BACKGROUND: Gamma knife thalamotomy (GKT) has been used as a therapeutic option 
for patients with disabling tremor refractory to medications. Impressive 
improvement of tremor has been reported in the neurosurgical literature, but the 
reliability of such data has been questioned.
OBJECTIVE: To prospectively evaluate clinical outcomes after GKT for disabling 
tremor with blinded assessments.
DESIGN: Prospective study with blinded independent neurologic evaluations.
SETTING: University hospital.
PATIENTS: Consecutive patients who underwent unilateral GKT for essential tremor 
and Parkinson disease tremor at our center. These patients were unwilling or 
deemed unsuitable candidates for deep brain stimulation or other surgical 
procedures.
INTERVENTIONS: Unilateral GKT and regular follow-up evaluations for up to 30 
months, with blinded video evaluations by a movement disorders neurologist.
MAIN OUTCOME MEASURES: Clinical outcomes, as measured by the Fahn-Tolosa-Marin 
Tremor Rating Scale and activities of daily living scores, and incidence of 
adverse events.
RESULTS: From September 1, 2006, to November 30, 2008, 18 patients underwent 
unilateral GKT for essential tremor and Parkinson disease tremor at our center. 
Videos for 14 patients (11 with essential tremor, 3 with Parkinson disease 
tremor) with at least 6 months' postoperative follow-up were available for 
analysis (mean [SD] follow-up duration, 19.2 [7.3] months; range, 7-30 months). 
The Fahn-Tolosa-Marin Tremor Rating Scale activities of daily living scores 
improved significantly after GKT (P = .03; median and mean change scores, 2.5 
and 2.7 points, respectively [range of scale was 0-27]), but there was no 
significant improvement in other Fahn-Tolosa-Marin Tremor Rating Scale items (P 
= .53 for resting tremor, P = .24 for postural tremor, P = .62 for action 
tremor, P = .40 for drawing, P > .99 for pouring water, P = .89 for head 
tremor). Handwriting and Unified Parkinson's Disease Rating Scale activities of 
daily living scores tended to improve (P = .07 and .11, respectively). Three 
patients developed delayed neurologic adverse events.
CONCLUSIONS: Overall, we found that GKT provided only modest antitremor 
efficacy. Of the 2 patients with essential tremor who experienced marked 
improvement in tremor, 1 subsequently experienced a serious adverse event. 
Further prospective studies with careful neurologic evaluation of outcomes are 
necessary before GKT can be recommended for disabling tremor on a routine 
clinical basis.