Stereotactic Radiosurgery for Essential Tremor and Parkinsonian Tremor

This study tests whether a non-invasive radiation treatment called stereotactic radiosurgery (a highly precise, one-time beam of radiation aimed at the brain) can safely and effectively reduce severe tremors in people with essential tremor or Parkinson's tremor that cannot be controlled with medication alone. **You may be eligible if...** - A neurologist has confirmed you have essential tremor or Parkinson's tremor that medications have not adequately controlled - You prefer radiation treatment over brain surgery or a surgically implanted device (deep brain stimulation) - You are at least 18 years old **You may NOT be eligible if...** - You have had previous radiation to the part of the brain being targeted - You cannot have an MRI scan of the brain - You have already had surgical tremor treatment on the same side of the brain - Your estimated life expectancy is less than 1 year Talk to your doctor to see if this trial is right for you.