To evaluate the long term safety and efficacy of GK thalamotomy in patients with medically refractory ET who are not considered good candidates for Deep Brain Stimulation.

All patients with medically refractory ET who underwent GK thalamotomy at our center were included. Based on retrospective chart review, tremor severity and improvement was assessed using Clinical Global Impression Severity (CGI-S) and Improvement (CGI-I) scales at baseline (before GK procedure) and at three visits after the procedure. With a phone interview, activities of daily living were scored on Essential Tremor Rating Assessment Scale (TETRAS). Safety was assessed based on chart review of reported GK complications.

Forty seven patients were included, age 74 ± 14.38, 66% were male. Tremor severity improved from CGI-S 3.91 ± 0.75 at baseline to 2.81 ± 0.97 (p< 0.07) at 6.03 ± 1.74 months, 2.64 ± 0.79 (p <0.0060) at 11.41 ± 1.97 months, and 2.22 ± 0.67 (p <0.0060)  at 36.78 ± 31.89 months. Patients reported tremor to be ‘much improved’ CGI-I 1.95 ± 1.13 on their most recent visit. Twenty four patients were available for phone interview and reported improvement in their ADL’s based on TETRAS from 3.5 ± 0.72 (moderate to severe disability) to 2.04 ± 1.33 (mild) (p<0.001) at 32.92 ± 40.14 months. Complications were generally mild. Three patients had evidence of radiation necrosis on imaging (two developed ataxia, one had hemiparesis which responded to steroids).

In this large single center study, GK was found to provide sustained long term efficacy and safety for patients with medically refractory essential tremor. GK can be considered for patients who are not candidates for DBS.