Gamma Knife Thalamotomy of Medication Refractory Tremor Disorders

Abstract

To Investigate the effectiveness and safety of use of Gamma Knife radiosurgery for lesioning the Ventral Intermediate Thalamic Nucleus (VIM) for management of medication refractory tremor disorders. Patients with medication refractory tremor disorders were treated utilizing Gamma Knife radiosurgery. Patients received 130 Gy targeting the VIM nucleus utilizing a single 4 mm collimator shot. Plugs were customized to limit dose to the adjacent internal capsule. Patients were then followed for 2 years with serial standardized Fahn-Tolosa-Marin Tremor scale evaluation and any adverse events were recorded. Results from this testing were tabulated with numerical scores in four separate categories including postural, handwriting, drawing, and functioning. From 2/2013 through 8/2018, 18 patients were treated to 20 lesions. Median age was 69 (range 34-87). Sixteen treatments were directed at the left VIM nucleus to treat a right sided tremor. All of these 16 treatments were directed at the dominant hand. Two of the four patients treated to the non-dominant hand (right VIM nucleus) had also been treated previously to the contralateral side 1 year prior. Fahn-Tolosa-Marin testing was performed at 3-6 month intervals. Median follow up was 18 months (range 0-26) with one patient lost to follow up. 17/19 (89.5%)treatments demonstrated significant improvements on follow up. There were improvements in all assessed scores. Median postural scores improved from 6.0 to 3.0 (p <0.01), handwriting scores from 3.0 to 1.0 ( p<0.01), drawing scores from 9.0 to 3.0 (p<0.01), and functioning scores from 18 to 9.5 (p<0.01). Median time to improvement was 6 months (Range3-24 months). No acute or chronic adverse events were reported in any patient. Gamma Knife Thalamotomy is a safe and effective treatment for tremor disorders. With great care in the delineation of the internal capsule, no adverse events were noted. Treatments can safely be administered in a community setting. Patients who are deemed to be poor candidates for deep brain stimulation including the elderly, patients with pulmonary and cardiac comorbidities, and patients on anticoagulation should be considered for treatment.