Brain magnetic resonance imaging and multimodal evoked potentials in benign and secondary progressive multiple sclerosis

Clinical diagnostic utility of transcranial magnetic stimulation in neurological disorders. Updated report of an IFCN committee

The review provides a comprehensive update (previous report: Chen R, Cros D, Curra A, Di Lazzaro V, Lefaucheur JP, Magistris MR, et al. The clinical diagnostic utility of transcranial magnetic stimulation: report of an IFCN committee. Clin Neurophysiol 2008;119(3):504-32) on clinical diagnostic utility of transcranial magnetic stimulation (TMS) in neurological diseases. Most TMS measures rely on stimulation of motor cortex and recording of motor evoked potentials. Paired-pulse TMS techniques, incorporating conventional amplitude-based and threshold tracking, have established clinical utility in neurodegenerative, movement, episodic (epilepsy, migraines), chronic pain and functional diseases. Cortical hyperexcitability has emerged as a diagnostic aid in amyotrophic lateral sclerosis. Single-pulse TMS measures are of utility in stroke, and myelopathy even in the absence of radiological changes. Short-latency afferent inhibition, related to central cholinergic transmission, is reduced in Alzheimer's disease. The triple stimulation technique (TST) may enhance diagnostic utility of conventional TMS measures to detect upper motor neuron involvement. The recording of motor evoked potentials can be used to perform functional mapping of the motor cortex or in preoperative assessment of eloquent brain regions before surgical resection of brain tumors. TMS exhibits utility in assessing lumbosacral/cervical nerve root function, especially in demyelinating neuropathies, and may be of utility in localizing the site of facial nerve palsies. TMS measures also have high sensitivity in detecting subclinical corticospinal lesions in multiple sclerosis. Abnormalities in central motor conduction time or TST correlate with motor impairment and disability in MS. Cerebellar stimulation may detect lesions in the cerebellum or cerebello-dentato-thalamo-motor cortical pathways. Combining TMS with electroencephalography, provides a novel method to measure parameters altered in neurological disorders, including cortical excitability, effective connectivity, and response complexity.

Fluid biomarker and electrophysiological outcome measures for progressive MS trials

Progressive multiple sclerosis (MS) is characterized by insidious clinical worsening that is difficult to accurately quantify and predict. Biofluid markers and electrophysiological measures are potential candidate outcome measures in clinical trials, allowing the quantification of nervous damage occurring in the disease. Neurofilaments are highly specific neuronal proteins. They may have come closest to such applications by their higher concentrations repeatedly demonstrated in cerebrospinal fluid (CSF) in all stages of MS, during relapses, their responsiveness to disease-modifying treatments in relapsing and progressive MS and their associations with measures of inflammatory and degenerative magnetic resonance imaging (MRI) outcomes. Digital single-molecule array (Simoa) technology improves accuracy of bioassays in the quantification of neurofilament light chain (NfL) in serum and plasma. NfL seems to mark a common final path of neuroaxonal injury independent of specific causal pathways. CSF and blood levels of NfL are highly correlated across various diseases including MS, suggesting that blood measurements may be useful in assessing response to treatment and predicting future disease activity. Other biomarkers like matrix metalloproteinases, chemokines, or neurotrophic factors have not been studied to a similar extent. Such measures, especially in blood, need further validation to enter the trial arena or clinical practice. The broadening armamentarium of highly sensitive assay technologies in the future may shed even more light on patient heterogeneity and mechanisms leading to disability in MS. Evoked potentials (EPs) are used in clinical practice to measure central conduction of central sensorimotor pathways. They correlate with and predict the severity of clinical involvement of their corresponding function. Their validation for use in multicenter studies is still lacking, with the exception of visual EPs. If further validated, EPs and fluid biomarkers would represent useful outcome measures for clinical trials, being related to specific mechanisms of the ongoing pathologic changes.

Benign multiple sclerosis: aspects of cognition and neuroimaging

The existence of a benign multiple sclerosis (BMS) form is a controversial subject. Recent studies of these patients reveal different levels of cognitive impairment, despite the apparent preservation of motor function. The objective of this study was to review and analyze a number of publications that discuss the general aspects of this disease form, such as the definition criteria, prevalence, and clinical and neuroimaging markers. A systematic review of published data on BMS up to October 2015 was performed. Thirty-one published articles were analyzed. The estimated frequency of BMS varied between 6% and 73%. Cognitive impairment was recognized as affecting 17% to 47% of the subjects and presented significant correlation with neuroimaging, such as brain atrophy, increased lesion volume in T2 magnetic resonance assay, and regional grey matter atrophy. The current criteria overestimated the frequency of BMS and, for that reason, this highlights the importance of validating the diagnostic methods practiced.

Multimodal evoked potentials for functional quantification and prognosis in multiple sclerosis

BACKGROUND

Functional biomarkers able to identify multiple sclerosis (MS) patients at high risk of fast disability progression are lacking. The aim of this study was to evaluate the ability of multimodal (upper and lower limbs motor, visual, lower limbs somatosensory) evoked potentials (EP) to monitor disease course and identify patients exposed to unfavourable evolution.

METHODS

One hundred MS patients were assessed with visual, somatosensory and motor EP and rated on the Expanded Disability Status Scale (EDSS) at baseline (T0) and about 6 years later (T1). The Spearman correlation (rS) was used to evaluate the relationship between conventional EP scores and clinical findings. Multiple (logistic) regression analysis estimated the predictive value of baseline electrophysiological data for three clinical outcomes: EDSS, annual EDSS progression, and the risk of EDSS worsening.

RESULTS

In contrast to longitudinal correlations, cross-sectional correlations between the different EP scores and EDSS were all significant (0.33 ≤ rS < 0.67, p < 0.001). Baseline global EP score and EDSS were highly significant predictors (p < 0.0001) of EDSS progression 6 years later. The baseline global EP score was found to be an independent predictor of the EDSS annual progression rate (p < 0.001), and of the risk of disability progression over time (p < 0.005). Based on a ROC curve determination, we defined a Global EP Score cut off point (17/30) to identify patients at high risk of disability progression illustrated by a positive predictive value of 70%.

CONCLUSION

This study provides a proof of the concept that electrophysiology could be added to MRI and used as another complementary prognostic tool in MS patients.

Use of transcranial magnetic stimulation in the treatment of selected movement disorders

Transcranial magnetic stimulation (TMS) is a valuable technique for assessing the underlying neurophysiology associated with various neuropathologies, and is a unique tool for establishing potential neural mechanisms responsible for disease progression. Recently, repetitive TMS (rTMS) has been advanced as a potential therapeutic technique to treat selected neurologic disorders. In healthy individuals, rTMS can induce changes in cortical excitability. Therefore, targeting specific cortical areas affected by movement disorders theoretically may alter symptomology. This review discusses the evidence for the efficacy of rTMS in Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and multiple sclerosis. It is hoped that gaining a more thorough understanding of the timing and parameters of rTMS in individuals with neurodegenerative disorders may advance both clinical care and research into the most effective uses of this technology.

Central motor conduction time

Central motor conduction time (CMCT) is the time taken for neural impulses to travel through the central nervous system on their way to the target muscles. When the motor cortex is stimulated with transcranial magnetic stimulation (TMS), CMCT is calculated by subtracting the peripheral conduction time from the motor evoked potential latency elicited by motor cortical TMS. CMCT in infants and children reaches adult level at about age of 6 years for the lower limbs. The alterations of CMCT in various neurological conditions are reviewed in this chapter. Prolongation of CMCT occurs due to slowing of conduction through rapidly conducting corticospinal fibers, as seen in various disorders such as demyelinating diseases (multiple sclerosis, MS), amyotrophic lateral sclerosis, structural lesions in the corticospinal tract such as stroke and compressive myelopathy, and neurodegenerative disorders including multiple system atrophy and progressive supranuclear palsy. As CMCT is prolonged in certain clinical conditions, it is of diagnostic value in some neurological disorders such as myelopathy, amyotrophic lateral sclerosis, and MS when used together with other clinical and electrophysiological measures. It could also be used as a prognostic marker in some of neurological conditions, such as myelopathy and MS.

Benign multiple sclerosis: a new definition of this entity is needed

Background: To study a cohort of benign multiple sclerosis (BMS) patients beyond physical disability, including the evaluation of cognitive and social function, as well as fatigue, pain and MRI studies.

Methods: A cohort of 342 patients was prospectively followed for 10.9 ± 0.71 years. Forty-three patients (12.5%) met the BMS diagnosis criteria [Expanded Disability Status Scale (EDSS) < 3 after at least 10 years’ disease duration], undergoing full neurological examination every 6 months. Neuropsychological status, pain, fatigue, social functioning and work-related disability, as well as brain MRIs, were assessed yearly.

Results: By the end of follow-up, 20 of 43 BMS patients (47%) had suffered cognitive impairment and 23 (53.3%) referred depression. Furthermore, 21 (48.8%) reported significant changes in pain intensity, with fatigue and environmental severity scores significantly increasing over time in 33–35% of patients. Finally, 32 BMS patients (74%) showed significant increase in the number of new or enlarging T2 lesions, gadolinium-enhanced lesions, and persistent black holes, without changes in EDSS. Thirty-five of 43 patients (81%) fulfilling the BMS diagnostic criteria showed significant worsening of cognitive function, fatigue, pain or depression during the 10-year follow-up.

Conclusions: Currently accepted criteria for BMS diagnosis may cause overestimation of true prevalence, underscoring the need for routine monitoring of non-motor symptoms and imaging studies, to help physicians improve diagnostic accuracy as well as therapeutic decision-making in this subgroup of MS patients.

Relationship between brain MRI lesion load and short-term disease evolution in non-disabling MS: a large-scale, multicentre study

BACKGROUND AND OBJECTIVES

We evaluated clinical and conventional MRI features of a large population of patients with non-disabling MS to identify potential markers of a benign disease course.

METHODS

In seven MAGNIMS centres we retrospectively identified 182 patients with benign (B) MS (EDSS score ≤ 3.0, disease duration ≥ 15 years) and 187 patients with non-disabling relapsing-remitting MS (NDRRMS) (Expanded Disability Status Scale score ≤ 3.0, disease duration between 5 and 14 years), in whom clinical data were collected within two weeks from a brain T2-weighted scan. Brain T2 lesion volume (LV) was measured in all patients. In 146 BMS and 146 NDRRMS patients, clinical data were also available after a median follow up of 29 months (range: 7-104 months).

RESULTS

Mean LV was higher in BMS than in NDRRMS patients (p<0.001), but the mean ratio between LV and disease duration was higher in NDRRMS than in BMS patients (1.1 vs. 0.6 ml/year, p<0.001). In BMS patients, brain LV was correlated with EDSS score increase at follow up (r=0.18, p=0.03).

CONCLUSIONS

An overall low rate of brain LV increase during a long-lasting disease course might be a feature of BMS. In BMS patients, a high brain LV might be associated with worsening of locomotor disability at short-term follow up.

T2 hypointensity in the deep gray matter of patients with benign multiple sclerosis

Background

Gray matter (GM) magnetic resonance imaging (MRI) T2 hypointensity, a putative marker of iron deposition, commonly occurs in multiple sclerosis (MS). However, GM T2 hypointensity in benign MS (BMS) has not yet been characterized.

Objective

To determine the presence of deep GM T2 hypointensity in BMS, compare it to secondary progressive (SP) MS and assess its association with clinical and diffusion tensor (DT) MRI measures.

Methods

Thirty-five cognitively unimpaired BMS, 26 SPMS patients, and 25 healthy controls were analyzed for normalized T2-intensity in the basal ganglia and thalamus, global T2 hyperintense lesion volume, global atrophy, and white matter and GM DT metrics.

Results

BMS and SPMS patients showed deep GM T2 hypointensity compared with controls. T2 hypointensity was similar in both MS subgroups and moderately correlated ( r = −0.45 to 0.42) with DT MRI metrics. GM T2 hypointensity in BMS showed a weak to moderate correlation ( r = −0.44 to −0.35) with disability.

Conclusions

GM in BMS is not spared from structural change including iron deposition. However, while T2 hypointensity is related to global tissue disruption reflected in DT MRI, the expression of benign versus non-benign MS is likely related to other factors.

