The latency distribution of motor evoked potentials in patients with multiple sclerosis.
OBJECTIVE
To compare the individual latency distributions of motor evoked potentials (MEP) in patients with multiple sclerosis (MS) to the previously reported results in healthy subjects (Firmin et al., 2011).


METHODS
We applied the previously reported method to measure the distribution of MEP latencies to 16 patients with MS. The method is based on transcranial magnetic stimulation and consists of a combination of the triple stimulation technique with a method originally developed to measure conduction velocity distributions in peripheral nerves.


RESULTS
MEP latency distributions in MS typically showed two peaks. The individual MEP latency distributions were significantly wider in patients with MS than in healthy subjects. The mean triple stimulation delay extension at the 75% quantile, a proxy for MEP latency distribution width, was 7.3 ms in healthy subjects and 10.7 ms in patients with MS.


CONCLUSIONS
In patients with MS, slow portions of the central motor pathway contribute more to the MEP than in healthy subjects. The bimodal distribution found in healthy subjects is preserved in MS.


CONCLUSIONS
Our method to measure the distribution of MEP latencies is suitable to detect alterations in the relative contribution of corticospinal tract portions with long MEP latencies to motor conduction.
Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Switzerland.
Lea
L
Firmin
Samuel
S
Müller
Kai M
KM
Rösler
D000328:Adult; D016022:Case-Control Studies; D004525:Efferent Pathways / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000503:physiopathology*; D009431:Neural Conduction / Q000502:physiology; D010525:Peripheral Nerves / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods