Modulation of symptomatic palatal tremor by magnetic stimulation of the motor cortex.
OBJECTIVE
Magnetic stimulation of the motor cortex can be used to determine the involvement of the cortex in rhythmic movement disorders. Symptomatic palatal tremor (SPT) is thought to come from a pacemaker that is relatively resistant to internal and external stimulation. In this study, we investigated the effect of magnetic stimulation of motor cortex on SPT.


METHODS
Five male patients, aged 67-79 years, with SPT after brain stem infarction or hemorrhage, all had a synchronous mouth angle twitch with the palatal movement. Electromyographic activity was recorded with a monopolar needle electrode from orbicularis oris. In experiment 1, transcranial magnetic stimulation (TMS) was delivered at 200% motor threshold (MT) to reset SPT. In experiment 2, the effect of TMS intensities was studied at 80-240% MT in two SPT patients. To determine the influence of the TMS, we used the resetting index (RI).


RESULTS
TMS reset the tremor in all 5 SPT patients at 200% MT with RIs of 0.86-0.96. The latency of the tremor reappearance after TMS was longer than the pre-stimulus tremor interval, and the intervals between the subsequent tremor bursts were also prolonged. The degree of tremor resetting was closely correlated with the magnetic stimulus intensity and the latency of the tremor reappearance after TMS.


CONCLUSIONS
Stimulation of the motor cortex may modulate the generator of SPT.
Chen
J T
JT
Department of Neurology, The Neurological Institute, Taipei Veterans General Hospital, 201. Section II, Shih-Pai Road, Pei-tou District, 11217, Taipei, Taiwan.
Yu
H Y
HY
Wu
Z A
ZA
Kao
K P
KP
Hallett
M
M
Liao
K K
KK
D000368:Aged; D001683:Biological Clocks; D020526:Brain Stem Infarctions / Q000150:complications*; D004558:Electric Stimulation / Q000295:instrumentation; D006801:Humans; D008280:Magnetics; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D010156:Palatal Muscles / Q000294:innervation / Q000503:physiopathology*; D010507:Periodicity; D011930:Reaction Time; D012044:Regression Analysis; D014202:Tremor / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy