Pyramidal tract lesions and movement-associated cortical recruitment in patients with MS

Supplementary and Premotor Cortical Activation During Manual Dexterity Involving Motor Imagery in Multiple Sclerosis: A Functional Near-Infrared Spectroscopy Study

BACKGROUND

Investigating brain activation during motor imagery (MI) tasks in people with multiple sclerosis (pwMS) can increase the knowledge of the neural mechanisms underlying motor dysfunction in MS and, hopefully, aid in developing improved rehabilitation strategies.

OBJECTIVE

To investigate brain activation in the supplementary motor area and premotor cortex via functional near-infrared spectroscopy (fNIRS) during a hand manipulation task, and comparing MI with actual practice (AP) in pwMS.

METHODS

Each subject completed a sequence of 4 consecutive manual dexterity trials wearing an fNIRS device. The tasks included the following conditions: AP dominant hand, MI dominant hand, AP non-dominant hand, and MI non-dominant hand.

RESULTS

Twenty pwMS (mean Expanded Disability Status Scale = 4.75 [3.0-6.5]) and 20 healthy controls (HC) participated in the study. According to the fNIRS timeline course, a similar increase (compared with baseline) was observed in the relative oxygenated hemoglobin (HbO) concentration during the MI and AP tasks, which was immediately followed by a decrease (for either hand) in the pwMS and the HC groups. A difference in the relative HbO concentration between the HC and pwMS was detected solely when the 2 groups mentally replicated the manual dexterity task movements in the MI condition (dominant hand). The increase was higher in the HC group (P = .030).

CONCLUSIONS

Despite exhibiting manual dexterity difficulties, pwMS demonstrated comparable neural activation patterns as the HCs during MI tasks in regions associated with motor planning and complex movement control, thus, suggesting that deficits in manual dexterity among pwMS may not solely originate from impairments in the motor planning processes.

Turning and multitask gait unmask gait disturbance in mild-to-moderate multiple sclerosis: Underlying specific cortical thinning and connecting fibers damage

Multiple sclerosis (MS) causes gait and cognitive impairments that are partially normalized by compensatory mechanisms. We aimed to identify the gait tasks that unmask gait disturbance and the underlying neural correlates in MS. We included 25 patients with MS (Expanded Disability Status Scale score: median 2.0, interquartile range 1.0-2.5) and 19 healthy controls. Fast-paced gait examinations with inertial measurement units were conducted, including straight or circular walking with or without cognitive/motor tasks, and the timed up and go test (TUG). Receiver operating characteristic curve analysis was performed to distinguish both groups by the gait parameters. The correlation between gait parameters and cortical thickness or fractional anisotropy values was examined by using three-dimensional T1-weighted imaging and diffusion tensor imaging, respectively (corrected p < .05). Total TUG duration (>6.0 s, sensitivity 88.0%, specificity 84.2%) and stride velocity during cognitive dual-task circular walking (<1.12 m/s, 84.0%, 84.2%) had the highest discriminative power of the two groups. Deterioration of these gait parameters was correlated with thinner cortical thickness in regional areas, including the left precuneus and left temporoparietal junction, overlapped with parts of the default mode network, ventral attention network, and frontoparietal network. Total TUG duration was negatively correlated with fractional anisotropy values in the deep cerebral white matter areas. Turning and multitask gait may be optimal to unveil partially compensated gait disturbance in patients with mild-to-moderate MS through dynamic balance control and multitask processing, based on the structural damage in functional networks.

Task- and resting-state fMRI studies in multiple sclerosis: From regions to systems and time-varying analysis. Current status and future perspective

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Functional MRI is able to detect adaptive and maladaptive abnormalities at different MS stages.

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Increased fMRI activity is a feature of early MS, while progressive exhaustion of adaptive mechanisms is detected later on in the disease.

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Collapse of long-range connections and impaired hub integration characterize MS network reorganization.

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Time-varying connectivity analysis provides useful and complementary pieces of information to static functional connectivity.

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New perspectives might be the use of multimodal MRI and artificial intelligence.

Multiple sclerosis (MS) is a neurological disorder affecting the central nervous system and features extensive functional brain changes that are poorly understood but relate strongly to clinical impairments. Functional magnetic resonance imaging (fMRI) is a non-invasive, powerful technique able to map activity of brain regions and to assess how such regions interact for an efficient brain network. FMRI has been widely applied to study functional brain changes in MS, allowing to investigate functional plasticity consequent to disease-related structural injury. The first studies in MS using active fMRI tasks mainly aimed to study such plastic changes by identifying abnormal activity in salient brain regions (or systems) involved by the task. In later studies the focus shifted towards resting state (RS) functional connectivity (FC) studies, which aimed to map large-scale functional networks of the brain and to establish how MS pathology impairs functional integration, eventually leading to the hypothesized network collapse as patients clinically progress. This review provides a summary of the main findings from studies using task-based and RS fMRI and illustrates how functional brain alterations relate to clinical disability and cognitive deficits in this condition. We also give an overview of longitudinal studies that used task-based and RS fMRI to monitor disease evolution and effects of motor and cognitive rehabilitation. In addition, we discuss the results of studies using newer technologies involving time-varying FC to investigate abnormal dynamism and flexibility of network configurations in MS. Finally, we show some preliminary results from two recent topics (i.e., multimodal MRI analysis and artificial intelligence) that are receiving increasing attention. Together, these functional studies could provide new (conceptual) insights into disease stage-specific mechanisms underlying progression in MS, with recommendations for future research.

