Gamma Knife Thalamotomy for Medically-Refractory Tremor in Patients not Suitable for DBS

Keywords: tremor, thalamotomy, gamma knife, outcome, Parkinson's Disease

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     The surgical management of disabling tremor has increased with the availability of deep brain stimulation. However with an aging population and a greater population of patients living longer with medical comorbidities, non-invasive approaches for tremor care are desired.
     We evaluated outcomes in patients who had a unilateral Gamma Knife thalamotomy (GKT) for medically-refractory tremor in whom open surgery was not a viable option from 1996 to 2011.
     86 patients (88 procedures) underwent GKT for disabling tremor after medical therapy had failed. Their mean age was 71 years. Most patients had concomitant medical illnesses. Tremor was due to essential tremor (n=48; 19 < age 80 and 3 < 90), Parkinson’s Disease (29; 11 < age 80) or multiple sclerosis (11).
     A single 4-mm isocenter was used to target a maximum dose of 140 Gy to the nucleus ventralis intermedius. Items from the Fahn-Tolosa-Marin clinical tremor rating scale were used to grade tremor, handwriting and ability to drink.
     The median follow-up was 23 months. The mean tremor score was 3.28 ± 0.79 preoperatively and 1.81 ± 1.15 (p < 0.0001) after radiosurgery. The mean handwriting score was 2.78 ± 0.82 before GKT and 1.62 ± 1.04 (p < 0.0001) afterward. The mean drinking score was 3.14 ± 0.78 preoperatively and 1.80 ± 1.15 (p < 0.0001) afterward. After radiosurgery, 57 patients (66%) showed improvement in all three scores, 11 patients (13%) in two scores, two patients (2%) in just one score, and 16 patients (19%) did not show improvement in any of the scores. There were two complications involving temporary hemiparesis.
     This is a retrospective study.
     Gamma Knife thalamotomy is a safe and effective therapy for medically refractory tremor, with the majority of patients (81%) showing improvement in at least one functional score.
      Carefully performed, we think this is an excellent option for patients who cannot undergo deep brain stimulation or radiofrequency thalamotomy.


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