Role of B:T cell ratio in suppression of clinical signs: a model for silent MS

B10.S mice have been considered resistant to experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. However, sensitization with a myelin oligodendrocyte glycoprotein (MOG) peptide, MOG(92-106), induced clinical signs in 30% of mice and central nervous system (CNS) pathology in 93% of mice. Symptomatic mice had more demyelination, inflammation, perivascular cuffing and axonal damage in the CNS compared to asymptomatic mice, but no strong correlations between CNS pathology and clinical score were found. Interestingly, the ratio of B cells to T cells in cellular infiltrates correlated with clinical score. This suggests that the balance between B and T cells contributes to expression of clinical signs.

The topographical distribution of tissue injury in benign MS: a 3T multiparametric MRI study

We compared the global and regional distribution of white matter (WM) and gray matter (GM) damage and T2-visible lesion between patients with benign (B) and relapsing remitting (RR) multiple sclerosis (MS). BMS and RRMS patients did not differ in terms of global volumes and diffusion tensor (DT) MRI metrics of the WM and GM. Compared to controls, BMS and RRMS patients had bilateral thalamic loss. Compared to controls, BMS and RRMS patients had lower WM fractional anisotropy (FA) in the corpus callosum (CC) and in several regions of temporal and occipital lobes. BMS also had a decreased WM FA in the parietal lobes. RRMS patients had also lower WM FA in several regions of the frontal lobes. Compared to BMS, RRMS patients had decreased WM FA in the frontal lobes, while the opposite comparison showed lower WM FA in the CC, the temporal lobes and the cuneus in BMS. Contrasted to controls, both MS groups showed several regions of increased MD in WM and GM, but no difference was found between MS sub-groups. T2-visible lesions were mainly located in the posterior regions of the brain in BMS patients, while they involved also regions in the frontal lobes, in RRMS patients. BMS and RRMS patients differ in terms of the topographical distribution of WM damage rather than in the overall extent of brain structural changes. The less prominent involvement of the frontal lobe WM and of the NAWM in general in BMS might be associated to their favorable clinical status.

Clinically benign multiple sclerosis despite large T2 lesion load: can we explain this paradox?

Magnetic resonance imaging (MRI) techniques such as magnetization transfer imaging and magnetic resonance spectroscopy (MRS) may reveal otherwise undetectable tissue damage in multiple sclerosis (MS) and can serve to explain more severe disability than expected from conventional MRI. That an inverse situation may exist where non-conventional quantitative MRI and MRS metrics would indicate less abnormality than expected from T2 lesion load to explain preserved clinical functioning was hypothesized. Quantitative MRI and MRS were obtained in 13 consecutive patients with clinically benign MS (BMS; mean age 44 +/- 9 years) despite large T 2 lesion load and in 15 patients with secondary progressive MS (SPMS; mean age 47 +/- 6 years) matched for disease duration. The magnetization transfer ratio (MTR), magnetization transfer rate (kfor), brain parenchymal fraction (BPF) and brain metabolite concentrations from proton MRS were determined. BMS patients were significantly less disabled than their SPMS counterparts (mean expanded disability status score: 2.1 +/- 1.1 versus 6.2 +/- 1.1; P < 0.001) and had an even somewhat higher mean T2 lesion load (41.2 +/- 27.1 versus 27.9 +/- 24.8 cm3; P = 0.19). Normal appearing brain tissue histogram metrics for MTR and kfor, mean MTR and kfor of MS lesions and mean BPF were similar in BMS and SPMS patients. Levels of N-acetyl-aspartate, choline and myoinositol were comparable between groups. This study thus failed to explain the preservation of function in our BMS patients with large T2 lesion load by a higher morphologic or metabolic integrity of the brain parenchyma. Functional compensation must come from other mechanisms such as brain plasticity.

Drug Insight: interferon treatment in multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disease of the CNS. Between 1987 and 1997, clinical trials of three preparations of recombinant interferon-beta were conducted in patients with MS, ushering in a new therapeutic era. These medications have demonstrable benefits and seem to be safe; they represent an important advance in MS treatment. All three formulations of interferon-beta had modest effects on relapses and short-term progression of disability, but the effects on MRI lesion parameters were more substantial. The benefits were greater in clinically isolated syndromes and relapsing-remitting MS than in secondary progressive MS. Although these drugs have been shown to be effective, however, their long-term impact on clinically relevant disability progression is uncertain, and there are many areas of controversy in the MS field regarding the use of these products. There is still a need for more effective treatments, which might include new agents or combination therapies.

Multimodal evoked potentials to assess the evolution of multiple sclerosis: a longitudinal study

BACKGROUND

Evoked potentials are used in the functional assessment of sensory and motor pathways. Their usefulness in monitoring the evolution of multiple sclerosis has not been fully clarified.

OBJECTIVE

The aim of this longitudinal study was to examine the usefulness of multimodal evoked potential in predicting paraclinical outcomes of disease severity and as a prognostic marker in multiple sclerosis.

METHODS

Eighty four patients with clinically definite multiple sclerosis underwent Expanded Disability Status Scale (EDSS) and functional system scoring at study entry and after a mean (standard deviation) follow-up of 30.5 (11.7) months. Sensory and motor evoked potentials were obtained in all patients at study entry and at follow-up in 64 of them, and quantified according to a conventional score.

RESULTS

Cross-sectionally, the severity of each evoked potential score significantly correlated with the corresponding functional system (0.32 < R < 0.60, p < 0.01, for all but follow-up visual evoked potential) and with EDSS (0.34 < R < 0.61; p < 0.001 for all but brain stem evoked potential). EDSS significantly correlated with global evoked potential score severity (baseline R = 0.60, follow-up R = 0.46, p < 0.001). Using longitudinal analysis, only changes in somatosensory evoked potential scores were significantly correlated with changes of sensory functional system (R = 0.34, p = 0.006). However, patients with multiple sclerosis with disability progression at follow-up had more severe baseline evoked potential scores than patients who remained stable. Patients with severe baseline global evoked potential score (higher than the median value) had a risk of 72.5% to progress on disability at follow-up, whereas patients with multiple sclerosis with lower scores had a risk of only 36.3%.

CONCLUSIONS

These results suggest that evoked potential is a good marker of the severity of nervous damage in multiple sclerosis and may have a predictive value regarding the evolution of disability.

EFNS guidelines on the use of neuroimaging in the management of multiple sclerosis

Magnetic resonance (MR)-based techniques are widely used for the assessment of patients with suspected and definite multiple sclerosis (MS). However, despite the publication of several position papers, which attempted to define the utility of MR techniques in the management of MS, their application in everyday clinical practice is still suboptimal. This is probably related, not only, to the fact that the majority of published guidelines focused on the optimization of MR technology in clinical trials, but also to the continuing development of modern, quantitative MR-based techniques, that have not as yet entered the clinical arena. The present report summarizes the conclusions of the 'EFNS Expert Panel of Neuroimaging of MS' on the application of conventional and non-conventional MR techniques to the clinical management of patients with MS. These guidelines are intended to assist in the use of conventional MRI for the diagnosis and longitudinal monitoring of patients with MS. In addition, they should provide a foundation for the development of more widespread but rational clinical applications of non-conventional MR-based techniques in studies of MS patients.

Benign course in multiple sclerosis: a review

Since the 1950s, it has been recognized that a subgroup of multiple sclerosis (MS) patients exists that shows little or no progression in the severity of the disease over time. This group is referred to as 'benign' MS. Although a substantial amount of research in MS indicates a multifactorial background in disease severity, to date it is still difficult to predict whether the course will be benign at onset and it is difficult to find factors that influence the course of the disease over time. Maintaining or restoring neural conduction inside a central nervous system lesion seems to be the essence of staying 'benign'.

Intracellular oxidative activity and respiratory burst of leukocytes isolated from multiple sclerosis patients

Oxidative damage induced by free radicals and reactive oxygen species (ROS) have been suggested to play an important role in the development of autoimmune diseases such as multiple sclerosis (MS) disease and it has been hypothesised that oxidative injury could mediate demyelination and axonal injury in MS subjects. In our study, we compared intracellular oxidative activity and the respiratory burst activity in MS patients (n=20) and healthy controls (n=15) using leukocytes as cellular model. At this purpose, intracellular ROS levels were evaluated by fluorometric assay using the 2'-7'-dichlorodihydrofluorescin diacetate probe (H(2)DCFDA) in untreated or in leukocytes stimulated with phorbol-12-myristate-13-acetate (PMA). Our results demonstrate that the intracellular spontaneous ROS production in leukocytes from MS patients was higher with respect to cells from control subjects (p<0.001). PMA addition induced a higher formation of ROS both in leukocytes from MS patients and controls (p<0.001). The PMA-induced production of ROS was significantly higher in leukocytes from MS with respect to controls (p<0.001). Significant positive correlations were established between intracellular spontaneous or PMA-induced production of ROS in leukocytes isolated from MS patients and the clinical parameters used to evaluate disease disability such as expanded disability status scale (EDSS), brain lesions evaluated by MRI and visual evoked potential (VEP) (p<0.001). In conclusion, our results demonstrate higher levels of intracellular ROS in untreated or in PMA-treated leukocytes isolated from MS patients with respect to healthy subjects confirming the role of oxidative stress in multiple sclerosis.

Pattern reversal visual evoked potentials as a measure of visual pathway pathology in multiple sclerosis

BACKGROUND

Pattern reversal visual evoked potentials (PRVEPs) have a well-documented role in diagnosis of multiple sclerosis (MS), but their value as a visual function surrogate remains controversial.

METHODS

We evaluated PRVEP in 37 patients with MS who were participating in a long-term follow-up study following a phase III trial of interferon beta-1a (Avonex). Patients were examined to determine the Kurtzke Extended Disability Status Score (EDSS), multiple sclerosis functional composite (MSFC), contrast letter acuity (CLA), and had cranial MRI scans to determine whole brain atrophy (BPF). PRVEP was evaluated for P100 latency, amplitude, and waveform morphology. Two summary scores were created: for Score A, abnormal latencies, morphologies, and amplitudes of each individual eye were added; for Score B, abnormal latencies, morphologies, and amplitude ratio between eyes was determined. Sixteen patients in this group also had PRVEP at the time they enrolled in the clinical trial, eight years previously.

RESULTS

At the follow-up exam, over 75% of patients had abnormal PVEP parameters while visual acuity (VA) was abnormal only in 59%. Increased PRVEP latency over the eight-year period correlated with deterioration assessed by EDSS (P = 0.006), BPF (P = 0.0001), and MSFC (P = 0.0041). Score A was significantly correlated with EDSS, BPF, CLA, cognitive function, and quality of life assessed with the Sickness Impact profile. No correlation was seen with the MSFC.

CONCLUSIONS

The results indicate that PRVEP measures MS-related pathology, and can provide not only diagnostic but also prognostic information during evaluation of MS patients.

Sensitivity of laser-evoked potentials versus somatosensory evoked potentials in patients with multiple sclerosis

OBJECTIVE

Somatosensory evoked potentials (SEPs) play a less important role in the diagnosis of multiple sclerosis (MS) than visually evoked potentials. Since standard SEPs only reflect the dorsal column function, we now investigated spinothalamic tract function in patients with MS using laser-evoked potentials (LEPs).

METHODS

LEPs to thulium laser stimuli (3ms, 540 mJ, 5mm diameter) were recorded from 3 midline positions (Fz, Cz, Pz) in 20 patients with MS, and 6 patients with possible but unconfirmed MS. Peak latencies and peak-to-peak amplitude of the vertex potential negativity (N2) and positivity (P2) were evaluated and compared with normative values from 22 healthy control subjects. Median and tibial nerve SEPs were recorded with standard methods. Depending on the results of sensory testing, two skin areas (both hands, both feet, or one hand and foot of the same body side) were assessed in each patient.

RESULTS

In group comparisons, LEPs in patients with MS were significantly delayed and reduced in amplitude compared with healthy subjects (P<0.001) or patients with suspected but unconfirmed MS (P<0.05). In intraindividual comparisons within the patients with MS, LEP amplitude was significantly lower (P<0.01) and latencies were significantly longer (N2: P<0.01; P2: P<0.05) for a clinically hypoalgesic skin area than an unaffected control area. On a single case basis, LEPs were abnormal in 12 (60%) and SEPs in 8 (40%) of the patients with MS; combined analysis of LEPs and SEPs raised sensitivity to 75% (15 patients). LEPs were also abnormal for 7 skin areas with clinically normal nociception and thermal sensitivity, indicating subclinical lesions. Standard SEPs detected subclinical lesions in 5 areas with normal tactile sensitivity.

CONCLUSIONS

In patients with multiple sclerosis, spinothalamic tract function and LEPs were impaired more often than dorsal column function and SEPs. LEPs also detected subclinical lesions. Combined assessment of LEPs and SEPs can help to document dissemination of demyelinating CNS lesions and thus contribute to the diagnosis of multiple sclerosis.

Cortical silent period and motor evoked potentials in patients with multiple sclerosis

In order to determine the importance of central motor conduction time (CMCT) and silent period (SP) in patients with multiple sclerosis (MS), we enrolled this clinical and electrophysiological study. Additionally, we planned to compare the correlation between electrophysiological findings and clinical status. We examined 58 patients with definite MS and 31 controls. Patients were classified as relapsing-remitting (N: 37), secondary progressive (N: 21) groups. Eleven out of 58 patients with MS had no neurological findings (subclinical patients). We evaluated CMCT and the duration of SP. Prolonged CMCT latency was shown in 75.2% of patients. We observed SP abnormalities in 69% of patients. In subclinical patients, SP abnormalities (six of 11) were observed more common than CMCT (two of 11). The duration of SP was extremely prolonged in MS patients with cerebellar dysfunction. When the both electrophysiological parameters are taken into account, the abnormality ratio was determined as 89.7%. Our results indicate that CMCT and SP analysis are complementary tests in evaluating motor pathways of patients with MS. We observed a relationship between cerebellar dysfunction and SP prolongation. It is suggested that, SP can be applied in patients with pure cerebellar dysfunction and it can be a valuable test in subclinical cases with MS.

Adaptive functional changes in the cerebral cortex of patients with nondisabling multiple sclerosis correlate with the extent of brain structural damage

In multiple sclerosis, the mechanisms underlying the accumulation of disability are poorly understood. Recently, it has been suggested that adaptive cortical changes may limit the clinical impact of multiple sclerosis injury. In this study, functional magnetic resonance imaging and a general search method were used to assess patterns of brain activation associated with a simple motor task in 14 right-handed, nondisabled relapsing-remitting multiple sclerosis patients that were compared to those from 15 right-handed, sex- and age-matched healthy volunteers. Also investigated were the extent to which the functional magnetic resonance imaging changes correlated with T2 lesion volume and severity of multiple sclerosis pathology in lesions and normal-appearing brain tissue, measured using magnetisation transfer and diffusion tensor magnetic resonance imaging. Compared to controls, multiple sclerosis patients showed increased activation in the contralateral primary sensorimotor cortex, bilaterally in the supplementary motor area, bilaterally in the cingulate motor area, in the contralateral ascending bank of the sylvian fissure, and in the contralateral intraparietal sulcus. T2 lesion volume was correlated with relative activation in the ipsilateral supplementary motor area, and in the ipsilateral and contralateral cingulate motor area. Average lesion magnetisaiton transfer ratio and average lesion water diffusivity were correlated with relative activation in the contralateral sensorimotor cortex. Average lesion magnetisation transfer ratio was also correlated with relative activation in the ipsilateral cingulate motor area. Average water diffusivity and peak height of the normal-appearing brain tissue diffusivity histogram were both correlated with relative activation in the contralateral intraparietal sulcus. This study shows that cortical activation occurs over a rather distributed sensorimotor network in nondisabled relapsing-remitting multiple sclerosis patients. It also suggests that increased recruitment of this cortical network contributes to the limitation of the functional impact of white matter multiple sclerosis injury.

Quantitative functional MR imaging of the visual cortex at 1.5 T as a function of luminance contrast in healthy volunteers and patients with multiple sclerosis

BACKGROUND AND PURPOSE

In patients with multiple sclerosis (MS), a few preliminary functional MR (fMR) imaging studies of the visual cortex reveal information about magnitude differences between healthy individuals and patients with MS at only a single luminance level. We therefore investigated whether varying luminance contrast levels can help uncover subtle changes in fMR imaging characteristics of the visual cortex in healthy volunteers and patients with MS.

METHODS

Blood oxygenation level-dependent fMR imaging signal changes in the primary visual cortex were examined as a function of luminance contrast at 1.5 T in 10 healthy volunteers and nine patients with MS. Ten axial sections through the calcarine fissure were obtained with an echo-planar T2*-weighted imaging sequence (4000/54/1 [TR/TE/excitation]; field of view, 220 mm; voxel size, 1.72 x 1.72 x 5 mm). The imaging series consisted of an alternating 20-second rest epoch (black screen) with a 20-second activation epoch (flickering checkerboard) repeated six times. Each imaging series used a graded increase of eight luminance contrast levels. A paired t test between rest and activation images was used to analyze significant (P <.001) contiguous voxels in the region of interest (primary visual cortex).

RESULTS

A progressive increase in fMR imaging activation across all luminance contrast levels in healthy controls and patients with MS was shown. The patients with MS had a significantly lower magnitude in the number of fMR imaging activated voxels at all luminance contrast levels (P <.001). A statistically significant increase in fMR imaging activation (activation threshold) was seen at the second luminance contrast level in controls and at the seventh level in patients with MS.

CONCLUSION

Quantifiable changes in blood oxygenation level-dependent signal and a progressive increase in activated voxels within the primary visual cortex with increasing luminance contrast were demonstrated at 1.5 T in controls. The patients with MS showed a significant decrease in the number of activated voxels and an increase in activation threshold compared with healthy controls.

Neurophysiological investigations in multiple sclerosis

The advent of magnetic resonance imaging techniques has greatly reduced the diagnostic value of neurophysiological tests, particularly evoked potentials, in multiple sclerosis patients, because of the higher sensitivity in revealing subclinical involvement of the central nervous system. Technical progress and new methods of investigating afferent and efferent nervous pathways would seem to increase the sensitivity in detecting neural dysfunction, but the 'clinical gain' is modest at best. More promising is the utilization of neurophysiological tests to quantify the severity of white matter involvement. Transversal and longitudinal studies have demonstrated good correlations between neurophysiological parameters and disability measures, indicating that a battery of neurophysiological tests could be useful in monitoring the disease evolution in single patients and as surrogate endpoints in clinical trials. Further studies are needed for a better definition of the applications of evoked potentials and other neurophysiological techniques. Finally, event-related potentials and advanced electroencephalogram techniques, such as coherence analysis, could provide useful information on the pathophysiology of cognitive dysfunction, so common in multiple sclerosis patients, and with a strong impact on the quality of life.