Cortical activity and gait parameter characteristics in people with multiple sclerosis during unobstructed gait and obstacle avoidance

BACKGROUND

People with Multiple Sclerosis (PwMS) present higher cortical activity during walking. However, the cortical activity during gait while avoiding an obstacle is still not clear.

OBJECTIVE

To investigate cortical activity and gait spatial-temporal parameters in PwMS during two different gait tasks (i.e., unobstructed and obstacle avoidance).

METHOD

Fifteen PwMS and 15 healthy controls (CG) were recruited. Participants performed ten trials in each gait condition, wearing a 64-electrode cap electroencephalogram (EEG) at 1024 Hz. Kinematic data were obtained through 10 Vicon® cameras at 200 Hz. EEG was analyzed through four cortical areas (frontal, motor, parietal, and occipital cortex areas) and five frequency bands (delta, theta, alpha, beta, and gamma) obtained through the power spectral density. In addition, spatial-temporal gait parameters (e.g., step length and velocity) were measured. Two-way ANOVA (group x gait condition) and MANOVA (group x gait condition) were used to compare gait and EEG parameters, respectively. One-way ANOVA was used to compare groups in the crossing phase of the obstacle avoidance condition.

RESULTS

PwMS presented lower step length and velocity, and higher cortical activity in frontal (beta and gamma) and parietal (gamma) cortical areas in both gait conditions compared to CG. Moreover, PwMS presented increased cortical activation (frontal and parietal) and decreased step length and velocity in obstacle avoidance compared with unobstructed gait. In addition, PwMS required more cortical resources (frontal and parietal) than CG to accomplish both gait conditions. During the obstacle avoidance task, it was further observed that PwMS positioned their feet closer to the obstacle, before and after the task, compared to CG.

CONCLUSION

PwMS demand higher cortical resources to accomplish gait tasks, mainly when it is necessary to negotiate an obstacle in the pathway. This higher cortical activity may be a compensatory mechanism to deal with damage in subcortical structures caused by multiple sclerosis.

Symptom-associated change of motor-related neuromagnetic fields in a patient with multiple sclerosis: A case report

The objective of this study was to investigate functional abnormalities of the brain in a patient with multiple sclerosis (MS) by using magnetoencephalography (MEG) and a finger-tapping task. A 46-year-old woman that presented with motor weakness of left hand and was diagnosed with MS. Conventional magnetic resonance imaging demonstrated a white matter lesion with hyperintensity on T2-weighted images in the right motor area. MEG recordings were performed during the period of motor weakness and after clinical improvement. Neuromagnetic brain activation was elicited by a simple, visually cued finger movement. The Equivalent current dipole (ECD) strength of the movement-evoked field (MEF) in the affected hemisphere was significantly decreased relative to the unaffected hemisphere. After improvement in motor weakness, we found that the lower amplitude of the readiness field and decreased ECD strength of the MEF observed in affected hemisphere during motor weakness had recovered. Analysis of motor-related neuromagnetic fields revealed that MEG may be used to detect diffuse changes in the brain that are not observable by conventional imaging of white matter regions in MS. We further found that brain activities can change after improvement in motor weakness.

How changes in brain activity and connectivity are associated with motor performance in people with MS

People with multiple sclerosis (MS) exhibit pronounced changes in brain structure, activity, and connectivity. While considerable work has begun to elucidate how these neural changes contribute to behavior, the heterogeneity of symptoms and diagnoses makes interpretation of findings and application to clinical practice challenging. In particular, whether MS related changes in brain activity or brain connectivity protect against or contribute to worsening motor symptoms is unclear. With the recent emergence of neuromodulatory techniques that can alter neural activity in specific brain regions, it is critical to establish whether localized brain activation patterns are contributing to (i.e. maladaptive) or protecting against (i.e. adaptive) progression of motor symptoms. In this manuscript, we consolidate recent findings regarding changes in supraspinal structure and activity in people with MS and how these changes may contribute to motor performance. Furthermore, we discuss a hypothesis suggesting that increased neural activity during movement may be either adaptive or maladaptive depending on where in the brain this increase is observed. Specifically, we outline preliminary evidence suggesting sensorimotor cortex activity in the ipsilateral cortices may be maladaptive in people with MS. We also discuss future work that could supply data to support or refute this hypothesis, thus improving our understanding of this important topic.

Evidence of impaired brain activity balance after passive sensorimotor stimulation in multiple sclerosis

OBJECTIVES

Examination of sensorimotor activation alone in multiple sclerosis (MS) patients may not yield a comprehensive view of cerebral response to task stimulation. Additional information may be obtained by examining the negative BOLD response (deactivation). Aim of this work was to characterize activation and deactivation patterns during passive hand movements in MS patients.

