ExAblate Transcranial MR Guided Focused Ultrasound in the Treatment of Essential Tremor

Inclusion Criteria:

   1. Men and women, between 18 and 80 years, inclusive

   2. Patients who are able and willing to give consent and able to attend all study visits

   3. A diagnosis of ET as confirmed from clinical history and examination by a movement
   disorder neurologist

   4. Tremor refractory to adequate trials of at least two medications, one of which should
   be either propranolol or primidone. An adequate medication trial is defined as a
   therapeutic dose of each medication or the development of side effects as the
   medication dose is titrated.

   5. Vim nucleus of thalamus can be target by the ExAblate device. The Vim region of the
   thalamus must be apparent on MRI such that targeting can be performed with either
   direct visualization or by measurement from a line connecting the anterior and
   posterior commissures of the brain.

   6. Able to communicate sensations during the ExAblate MRgFUS treatment

   7. Postural or intention tremor severity score of greater than or equal to 2 in the
   dominant hand/arm as measured by the CRST rating scale.

   8. Stable doses of all medications for 30 days prior to study entry and for the duration
   of the study.

   9. May have bilateral appendicular tremor

10. Significant disability due to essential tremor despite medical treatment (CRST score
   of 2 or above in any one of the items 16-23 from the Disability subsection of the
   CRST: [speaking, feeding other than liquids, bringing liquids to mouth, hygiene,
   dressing, writing, working, and social activities])

11. Inclusion and exclusion criteria have been agreed upon by two members of the medical
   team.

Exclusion Criteria:

   1. Patients with unstable cardiac status including:

   1.1 Unstable angina pectoris on medication 1.2 Patients with documented myocardial
   infarction within six months of protocol entry 1.3 Congestive heart failure requiring
   medication (other than diuretic) 1.4 Patients on anti-arrhythmic drugs

   2. Patients exhibiting any behavior(s) consistent with ethanol or substance abuse as
   defined by the criteria outlined in the DSM-IV as manifested by one (or more) of the
   following occurring within a 12 month period:

      - Recurrent substance use resulting in a failure to fulfill major role obligations
      at work, school, or home (such as repeated absences or poor work performance
      related to substance use; substance-related absences, suspensions, or expulsions
      from school; or neglect of children or household).

      - Recurrent substance use in situations in which it is physically hazardous (such
      as driving an automobile or operating a machine when impaired by substance use)

      - Recurrent substance-related legal problems (such as arrests for substance related
      disorderly conduct)

      - Continued substance use despite having persistent or recurrent social or
      interpersonal problems caused or exacerbated by the effects of the substance (for
      example, arguments with spouse about consequences of intoxication and physical
      fights).

   3. Severe hypertension (diastolic BP > 100 on medication)

   4. Patients with standard contraindications for MR imaging such as non-MRI compatible
   implanted metallic devices including cardiac pacemakers, size limitations, etc.

   5. Known intolerance or allergies to the MRI contrast agent (e.g. Gadolinium or
   Magnevist) including advanced kidney disease

   6. Severely impaired renal function (estimated glomerular filtration rate < 45ml/min/1.73
   m2) or receiving dialysis

   7. History of abnormal bleeding and/or coagulopathy

   8. Receiving anticoagulant (e.g. warfarin) or antiplatelet (e.g. aspirin) therapy within
   one week of focused ultrasound procedure or drugs known to increase risk or hemorrhage
   (e.g. Avastin) within one month of focused ultrasound procedure

   9. Active or suspected acute or chronic uncontrolled infection

10. History of intracranial hemorrhage

11. Cerebrovascular disease (multiple CVA or CVA within 6 months)

12. Individuals who are not able or willing to tolerate the required prolonged stationary
   supine position during treatment (can be up to 4 hrs of total table time.)

13. Symptoms and signs of increased intracranial pressue (e.g. headache, nausea, vomiting,
   lethargy, and papilledema)

14. Are participating or have participated in another clinical trial in the last 30 days

15. Patients unable to communicate with the investigator and staff.

16. Presence of any other neurodegenerative disease like parkinson-plus syndromes
   suspected on neurological examination. These include: multisystem atrophy, progressive
   supranuclear palsy, dementia with Lewy bodies, and Alzheimer"s disease.

17. Anyone suspected to have the diagnosis of idiopathic Parkinson"s disease. This
   includes excluding anyone with the presence of parkinsonian features including
   bradykinesia rigidity, or postural instability. Subjects who exhibit only mild resting
   tremor but no other symptoms or signs of PD may be included.

18. Presence of significant cognitive impairment as determined with a score ≤ 24 on the
   Mini Mental Status Examination (MMSE)

19. History of immunocompromise, including patient who is HIV positive

20. Known life-threatening systemic disease

21. Patients with a history of seizures within the past year

22. Patients with current or a prior history of any psychiatric illness will be excluded.
   Any presence or history of psychosis will be excluded. Patients with mood disorders
   including depression will be excluded. For the purpose of this study, we consider a
   significant mood disorder to include any patient who has:

      - been under the care of a psychiatrist for over 3 months

      - taken antidepressant medications for greater than 6 months

      - has participated in cognitive-behavioral therapy

      - been hospitalized for the treatment of a psychiatric illness

      - received transcranial magnetic stimulation

      - received electroconvulsive therapy

23. Patients with risk factors for intraoperative or postoperative bleeding (platelet
   count less than 100,000 per cubic millimeter, PT > 14, PTT > 36 or INR > 1.3) or a
   documented coagulopathy

24. Patients with brain tumors

25. Any illness that in the investigator's opinion preclude participation in this study.

26. Pregnancy or lactation.

27. Legal incapacity or limited legal capacity.

28. Patients who have had deep brain stimulation or a prior stereotactic ablation of the
   basal ganglia