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Motor evoked potentials and disability in secondary progressive multiple sclerosis
D Facchetti1, R Mai, A Micheli
1Neurophysiology Service, Salvatore Maugeri Foundation, IRCCS, Gussago, Italy.
Summary
Spinal cord involvement, not brain lesions, significantly impacts disability in secondary progressive multiple sclerosis (MS). Longer spinal motor conduction times correlate with MS severity, suggesting corticospinal tract damage is key.
Area of Science:
- Neuroscience
- Clinical Neurology
- Neurophysiology
Background:
- Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system.
- Understanding the mechanisms of disability progression in MS is crucial for effective management.
- Relapsing-remitting MS (RRMS) and secondary progressive MS (SPMS) represent distinct disease courses with varying pathophysiological underpinnings.
Purpose of the Study:
- To investigate the neurophysiological correlates of disability in patients with relapsing-remitting and secondary progressive multiple sclerosis.
- To differentiate the contributions of central (brain) and spinal cord pathways to MS-related disability.
- To evaluate the relationship between evoked potentials, motor evoked potentials, spinal motor conduction times, and clinical disability scores.
Main Methods:
- Multimodal evoked potentials (EPs), motor evoked potentials (MEPs), and spinal motor conduction time evaluations were performed on 40 RRMS and 13 SPMS patients.
- Clinical disability was assessed using the Expanded Disability Status Scale (EDSS) and functional system scales.
- Brain lesion load was quantified using magnetic resonance imaging (MRI) in SPMS patients.
Main Results:
- Spinal motor conduction time was significantly prolonged in SPMS patients compared to controls and RRMS patients, correlating with higher EDSS and pyramidal scores.
- Brain lesion load and number of lesions in SPMS did not correlate with disability scores.
- SPMS patients exhibited significantly higher frequencies of abnormalities in various evoked potentials, including visual, somatosensory, brainstem auditory, and motor evoked potentials, compared to RRMS patients.
Conclusions:
- Disability in secondary progressive multiple sclerosis is primarily associated with progressive corticospinal tract involvement within the spinal cord.
- Spinal cord conduction abnormalities are a more significant indicator of disability progression in SPMS than brain lesion load.
- Evoked potential abnormalities reflect widespread central nervous system dysfunction, with greater severity in SPMS.