Transient arrest of psychogenic tremor induced by contralateral ballistic movements.
One of the clinical characteristics of psychogenic tremors (PT) is the disruption or transient cessation of tremor with distractive manoeuvres, including those involving the performance of voluntary movements with the contralateral hand. Seven patients with PT, 11 patients with Parkinson's disease (PD), 10 patients with essential tremor (ET) and 10 normal volunteers mimicking tremor (NV) were requested to perform a fast unilateral wrist movement to close a switch, at the perception of a visual cue, either at rest or during maintenance of a posture. We measured the time-locked changes in frequency and amplitude occurring in tremor oscillations of the contralateral hand. The reaction time task induced a significant reduction in amplitude or cessation of contralateral tremor oscillations in PT and NV, but not in PD and ET. The effect occurred with a delay with respect to the onset of the contralateral movement without significant differences in PT versus NV (p > 0.05). The physiological mechanisms accounting for the effect seen on tremor of NV and PT may involve the interhemispheric inhibition that accompanies the execution of a unilateral motor task. Tremor circuits in patients with PD and ET may be impervious to these inhibitory commands. The documentation and quantitation of the effects of a ballistic movement on contralateral rhythmic activity are of clinical relevance for the identification of patients with PT.
Kumru
Hatice
H
Unitat d'EMG, Servei de Neurologia, Hospital Clínic, Facultad de Medicina, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, Villarroel, 170, Barcelona 08036, Spain.
Valls-Solé
Josep
J
Valldeoriola
Francesc
F
Marti
Maria José
MJ
Sanegre
Maria Teresa
MT
Tolosa
Eduardo
E
D000368:Aged; D000704:Analysis of Variance; D003463:Cues; D004576:Electromyography / Q000379:methods; D020329:Essential Tremor / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D010300:Parkinson Disease / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012146:Rest / Q000502:physiology; D013997:Time Factors; D014202:Tremor / Q000503:physiopathology*; D014953:Wrist / Q000503:physiopathology