Functional Magnetic Resonance Imaging and Multiple Sclerosis: The Evidence for Neuronal Plasticity

Effects of childhood trauma experience and BDNF Val66Met polymorphism on brain plasticity relate to emotion regulation

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism may modulate the link between childhood trauma experience and psychopathology by altering trophic signaling on neuroplasticity. However, few multimodal magnetic resonance imaging (MRI) researches have investigated this gene-environment interaction on both structural and functional plasticity, thereby advancing knowledge about the etiology, prevention, and customized therapeutic directions of mental disease in individuals with childhood trauma experience. We recruited a large non-clinical sample of young adults that completed Childhood Trauma Questionnaire (CTQ), behavioral scores, multimodal MRI scans, and genotyping. Morphometric similarity network (MSN) and independent component analysis were adopted to quantify brain structural and functional changes. Gene-environment-brain-behavior relationships were identified by multiple regression and mediation effect analysis. CTQ score was positively associated with depression and anxiety scores. We found interactions on MSN in sensorimotor, temporal, and orbitofrontal cortex. For intra-network connectivity, significant interaction was noted in clusters within sensorimotor network. For inter-network connectivity, connectivity between dorsal attention network and salience network showed an interactive effect. For mean connectivity strength of each network, we found a main effect of CTQ score on self-reference network that was an outstanding mediator supporting the relationship between CTQ score and anxiety. Our findings demonstrate that childhood trauma and the BDNF Val66Met polymorphism are associated with brain plasticity involving emotion regulation, structurally and functionally, which may contribute to understanding psychotic mechanisms and predicting differential susceptibility. Imaging genetics may be useful as biomarkers to provide early assessment and guide cognitive interventions to avoid or decrease the risk of developing psychopathology.

Neural correlates of effort-dependent and effort-independent cognitive fatigue components in patients with multiple sclerosis

Background:

Among patients with multiple sclerosis (MS), fatigue is the most commonly reported symptom. It can be subdivided into an effort-dependent (fatigability) and an effort-independent component (trait-fatigue).

Objective:

The objective was to disentangle activity changes associated with effort-independent “trait-fatigue” from those associated with effort-dependent fatigability in MS patients.

Methods:

This study employed behavioral measures and functional magnetic imaging to investigate neural changes in MS patients associated with fatigue. A total of 40 MS patients and 22 age-matched healthy controls performed in a fatigue-inducing N-back task. Effort-independent fatigue was assessed using the Fatigue Scale of Motor and Cognition (FSMC) questionnaire.

Results:

Effort-independent fatigue was observed to be reflected by activity increases in fronto-striatal-subcortical networks primarily involved in the maintenance of homeostatic processes and in motor and cognitive control. Effort-dependent fatigue (fatigability) leads to activity decreases in attention-related cortical and subcortical networks.

Conclusion:

These results indicate that effort-independent (fatigue) and effort-dependent fatigue (fatigability) in MS patients have functionally related but fundamentally different neural correlates. Fatigue in MS as a general phenomenon is reflected by complex interactions of activity increases in control networks (effort-independent component) and activity reductions in executive networks (effort-dependent component) of brain areas.

Autoimmune Comorbidities Are Associated with Brain Injury in Multiple Sclerosis

BACKGROUND AND PURPOSE

The effect of comorbidities on disease severity in MS has not been extensively characterized. We determined the association of comorbidities with MR imaging disease severity outcomes in MS.

MATERIALS AND METHODS

Demographic and clinical history of 9 autoimmune comorbidities confirmed by retrospective chart review and quantitative MR imaging data were obtained in 815 patients with MS. The patients were categorized on the basis of the presence/absence of total and specific comorbidities. We analyzed the MR imaging findings, adjusting for key covariates and correcting for multiple comparisons.

RESULTS

Two hundred forty-one (29.6%) study subjects presented with comorbidities. Thyroid disease had the highest frequency (n = 97, 11.9%), followed by asthma (n = 41, 5%), type 2 diabetes mellitus (n = 40, 4.9%), psoriasis (n = 33, 4%), and rheumatoid arthritis (n = 22, 2.7%). Patients with MS with comorbidities showed decreased whole-brain and cortical volumes (P < .001), gray matter volume and magnetization transfer ratio of normal-appearing brain tissue (P < .01), and magnetization transfer ratio of gray matter (P < .05). Psoriasis, thyroid disease, and type 2 diabetes mellitus comorbidities were associated with decreased whole-brain, cortical, and gray matter volumes (P < .05). Psoriasis was associated with a decreased magnetization transfer ratio of normal-appearing brain tissue (P < .05), while type 2 diabetes mellitus was associated with increased mean diffusivity (P < .01).

