Transcranial Stimulation for Essential Tremor

Essential tremor (ET) is a movement disorder characterized by tremor of both hands, and often head and voice, affecting approximately 4.8-6.7 million individuals over the age of 40 in the United States alone. Hand tremor can limit basic activities of daily living like feeding, drinking, writing and dressing. While medications can be effective for tremor, they are often poorly tolerated due to their sedative or neuronal activity depressant properties. Surgical options such as deep brain stimulation of the ventral intermedius thalamus (Vim DBS) can be highly effective but its invasive nature limits its popularity. Noninvasive brain stimulation has demonstrated the ability to reduce tremor but precisely where to target brain stimulation to achieve the best results is currently unknown.

Repetitive transcranial magnetic stimulation (rTMS) enables noninvasive, selective and sustained modulation of specific neural networks, and can lead to clinical benefits in debilitating neurologic and psychiatric disorders, including medication-resistant depression, paresis following stroke or traumatic brain injury, Parkinson's disease, or dementia. There is also recent evidence that rTMS of the cerebellum can relieve hand tremor due to essential tremor. TMS uses electromagnetic induction to generate controlled currents in targeted brain structures that can be identified and defined using MRI-based neuronavigation. TMS is safe if appropriate guidelines are adhered to. To date, the impact of rTMS on ET has not been sufficiently established, but pilot studies offer promising results.

The investigators are testing whether MRI-guided neuronavigated cerebellar paired pulse TMS demonstrates abnormal physiologic measures in ET subjects compared to controls and whether there is reduction of tremor via cerebellar rTMS in patients with ET. The investigators plan to collect imaging, functional and neurophysiological assessments before and after the rTMS to identify the mechanistic underpinnings of rTMS-induced changes in tremor and cerebello-cortical inhibition.