The Bereitschaftspotential in essential tremor

Abstract Objective Essential tremor (ET) is an involuntary postural oscillation. It is unclear to which extent motor cortical activity in preparation of volitional movement is abnormal in ET. We measured the Bereitschaftspotential (BP) to address this question. Methods Given the known influence of the cerebello-dentato-thalamo-cortical projection in the generation of the BP, patients were divided into two groups, defined by purely postural tremor (ET PT ) or additional presence of intention tremor (ET IT ) and compared to healthy controls. BP was recorded during self-paced rapid wrist extension movements. Results The late BP (500–0 ms before movement onset) was increased over the mid-frontal area in ET PT , whereas it was reduced over the mid-parietal area in ET IT when compared to healthy controls. In addition, the late BP was reduced over a widespread centro-parietal area in ET IT compared to ET PT . Conclusions Findings suggest that presence vs. absence of cerebellar signs (intention tremor) in ET results in differential affection of volitional preparatory motor cortical activity. The BP increase in ET PT may indicate compensatory activity, whereas the widespread centro-parietal BP reduction in ET IT suggests dysfunction of the cerebello-dentato-thalamo-cortical projection. Significance Reduction of the late BP amplitude may serve as a surrogate marker for dysfunction of the cerebello-dentato-thalamo-cortical projection in ET.