurological disease of the central nervous system. The pathogenesis of MS is not fully understood. Histopathology implicates both demyelination and axonal degeneration as the major contributors to the accumulation of disability. The application of several in vivo quantitative magnetic resonance imaging (MRI) methods to both lesioned and normal-appearing brain tissue has not yet provided a solid conclusive support of the hypothesis that MS might be a diffuse disease. In this work, we adopted FreeSurfer to provide standardized macrostructure or volumetry of lesion free normal-appearing brain tissue in combination with multiple quantitative MRI metrics (T(2) relaxation time, diffusion tensor anisotropy and diffusivities) that characterize tissue microstructural integrity. By incorporating a large number of healthy controls, we have attempted to separate the natural age-related change from the disease-induced effects. Our work shows elevation in diffusivity and relaxation times and reduction in volume in a number of normal-appearing white matter and gray matter structures in relapsing-remitting multiple sclerosis patients. These changes were related in part with the spatial distribution of lesions. The whole brain lesion load and age-adjusted expanded disability status score showed strongest correlations in regions such as corpus callosum with qMRI metrics that are believed to be specific markers of axonal dysfunction, consistent with histologic data of others indicating axonal loss that is independent of focal lesions. Our results support that MS at least in part has a neurodegenerative component.

Cerebral acetylcholinesterase activity is not decreased in MS patients with cognitive impairment

BACKGROUND

Neuropsychological studies have extensively described the presence of cognitive dysfunction in MS patients. One possible pharmacological treatment of the impairment could be based on acetylcholinesterase inhibitors (AChEIs), which have shown efficacy in alleviating cognitive impairment in many other disorders. The findings on the efficacy of AChEI medication in MS associated cognitive symptoms are preliminary and no studies concerning cerebral acetylcholinesterase (AChE) activity in these patients have been published.

OBJECTIVE

The objective of the study was to examine cerebral AChE activity in cognitively deteriorated MS patients. Cerebral AChE activity of 10 MS patients with secondary progressive disease and marked cognitive impairment, and 10 healthy controls, was studied with positron emission tomography using tracer (11)C-MP4A.

METHODS

The cognitive profile of the patients was assessed with CERAD (Consortium to Establish a Registry for Alzheimer's Disease).

RESULTS

No differences in cortical AChE activity between MS patients and controls were seen.

CONCLUSIONS

In the patient group regional AChE activities had inverse correlations with Word learning and MMSE (Mini-Mental State Examination) scores. In the group of cognitively deteriorated MS patients no change in cerebral AChE activity, compared with controls, was observed, but within the patient group more pronounced cognitive symptoms were associated with higher cerebral AChE activity.

T2' imaging indicates decreased tissue metabolism in frontal white matter of MS patients

BACKGROUND AND PURPOSE

T2'-Magnetic resonance imaging (MRI) allows estimation of oxygen metabolism in normal appearing white and gray matter (NAWM and NAGM) and is sensitive to local iron deposition. We hypothesized that T2' imaging is feasible in routine use and reveals differences between MS patients and healthy subjects.

METHODS

T2- and T2*-weighted images were acquired in 23 MS patients (Mean age: 36.8, range: 23-58 years) and 23 age-matched healthy subjects. Quantitative T2- and T2*-values were determined in six regions of interest (ROIs).

RESULTS

The T2' values in thalamus and caudate nucleus were significantly lower in MS patients than in healthy subjects (139 ms vs 157 ms, P < 0.001 and 97 ms vs 115 ms, P < 0.01). The NAWM in the frontal lobe revealed significant higher T2' values than in healthy subjects (217 ms vs 170 ms, P < 0.001). The subcortical NAWM revealed significant lower T2' values than in healthy subjects (174 ms vs 187 ms, P < 0.028).

CONCLUSION

T2' values differed significantly between MS patients and healthy subjects. The reduced T2' values in the basal ganglia are presumably related to higher iron concentration whereas the increased T2' in frontal NAWM most probably reflects reduced tissue metabolism. T2' imaging is feasible for routine-use and promising for monitoring therapy effects.

Cognitive deficits in multiple sclerosis patients with cerebellar symptoms

Background

Cerebellar dysfunction is common in patients with multiple sclerosis (MS). However, neuropsychological studies of this clinical feature are lacking.

Objective

We investigate the neuropsychological features in relapsing-remitting MS (RR-MS) patients with and without cerebellar dysfunction.

Methods

Twenty-one RR-MS patients with cerebellar dysfunction (RR-MSc), characterized by prevalent ataxic gait and nystagmus, and 21 RR-MS patients without any cerebellar manifestation (RR-MSnc) pair-matched for demographical and clinical variables were studied. All patients from each group underwent an extensive battery of neuropsychological tests. Magnetic resonance imaging analysis included hyperintense fast fluid-attenuated inversion-recovery lesion load in the whole brain as well as in the four lobes separately.

Results

Any significant differences were detected in total and regional lesion load measurements between the two groups. RR-MSc group performed equally as well as the RR-MSnc group on many of the cognitive exploration measures. Nevertheless, the RR-MSc group performed more poorly than the RR-MSnc group on attention tests (Symbol Digit Modalities Test) and verbal fluency tests (Controlled Oral Word Association Test); neither of the test results proved to be affected by regional lesion loads.

Conclusion

These results highlight the importance of considering cognitive deficits associated with the presence of cerebellar symptoms in RR-MS.

Thalamic involvement and its impact on clinical disability in patients with multiple sclerosis: a diffusion tensor imaging study at 3T

BACKGROUND AND PURPOSE

Several studies suggest that grey matter involvement may play a role in multiple sclerosis (MS) pathology. Diffusion tensor imaging (DTI) at 3T was used to investigate the presence of damage to the normal-appearing thalamus in MS and its relationship with disability.

MATERIALS AND METHODS

Twenty-four patients with relapsing-remitting (RR, n = 13, age = 41.7 +/- 6.1, Expanded Disability Status Scale [EDSS] score = 2.2 +/- 1.2) and secondary-progressive (n = 11, age = 46.9 +/- 9.6, EDSS = 5.9 +/- 1.0) MS and 24 age- and sex-matched healthy volunteers were studied. Fractional anisotropy (FA) and mean diffusivity (MD) were measured in regions of interest of normal-appearing thalamus. We examined group differences in MD and FA and correlations between DTI-derived metrics and clinical or imaging measures of disease.

RESULTS

Patients with MS had higher thalamic FA (P < .0001) and MD (P = .035) than volunteers. MD values correlated with the Paced Auditory Serial Addition Task (r = -0.43, P = .034) and motor EDSS (r = 0.47, P = .021) scores. In patients with RRMS, MD values correlated with global EDSS (r = 0.75, P = .003) and motor EDSS (r = 0.68, P = .010). Correlations were found between MD values and T1 and T2 lesion load (r = 0.58, P < .05) and brain parenchymal fraction (r = -0.46, P < .05).

CONCLUSIONS

DTI was able to detect abnormalities in normal-appearing thalamus of patients with MS. The strength of association between thalamic DTI measures and functional impairment was in the same range as those seen with standard MR imaging disease measures. The assessment of the integrity of the thalamus with DTI is a promising metric as a marker of disease for future studies.

Regional grey matter atrophy in clinically isolated syndromes at presentation

BACKGROUND

The presence and degree of neuronal degeneration already existing in patients at their initial presentation with a clinically isolated syndrome suggestive of multiple sclerosis (CIS) is unclear, and whole brain or whole normalised grey matter analyses have not demonstrated significant atrophy in CIS cohorts at clinical presentation. Voxel-based analyses allow detection of regional atrophy throughout the brain and, therefore, may be sensitive to regional atrophy in CIS patients, and these changes may correspond with clinical disability.