METHODS

13 relapsing remitting-MS patients (RRMS), 18 secondary progressive-MS patients (SPMS) and 15 healthy controls (HC) underwent an fMRI study during passive right-hand movements. Activation and deactivation contrasts in the three groups were entered into ANOVA, age and gender corrected. Post-hoc analysis was performed with one-sample and two-sample t-tests. For each patient we obtained lesion volume (LV) from both T1- and T2-weighted images.

RESULTS

Activations showed a progressive extension to the ipsilateral brain hemisphere according to the group and the clinical form (HC<RRMS<SPMS). Significant deactivation of the ipsilateral cortical sensorimotor areas was reduced in both patient groups with respect to HC. Deactivation of posterior cortical areas belonging to the default mode network (DMN), was increased in RRMS, but not in SPMS, with respect to HC. The amount of activation in the contralateral sensorimotor cortex was significantly correlated with that of deactivation in the DMN in HC and RRMS, but not in SPMS. Both increased activation and decreased deactivation patterns correlated with LV.

CONCLUSION

In RRMS patients, increased cortical activation was associated with increased deactivation of the posterior cortex suggesting a greater resting-state activity in the DMN, probably aimed at facilitating sensorimotor circuit engagement during task performance. In SPMS the coupling between increased sensorimotor activation/increased DMN deactivation was not observed suggesting disorganization between anticorrelated functional networks as a consequence of a higher level of disconnection.

Superficial brain stimulation in multiple sclerosis

Central motor conduction time (CMCT) is the most frequently studied measure derived from transcranial magnetic stimulation (TMS) in multiple sclerosis (MS); it is abnormal in 57-93% of patients. Addition of the triple stimulation technique and combining motor with other evoked potentials (EPs) increases sensitivity. Cross-sectional correlations of TMS measures with clinical assessments of motor dysfunction or global disability are high. Longitudinally, CMCT is sensitive to both worsening and improvement of motor function, showing its potential to detect therapeutic responses. Moreover, combined multimodal EPs are valid quantitative predictors of the clinical course over periods ranging from 2 to 14 years. Measures of transcallosal connectivity (ipsilateral silent period and interhemispheric inhibition) are altered even in early MS, and yield complementary information on subclinical changes. Pathological brain plasticity in MS has been demonstrated by paired associative stimulation studies revealing a compensatory role of the ipsilateral motor and premotor areas. Central motor fatigue is associated with reduced motor EP amplitudes and increased cortical silent periods in normal controls, whereas patients with MS suffering from subjective fatigue show various abnormalities in cortical modulation of the motor system.

Neuroplasticity and functional recovery in multiple sclerosis

The development of therapeutic strategies that promote functional recovery is a major goal of multiple sclerosis (MS) research. Neuroscientific and methodological advances have improved our understanding of the brain's recovery from damage, generating novel hypotheses about potential targets and modes of intervention, and laying the foundation for development of scientifically informed recovery-promoting strategies in interventional studies. This Review aims to encourage the transition from characterization of recovery mechanisms to development of strategies that promote recovery in MS. We discuss current evidence for functional reorganization that underlies recovery and its implications for development of new recovery-oriented strategies in MS. Promotion of functional recovery requires an improved understanding of recovery mechanisms that can be modulated by interventions and the development of robust measurements of therapeutic effects. As imaging methods can be used to measure functional and structural alterations associated with recovery, this Review discusses their use to obtain reliable markers of the effects of interventions.

Impaired cortical deactivation during hand movement in the relapsing phase of multiple sclerosis: a cross-sectional and longitudinal fMRI study

BACKGROUND

Little is known about the cortical activation changes during clinical relapses in multiple sclerosis (MS).

OBJECTIVE

To assess cross-sectional and longitudinal differences in functional magnetic resonance imaging (fMRI) cortical patterns between the relapsing and stable phases of MS.

METHODS

We studied 32 patients with relapsing-remitting MS with mild disability: 19 within 48 h of symptom onset of a new relapse (G1) and 13 in the stable phase, relapse-free for at least 6 months (G2). All patients underwent fMRI twice, upon entry (time 1) and 30-50 days later (time 2), during right-hand movement.

RESULTS

No between-group differences were observed in age, disability or T2 lesion load. Between-group analysis showed a significant difference in the ipsilateral precentral gyrus (IPG) activation at time 1. Activity differences in the IPG expressed reduced deactivation in G1 compared with G2. Longitudinal changes in brain activity in the IPG were significantly greater in G1 than G2. G1 patients with a slow clinical recovery (n = 8) showed different activity at baseline and greater activity changes over time in the IPG than patients with a fast recovery (n = 11).

CONCLUSION

This study shows that the relapsing phase is associated with reduced brain deactivation in the IPG, which is more marked in patients with a slow clinical recovery. Increased cortical excitability associated with inflammation may determine functional modifications within the ipsilateral motor area.

Motor callosal disconnection in early relapsing-remitting multiple sclerosis

In relapsing-remitting multiple sclerosis (RRMS) the corpus callosum (CC) is often and early affected by macroscopic lesions when investigated by conventional MRI. We sought to determine to which extent microstructural and effective disconnection of the CC are already present in RRMS patients at the earliest stages of the disease prior to evidence of macroscopic CC lesion. We compared 16 very early RRMS patients (median expanded disability status scale (EDSS), 1.5; range, 0-2.0) to an age-matched group of healthy controls and focused analysis to the motor CC, i.e. that part of the CC relaying interhemispheric motor information. A combined functional magnetic resonance imaging/diffusion tensor imaging fiber-tracking procedure was applied to identify the callosal motor fibers (CMFs) connecting the hand areas of the primary motor cortices of the two hemispheres. Fractional anisotropy (FA) within the motor CC (FA-CC) assessed the CMF microstructural integrity. Bifocal paired transcranial magnetic stimulation (TMS) tested short-interval interhemispheric inhibition (S-IHI), an established measure of CMF effective connectivity. FA-CC and S-IHI were significantly reduced in early RRMS compared to healthy controls. Furthermore, a significant linear correlation between microstructure (FA-CC) and function (S-IHI) in the controls was broken down in the patients. These abnormalities were obtained in the absence of macroscopic CMF lesion in conventional MRI, and whilst motor hand/arm function in the nine-hole-peg test and corticospinal conduction time were normal. Findings suggest that reductions in FA and S-IHI may serve as surrogate markers of motor callosal disconnection at the earliest stages of RRMS prior to development of macroscopic lesion.

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.

Cortical functional reorganization and its relationship with brain structural damage in patients with benign multiple sclerosis

Background: Patients with multiple sclerosis (MS) who have a favourable clinical status several years after disease onset are classified as ‘benign’. In many cases brain tissue damage does not differ between benign MS and the ‘classical’ MS forms.

Objective: To assess whether the favourable clinical course in benign MS could be explained by the presence of an efficient functional cortical reorganization.

Method: Twenty-five right-handed patients with benign MS (defined as having Expanded Disability Status Scale ≤ 3 and disease duration >15 years) underwent functional MRI during a simple motor task (right-hand tapping) to assess movement-associated brain activation. This was compared with that of 10 patients with relapsing—remitting MS and 10 normal controls. Benign MS patients also underwent conventional brain MRI and magnetization transfer imaging, which was compared with an identical examination obtained 1 year before. Quantitative structural magnetic resonance measures were baseline and changes over time in T2-lesion volume, magnetization transfer ratio in T2 lesions and normal-appearing brain and total brain volume.

Results: Movement-related activation was greater in patients with benign MS than in those with relapsing—remitting MS or normal controls, extensively involving bilateral regions of the sensorimotor network as well as basal ganglia, insula and cerebellum. Greater activation correlated with lower T2-lesion magnetization transfer ratio, and with decreasing brain volume and increasing T2 lesion volume.

Conclusions: The results suggest that bilateral brain networks, beyond those normally engaged in motor tasks, are recruited during a simple hand movement in patients with benign MS. This increased activation is probably the expression of an extensive, compensatory and tissue-damage related functional cortical reorganization. This can explain, at least in part, the favourable clinical expression of patients with benign MS.

Abnormal connectivity of the sensorimotor network in patients with MS: a multicenter fMRI study

In this multicenter study, we used dynamic causal modeling to characterize the abnormalities of effective connectivity of the sensorimotor network in 61 patients with multiple sclerosis (MS) compared with 74 age-matched healthy subjects. We also investigated the correlation of such abnormalities with findings derived from structural MRI. In a subgroup of subjects, diffusion tensor (DT) MRI metrics of the corpus callosum and the left corticospinal tract (CST) were also assessed. MS patients showed increased effective connectivity relative to controls between: (a) the left primary SMC and the left dorsal premotor cortex (PMd), (b) the left PMd and the supplementary motor areas (SMA), (c) the left secondary sensorimotor cortex (SII) and the SMA, (d) the right SII and the SMA, (e) the left SII and the right SII, and (f) the right SMC and the SMA. MS patients had relatively reduced effective connectivity between the left SMC and the right cerebellum. No interaction was found between disease group and center. Coefficients of altered connectivity were weakly correlated with brain T2 LV, but moderately correlated with DT MRI-measured damage of the left CST. In conclusion, large multicenter fMRI studies of effective connectivity changes in diseased people are feasible and can facilitate studies with sample size large enough for robust outcomes. Increased effective connectivity in the patients for the simple motor task suggests local network modulation contributing to enhanced long-distance effective connectivity in MS patients. This extends and generalizes previous evidence that enhancement of effective connectivity may provide an important compensatory mechanism in MS.

Magnetic resonance imaging as a potential surrogate for relapses in multiple sclerosis: a meta-analytic approach

OBJECTIVE

The aim of this work was to evaluate whether the treatment effects on magnetic resonance imaging (MRI) markers at the trial level were able to predict the treatment effects on relapse rate in relapsing-remitting multiple sclerosis.

METHODS

We used a pooled analysis of all the published randomized, placebo-controlled clinical trials in relapsing-remitting multiple sclerosis reporting data both on MRI variables and relapses. We extracted data on relapses and on MRI "active" lesions. A regression analysis weighted on trial size and duration was performed to study the relation between the treatment effect on relapses and the treatment effect on MRI lesions. We validated the estimated relation on an independent set of clinical trials satisfying the same inclusion criteria but with a control arm other than placebo.

