The study will investigate Essential Tremor and Parkinson's Disease patients who underwent Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS). We will evaluate the effect of lesion characteristics on tremor and on quality of life after the procedure as compared with the baseline prior to the procedure.

The purpose of the study is to investigate the effect of lesion characteristics in ExAblate Transcranial Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) of the Vim thalamic nucleus. Clinical measures will be used to study patients suffering from medication-refractory tremor, Essential Tremor or idiopathic Parkinson's Disease.

This study is designed as a prospective, observational, and clinical study. Assessments will be made before and after MRgFUS for; clinical tremor relief, quality of life (QoL) improvements, assessment of adverse events, and correlations of these measures with the size and shape of the lesion and the surrounding edema .

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.

Patients which were diagnosed with ET or Idiopathic PD with medication refractory tremor that underwent MRgFUS procedure.

IPD