Low frequency repetitive transcranial magnetic stimulation over premotor cortex can improve cortical tremor

Objective To examine the effects of a 30 min, 1 Hz subthreshold rTMS in a case of cortical tremor which is caused by hyperexcitability of sensorimotor cortex. Methods Stimulation was applied over primary and, in a second time, over premotor cortex (M1 and PMC, respectively). Tremor was monitored by accelerometers placed on the index fingers of hands outstretched, before and several times after rTMS. Each rTMS session consisted of 1800 pulses delivered at 1 Hz with an intensity of 90% of resting motor threshold. Results PMC but not M1 stimulation led to a decrease of the postural tremor (90% decrease of acceleration total spectral power). This functional benefit was associated to normalization of electrophysiologic parameters (short-interval intracortical inhibition and cortical silent period duration). Moreover, when stimulating PMC during two daily sessions, improvement of the tremor was longer than one day stimulation and this benefit was associated with functional improvement. Conclusions This study shows that 1 Hz rTMS over premotor cortex can improve cortical tremor. Significance These results raise the interest of the motor cortical stimulation as a possible therapeutic target for treatment of action tremor.