Nuclear magnetic resonance monitoring of treatment and prediction of outcome in multiple sclerosis

Magnetic resonance (MR) techniques provide an objective, sensitive and quantitative assessment of the evolving pathology in multiple sclerosis. There is an increasing definition of the pathological specificity of newer techniques, and more robust correlations with clinical evolution are emerging. As the pathophysiological basis of in vivo nuclear MR signal abnormalities is further elucidated, it is likely that the importance of MR as a tool to monitor new therapies will increase.

Measuring evoked responses in multiple sclerosis

Evoked potentials (EPs) have been widely utilised in Multiple Sclerosis (MS) patients to demonstrate the involvement of sensory and motor pathways. Their diagnostic value is based on the ability to reveal clinically silent lesions and to objectivate the central nervous system damage in patients who complain frequently of vague and indefinite disturbances which frequently occurs in the early phases of the disease. The advent of magnetic resonance imaging (MRI) techniques has greatly reduced the clinical utilisation of EPs, which is not fully justifiable, as the information provided by EPs are quite different from those provided by MRI. The abnormalities of evoked responses reflect the global damage of the evoked nervous pathway and are significantly correlated with the clinical findings, while the vast majority of MRI lesions are not associated to symptoms and signs. Transversal and longitudinal studies have demonstrated that EP changes in MS are more strictly related to disability than MRI lesion burden. On the contrary, MRI is more sensitive than EPs in revealing the disease activity. Evoked responses modifications observed in MS are not disease-specific; moreover longitudinal studies showed latency and morphology changes of evoked responses not always related to clinical changes. Such a dissociation can be explained both by technical factors and by subclinical disease activity. To reduce the negative impact of technical aspects, only reproducible parameters of the evoked responses should be used to monitor disease evolution and therapeutic interventions.

Sensory impairments in spinal multiple sclerosis: a combined clinical, magnetic resonance imaging and somatosensory evoked potential study

Thirty-one cases (26 patients) of clinically definite multiple sclerosis with predominant spinal cord involvement were studied retrospectively, focusing in particular on the results of sensory testings which were compared with the findings of spinal cord magnetic resonance imaging (MRI) and somatosensory evoked potentials (SEPs). Factor analysis of the sensory impairments showed two factors corresponding to superficial (pain and light-touch) and deep (position and 'thumb/big toe localizing') sensations. Vibratory sense depended on both factors, but more on deep sensations. Multiple regression analysis of the SEP abnormalities and sensory deficits showed that impaired deep sensations contributed to abnormal SEPs, but the results of clinical sensory testings and SEPs were dissociated in 31% of the extremities examined. The MRI sagittal images correlated well with the levels of sensory impairments, whereas the axial images showed a poor relationship to the extent of sensory impairments. We concluded that the use of SEPs as well as MRI is not always superior to such clinical sensory tests as the 'thumb/big toe localizing tests'.

Evoked potential abnormality scores are a useful measure of disease burden in relapsing-remitting multiple sclerosis

Fifty patients with relapsing-remitting multiple sclerosis were examined and studied with serial evoked potential and magnetic resonance imaging (MRI) measurements as part of a clinical trial. An evoked potential abnormality score (EPAS) for each testing session was calculated consisting of the total number of abnormal tests. The EPAS correlated well with Expanded Disability Status Scale (EDSS) at years 0, 1, and 2, with Spearman correlation coefficient scores of 0.68, 0.66, and 0.72, respectively. MRI lesion volume correlations ranged from 0.27 to 0.34 for the EDSS. EPAS are a potentially useful surrogate measure of clinical disability in relapsing-remitting multiple sclerosis.

Neurophysiological and cognitive markers of disease evolution in multiple sclerosis

Both evoked potentials and cognitive tests may provide useful information which cannot be derived from the clinical observation. For this reason, there have been some attempts to use EPs in monitoring the natural history of the disease and in assessing the efficacy of therapeutic trials. However, no conclusion can be derived from the few available data. Although MRI is more sensitive than EPs in revealing new lesions in brain, cerebellum and brainstem, EPs are more sensitive in revealing optic nerve and spinal cord lesions. Moreover, the poor relationship between brain MRI abnormalities and disability has raised the possibility that cognitive evaluation may be an additional sensitive marker of brain involvement over time. Since the gold standard for the assessment of disease activity is uncertain, it is therefore advisable that frequent MRI, EPs and cognitive assessment may integrate clinical outcomes measured by conventional scales, both in the study of the natural disease course and in monitoring clinical trials.

Oligodendrocyte and axon pathology in clinically silent multiple sclerosis lesions

Oligodendrocyte and axon pathology was studied in 11 autopsy cases of clinically silent multiple sclerosis. A total of 54 lesions, either demyelinated or late remyelinated, were distributed through the whole brain and spinal cord with 39% of the lesions located in periventricular areas. Determination of axon density revealed an average reduction of 64% and 59% in demyelinated and remyelinated lesions with an extreme variation between different plaques and cases. Oligodendrocytes were identified by immunocytochemistry for myelin oligodendrocyte glycoprotein (MOG) and in situ hybridization for proteolipid protein (PLP) mRNA. Oligodendrocytes were almost completely lost in demyelinated lesions; remyelinated lesions revealed preservation of a considerable number of oligodendrocytes within the lesions. At the border between plaques and the periplaque white matter, similar oligodendrocyte numbers as in remyelinated lesions were found. Different factors including lesion site, axonal preservation and remyelination may thus contribute to the clinical nonappearance of multiple sclerosis lesions.

Clinical significance of reduced cerebral metabolism in multiple sclerosis: a combined PET and MRI study

Magnetic resonance imaging (MRI) in patients with multiple sclerosis (MS) has provided major insights into the disease's natural history, and many studies have focussed on possible correlations between MRI findings and the clinical manifestations of MS. In contrast, there are few reports on possible relationships between functional imaging data and cognitive function. The present study assessed the relationship between clinical presentation and combined anatomical and functional imaging data in MS. Twenty patients with definite MS underwent MRI and positron emission tomography (PET) to evaluate cerebral blood flow (rCBF) and oxygen metabolism (rCMRO2). The relationships between these neuroimaging findings and clinical data, including the Expanded Disability Status Scale (EDSS), Mini-mental status scale, Hasegawa Dementia Scale and relapse time, were evaluated with Spearman's rank correlation coefficients. A general reduction in rCBF and rCMRO2 in the gray and white matter were found in the MS patients. EDSS was correlated with the number and size of the lesions on MRI and was negatively correlated with rCMRO2. A correlation between the decrease in rCMRO2 and the level of cognitive impairment was also found. The severity of cerebral hypometabolism was also related to the number of relapses. Morphological and functional findings obtained by MRI and PET are closely related to the clinical status in MS. Our results suggest that measurement of cerebral metabolism in MS has the potential to be an objective marker for monitoring disease activity and to provide prognostic information.

Motor evoked potentials and disability in secondary progressive multiple sclerosis

BACKGROUND

To investigate the mechanisms underlying disability in multiple sclerosis (MS), 40 patients with the relapsing-remitting form of the disease and 13 patients with secondary progressive MS underwent multimodal evoked potential (EP), motor evoked potential (MEP), and spinal motor conduction time evaluation. Clinical disability was evaluated by the expanded disability status scale (EDSS) and functional system scales. In secondary progressive MS patients, magnetic resonance imaging (MRI) was used to obtain a semiquantitATive estimate of the total lesion load of the brain.

RESULTS

Spinal motor conduction time was significantly longer in secondary progressive MS patients than controls (p < 0.001) and relapsing-remitting MS patients (p < 0.05), but did not differ between relapsing-remitting patients and controls. Spinal motor conduction times also correlated directly with EDSS scores (p < 0.001) and pyramidal functional system scores (p < 0.001). Brain lesion load (4960.3 +/- 3719.0 mm2) and the total number of lesions (67.7 +/- 37.0) in secondary progressive MS did not correlate with disability scores. For the following EPs, the frequencies of abnormalities were significantly higher in secondary progressive MS patients than relapsing-remitting patients: visual evoked potentials (p < 0.05), somatosensory evoked potentials and upper limb motor evoked potentials (p < 0.01), and brainstem auditory evoked potentials, lower limb somatosensory evoked potentials and lower limb motor evoked potentials (p < 0.001).

CONCLUSIONS

These findings suggest that disability in secondary progressive MS patients is mainly due to progressive involvement of corticospinal tract in the spinal cord.

Value of magnetic resonance imaging in assessing efficacy in clinical trials of multiple sclerosis therapies

Magnetic resonance imaging (MRI) has become an important technique for monitoring the effectiveness of putative treatments for multiple sclerosis (MS) because of its high sensitivity, objectivity, and noninvasive nature. Its importance as a surrogate measure of disease, however, is an issue that is more difficult to validate than might seem to be the case. In this review, we describe the role of MRI in the assessment of putative therapies for MS. New magnetic resonance techniques and methods of image analyses aimed at better demonstrating the nature and extent of disease are discussed, and the role of MRI in published MS therapeutic trials is examined. MRI is a frequently used secondary outcome measure for putative treatment strategies for MS. Although it is sensitive to changes in the inflammatory component of the MS disease process, poor correlation has been noted between MRI findings and long-term patient outcome. There is a widespread expectation that new magnetic resonance techniques--such as fluid-attenuated inversion recovery, magnetization transfer imaging, and magnetic resonance spectroscopy--will ultimately be useful for characterization of pathologic changes within the MS lesion and more generally of the MS disease process. Whether magnetic resonance changes seen in experimental therapies predict the long-term clinical course of the disease remains to be determined.

Specific power calculations for magnetic resonance imaging (MRI) in monitoring active relapsing-remitting multiple sclerosis (MS): implications for phase II therapeutic trials

Inhomogeneous patient samples have been used in previous studies to determine the power of magnetic resonance imaging (MRI) for trial monitoring in multiple sclerosis (MS). These power-calculations might not be applicable to the active relapsing-remitting patient who is preferably included in trials. In order to reevaluate the power-calculations for MRI in the monitoring of treatment in strictly relapsing-remitting MS and to compare the power of different trial designs we studied 12 relapsing-remitting MS patients prospectively for a median period of 12 months using monthly clinical assessments and gadolinium-enhanced MRI. A median number of two clinical relapses/patient occurred of which a median of one was treated with steroids. A median of 1.59 new lesions/scan/patient was detected (range 0-8). The total number of new active lesions correlated significantly with study period relapses (SRCC = 0.72, P = 0.023). Computer simulations using the bootstrap technique yielded mostly lower power values for a parallel groups design than in previous studies except for short follow-periods in larger samples. In this-sample the open cross-over design was found to be between 20 and 40% more powerful. Results of power-calculations are clearly sample dependent implying that for treatment trial monitoring using MRI in relapsing-remitting MS conservative sample size estimates are to be used. In an active patient group open cross-over trial designs could be a very powerful alternative to parallel groups design.

Magnetic resonance in monitoring the natural history of multiple sclerosis and the effects of treatment

In this review the main contributions of magnetic resonance (MR) techniques in the monitoring of multiple sclerosis (MS) course, both natural or modified by treatments, are presented. MR measures well correlate with short-term disease evolution and therefore their use is appropriate as primary end-points in preliminary clinical trials evaluating the effects of new treatments. In contrast, the correlation between MR measures and long-term clinical evolution in clinically definite MS is less clear, thus indicating that such measures can be used at present only as a secondary end-point in large scale definitive trials. The results coming from the clinical application of newer MR techniques with higher pathological specificity are also presented and their possible future roles in monitoring treatment aimed at preventing development of disability in MS are discussed.

