Motor evoked potentials in multiple sclerosis patients without walking limitation: amplitude vs. conduction time abnormalities
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Published on: June 15, 2018
Andrea Gagliardo1, Francesca Galli, Antonello Grippo
1Clinical Neurophysiology Unit, Department of Neurological and Psychiatric Sciences, Careggi Hospital, University of Florence, Viale Morgagni 85, 50100 Florence, Italy. andrigl@tin.it
Abstract:
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.
Insights
Motor Evoked Potentials (MEPs) reveal subtle motor pathway dysfunction in early Multiple Sclerosis (MS) patients. Amplitude and area changes are more common than central motor conduction time alterations, suggesting their utility as early biomarkers.
Area of Science:
- Neuroscience
- Clinical Neurology
- Biomedical Engineering
Background:
- Multiple Sclerosis (MS) is a demyelinating disease affecting motor pathways.
- Assessing motor dysfunction in early-stage MS, particularly in non-ambulatory patients, is crucial for monitoring disease progression.
Purpose of the Study:
- To investigate motor pathway dysfunction in Relapsing-Remitting MS patients without walking limitations using Motor Evoked Potentials (MEPs).
- To compare MEP parameters between MS patients and healthy controls, and between different disability levels within the MS group.
- To identify early electrophysiological markers of motor pathway dysfunction in MS.
Main Methods:
- Transcranial magnetic stimulation was used to elicit MEPs in 32 MS patients (EDSS ≤ 3.5) and 20 healthy controls.
- Measured MEP parameters included motor thresholds, central motor conduction time (CMCT), and amplitude/area ratios.
- MS patients were categorized into non-disabled (ND; EDSS 0-1.5) and disabled (D; EDSS 2-3.5) groups.
Main Results:
- Significant differences in MEP values were observed between MS patients and controls.
- MEP parameters differed significantly between the ND and D groups.
- Amplitude or area alterations were found in 75% of patients, significantly higher than CMCT alterations (56.2%).
- CMCT increase was associated with reduced amplitude/area, but amplitude/area reductions also occurred with normal CMCT.
Conclusions:
- MEP amplitude and area alterations are common, even in early MS with minimal neurological signs, and may precede CMCT changes.
- These amplitude/area changes represent a significant marker of motor pathway dysfunction in MS.
- MEP amplitude and area decrease should be considered valuable biomarkers in clinical trials and follow-up studies for MS, alongside CMCT.
