Unilateral Gamma Knife radiosurgery (GKS) targeting the ventral intermediate (VIM) nucleus of the thalamus has been shown to improve contralateral tremor in patients with refractory essential tremor, with a favorable safety profile. A phase 2 trial evaluated the safety and efficacy of staged bilateral VIM-GKS in 33 patients with severe essential tremor and no significant speech or balance problems. At the 12-month follow-up, one adverse event involving hemiproprioceptive ataxia and dysarthria occurred 11 months after VIM-GKS due to a hyper-response. The mean interval between the first and second procedures was 28.7 months.

Tremor severity, disability, and functional impact scores improved significantly by 58.5%, 84.8%, and 68.6%, respectively. While four patients did not respond, the remaining 29 experienced a mean 74.4% improvement in treated upper-limb tremor. No significant worsening…