Motor evoked potentials in multiple sclerosis patients without walking limitation: amplitude vs. conduction time abnormalities.
We used Motor Evoked Potentials (MEPs), elicited by transcranial magnetic stimulation, for assessing a motor pathways dysfunction in a selected group of Multiple Sclerosis (MS) patients, without limitation in walking. We selected 32 Relapsing Remitting MS patients, in remission phase, with EDSS < or = 3.5 and 20 healthy individuals with similar height and age distribution. We measured the following MEP parameters: motor thresholds; central motor conduction time (CMCT); amplitude and area, both expressed as MEP/CMAP ratio. Patients were divided into two groups according to the EDSS score: non-disabled group (ND; EDSS 0-1.5) and disabled group (D; EDSS 2-3.5). Mean average MEP values were significantly different in the patients compared with the controls. Even in MS patients with no or minor neurological signs (ND group), MEP parameters showed differences from controls and furthermore all MEP parameters were significantly different in the D group compared with the ND group. The 75% of the patients had an amplitude or area alteration; this percentage was significantly higher than the percentage of patients with a CMCT alteration (56.2%). In addition, CMCT increase was always associated with reduced amplitude and area, but amplitude and area alterations were present also in patients with normal CMCT. In early stages of MS, the higher percentage shown in alteration of MEP amplitudes and areas as opposed to CMCTs has not previously been highlighted in the literature. Independently of its pathogenesis (demyelination or axonal loss), the amplitude or area decrease should be considered in clinical trials and in follow-up studies, as a marker of the motor pathways dysfunction, at least as much as CMCT increase.
Gagliardo
Andrea
A
Clinical Neurophysiology Unit, Department of Neurological and Psychiatric Sciences, Careggi Hospital, University of Florence, Viale Morgagni 85, 50100 Florence, Italy. andrigl@tin.it
Galli
Francesca
F
Grippo
Antonello
A
Amantini
Aldo
A
Martinelli
Cristiana
C
Amato
Maria Pia
MP
Borsini
Walter
W
D000328:Adult; D016022:Case-Control Studies; D004185:Disability Evaluation; 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 / Q000528:radiation effects; D011930:Reaction Time / Q000502:physiology* / Q000528:radiation effects; D012189:Retrospective Studies; D012720:Severity of Illness Index; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D016138:Walking