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.
FINDINGS: 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.
INTERPRETATION: 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.
FUNDING: Focused Ultrasound Foundation.