Background. Thalamotomy is effective in alleviating tremor in Parkinson's 
disease (PD). Methods. Seven PD patients, mean age 59.4 ± 9.8 years (range, 
46-74) with a mean disease duration of 5.4 ± 2.8 years (range, 2-10) suffering 
from severe refractory tremor, underwent ventral intermediate nucleus 
thalamotomy using MRI guided focused ultrasound (MRgFUS), an innovative 
technology that enables noninvasive surgery. Results. Tremor stopped in the 
contralateral upper extremity in all patients immediately following treatment. 
Total UPDRS decreased from 37.4 ± 12.2 to 18.8 ± 11.1 (p = 0.007) and PDQ-39 
decreased from 42.3 ± 16.4 to 21.6 ± 10.8 (p = 0.008) following MRgFUS. These 
effects were sustained (mean follow-up 7.3 months). Adverse events during MRgFUS 
included headache (n = 3), dizziness (n = 2), vertigo (n = 4), and lip 
paresthesia (n = 1) and following MRgFUS were hypogeusia (n = 1), unsteady 
feeling when walking (n = 1, resolved), and disturbance when walking tandem (n = 
1, resolved). Conclusions. Thalamotomy using MRgFUS is safe and effective in PD 
patients. Large randomized studies are needed to assess prolonged efficacy and 
safety.