RESULTS

A set of 23 randomized, double-blind, placebo-controlled trials in relapsing-remitting multiple sclerosis was identified, for a total of 63 arms, 40 contrasts, and 6,591 patients. A strong correlation was found between the effect on the relapses and the effect on MRI activity. The adjusted R(2) value of the weighted regression line was 0.81. The regression equation estimated using the placebo-controlled trials gave a satisfactory prediction of the treatment effect on relapses when applied to the validation set.

INTERPRETATION

More than 80% of the variance in the effect on relapses between trials is explained by the variance in MRI effects. Smaller and shorter phase II studies based on MRI lesion end points may give indications also on the effect of the treatment on relapse end points.

Impairment of movement-associated brain deactivation in multiple sclerosis: further evidence for a functional pathology of interhemispheric neuronal inhibition

Motor control demands coordinated excitation and inhibition across distributed brain neuronal networks. Recent work has suggested that multiple sclerosis (MS) may be associated with impairments of neuronal inhibition as part of more general progressive impairments of connectivity. Here, we report results from a prospective, multi-centre fMRI study designed to characterise the changes in patients relative to healthy controls during a simple cued hand movement task. This study was conducted at eight European sites using 1.5 Tesla scanners. Brain deactivation during right hand movement was assessed in 56 right-handed patients with relapsing-remitting or secondary progressive MS without clinically evident hand impairment and in 60 age-matched, healthy subjects. The MS patients showed reduced task-associated deactivation relative to healthy controls in the pre- and postcentral gyri of the ipsilateral hemisphere in the region functionally specialised for hand movement control. We hypothesise that this impairment of deactivation is related to deficits of transcallosal connectivity and GABAergic neurotransmission occurring with the progression of pathology in the MS patients. This study has substantially extended previous observations with a well-powered, multicentre study. The clinical significance of these deactivation changes is still uncertain, but the functional anatomy of the affected region suggests that they could contribute to impairments of motor control.

Application of fMRI to the study of multiple sclerosis: an update

During the past decade, functional MRI studies in patients with multiple sclerosis (MS) have consistently shown that the variable effectiveness of recovery mechanisms following disease-related tissue injury is one of the factors that might explain, at least partially, the paucity of the correlation between clinical and MRI findings in these patients. More recently, technical developments resulted in an improvement of acquisition and post-processing schemes that, in turn, allowed us to further characterize the functional and structural abnormalities of specific regions of the CNS, thus ameliorating the understanding of the mechanisms associated with the clinical manifestations and disability accumulation in MS. This review focuses on such recent achievements and provides an update of functional MRI studies of MS performed in the past few years.

Relating functional changes during hand movement to clinical parameters in patients with multiple sclerosis in a multi-centre fMRI study

We performed a prospective multi-centre study using functional magnetic resonance imaging (fMRI) to better characterize the relationships between clinical expression and brain function in patients with multiple sclerosis (MS) at eight European sites (56 MS patients and 60 age-matched, healthy controls). Patients showed greater task-related activation bilaterally in brain regions including the pre- and post-central, inferior and superior frontal, cingulate and superior temporal gyri and insula (P < 0.05, all statistics corrected for multiple comparisons). Both patients and healthy controls showed greater brain activation with increasing age in the ipsilateral pre-central and inferior frontal gyri (P < 0.05). Patients, but not controls, showed greater brain activation in the anterior cingulate gyrus and the bilateral ventral striatum (P < 0.05) with less hand dexterity. An interaction between functional activation changes in MS and age was found. This large fMRI study over a broadly selected MS patient population confirms that movement for patients demands significantly greater cognitive 'resource allocation' and suggests age-related differences in brain responses to the disease. These observations add to evidence that brain functional responses (including potentially adaptive brain plasticity) contribute to modulation of clinical expression of MS pathology and demonstrate the feasibility of a multi-site functional MRI study of MS.

Effect of corpus callosum damage on ipsilateral motor activation in patients with multiple sclerosis: a functional and anatomical study

Functional MRI (fMRI) studies have shown increased activation of ipsilateral motor areas during hand movement in patients with multiple sclerosis (MS). We hypothesized that these changes could be due to disruption of transcallosal inhibitory pathways. We studied 18 patients with relapsing-remitting MS. Conventional T1- and T2-weighted images were acquired and lesion load (LL) measured. Diffusion tensor imaging (DTI) was performed to estimate fractional anisotropy (FA) and mean diffusivity (MD) in the body of the corpus callosum (CC). fMRI was obtained during a right-hand motor task. Patients were studied to evaluate transcallosal inhibition (TCI, latency and duration) and central conduction time (CCT). Eighteen normal subjects were studied with the same techniques. Patients showed increased MD (P < 0.0005) and reduced FA (P < 0.0005) in the body of the CC. Mean latency and duration of TCI were altered in 12 patients and absent in the others. Between-group analysis showed greater activation in patients in bilateral premotor, primary motor (M1), and middle cingulate cortices and in the ipsilateral supplementary motor area, insula, and thalamus. A multivariate analysis between activation patterns, structural MRI, and neurophysiological findings demonstrated positive correlations between T1-LL, MD in the body of CC, and activation of the ipsilateral motor cortex (iM1) in patients. Duration of TCI was negatively correlated with activation in the iM1. Our data suggest that functional changes in iM1 in patients with MS during a motor task partially represents a consequence of loss of transcallosal inhibitory fibers.

