The Bereitschaftspotential in essential tremor.
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.


CONCLUSIONS
Reduction of the late BP amplitude may serve as a surrogate marker for dysfunction of the cerebello-dentato-thalamo-cortical projection in ET.
Lu
Ming-Kuei
MK
Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taiwan.
Jung
Patrick
P
Bliem
Barbara
B
Shih
Hsu-Tzu
HT
Hseu
Yi-Ting
YT
Yang
Yu-Wan
YW
Ziemann
Ulf
U
Tsai
Chon-Haw
CH
D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003265:Contingent Negative Variation / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D004576:Electromyography / Q000379:methods; D020329:Essential Tremor / Q000473:pathology / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009068:Movement / Q000502:physiology; D009716:Numerical Analysis, Computer-Assisted; D011187:Posture / Q000502:physiology*; D011930:Reaction Time; D014953:Wrist / Q000294:innervation