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Published on: December 9, 2015
Intracortical excitability in patients with relapsing-remitting and secondary progressive multiple sclerosis
1Department of Neurological Sciences, University of Rome Sapienza, Viale dell'Università, 30, 00185, Rome, Italy.
Journal of Neurology
|March 3, 2009
Summary
Transcranial magnetic stimulation (TMS) reveals altered motor cortex excitability in multiple sclerosis (MS) patients, correlating with disease severity. Intracortical excitability differs based on MS clinical course, particularly in progressive forms.
Area of Science:
- Neuroscience
- Clinical Neurology
- Neurophysiology
Background:
- Multiple sclerosis (MS) is a chronic autoimmune disease affecting the central nervous system.
- Motor cortex excitability changes are implicated in MS pathophysiology.
- Current understanding of the relationship between motor cortex excitability and MS clinical course requires further investigation.
Purpose of the Study:
- To investigate correlations between primary motor cortex excitability, measured by transcranial magnetic stimulation (TMS), and clinical severity in multiple sclerosis (MS) patients.
- To differentiate TMS-derived excitability patterns across different MS subtypes (relapsing-remitting vs. secondary progressive) and healthy controls.
Main Methods:
- Single and paired-pulse transcranial magnetic stimulation (TMS) was used to assess motor cortex excitability in 30 MS patients and 17 healthy controls.
- Key TMS parameters included motor threshold (MTh), motor-evoked potential (MEP) amplitude, intracortical inhibition (ICI), and facilitation (ICF).
- Central motor conduction time (CMCT) and Expanded Disability Status Scale (EDSS) scores were also evaluated and correlated with TMS findings and MRI lesion load.
Main Results:
- Secondary progressive MS (SPMS) patients exhibited higher EDSS scores, higher MTh, and smaller MEP amplitudes compared to relapsing-remitting MS (RRMS) patients and controls.
- All MS patients showed prolonged CMCTs. Intracortical inhibition (ICI) was significantly reduced in SPMS patients.
- EDSS scores significantly correlated with TMS measures (MEP, ICI, CMCT, MTh), but not with MRI lesion load.
Conclusions:
- Primary motor cortex excitability, as assessed by TMS, differs significantly based on the clinical course of MS.
- Intracortical excitability remains largely normal in MS patients with low disability (low EDSS) but is altered in those with higher disability.
- TMS measures, particularly those reflecting intracortical excitability, are sensitive indicators of MS clinical severity and progression.
