title: MR-guided focused ultrasound thalamotomy for essential tremor: a proof-of-concept study.
abstract: BACKGROUND
  Essential tremor is the most common movement disorder and is often refractory to medical treatment. Surgical therapies, using lesioning and deep brain stimulation in the thalamus, have been used to treat essential tremor that is disabling and resistant to medication. Although often effective, these treatments have risks associated with an open neurosurgical procedure. MR-guided focused ultrasound has been developed as a non-invasive means of generating precisely placed focal lesions. We examined its application to the management of essential tremor.
  
  
  METHODS
  Our study was done in Toronto, Canada, between May, 2012, and January, 2013. Four patients with chronic and medication-resistant essential tremor were treated with MR-guided focused ultrasound to ablate tremor-mediating areas of the thalamus. Patients underwent tremor evaluation and neuroimaging at baseline and 1 month and 3 months after surgery. Outcome measures included tremor severity in the treated arm, as measured by the clinical rating scale for tremor, and treatment-related adverse events.
  
  
  RESULTS
  Patients showed immediate and sustained improvements in tremor in the dominant hand. Mean reduction in tremor score of the treated hand was 89·4% at 1 month and 81·3% at 3 months. This reduction was accompanied by functional benefits and improvements in writing and motor tasks. One patient had postoperative paraesthesias which persisted at 3 months. Another patient developed a deep vein thrombosis, potentially related to the length of the procedure.
  
  
  CONCLUSIONS
  MR-guided focused ultrasound might be a safe and effective approach to generation of focal intracranial lesions for the management of disabling, medication-resistant essential tremor. If larger trials validate the safety and ascertain the efficacy and durability of this new approach, it might change the way that patients with essential tremor and potentially other disorders are treated.
  
  
  BACKGROUND
  Focused Ultrasound Foundation.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Krembil Neuroscience Centre, Toronto Western Hospital, University of Toronto, Toronto, ON M5T 2S8, Canada.
authors.forename: Nir
authors.initials: N
authors.lastname: Lipsman
authors.forename: Michael L
authors.initials: ML
authors.lastname: Schwartz
authors.forename: Yuexi
authors.initials: Y
authors.lastname: Huang
authors.forename: Liesly
authors.initials: L
authors.lastname: Lee
authors.forename: Tejas
authors.initials: T
authors.lastname: Sankar
authors.forename: Martin
authors.initials: M
authors.lastname: Chapman
authors.forename: Kullervo
authors.initials: K
authors.lastname: Hynynen
authors.forename: Andres M
authors.initials: AM
authors.lastname: Lozano
mesh_terms: D000368:Aged; D002170:Canada; D020329:Essential Tremor / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D013788:Thalamus / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome