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

Clinical neurophysiology in the prognosis and monitoring of traumatic spinal cord injury

Preclinical studies for the repair of spinal cord injury (SCI) and potential therapies for accessing the inherent plasticity of the central nervous system (CNS) to promote recovery of function are currently moving into the translational stage. These emerging clinical trials of therapeutic interventions for the repair of SCI require improved assessment techniques and quantitative outcome measures to supplement the American Spinal Injuries Association (ASIA) Impairment Scales. This chapter attempts to identify those electrophysiological techniques that show the most promise for provision of objective and quantitative measures of sensory, motor, and autonomic function in SCI. Reviewed are: (1) somatosensory evoked potentials, including dermatomal somatosensory evoked potentials, and the electrical perceptual threshold as tests of the dorsal (posterior) column pathway; (2) laser evoked potentials and contact heat evoked potentials as tests of the anterior spinothalamic tract; (3) motor evoked potentials in limb muscles, in response to transcranial magnetic stimulation of the motor cortex as tests of the corticospinal tract, and the application of the technique to assessment of trunk and sphincter muscles; and (4) the sympathetic skin response as a test of spinal cord access to the sympathetic chain.

Prediction of long-term disability in multiple sclerosis

BACKGROUND

Little is known about the predictive value of neurophysiological measures for the long-term course of multiple sclerosis (MS).

OBJECTIVE

To prospectively investigate whether combined visual (VEP) and motor evoked potentials (MEP) allow prediction of disability over 14 years.

METHODS

A total of 30 patients with relapsing-remitting and secondary progressive MS were prospectively investigated with VEPs, MEPs and the Expanded Disability Status Scale (EDSS) at entry (T0) and after 6, 12 and 24 months, and with cranial MRI scans at entry (T2-weighted and gadolinium-enhanced T1-weighted images). EDSS was again assessed at year 14 (T4). The association between evoked potential (EP), magnetic resonance (MR) data and EDSS was measured using Spearman's rank correlation. Multivariable linear regression was performed to predict EDSS(T4) as a function of z-transformed EP-latencies(T0). The model was validated using a jack-knife procedure and the potential for improving it by inclusion of additional baseline variables was examined.

RESULTS

EDSS values(T4) correlated with the sum of z-transformed EP-latencies(T0) (rho = 0.68, p < 0.0001), but not with MR-parameters(T0). EDSS(T4) as predicted by the formula EDSS(T4) = 4.194 + 0.088 * z-score P100(T0) + 0.071 * z-score CMCT(UE, T0) correlated with the observed values (rho = 0.69, p < 0.0001).

CONCLUSION

Combined EPs allow prediction of long-term disability in small groups of patients with MS. This may have implications for the choice of monitoring methods in clinical trials and for daily practice decisions.

Computational classifiers for predicting the short-term course of Multiple sclerosis

BACKGROUND

The aim of this study was to assess the diagnostic accuracy (sensitivity and specificity) of clinical, imaging and motor evoked potentials (MEP) for predicting the short-term prognosis of multiple sclerosis (MS).

METHODS

We obtained clinical data, MRI and MEP from a prospective cohort of 51 patients and 20 matched controls followed for two years. Clinical end-points recorded were: 1) expanded disability status scale (EDSS), 2) disability progression, and 3) new relapses. We constructed computational classifiers (Bayesian, random decision-trees, simple logistic-linear regression-and neural networks) and calculated their accuracy by means of a 10-fold cross-validation method. We also validated our findings with a second cohort of 96 MS patients from a second center.

RESULTS

We found that disability at baseline, grey matter volume and MEP were the variables that better correlated with clinical end-points, although their diagnostic accuracy was low. However, classifiers combining the most informative variables, namely baseline disability (EDSS), MRI lesion load and central motor conduction time (CMCT), were much more accurate in predicting future disability. Using the most informative variables (especially EDSS and CMCT) we developed a neural network (NNet) that attained a good performance for predicting the EDSS change. The predictive ability of the neural network was validated in an independent cohort obtaining similar accuracy (80%) for predicting the change in the EDSS two years later.

CONCLUSIONS

The usefulness of clinical variables for predicting the course of MS on an individual basis is limited, despite being associated with the disease course. By training a NNet with the most informative variables we achieved a good accuracy for predicting short-term disability.

Safety and feasibility of autologous bone marrow cellular therapy in relapsing-progressive multiple sclerosis

In this phase I study, we assessed the safety and feasibility of intravenous, autologous bone marrow (BM) cell therapy, without immunosuppressive preconditioning, in six patients with clinically definite, relapsing-progressive multiple sclerosis (MS). Assessment of efficacy was a secondary objective and employed clinical disability rating scales, multimodal evoked potential (MMEP) recordings, and magnetic resonance imaging (MRI) scans. Cells were harvested, filtered and infused intravenously in a day-case procedure that was well tolerated by patients and was not associated with any serious adverse events (AEs). Over a period of 12 months after the therapy, clinical disability scores showed either no change (Extended Disability Status Score, EDSS) or improvement (MS impact scale-29, MSIS-29), and MMEPs showed neurophysiological improvement. MRI scans did not show any significant changes over a post-therapy period of 3 months. The lack of serious adverse effects and the suggestion of a beneficial effect in this small sample of patients with progressive disease justify conducting a larger phase II/III study to make a fuller assessment of the efficacy of mobilization of autologous BM in patients with MS.

