Motor Evoked Potentials and Disability in Secondary Progressive Multiple Sclerosis

Abstract

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 mm 2 ) 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. RESUME: Potentiels evoques moteurs et invalidity dans la sclerose en plaques secondaire progressive. Introduction: Nous avons investigue les mecanismes sous-jacents a 1'invalidite dans la sclerose en plaques (SEP) au moyen des potentiels evoques multimodaux (PE), des potentiels evoques moteurs (PEM) et du temps de conduction moteur spinal chez 40 patients atteints de la forme recurrente-remittente et de 13 patients atteints de SEP secondaire progressive. L'invalidite clinique a ete evaluee au moyen de l'echelle d'invalidite elargie (EIE) et d'echelles des systemes fonctionnels. Dans la SEP secondaire progressive, 1'imagerie par resonance magnetique (RMN) a ete utilisee pour estimer semiquantitativement la charge lesionnelle totale du cerveau. R'esultats: Le temps de conduction moteur spinal etait significativement plus long chez les patients atteints de SEP secondaire progressive que chez les controles (p < 0.001) et les patients atteints de la forme recurrente-remittente (p <0 .05), mais etait semblable chez les patients atteints de la forme recurrente-remittente et les controles. Les temps de conduction moteurs spinaux etaient directement correles avec les scores EIE (p < 0.001) et les scores du systeme pyramidal (p < 0.001). La charge lesionnelle du cerveau (4960.3 ± 3719.0 mm 2 ) et le nombre total de lesions (67.7 ± 37.0) ...

Intracortical excitability in patients with relapsing–remitting and secondary progressive multiple sclerosis

“…Confirming previous reports [9], our patients' CMCT values correlated significantly with their EDSS scores. CMCT could therefore be considered a neurophysiological marker of disease and also a reliable measure for quantifying the involvement of central motor pathways and clinical deficits.…”

Corticomotor organisation and motor function in multiple sclerosis

“…Previously, a correlation between central motor conduction time and the maximum force of phasic muscle contraction in MS has been described [29]; however, a correlation was not observed with finer measures of hand dexterity (Purdue pegboard or tapping frequency). Likewise, the EDSS and a pyramidal functional system score have been shown to correlate with central motor conduction times and transcallosal inhibition in relapsing-remitting and secondary progressive MS [9,23]. In the present study, we have shown that not only corticomotor conduction, but motor threshold and MEP amplitude, are correlated with the EDSS and a dexterity task, supporting the accepted notion that the degree of conduction block in the corticospinal tract has a major role in motor disability in MS.…”

The use of transcranial magnetic stimulation in diagnosis, prognostication and treatment evaluation in multiple sclerosis

“…They reported a marked increase in CMCT in the group with progressive MS (SPMS and PPMS combined), independent of disease duration, number of spinal lesions or clinical motor deficit. Facchetti et al, (1997) also demonstrated a significant increase in CMCT, correlating with EDSS and pyramidal Functional System score, as well as a higher incidence of abnormal SSEP, MEP and BAEP in patients with SPMS when compared to those with RRMS and to healthy controls.…”