Motor pathway abnormality in multiple sclerosis

Abstract

Background: Multiple Sclerosis (MS) is a chronic autoimmune demyelinating disease of the central nervous system. Motor symptoms represent one of the most frequent and disabling syndrome of MS. Transcranial magnetic stimulation is a technique used for the investigation of the cortico-spinal tract able to measure the modifi cation at any level of motor pathway. The aim of the study was to determine the possible correlation of motor evoked potentials (MEP) abnormalities with clinical disability and the clinical diagnostic utility of transcranial magnetic stimulation. Materials and methods: Fifty four patients with clinically definite multiple sclerosis and eighteen healthy volunteers were included in the study. Patients were divided in three subgroups according to the degree of pyramidal impairment calculated with Expanded Disability Status Scale. Transcranial magnetic stimulation (TMS) parameters were evaluated using single pulse TMS and a figure of eight coil. Parameters determined included: motor threshold, central motor conduction time (CMCT), latencies and amplitude of MEP at 120% of motor threshold. Results: Patients with MS had signifi cantly higher motor threshold, prolonged CMCT and reduced MEP amplitudes as compared to controls. Spinal cord latencies were similar in patients and controls. Conclusion: Transcranial magnetic stimulation represents a useful tool able to measure motor parameters, to reveal the motor pathways involvement and bring useful information about the degree of pyramidal dysfunction. There was a significant correlation between abnormalities of MEP parameters and clinical disability. This technique allows evaluating the status of disease and could be a measure of treatment efficiency in multiple sclerosis.

Keywords

• multiple sclerosis
• transcranial magnetic stimulation
• pyramidal disability