fMRI changes in relapsing-remitting multiple sclerosis patients complaining of fatigue after IFNbeta-1a injection

If fatigue in multiple sclerosis (MS) is related to an abnormal activation of the sensorimotor brain network, the activity of such a network should vary with varying fatigue. We studied 22 patients treated with interferon beta 1a (IFNbeta-1a; Avonex, Biogen, Cambridge, MA) with no fatigue (10) and with reversible fatigue (12). fMRI examinations were performed: 1) the same day of IFNbeta-1a injection (no fatigue; entry), 2) the day after IFNbeta-1a injection (fatigue; time 1), and 3) 4 days after IFNbeta-1a injection (no fatigue; time 2). Patients performed a simple motor task with the right, clinically unaffected hand. At time 1, compared with entry and time 2, MS patients with reversible fatigue showed an increased activation of the thalamus bilaterally. In MS patients without fatigue thalamus was more activated at entry than at time 1. In both groups at entry the primary SMC and the SMA were more activated than at times 1 and 2. At entry and time 1, when compared to patients with reversible fatigue, those without showed increased activations of the SII. Conversely, patients with reversible fatigue had increased activations of the thalamus and of several regions of the frontal lobes. An abnormal recruitment of the fronto-thalamic circuitry is associated with IFNbeta-1a-induced fatigue in MS patients.

Functional MRI in multiple sclerosis

There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not simply depend on the extent of tissue destruction, but rather represents a complex balance among tissue damage, tissue repair, and cortical reorganization. Functional magnetic resonance imaging (fMRI) provides information about the extent and nature of brain plasticity, which follows MS structural injury and might have the potential to limit the clinical manifestations of the disease. An altered recruitment of regions normally devoted to the performance of a given task and/or the recruitment of additional areas, which are not typically activated by healthy people for performing that given task, have been described in patients with MS, independent of their clinical phenotype when investigating the visual, cognitive, and motor systems. These functional changes have been related to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific central nervous system (CNS) structures, including the spinal cord and the optic nerve. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. An increased recruitment of the cerebral networks might represent a first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent "second-order" compensatory areas, and, on the other, contribute to the clinical manifestations of the disease.

Spiral drawing performance as an indicator of fine motor function in people with multiple sclerosis

This study investigated spiral drawing performance as an indicator of fine motor function, as well as to gain insight into adaptive movement strategies used by people with multiple sclerosis (MS). Seven people with MS, nine younger controls (mean age of 20) and eight older controls (mean age of 40) drew spirals on a graphics tablet at a comfortable speed and size. Spirography (i.e., a subjective visual assessment of the static trace) revealed indications of reduced control of the pen for people with MS. Analysis of the movements showed that people with MS tended to draw the spirals slower and with less pen pressure than controls. All groups increased their speed and pressure along with spiral size, but this increase was much steeper for the controls. MS participants drew spirals with more variability around an ideal trajectory, highlighting fine motor control degradation. MS patients tended to use a smaller scaling ratio, resulting in smaller spirals for a given number of revolutions. The younger and older control groups drew the spirals in a similar manner, and age was not a significant factor in any of the analyses. It is argued that the relatively lower pressure used, and slower, smaller movements (particularly during the more difficult outer sections of the spiral) are in part an adaptive strategy used to reduce movement variability. These results demonstrate the utility of the analysis of spiral movements as an objective technique for assessing motor control degradation, which can compliment the subjective rating based on the static pen trace. As such, it can provide further insight into the biomechanical strategies used when performing fine movements.

Sensorimotor organization in double cortex syndrome

Subcortical band heterotopia is a diffuse malformation of cortical development related to pharmacologically intractable epilepsy. On magnetic resonance imaging (MRI), patients with "double cortex" syndrome (DCS) present with a band of heterotopic gray matter separated from the overlying cortex by a layer of white matter. The function and connectivity of the subcortical heterotopic band in humans is only partially understood. We studied six DCS patients with bilateral subcortical band heterotopias and six healthy controls using functional MRI (fMRI). In controls, simple motor task elicited contralateral activation of the primary motor cortex (M1) and ipsilateral activation of the cerebellum and left supplementary motor area (SMA). All DCS patients showed task-related contralateral activation of both M1 and the underlying heterotopic band. Ipsilateral motor activation was seen in 4/6 DCS patients. Furthermore, there were additional activations of nonprimary normotopic cortical areas. The sensory stimulus resulted in activation of the contralateral primary sensory cortex (SI) and the thalamus in all healthy subjects. The left sensory task also induced a contralateral activation of the insular cortex. Sensory activation of the contralateral SI was seen in all DCS patients and secondary somatosensory areas in 5/6. The heterotopic band beneath SI became activated in 3/6 DCS patients. Activations were also seen in subcortical structures for both paradigms. In DCS, motor and sensory tasks induce an activation of the subcortical heterotopic band. The recruitment of bilateral primary areas and higher-order association normotopic cortices indicates the need for a widespread network to perform simple tasks.