Brain and spinal cord MR in benign multiple sclerosis: a follow-up study

We performed a clinical and magnetic resonance (MR) longitudinal study in 19 patients with benign multiple sclerosis (MS) to achieve a better definition of the nature of disability in MS. Patients with higher lesion volumes on conventional T2-weighted images at entry were those with more frequent relapses (p = 0.0004) and more new MR lesions (p = 0.003) during the follow up. However, 1/3 of these new lesions were located periventricularly and about 2/3 were small or intermediate in size. Two of the 11 patients (18%) with higher lesion volumes at entry developed progressive neurological deficits: in these two patients the new lesions seen on conventional T2 images had lower magnetization transfer ratios (p = 0.005) than those present in patients who remained clinically stable and a marked increase in hypointense lesion volumes on T1-weighted images was also found. Spinal cord cross-sectional area at C5 and MTR values for the seemingly normal white matter were similar to those found in normal controls. This study suggests that patients with benign MS have two different patterns of disease evolution, one characterized by very low clinical and MR activities, the other in which the lack of disabling symptomatology might be related to factors like site, size and nature of lesions. It also indicates that in patients with benign MS and high MR lesion loads the risk of developing a secondary progressive form of the disease is still present even after many years after onset.

Apparent diffusion coefficients in benign and secondary progressive multiple sclerosis by nuclear magnetic resonance

The diffusion characteristics of water in brain white matter were studied in patients with benign and secondary progressive multiple sclerosis (MS), and also in normal controls. In the MS patients, both lesions and normal-appearing white matter (NAWM) were examined to assess whether pathological differences might be evident from the diffusion behavior. A volume-selective technique was used to reduce data acquisition time and improve the reliability and precision of the measurements. This also allowed the time-dependence of apparent diffusion coefficients to be assessed. While lesions from both patient groups showed an elevated diffusion coefficient, no differences between the two groups were found. In addition, NAWM was elevated for both patient groups compared with the control group, although this was only statistically significant for patients with a benign disease course. The degree of elevation of the diffusion coefficient within the individual lesions measured was not related to the disability of the patient. Pathological differences between lesions in patients with different disease courses, if they exist, have not been detected in this study of brain water diffusion.

Correlation between brain MRI lesion volume and disability in patients with multiple sclerosis

In this study we evaluated the relationships between clinical variables and lesion volumes measured from magnetic resonance imaging (MRI) scans in a large cohort of multiple sclerosis (MS) patients. One hundred and thirty patients with MS entered the study: 36 patients had relapsing-remitting (RR), 39 benign (B), 42 secondary progressive (SP) and 13 primary progressive (PP) courses. There was a significant correlation (r = 0.3; p = 0.0006) between the total lesion load and the EDSS score when the whole cohort of patients was considered. This correlation increased (r = 0.5) when only patients with RRMS and SPMS were considered. Our data indicate that a correlation between disability and MRI lesion volume in MS exists, but its strength is moderate.

A spinal cord MRI study of benign and secondary progressive multiple sclerosis

This study was performed to achieve a better definition of the nature of the disability in multiple sclerosis (MS). Axial spinal cord magnetic resonance imaging (MRI) at C5 was obtained in 15 patients with benign MS, 17 patients with secondary progressive MS and 10 healthy controls. Patients with secondary progressive MS had smaller spinal cord cross-sectional area (P = 0.01) and transverse diameter (P = 0.006) than patients with benign MS. The degree of disability was inversely correlated with both the cross-sectional area (r = -0.6, P = 0.0018) and transverse diameter (r = -0.5, P = 0.0032) of the cord. Spinal cord atrophy was found in 7 (41%) patients with secondary progressive MS and in 2 (13%) with benign MS. These findings suggest that destructive pathology within MS lesions might play a relevant role in the development of disability in MS.

Guidelines for the use of magnetic resonance techniques in monitoring the treatment of multiple sclerosis. US National MS Society Task Force

Because of the major difficulties in measuring clinical end points in multiple sclerosis (MS) treatment trials, there has been much enthusiasm for using magnetic resonance imaging (MRI) findings as an alternative outcome. To provide international consensus guidelines for the use of MRI in MS clinical trials, a task force of the US National MS Society was convened. The recommendations of the task force are presented in this review. Given the high sensitivity for detecting pathological activity in relapsing-remitting and secondary progressive MS, monthly T2-weighted and gadolinium-enhanced brain MRI is an excellent tool for short-term exploratory trials of new agents where it serves as the primary end point; in particular, failure to demonstrate a reduction in lesion activity avoids the time, cost, and risks of a larger clinical end point study. However, conventional MRI findings have a limited correlation with disability in established MS. The primary end point of a definitive trial should therefore be clinical, although serial MRI at 6- to 12-month intervals is a useful secondary end point in providing an index of pathological progression. In trials of patients presenting with clinically isolated syndromes suggestive of MS, MRI findings can be used in the entry criteria, and as a secondary outcome measure, but conversion to clinically definite MS should be the primary outcome. The pathological substrates of irreversible disability are demyelination and axonal loss. Putative magnetic resonance markers for these processes include decreased N-acetylaspartate on proton magnetic resonance spectroscopy, decreased magnetization transfer ratios, hypointensity on T1-weighted images, and loss of short T2 water fractions, some of which relate more closely to disability than conventional MRI findings. Further technical developments should lead to more accurate quantitation, greater pathological specificity, and stronger clinical correlations.

Comparison of triple dose versus standard dose gadolinium-DTPA for detection of MRI enhancing lesions in patients with primary progressive multiple sclerosis

This study was performed to evaluate whether a triple dose of gadolinium-DTPA (Gd-DTPA) increases the sensitivity of brain MRI for detecting enhancing lesions in patients with primary progressive multiple sclerosis (PPMS). T1 weighted brain MRI was obtained for 10 patients with PPMS in two sessions. In the first session, one scan was obtained five to seven minutes after the injection of 0.1 mmol/kg Gd-DTPA (standard dose). In the second session, six to 24 hours later, one scan before and two scans five to seven minutes and one hour after the injection of 0.3 mmol/kg Gd-DTPA (triple dose) were obtained. Four enhancing lesions were detected in two patients when the standard dose of Gd-DTPA was used. The numbers of enhancing lesions increased to 13 and the numbers of patients with such lesions to five when the triple dose of Gd-DTPA was used and to 14 and six in the one hour delayed scans. The mean contrast ratio for enhancing lesions detected with the triple dose of Gd-DTPA was higher than those for lesions present in both the standard dose (P < 0.0009) and the one hour delayed scans (P = 0.04). These data indicate that with a triple dose of Gd-DTPA many more enhancing lesions can be detected in patients with PPMS. This is important both for planning clinical trials and for detecting the presence of inflammation in vivo in the lesions of such patients.