Variability of cortically evoked motor responses in multiple sclerosis

Area of Science:

• Neuroscience
• Clinical Electrophysiology
• Neurology

Background:

• Multiple Sclerosis (MS) is a demyelinating disease affecting the central nervous system.
• Pyramidal tract dysfunction is a common clinical manifestation in MS.
• Electromyography (EMG) is used to assess peripheral nerve and muscle function.

Purpose of the Study:

• To investigate central motor conduction time (CMCT) and onset latency variability (MCD) in the first dorsal interosseous (FDI) muscle following magnetic motor cortex stimulation.
• To compare neurophysiological findings in normal subjects and patients with MS.
• To correlate electrophysiological abnormalities with clinical signs of pyramidal tract dysfunction.

Main Methods:

• Magnetic motor cortex stimulation was applied to 20 normal subjects and 21 MS patients.
• Electromyographic (EMG) responses of the first dorsal interosseous (FDI) muscle were recorded.
• Central motor conduction time (CMCT) and onset latency variability (mean consecutive difference; MCD) were calculated.

Main Results:

• CMCT was prolonged in 19 out of 42 muscles (12 patients) in the MS group.
• Increased onset latency variability (MCD) was observed in 20 out of 42 muscles (14 patients) with MS.
• Abnormal onset latency variability correlated with impaired fine finger movements and increased finger jerks in MS patients.

Conclusions:

• This study confirms prolonged CMCT in MS patients.
• Abnormal onset latency variability is a significant neurophysiological finding in MS.
• Onset latency variability may serve as a valuable measure of pyramidal tract function in MS.