Functional pathway-defined MRI diffusion measures reveal increased transverse diffusivity of water in multiple sclerosis

The diffusion properties of water are sensitive to microscopic changes in the white matter of multiple sclerosis (MS) patients. Typical MRI measures of disease burden in MS demonstrate modest to poor correlation with disability. Functional MRI and DTI-based fiber tracking were used to define the interhemispheric white matter pathway connecting bilateral supplementary motor areas (SMA) in 16 MS patients sand 16 control subjects. Fractional anisotropy (FA), mean diffusivity (MD), longitudinal (lambda(1)) and transverse diffusivity (lambda(2)) were measured along this pathway in all subjects. Mean FA was 0.587 +/- 0.032 for patients and 0.608 +/- 0.020 for controls (P < 0.02). Mean MD was (0.821 +/- 0.055) x 10(-3) mm(2) s(-1) for patients and (0.770 +/- 0.020) x 10(-3) mm(2) s(-1) for controls (P < 0.004). Mean lambda(1) values were (1.462 +/- 0.099) x 10(-3) mm(2) s(-1) for patients and (1.400 +/- 0.034) x 10(-3) mm(2) s(-1) for controls (P < 0.02). Mean lambda(2) values were (0.500 +/- 0.047) x 10(-3) mm(2) s(-1) for patients and (0.454 +/- 0.027) x 10(-3) mm(2) s(-1) for controls (P < 0.001). In addition, the correlation between the Multiple Sclerosis Functional Composite (MSFC) and transverse diffusivity was -0.341 (P < 0.05). The component test of the MSFC most related to the SMA pathway studied with our MRI method (Nine-hole Peg Test) showed significant correlation with transverse diffusivity (r = 0.392, P < 0.02), indicating that probing functional pathways with MRI measures can lead to a better reflection of disease status.

Loss of interhemispheric inhibition in patients with multiple sclerosis is related to corpus callosum atrophy

Axonal injury and loss in the corpus callosum (CC) is characteristic of the pathology of multiple sclerosis (MS). Functional magnetic resonance imaging (fMRI) potentially allows neurophysiological consequences of this interhemispheric axonal loss to be defined quantitatively. Here we have used 3T fMRI to study the activation in the contralateral primary sensorimotor cortex and deactivation (mediated by transcallosal tracts) in the homologous ipsilateral region in 14 patients with MS and in 14 matched healthy controls during a simple hand-tapping task. Both healthy controls and MS patients showed similar activation in the motor cortex contralateral to the hand moved, but the patients showed a significantly smaller relative deactivation in the ipsilateral motor cortex (P = 0.002). The difference was accounted for by the sub-group of MS patients who previously had impairment of motor function of the hand tested (MS-phd). The CC of the whole patient group was significantly thinner than for the controls (P = 0.001). Atrophy of the CC was correlated with loss of deactivation for the whole patient group (r = -0.50, P = 0.035), but particularly for MS-phd (r = -0.914, P = 0.004). Interhemispheric physiological inhibition thus is impaired in patients with MS, potentially contributing to impairment of motor control. This work suggests one way in which FMRI monitoring of the transcallosal interactions in motor cortex could become a tool for evaluation of therapies that may enhance function in reversibly impaired pathways.

Functional brain reorganization in multiple sclerosis: evidence from fMRI studies

In patients with multiple sclerosis (MS), the severity of clinical signs is not closely related to indices of structural brain damage provided by conventional magnetic resonance MR. Accordingly, patients with MS may show symptom recovery while progressively accumulating tissue damage. Changes in functional organization of the cerebral cortex have been reported in functional magnetic resonance (fMRI) studies that have compared the activation patterns during motor, visual, and cognitive tasks of patients with MS with those of healthy controls. fMRI studies on MS have provided the results that are difficult to compare and may be discrepant because of differences in the criteria used for patient selection, the activation paradigm, the experimental design, and the MR acquisition parameters. Nevertheless, they do provide a new, interesting tool that sheds light on how the brain changes its functional organization in response to MS. In patients with MS, functional brain reorganization mainly consists of an increase in the extent of activation of the brain areas used by healthy subjects, as well as the recruitment of additional brain areas. These findings have been interpreted as adaptive or compensatory mechanisms that allow normal performance despite neural damage or loss. However, brain functional activity may also change in response to clinical disability, though the precise role of brain functional changes in MS has yet to fully understand. Longitudinal studies designed to explore the effects of both rehabilitation and pharmacological agents on brain plasticity might shed light on this issue.

Simultaneous functional magnetic resonance imaging in the rat spinal cord and brain

Functional magnetic resonance imaging (fMRI) method was developed to investigate the pattern and temporal relationship in neuronal pathways of brain and spinal cord. Signal intensity changes correlating with stimulation patterns were observed simultaneously in the rat spinal cord and brain using fMRI at 9.4 T. Electrical stimulation of the forepaw was used to elicit activity. A quadrature volume RF coil covering both brain and the cervical spinal cord was used. Sets of fast spin echo (FSE) images were acquire simultaneously for both brain and spinal cord fMRI. Experiments were repeated in single animal and across animals. Activities within the dorsal horn of the spinal cord and within the somatosensory cortex were observed consistently within each animal as well as across animals.

