• Chihiro Ohye, Yoshinori Higuchi, Toru Shibazaki, Takao Hashimoto, Toru Koyama, Tatsuo Hirai, Shinji Matsuda, Toru Serizawa, Tomokatsu Hori, Motohiro Hayashi, Taku Ochiai, Hirofumi Samura, and Katsumi Yamashiro.
• Functional and Gamma Knife Surgery Center, Hidaka Hospital, Takasaki, Japan.
• Neurosurgery. 2012 Mar 1;70(3):526-35; discussion 535-6.

BackgroundNo prospective study of gamma knife thalamotomy for intractable tremor has previously been reported.ObjectiveTo clarify the safety and optimally effective conditions for performing unilateral gamma knife (GK) thalamotomy for tremors of Parkinson disease (PD) and essential tremor (ET), a systematic postirradiation 24-month follow-up study was conducted at 6 institutions. We present the results of this multicenter collaborative trial.MethodsIn total, 72 patients (PD characterized by tremor, n = 59; ET, n = 13) were registered at 6 Japanese institutions. Following our selective thalamotomy procedure, the lateral part of the ventralis intermedius nucleus, 45% of the thalamic length from the anterior tip, was selected as the GK isocenter. A single 130-Gy shot was applied using a 4-mm collimator. Evaluation included neurological examination, magnetic resonance imaging and/or computerized tomography, the unified Parkinson's disease rating scale (UPDRS), electromyography, medication change, and video observations.ResultsFinal clinical effects were favorable. Of 53 patients who completed 24 months of follow-up, 43 were evaluated as having excellent or good results (81.1%). UPDRS scores showed tremor improvement (parts II and III). Thalamic lesion size fluctuated but converged to either an almost spherical shape (65.6%), a sphere with streaking (23.4%), or an extended high-signal zone (10.9%). No permanent clinical complications were observed.ConclusionGK thalamotomy is an alternative treatment for intractable tremors of PD as well as for ET. Less invasive intervention may be beneficial to patients.

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