Multimodal evoked potentials for functional quantification and prognosis in multiple sclerosis

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. 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. 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 aseline 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 %. 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

Isokinetic strength and fatigability in patients with multiple sclerosis. The relationship between gait speed and isokinetic parameters

peer reviewedIntroduction Multiple sclerosis (MS) is a chronic disease characterized by inflammation and demyelisation of the central nervous system. Decline of muscular performances, fatigue, weakness and spasticity are the most common and disabling symptoms characterizing this neurological disease. Undoubtedly, objective assessments of muscle function would be relevant to deliver the most appropriate treatment and to appraise possible training effects resulting from rehabilitation. The purposes of this study were to assess muscle strength and fatigue of knee flexors and extensors in patients with multiple sclerosis by means of an isokinetic dynamometer. Relations between isokinetic results and gait speed were also investigated. Methods Eight patients (49 +/- 7 years old) suffering from multiple sclerosis (with unaided gait) were included in this study. Bilateral knee flexor and extensor performances were assessed using a Cybex Norm dynamometer. Maximal isokinetic strength was measured at 60°/s (3 repetitions) and 180°/s (5 repetitions). Thereafter, patients performed a fatigue protocol consisting in 30 successive maximal-intensity knee flexions and extensions at 180°/s angular velocity. Fatigue was analysed using the cumulative work parameter (corresponding to the sum of work developed through the 30 movements) and a fatigue index (ratio between work developed during 3 last contractions and 3 first contractions). Gait speeds corresponded to the time necessary to subject for walking at maximal speed on a 7.62 m and 100 m long walkway. Results Isokinetic parameters (strength and fatigue) appeared to be decreased in MS patients comparatively to normative data [1]. Knee flexors/extensors ratio was reduced for some patients, yet MS subjects displayed no significant bilateral asymmetry, suggesting a bilateral weakness process. Significant negative correlations (- 0.76 < r < - 0.95, p < 0.05) between gait speeds (measured through a 7.62 m and 100 m long walkway) and hamstring isokinetic parameters (peak torque and cumulative work) were observed. In contrast, we did not find any correlation between gait speed and quadriceps isokinetic performances, except for the correlation between gait speed on 100 m long walkway and fatigue index (0.78 < r < 0.89, p < 0.05). Discussion and conclusion Objective evaluation of muscle performance deficiencies in patients with MS appears essential for designing a successful rehabilitation program. However, no consensus has been established with regard to the most relevant isokinetic protocol modalities for assessing patients suffering form central nervous system lesions. Our preliminary results underlined that gait speed was negatively correlated to hamstring isokinetic parameters (strength and cumulative work). Interestingly, no patient included in our study reported increased symptoms such as spasticity during or after the test, indicating that MS patients are able to perform strength and fatigue isokinetic assessments. References [1] Maquet D, Croisier JL, Renard C, Crielaard JM. Muscle performance in patients with fibromyalgia, Joint Bone Spine 69 :293-9, 2002

Do evoked potentials contribute to the functional follow-up and clinical prognosis of multiple sclerosis?

The clinical variability and complexity of multiple sclerosis (MS) challenges the individual clinical course prognostication. This study aimed to find out whether multimodal evoked potentials (EP) correlate with the motor components of multiple sclerosis functional composite (MSFCm) and predict clinically relevant motor functional deterioration. One hundred MS patients were assessed at baseline (T0) and about 7.5 years later (T1), with visual, somatosensory and motor EP and rated on the Expanded Disability Status Scale (EDSS) and the MSFCm, including the 9 Hole Peg Test and the Timed 25 Foot Walk (T25FW). The Spearman correlation coefficient (rS) was used to evaluate the cross-sectional and longitudinal relationship between EP Z scores and clinical findings. The predictive value of baseline electrophysiological data for clinical worsening (EDSS, 9-HPT, T25FW, MSFCm) during follow-up was assessed by logistic regression analysis. Unlike longitudinal correlations, cross-sectional correlations between EP Z scores and clinical outcomes were all significant and ranged between 0.22 and 0.67 (p\0.05). The global EP Z score was systematically predictive of EDSS and MSFCm worsening over time (all p\0.05). EP latency was a better predictor than amplitude, although weaker than latency and amplitude aggregation in the global EP Z score. The study demonstrates that EP numerical scores can be used for motor function monitoring and outcome prediction in patients with MS

La technique de la triple stimulation est elle un meilleur outil de quantification des dysfonctions motrices par rapport aux potentiels évoqués moteurs classqiues dans le domaine de la sclérose en plaques?

The triple stimulation technique (TST) was rarely used in multiple sclerosis (MS). This study aimed to compare TST and motor evoked potentials (MEP) for the quantification of motor dysfunction. Central motor conduction based on MEP (four limbs) and TST (upper limbs) was assessed in 28 MS patients with a median Expanded Disability Status Scale (EDSS) of 4. EDSS, timed 25-foot walk (T25FW), grasping strength and motor components of the MS functional composite (MSFCm) were evaluated. Regression analysis was used to assess the relationship between MEP, TST and clinical findings. TST was negatively correlated with EDSS (r = -0.74, p0.05). This study evidenced the value of TST as a quantification tool of motor dysfunction. TST appeared to reflect a global disability since it was correlated not only to hand function but also to walking capacity