Functional magnetic resonance imaging and multiple sclerosis

There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not result simply from the extent of tissue destruction, rather it represents a complex balance between tissue damage, tissue repair and cortical reorganization. Functional magnetic resonance imaging provides information regarding the extent and nature of brain plasticity following MS-related structural injury, with the potential to limit the clinical manifestations of the disease. An altered recruitment of regions devoted normally to the performance of a given task and/or the recruitment of additional areas that are not typically activated by healthy people for performing that given task have been described in patients with MS, independent of their clinical phenotype, when investigating visual, cognitive and motor systems. These functional changes have been related not only to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific brain structures, but also to the degree of spinal cord and optic nerve involvement. It has also been suggested that an altered recruitment of specific brain regions might be associated with the appearance of clinical symptoms in MS, such as fatigue. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. More recently, in patients at the earliest clinical stage of the disease, it has been shown that such changes might contribute to predicting the evolution to definite MS, and it has been postulated that dynamic changes of brain cortical activations might occur with the progression of the disease. An increased recruitment of the cerebral networks might represent the first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent second-order compensatory areas, and on the other, contribute to the accumulation of irreversible disability.

Cortical adaptation in patients with MS: a cross-sectional functional MRI study of disease phenotypes

BACKGROUND

Movement-associated cortical reorganisation is known to occur in multiple sclerosis (MS). We aimed to define the development of such cortical reorganisation by comparing data from patients with different disease phenotypes.

METHODS

We studied patients with different phenotypes of MS: 16 patients with a clinically isolated syndrome (CIS), 14 patients with relapsing-remitting MS (RRMS) and no disability, 15 patients with RRMS and mild clinical disability, and 12 patients with secondary progressive MS (SPMS). Patients did a simple motor task with their unimpaired dominant hand during MRI, which was compared across the phenotype groups.

FINDINGS

Patients with a CIS activated more of the contralateral primary sensorimotor cortex than those with RRMS and no disability, whereas patients with RRMS and no disability activated more of the supplementary motor area than those with a CIS. Patients with RRMS and no disability activated more of the primary sensorimotor cortex, bilaterally, and more of the ipsilateral supplementary motor area than patients with RRMS and mild clinical disability. Conversely, patients with RRMS and mild clinical disability activated more of the contralateral secondary somatosensory cortex and inferior frontal gyrus, and the ipsilateral precuneus. Patients with RRMS and mild clinical disability activated more of the contralateral thalamus and of the ipsilateral secondary somatosensory cortex than those with SPMS. However, patients with SPMS activated more of the inferior frontal gyrus, bilaterally, the middle frontal gyrus, bilaterally, the contralateral precuneus, and the ipsilateral cingulate motor area and inferior parietal lobule.

INTERPRETATION

Movement-associated cortical reorganisation in patients with MS seems to vary across individuals at different stages of disease. Our study suggests that early in the disease course more areas typically devoted to motor tasks are recruited. Then bilateral activation of these regions is seen, and late in the disease course, areas that healthy people recruit to do novel or complex tasks are activated.

MRI evidence for multiple sclerosis as a diffuse disease of the central nervous system

The classical view of MS as a chronic inflammatory demyelinating disease leading to the formation of focal central nervous system (CNS) white matter (WM) lesions has been recently challenged by pathological studies and by the extensive application of modern MRI-based techniques. There is now overwhelming evidence supporting the following statements: MS causes widespread tissue damage in the normal-appearing white matter (NAWM) of the brain and spinal cord, whose extent and severity is more strictly associated to the clinical manifestations of the disease than the extent of focal pathology. Discrete, macroscopic lesions are just the tip of the iceberg of MS pathology. Grey matter (GM) damage is a consistent feature of all MS phenotypes, which is progressive from the start of the relapsing-remitting phase of the disease. As is the case for WM, GM damage is also a mixture of focal lesions and diffuse pathology. High-field strength MR scanners are improving our ability to image focal GM lesions and modern MR-based techniques are enabling us to quantify in vivo the extent and severity of GM pathology, which have been shown to correlate only moderately with the amount of WM changes. At least part of GM pathology in MS is not secondary to retrograde degeneration of fibers traversing WM lesions. The neurodegenerative component of the disease is not a late phenomenon and it is not completely driven by inflammatory demyelination. In fact, neurodegeneration occurs very early in the course of MS and the correlation between MRI measures of inflammation and neurodegeneration is weak in all disease phases. The interplay of inflammation and neurodegeneration is a complex and still poorly understood phenomenon. At least part of MS-related neurodegeneration is not directly driven by Wallerian degeneration. Functional cortical changes can be seen in virtually all MS patients and are likely to play a central role in the ability of the MS brain to respond to tissue injury and, hence, limit the functional consequences of structural damage. MS disability is not just the result of tissue destruction but rather a balance between tissue destruction, tissue repair and adaptive cortical reorganization. All of this calls for the concept of MS as a focal, inflammatory demyelinating, WM disease to be reexamined and to start viewing MS as a diffuse CNS disease with an important neurodegenerative component. This is central for identifying novel and effective treatment strategies.