Characteristics of multiple sclerosis at onset and delay of diagnosis and treatment in Spain (the Novo Study)

Multiple sclerosis (MS) is a disease supposedly of autoimmune origin, with reactivity directed against myelin antigens. From the neuropathological point of view, MS produces inflammation, demyelination and axonal and neuronal degeneration. Inflammatory phenomena are predominant in the initial phase of the disease, followed later by neurodegenerative processes. Over the last decade, early treatment, during the most inflammatory phase of the disease, has been considered the best strategy to treat MS. Accordingly, we decided to determine the periods of delay between the first symptoms and the time to the first medical visit, the time to referral to a specialised MS unit, the delay in undertaking clinical and paraclinical tests, the diagnostic criteria used and the overall delay in diagnosis and treatment. The median time from onset of first symptoms to the first visit to a physician was 19.2 months, which represented the greatest delay. The median time between this initial medical consultation and the confirmation of the diagnosis by a specialised MS unit was 5.7 months, and the overall time from symptom onset to diagnosis was 24.9 months (2.08 years). The median time between onset of the first symptoms and the decision to give the first treatment was 2 years. The most important delay was that from symptom onset to the first medical visit, with the other delays being less. Thus, it is during this initial period that greater effort is required in order to reduce the time to diagnosis, by increasing awareness of the problem of MS among the general population and primary care physicians.

Do multimodal evoked potentials add information to MRI in clinically isolated syndromes?

The role of multimodal evoked potentials (MMEPs) in establishing multiple sclerosis (MS) diagnosis and prognosis has diminished nowadays. The objective of this article is to evaluate whether MMEPs add information to MRI in identifying patients with higher risk of relapse or development of disability after a clinically isolated syndrome (CIS). Patients who underwent visual, somato-sensory and brainstem auditory evoked potentials (EPs) were identified from a cohort of consecutive CIS. Patients also underwent brain MRI within 3 months of first attack. We analysed time to second attack and to Expanded Disability Status Scale (EDSS) score of 3.0 according to number of Barkhof criteria and number of abnormal MMEPs. A complete study was performed in 245 patients who were followed for a mean of 76.4 months (interquartile range: 61 to 96). Seventy-one patients (29%) had the three EPs normal, 115 patients (47%) had one abnormal EP; 40 patients (16%) had two; and 19 patients (8%) had three abnormal EPs. Baseline MRI determined the risk for converting to clinically definite MS and correlated with disability according to previous studies. EPs individually did not modify the risk of conversion or disability. However, the presence of three abnormal EPs increased the risk of reaching moderate disability (hazard ratio 7.0; 1.4—34.9) independently of baseline MRI. In conclusion, in the presence of three abnormal EPs could help identify CIS patients with a higher risk of developing disability, independently of MRI findings. However, the utility of MMEPs is limited by the low percentage of CIS patients having the three abnormal at baseline.

Electrophysiological and clinical correlates of corpus callosum atrophy in patients with multiple sclerosis

Multiple sclerosis (MS) is an idiopathic inflammatory demyelinating disorder of the central nervous system (CNS) characterized by demyelination and axonal degeneration. Corpus callosum (CC) is commonly involved during the disease process leading to atrophy (93%). Currently, there are no established markers of disease progression and the interplay of processes leading to brain atrophy in MS remains unknown. The primary aim of this study was to assess the frequency of CC atrophy in MS patients. Furthermore, the relationship between expanded disability status scale (EDSS) and transcranial magnetic stimulation (TMS) evoked motor potentials (MEP) were assessed to capture disease effects by independent parameters. Seventy-nine MS patients and 50 controls were included and their CC volumes were assessed. Out of 79 patients, 31 patients (39·2%) had CC atrophy. The distribution of EDSS scores among the group with CC atrophy [13 (32%) patients with EDSS 0-2; 11 (58%) patients with EDSS 2-4; 19 (24%) patients with EDSS ≥4] was not statistically significant (p>0·05). MEP latency was abnormal in 34 (43%) patients, 67 (85%) patients had abnormal MEP amplitude and CMCT was abnormal in 32 (41%) patients. The relation between EDSS and MEP was statistically significant among the patient population including the subgroup of patients with CC atrophy (p<0.05). Our results lacked to provide an association between disability and CC atrophy, but there was a correlation between CC atrophy and TMS evoked motor potentials. Early evolution of axonal degeneration and brain atrophy should be considered in terms of follow-up measures to provide long-term efficiency impacting disability, progression and brain atrophy.