CONCLUSIONS

The presence of comorbidities in patients with MS is associated with brain injury on MR imaging. Psoriasis, thyroid disease, and type 2 diabetes mellitus comorbidities were associated with more severe nonconventional MR imaging outcomes.

Functional Magnetic Resonance Imaging of Rats with Experimental Autoimmune Encephalomyelitis Reveals Brain Cortex Remodeling

Cortical reorganization occurring in multiple sclerosis (MS) patients is thought to play a key role in limiting the effect of structural tissue damage. Conversely, its exhaustion may contribute to the irreversible disability that accumulates with disease progression. Several aspects of MS-related cortical reorganization, including the overall functional effect and likely modulation by therapies, still remain to be elucidated. The aim of this work was to assess the extent of functional cortical reorganization and its brain structural/pathological correlates in Dark Agouti rats with experimental autoimmune encephalomyelitis (EAE), a widely accepted preclinical model of chronic MS. Morphological and functional MRI (fMRI) were performed before disease induction and during the relapsing and chronic phases of EAE. During somatosensory stimulation of the right forepaw, fMRI demonstrated that cortical reorganization occurs in both relapsing and chronic phases of EAE with increased activated volume and decreased laterality index versus baseline values. Voxel-based morphometry demonstrated gray matter (GM) atrophy in the cerebral cortex, and both GM and white matter atrophy were assessed by ex vivo pathology of the sensorimotor cortex and corpus callosum. Neuroinflammation persisted in the relapsing and chronic phases, with dendritic spine density in the layer IV sensory neurons inversely correlating with the number of cluster of differentiation 45-positive inflammatory lesions. Our work provides an innovative experimental platform that may be pivotal for the comprehension of key mechanisms responsible for the accumulation of irreversible brain damage and for the development of innovative therapies to reduce disability in EAE/MS.

SIGNIFICANCE STATEMENT

Since the early 2000s, functional MRI (fMRI) has demonstrated profound modifications in the recruitment of cortical areas during motor, cognitive, and sensory tasks in multiple sclerosis (MS) patients. Experimental autoimmune encephalomyelitis (EAE) represents a reliable model of the chronic-progressive variant of MS. fMRI studies in EAE have not been performed extensively up to now. This paper reports fMRI studies in a rat model of MS with somatosensory stimulation of the forepaw. We demonstrated modifications in the recruitment of cortical areas consistent with data from MS patients. To the best of our knowledge, this is the first report of cortical remodeling in a preclinical in vivo model of MS.

MRI characteristics of familial and sporadic multiple sclerosis patients

PURPOSE

To investigate the MRI characteristics in a large cohort of multiple sclerosis (MS) patients with and without a family history of MS.

METHODS

Enrolled in this prospective study were 758 consecutive MS patients (mean age 46.2 ± 10.1 years, disease duration 13.6 ± 9.2 years and EDSS 3.4 ± 2.1), of whom 477 had relapsing-remitting, 222 secondary-progressive, and 30 primary-progressive disease courses and 29 had clinically isolated syndrome. One hundred and ninety-six patients (25.9%) had a positive family history of MS. Patients were assessed using measurements of lesions, brain atrophy, magnetization transfer ratio (MTR) and diffusion-weighted imaging.

RESULTS

The familial MS group had greater T1-lesion volume (p=0.009) and a trend for lower MTR of T1-lesion volume (p=0.047) than the sporadic MS group. No clinical differences were found between familial versus sporadic group, or by a degree of affected relative subgroups.

CONCLUSIONS

While familial MS was associated with more severe T1-lesion volume and its MTR characteristics, there were no clinical status differences between familial and sporadic MS patients. Therefore, a better understanding of the genetic and/or epigenetic influences causing these differences can advance the understanding and management of MS.

