Inclusion Criteria:  A tremor syndrome of bilateral upper limb action tremor with at least 3 years' duration  Exclusion Criteria:  Patients who have decided not to receive DBS for control of their medication-refractory essential tremor. Patients with secondary tremor (ie not Essential Tremor), such as side effects from medications, secondary to another identified neurologic disease (eg multiple sclerosis, -----Parkinson's disease, dystonia). Prior history of deep brain stimulation. Prior history of thalamotomy. A history or signs of dystonia, ataxia or parkinsonism. Task specific tremor. Orthostatic tremor. Patients with cardiac pacemakers, defibrillators, or neurostimulators. Patients who require MRI, ECT, rTMS, or diathermy. Subjects with other type of neurological disease or injury.