Reduced pre-movement facilitation of motor evoked potentials in spinocerebellar degeneration

Objectives: The aim of this study was to clarify the cerebellar effects on the motor area of the cerebral cortex and abnormal control mechanisms of vo luntary movement in spinocerebellar degeneration (SCD). We used transcrania l magnetic stimulation (TMS) to study the change in the motor evoked potent ials (MEPs) before voluntary movement (pre-movement facilitation) in patien ts with SCD. Subjects and methods: Pre-movement facilitation of MEPs in subjects' muscle s was observed during their thumb movement intention. Patients with SCD, wh o showed cerebellar signs, without pyramidal or extrapyramidal signs, were examined. TMS was applied randomly during the interval between the "go" sig nal and the onset of voluntary EMG. The MEPs were recorded from the abducto r brevis pollicis muscle. Results: Patients with SCD showed a delay of task performance. In control s ubjects, the amplitude of MEPs was significantly facilitated (increased) pr ior to voluntary movement. In patients with SCD, pre-movement facilitation of the amplitude of MEPs was significantly decreased in the study with subt hreshold TMS. Conclusions: Disturbance of pre-movement facilitation in SCD may indicate i ncomplete cerebellar regulation of voluntary movements. (C) 2001 Elsevier S cience B.V. All rights reserved.