Loss of Coherence of Low Frequency Fluctuations of BOLD FMRI in Visual Cortex of Healthy Aged Subjects

Aging effects on blood-oxygen-level-dependent (BOLD) functional MRI (fMRI) have been studied using task induced hemodynamic responses with controversial findings. The present study systematically investigated the normal aging effect in the visual cortex using 3 indices of low frequency fluctuations of resting state BOLD fMRI, i.e., amplitude of low frequency fluctuations (ALFF), regional homogeneity (ReHo) and functional connectivity (FC). These 3 resting state measurements were compared with task induced BOLD activation in the visual cortex of 2 groups of 10 young and 10 elderly subjects. Our results showed reduced functional connectivity and regional homogeneity of low frequency fluctuations of BOLD fMRI in aged subjects as compared to young subjects. While the mean magnitude of BOLD activation and the mean amplitude of low frequency fluctuations of BOLD fMRI did not vary between the 2 age groups, larger variances were observed in both measures in aged subjects. These data suggest that normal aging may be associated with “loss of coherence” of low frequency fluctuations of resting state BOLD fMRI in the visual cortex, and may affect task induced BOLD response through increased inter- and intra-subject variability.

Objective assessment of motor fatigue in Multiple Sclerosis using kinematic gait analysis: a pilot study

Background

Fatigue is a frequent and serious symptom in patients with Multiple Sclerosis (MS). However, to date there are only few methods for the objective assessment of fatigue. The aim of this study was to develop a method for the objective assessment of motor fatigue using kinematic gait analysis based on treadmill walking and an infrared-guided system.

Patients and methods

Fourteen patients with clinically definite MS participated in this study. Fatigue was defined according to the Fatigue Scale for Motor and Cognition (FSMC). Patients underwent a physical exertion test involving walking at their pre-determined patient-specific preferred walking speed until they reached complete exhaustion. Gait was recorded using a video camera, a three line-scanning camera system with 11 infrared sensors. Step length, width and height, maximum circumduction with the right and left leg, maximum knee flexion angle of the right and left leg, and trunk sway were measured and compared using paired t-tests (α = 0.005). In addition, variability in these parameters during one-minute intervals was examined. The fatigue index was defined as the number of significant mean and SD changes from the beginning to the end of the exertion test relative to the total number of gait kinematic parameters.

Results

Clearly, for some patients the mean gait parameters were more affected than the variability of their movements while other patients had smaller differences in mean gait parameters with greater increases in variability. Finally, for other patients gait changes with physical exertion manifested both in changes in mean gait parameters and in altered variability. The variability and fatigue indices correlated significantly with the motoric but not with the cognitive dimension of the FSMC score (R = -0.602 and R = -0.592, respectively; P < 0.026).

Conclusions

Changes in gait patterns following a physical exertion test in patients with MS suffering from motor fatigue can be measured objectively. These changes in gait patterns can be described using the motor fatigue index and represent an objective measure to assess motor fatigue in MS patients. The results of this study have important implications for the assessments and treatment evaluations of fatigue in MS.

Advanced MRI in multiple sclerosis: current status and future challenges

MRI has rapidly become a leading research tool in the study of multiple sclerosis (MS). Conventional imaging is useful in diagnosis and management of the inflammatory stages of MS but has limitations in describing the degree of tissue injury and cause of progressive disability seen in later stages. Advanced MRI techniques hold promise for filling this void. These imaging tools hold great promise to increase understanding of MS pathogenesis and provide greater insight into the efficacy of new MS therapies.

Mechanisms of neuronal dysfunction and degeneration in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. Due to its high prevalence, MS is the leading cause of non-traumatic neurological disability in young adults in the United States and Europe. The clinical disease course is variable and starts with reversible episodes of neurological disability in the third or fourth decade of life. This transforms into a disease of continuous and irreversible neurological decline by the sixth or seventh decade. Available therapies for MS patients have little benefit for patients who enter this irreversible phase of the disease. It is well established that irreversible loss of axons and neurons are the major cause of the irreversible and progressive neurological decline that most MS patients endure. This review discusses the etiology, mechanisms and progress made in determining the cause of axonal and neuronal loss in MS.

MR relaxation in multiple sclerosis

This article provides an overview of relaxation times and their application to normal brain and brain and cord affected by multiple sclerosis. The goal is to provide readers with an intuitive understanding of what influences relaxation times, how relaxation times can be accurately measured, and how they provide specific information about the pathology of MS. The article summarizes significant results from relaxation time studies in the normal human brain and cord and from people who have multiple sclerosis. It also reports on studies that have compared relaxation time results with results from other MR techniques.

