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Reduced intracortical facilitation in patients with cerebellar degeneration
J Liepert1, K Wessel, P Schwenkreis
1Department of Neurology, Ruhr-University Bochum, BG-Kliniken Bergmannsheil, Germany.
Objectives:
Transcranial magnetic stimulation (TMS) was used to study intracortical inhibitory and excitatory phenomena in patients with cerebellar ataxia.
Methods:
Motor evoked potentials (MEP) following single and paired TMS were recorded from the first dorsal interosseus muscle (FDI) in 15 patients with autosomal-dominant or idiopathic cerebellar ataxia and 15 age matched normal controls.
Results:
MEP amplitudes after paired TMS with short interstimulus intervals (1-4 ms) showing intracortical inhibition in the control group were not significantly different in the patient group. In contrast, with longer interstimulus intervals (8-20 ms) mean MEP amplitudes were significantly reduced in the patient group, indicating a decrease of intracortical facilitation. The mean postexcitatory inhibition after TMS was also significantly prolonged in the patient group.
Conclusion:
Our findings support the idea that the cerebellum physiologically exerts a facilitatory influence on the motor cortex which is decreased in patients with a cerebellar degeneration.