Pre-lemniscal Radiation Deep Brain Stimulation for ET

Inclusion Criteria: 1. diagnosis of essential tremor based on clinical criteria established by the Essential Tremor Consortium 2. Moderate or severe axial-dominant (head/neck/voice) tremor (Tremor Rating Scale \[TRS\] face, tongue, voice, head or trunk tremor score of 2 or above) 3. May have bilateral appendicular tremor 4. Tremor refractory to at least two medications, including primidone and propranolol 5. Age between 21 and 75 6. Male or Female 7. Significant disability due to essential tremor despite medical treatment (TRS score of 2 or above in any one of the items 16-23 \[speaking, feeding other than liquids, bringing liquids to mouth, hygiene, dressing, writing, working, and social activities\]) Exclusion Criteria: 1. Tremor due to other etiologies 2. Pregnancy 3. Presence of any other neurodegenerative disease 4. Presence of significant cognitive impairment 5. Presence of any medical condition that precludes neurological surgery 6. Patients with another implanted stimulator or metallic implant, e.g. cochlear implant, cardiac pacemaker, spinal cord stimulator, aneurysm clips 7. Patients who have a known need for future MRIs using a full body radio-frequency (RF) coil or a head transmit coil that extends over the chest area or that do not comply with Medtronic's "MRI Guidelines for Medtronic Deep Brain Simulation Systems" 8. Patients with a history of seizures 9. Patients with psychiatric illness that are not well controlled 10. Patients with risk factors for intraoperative or postoperative bleeding (platelet count less than 125,000 per cubic millimeter, PT and PTT not within normal limits) 11. Patients with brain tumors