No prospective study of gamma knife thalamotomy for intractable tremor has previously been reported.  

     To clarify the safety and optimally effective conditions for performing unilateral gamma knife (GK) thalamotomy for tremors of Parkinson’s disease (PD) and essential tremor (ET), a prospective multi-institutional study was conducted by JLGK society (JLGK0301).

     In total, 72 patients (tremor dominant PD, n = 59; ET, n = 13) were registered at six institutes.

      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 isocenter. A single 130 Gy shot was applied using a 4-mm collimator. During the follow-up study, patients were examined at intervals of 3, 6, 12, 18 and 24 months postoperatively. 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.

     Final 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%). Notably, UPDRS scores showed tremor improvement (Parts II and III). Based on tremor scores of UPDRS Part III for the treated side, 58.1% of the PD patients and 60% of ET patients had score 0 (no tremor). Marked change in rigidity was statistically significant; however, gait and slow movement showed no significant change during follow-up. 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.

     This was a retrospective review.

     GK thalamotomy is an alternative treatment for intractable tremors.  

     Less invasive intervention may be beneficial to patients.