The Effect of Lesion Characteristics in MRgFUS on Tremor in Essential Tremor and Parkinson's Disease

Inclusion Criteria: * Men and women, between 18 and 80 years. * Patients who underwent the MRgFUS procedure. * Patients who are able and willing to give consent and able to attend all study visits and Radiologic follow-up examination by MRI. * A diagnosis of ET or Idiopathic PD as confirmed from clinical history and examination preformed by a movement disorders neurologist. * ET patients: tremor severity score of greater than or equal to 2 in the treated hand/arm as measured by postural or action item on the Clinical Rating Scale for Tremor (CRST). * PD patients: tremor severity score of equal or greater than 3 on either item 20 or item 21 of motor part in the Unified PD Rating Scale (UPDRS). * Substantial disability in the performance of at least two daily activities from the disability subsection of the scales UPDRS for PD patients or CRST for ET patients. * The patient must have a history of an unsatisfactory response to medical management. All patients will need to have tried and failed at least one drug. Alternatively, a patient may also qualify if tremor-suppressing medications are contraindicated due to a coexisting medical condition or drug allergy. * Stable doses of all medications for 30 days prior to study entry. Exclusion Criteria: * Patients which have not completed the MRgFUS procedure. * Patients which were diagnosed during the trial with additional diagnoses that can affect motor function, quality of life and symptoms of tremor.