Short-term adaptation to a simple motor task: a physiological process preserved in multiple sclerosis

Short-term adaptation indicates the attenuation of the functional MRI (fMRI) response during repeated task execution. It is considered to be a physiological process, but it is unknown whether short-term adaptation changes significantly in patients with brain disorders, such as multiple sclerosis (MS). In order to investigate short-term adaptation during a repeated right-hand tapping task in both controls and in patients with MS, we analyzed the fMRI data collected in a large cohort of controls and MS patients who were recruited into a multi-centre European fMRI study. Four fMRI runs were acquired for each of the 55 controls and 56 MS patients at baseline and 33 controls and 26 MS patients at 1-year follow-up. The externally cued (1 Hz) right hand tapping movement was limited to 3 cm amplitude by using at all sites (7 at baseline and 6 at follow-up) identically manufactured wooden frames. No significant differences in cerebral activation were found between sites. Furthermore, our results showed linear response adaptation (i.e. reduced activation) from run 1 to run 4 (over a 25 minute period) in the primary motor area (contralateral more than ipsilateral), in the supplementary motor area and in the primary sensory cortex, sensory-motor cortex and cerebellum, bilaterally. This linear activation decay was the same in both control and patient groups, did not change between baseline and 1-year follow-up and was not influenced by the modest disease progression observed over 1 year. These findings confirm that the short-term adaptation to a simple motor task is a physiological process which is preserved in MS.

New imaging techniques in the diagnosis of multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic disabling disorder histopathologically characterized by inflammation, demyelination and axonal loss. Conventional MRI has made most contributions to the diagnosis of MS. However, it is not sufficiently sensitive and specific to reveal the extent and severity of the damage in the disease. Other nuclear magnetic resonance (NMR) techniques including magnetic resonance spectroscopy, magnetization transfer imaging, diffusion weighted and diffusion tensor imaging, and functional MRI have provided additional information that improves the diagnosis and understanding of MS. Optical techniques including optical coherence tomography (OCT) and coherent anti-Stokes Raman scattering (CARS) microscopy have shown promise in diagnosis and mechanistic study of myelin diseases.

OBJECTIVE

To review new imaging techniques and their potential in diagnosis of MS.

METHOD

The principles of three imaging techniques (MRI, OCT and CARS) and their applications to MS studies are described. Their advantages and disadvantages are compared.

CONCLUSION

Conventional MRI remains a critical tool in the diagnosis of MS. Alternative NMR/MRI techniques have improved specificity for the detection of lesions and provided more quantitative information about MS. Optical techniques including OCT and CARS microscopy are opening up new ways for diagnosis and mechanistic study of myelin diseases.

Somatosensory evoked potentials reflect the upper limb motor performance in multiple sclerosis

OBJECTIVE

The aim of this multicentric study was to multidimensionally evaluate the relationship among somatosensory evoked potentials (SEPs) parameters, patient's perspective and clinical measures of the upper limb impairment in patients with multiple sclerosis (MS).

METHODS

We consecutively enrolled 39 MS patients. For median nerve SEPs we acquired the N9, P14, N20 responses and the N9-P14 and P14-N20 interpeak latencies on the dominant side. We also used a validated patient-oriented questionnaire (Disabilities of the Arm, Shoulder and Hand - DASH) and a test of dexterity quantification as the 9-Hole Peg Test (9-HPT).

RESULTS

A significant longer time to complete the 9-HPT (p<0.00006) was observed in patients with abnormal SEPs. Patients with undetectable N20 or P14 responses performed the 9-HPT in a significant longer time than patients with detectable responses (p<0.0006 and p<0.001 respectively). Concerning the perspective of patient (evaluated with the DASH questionnaire) significant differences in patients with undetectable P14 response (p<0.01) were observed.

CONCLUSIONS

Our data provide further information useful for interpretation of SEPs results, being the median nerve SEPs related to the upper limb performance in MS patients.

SIGNIFICANCE

These data increase the significance of SEPs both in clinical practice and in experimental studies in MS.

MRI in multiple sclerosis: what's inside the toolbox?