METHODS

This study used a modified voxel-based morphometry (VBM) method to correct for lesion effects to analyse regional atrophy and perform voxel-wise correlations between volume and clinical metrics in 41 untreated CIS patients at presentation compared with 49 healthy controls.

RESULTS

The results confirmed that there was no significant difference in whole normalised grey matter volume between CIS and controls, whereas VBM showed significant areas of bilateral thalamic, hypothalamic, putamen and caudate atrophy. Voxel-wise correlations with clinical measures showed that cerebellar volumes correlated with clinical cerebellar function, nine-hole peg test scores and the Multiple Sclerosis Functional Composite (MSFC) score, and that the MSFC score was also correlated with putamen volume. Lastly, T1 lesion volumes were found to correlate with thalamic and hippocampal atrophy, suggesting a link between white matter lesions and grey matter degeneration at the earliest stages of multiple sclerosis.

CONCLUSIONS

Atrophy is present in CIS patients at presentations, particularly in the thalamus, and other deep grey matter structures. Furthermore, the correlations with clinical metrics suggest the importance of this atrophy to clinical status and the correlation with T1 lesion load suggests a possible role of Wallerian degeneration.

Mood and anxiety disorders in patients with multiple sclerosis

Objective. This study aims to investigate the current prevalences of mood and anxiety disorders, as well as the sociodemographic and clinical features associated with these disorders in multiple sclerosis (MS). Method. A total of 74 patients with relapsing-remitting MS (42 patients in exacerbation phase, 32 patients in remission phase) were included in the study. Mood and anxiety disorders were diagnosed by means of the Structured Clinical Interview for DSM-IV (SCID-I). The Expanded Disability Status Scale (EDSS) was used to determine degree of disability due to MS. Results. Forty-five (60.8%) patients met the criterion of at least one mood or anxiety disorder. Major depression (33.8%) was the most common psychiatric diagnosis. Generalized anxiety disorder (18.9%), specific phobia (18.9%) and obsessive-compulsive disorder (OCD) (14.9%) were other frequent psychiatric disorders. Major depression, panic disorder and OCD were significantly more common among patients in the exacerbation phase compared to patients in the remission phase. The predictors of any depressive disorder were presence of exacerbation phase of MS and higher disability level, and the predictors of any anxiety disorder were presence of exacerbation phase of MS and shorter disease duration. Conclusions. Our results suggest that the patients with relapsing-remitting MS, particularly during exacerbation phase have high prevalence of mood and anxiety disorders.

Localized grey matter damage in early primary progressive multiple sclerosis contributes to disability

Disability in primary progressive multiple sclerosis (PPMS) has been correlated with damage to the normal appearing brain tissues. Magnetization transfer ratio (MTR) and volume changes indicate that much of this damage occurs in the normal appearing grey matter, but the clinical significance of this remains uncertain. We aimed to localize these changes to distinct grey matter regions, and investigate the clinical impact of the MTR changes. 46 patients with early PPMS and 23 controls underwent MT and high-resolution T1-weighted imaging. Patients were scored on the Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite and subtests (Nine-Hole Peg Test, Timed Walk Test, Paced Auditory Serial Addition Test [PASAT]). Grey matter volume and MTR were compared between patients and controls, adjusting for age. Mean MTR for significant regions within the motor network and in areas relevant to PASAT performance were correlated with appropriate clinical scores, adjusting for grey matter volume. Patients showed reduced MTR and atrophy in the right pre- and left post-central gyri, right middle frontal gyrus, left insula, and thalamus bilaterally. Reduced MTR without significant atrophy occurred in the left pre-central gyrus, left superior frontal gyri, bilateral superior temporal gyri, right insula and visual cortex. Higher EDSS correlated with lower MTR in the right primary motor cortex (BA 4). In conclusion, localized grey matter damage occurs in early PPMS, and MTR change is more widespread than atrophy. Damage demonstrated by reduced MTR is clinically eloquent.

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.