Neurophysiological markers

After the advent of immunomodulatory treatment in Multiple Sclerosis and after several options for early treatment have become available, the early identification of patients non responder has become a very important issue. Therefore, methods are needed for the detection of disease activity and, particularly in more advanced phases of the disease, of disease progression. Neurophysiological methods, mainly evoked potentials (EPs), are widely used in the functional assessment of sensory and motor pathways. Their usefulness in the assessment of disease activity is limited by the fact that, although they can also reveal clinically silent lesions, EPs abnormalities are present only if their corresponding pathway is involved. With this respect, EPs have been extensively replaced by magnetic resonance imaging (MRI), with the exception of optic nerve in which the sensitivity of EPs and MRI is similar. Nevertheless, EPs can be useful for the assessment of disease progression, since their abnormalities have been demonstrated to be more strictly related to disability than MRI lesion burden. With this perspective, EPs can still be useful in the identification of non responder by providing the clinician with objective functional assessment of eloquent pathways in patients with ambiguous new symptoms, for the confirmation of a dubious relapse, and by providing a method for detecting worsening of nervous conduction for the confirmation of disease progression.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE

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

Predictive role of evoked potential examinations in patients with clinically isolated optic neuritis in light of the revised McDonald criteria

To analyse the sensitivity and role of somatosensory and motor evoked potentials (EP) in patients with a first episode of clinically isolated optic neuritis (ON) in predicting the development and course of multiple sclerosis (MS), 27 patients with ON underwent EP and magnetic resonance imaging (MRI) examinations at presentation. Follow-up MRI scans were also performed (mean: 20, range: 4-48 months). It was found that 2/27 patients did not fulfill the MRI (McDonald) and clinical criteria of MS upon follow-up and also had normal EP results. Abnormal EP results were found in 6/27 patients and all of them had follow-up MRI results fulfilling the revised McDonald criteria of MS; 4/6 patients in this group were also diagnosed as clinically definitive MS. The majority, 19/27 patients had normal EP results, but went on to develop MS based on follow-up MRI results and McDonald criteria. Of these patients, however, only 3/19 converted to clinically definitive MS as well. The baseline MRI was abnormal in similar proportions (4/6 and 12/19) in these last two groups of patients. Thus, abnormal EP examinations at the first episode of ON can be considered as a predictive factor only for the earlier clinical conversion to MS - in this respect, however, being more sensitive than the initial MRI - and as such they may contribute to the delineation of the patient group who may benefit from early immunomodulatory treatment. They do not however have a predictive value for the development of MS itself as diagnosed by the McDonald criteria.

Multimodal evoked potentials measure and predict disability progression in early relapsing–remitting multiple sclerosis

In 37 patients with early relapsing–remitting multiple sclerosis (RRMS), a multimodal EP score (mEPS) and clinical scores (Expanded Disability Status Scale (EDSS) and multiple sclerosis functional composite (MSFC)) were obtained prospectively over 24 months. Changes in mEPS correlated with changes in EDSS (Spearman’s ρ = 0.69, p < 0.0001) and MSFC (ρ = –0.41, p < 0.02). Patients with relevant EDSS progression ( n = 7) showed stronger mEPS deterioration than clinically stable patients (10.8 ± 3.2 versus 1.3 ± 0.8, p < 0.005). Baseline mEPS was not significantly correlated with baseline EDSS but with EDSS after 24 months (ρ = 0.39, p < 0.02). The data suggest that serial mEPS measure and moderately predict clinically relevant disease activity in the therapeutically most relevant early stage of RRMS.

FTY720 sustains and restores neuronal function in the DA rat model of MOG-induced experimental autoimmune encephalomyelitis

FTY720 (fingolimod) is an oral sphingosine 1-phosphate (S1P) receptor modulator under development for the treatment of multiple sclerosis (MS). To elucidate its effects in the central nervous system (CNS), we compared functional parameters of nerve conductance in the DA rat model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) after preventive and therapeutic treatment. We demonstrate that prophylactic therapy protected against the emergence of EAE symptoms, neuropathology, and disturbances to visual and somatosensory evoked potentials (VEP, SEP). Moreover, therapeutic treatment from day 25 to 45 markedly reversed paralysis in established EAE and normalized the electrophysiological responses, correlating with decreased demyelination in the brain and spinal cord. The effectiveness of FTY720 in this model is likely due to several contributing factors. Evidence thus far supports its role in the reduction of inflammation and preservation of blood-brain-barrier integrity. FTY720 may also act via S1P receptors in glial cells to promote endogenous repair mechanisms that complement its immunomodulatory action.

Autologous mesenchymal bone marrow stem cells: practical considerations

A number of practical problems need to be addressed before any form of cell therapy can be widely applied in patients with multiple sclerosis. The choice of cell type is one considered elsewhere in this issue; others include the question of axon loss, that of continuing inflammatory disease activity, the mode of delivery of cells (bearing in mind the presence of innumerable lesions scattered throughout the CNS), the problem of measuring directly or indirectly the impact (if any) of an intervention, the timing of any treatment and perhaps above all the safety of the patient. All converge on the one increasingly relevant underlying question: when should stem cell treatments begin to be tested in patients? Here we review the progress in various of these practical problems in order to explain how we have arrived at the conclusion that the clinical science has progressed to a stage where the 'translation threshold' can be safely and appropriately crossed, and therefore why we have already commenced in Bristol a small pilot/feasibility study of autologous bone marrow cell treatment in patients with multiple sclerosis.