Magnetic resonance imaging (MRI) has played a central role in the diagnosis and management of multiple sclerosis (MS). In addition, MRI metrics have become key supportive outcome measures to explore drug efficacy in clinical trials. Conventional MRI measures have contributed to the understanding of MS pathophysiology at the macroscopic level yet have failed to provide a complete picture of underlying MS pathology. They also show relatively weak relationships to clinical status such as predictive strength for clinical progression. Advanced quantitative MRI measures such as magnetization transfer, spectroscopy, diffusion imaging, and relaxometry techniques are somewhat more specific and sensitive for underlying pathology. These measures are particularly useful in revealing diffuse damage in cerebral white and gray matter and therefore may help resolve the dissociation between clinical and conventional MRI findings. In this article, we provide an overview of the array of tools available with brain and spinal cord MRI technology as it is applied to MS. We review the most recent data regarding the role of conventional and advanced MRI techniques in the assessment of MS. We focus on the most relevant pathologic and clinical correlation studies relevant to these measures.

Advances in functional magnetic resonance imaging: technology and clinical applications

Functional MRI (fMRI) is a valuable method for use by clinical investigators to study task-related brain activation in patients with neurological or neuropsychiatric illness. Despite the relative infancy of the field, the rapid adoption of this functional neuroimaging technology has resulted from, among other factors, its ready availability, its relatively high spatial and temporal resolution, and its safety as a noninvasive imaging tool that enables multiple repeated scans over the course of a longitudinal study, and thus may lend itself well as a measure in clinical drug trials. Investigators have used fMRI to identify abnormal functional brain activity during task performance in a variety of patient populations, including those with neurodegenerative, demyelinating, cerebrovascular, and other neurological disorders that highlight the potential utility of fMRI in both basic and clinical spheres of research. In addition, fMRI studies reveal processes related to neuroplasticity, including compensatory hyperactivation, which may be a universally-occurring, adaptive neural response to insult. Functional MRI is being used to study the modulatory effects of genetic risk factors for neurological disease on brain activation; it is being applied to differential diagnosis, as a predictive biomarker of disease course, and as a means to identify neural correlates of neurotherapeutic interventions. Technological advances are rapidly occurring that should provide new applications for fMRI, including improved spatial resolution, which promises to reveal novel insights into the function of fine-scale neural circuitry of the human brain in health and disease.

Cognitive impairment in multiple sclerosis

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Magnetic resonance imaging advances in multiple sclerosis

Magnetic resonance imaging (MRI) has become a core component of clinical management and scientific research in multiple sclerosis (MS), providing essential information about tissue structure and function. MRI is now the most important laboratory diagnostic and longitudinal monitoring technology. A number of conventional MRI techniques, which include T2-weighted, T1-weighted, and gadolinium-enhanced imaging, are used to identify overt lesions and quantify tissue atrophy. MRI is highly sensitive in detecting brain and spinal cord involvement in MS and can visualize multifocal lesions, occult disease, and macroscopic atrophy. Advanced MRI techniques, such as magnetization transfer imaging, spectroscopy, diffusion-weighted imaging, and functional MRI, have added to our understanding of the pathogenesis of the disease. The precise role of these newer imaging approaches continues to be defined. In this supplement to the Journal of Neuroimaging, the authors review the role of conventional and advanced MRI techniques in detecting tissue changes in MS, diagnosing and monitoring patients, and charting the progression of disease in new and established patients.

Multiple sclerosis medical image analysis and information management

Magnetic resonance imaging (MRI) has become a central tool for patient management, as well as research, in multiple sclerosis (MS). Measurements of disease burden and activity derived from MRI through quantitative image analysis techniques are increasingly being used. There are many complexities and challenges in building computerized processing pipelines to ensure efficiency, reproducibility, and quality control for MRI scans from MS patients. Such paradigms require advanced image processing and analysis technologies, as well as integrated database management systems to ensure the most utility for clinical and research purposes. This article reviews pipelines available for quantitative clinical MRI research in MS, including image segmentation, registration, time-series analysis, performance validation, visualization techniques, and advanced medical imaging software packages. To address the complex demands of the sequential processes, the authors developed a workflow management system that uses a centralized database and distributed computing system for image processing and analysis. The implementation of their system includes a web-form-based Oracle database application for information management and event dispatching, and multiple modules for image processing and analysis. The seamless integration of processing pipelines with the database makes it more efficient for users to navigate complex, multistep analysis protocols, reduces the user's learning curve, reduces the time needed for combining and activating different computing modules, and allows for close monitoring for quality-control purposes. The authors' system can be extended to general applications in clinical trials and to routine processing for image-based clinical research.