Impact of different stimulation types on orthostatic tremor.
OBJECTIVE
Primary orthostatic tremor (OT) is thought to be generated by a unique supraspinal tremor generator. Here we studied the effect of ipsi- and contralateral stimulation of the central and peripheral nervous system on OT.


METHODS
In 7 patients with primary OT, surface EMG was recorded from both tibialis anterior muscles. We performed transcranial magnetic stimulation (TMS) over the vertex, and lumbar magnetic stimulation (LMS) over the lumbar spine. Supramaximal electrical nerve stimuli were applied to the tibial or peroneal nerve at the knee. Proprioceptive input was evoked by rhythmical submaximal stimulation of the tibial, peroneal or sural nerve at the ankle.


RESULTS
TMS reset OT significantly in the contralateral as well as the ipsilateral tibialis anterior muscle. The resetting in both muscles was identical. In contrast, peripheral input by means of LMS, supra- or submaximal nerve stimulation had no impact on OT.


CONCLUSIONS
Transcranial magnetic stimulation of one cortical leg area resets OT in both legs whereas OT is not modified by any peripheral stimuli applied in this study.


CONCLUSIONS
Our results support the hypothesis of n unique supraspinal OT generator. This generator receives a modulating input from the motor cortex.
Spiegel
J
J
Department of Neurology, University of the Saarland, Homburg/Saar, D-66421 Germany. nejspi@uniklinik-saarland.de
Fuss
G
G
Krick
C
C
Dillmann
U
U
D000368:Aged; D000842:Ankle; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography; D005260:Female; D006801:Humans; D007717:Knee; D007866:Leg / Q000503:physiopathology*; D008161:Lumbosacral Region; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010543:Peroneal Nerve / Q000503:physiopathology; D011187:Posture; D011434:Proprioception; D013116:Spinal Cord / Q000503:physiopathology*; D013497:Sural Nerve / Q000503:physiopathology; D013577:Syndrome; D013979:Tibial Nerve / Q000503:physiopathology; D014202:Tremor / Q000503:physiopathology*