Abstract

Background Deep brain stimulation (DBS) surgery has emerged as an important treatment modality for patients with post-traumatic tremor. However, ambiguity regarding the optimal lead location persists. Most cases support the ventral intermediate (Vim) thalamic nucleus as the optimal target, but there is evidence to suggest that DBS of the zona incerta (ZI), the nucleus ventral oralis anterior/posterior (VOA/VOP), and/or a combination of these targets may provide superior tremor control. Objectives We reviewed the cases of six patients with disabling post-traumatic tremor treated with DBS of the VIM, ZI, and globus pallidus internus (GPi) in order to identify the optimal lead location for DBS treatment of post-traumatic tremor. Methods and Materials We performed a retrospective analysis of all patients with post-traumatic tremor treated by the Vanderbilt DBS group in the past four years. We reviewed all available records of these patients’ trauma histories, presurgical assessments, surgical procedures, and subsequent tremor responses. The final patient in this group had been treated initially with Vim DBS in 2000 but suffered ineffective long-term tremor control. His subsequent surgery, performed in 2011, allows direct comparison of Vim and ZI DBS therapy in a single subject. Results All patients sustained significant head trauma with severe diffuse axonal injury. Three patients underwent unilateral Vim DBS for contralateral tremor, one underwent bilateral Vim DBS, one underwent bilateral GPi DBS (due to dystonic posturing in addition to tremor), and one benefitted from unilateral ZI DBS after previous Vim DBS had produced ineffective long-term control. The patients treated with unilateral Vim and ZI DBS experienced good tremor reduction without side effects. The patient treated with bilateral Vim DBS experienced moderate tremor reduction, though some dystonic posturing of the hands persisted. The patient treated with bilateral GPi DBS showed moderate tremor reduction as well as improvement in his contralateral dystonia. Percentage change in tremor ranged from 14.3% to 56.5%, and clinical global impression (CGI) ranged from 2 to 3. Conclusions Unilateral or bilateral Vim DBS and bilateral GPi DBS are safe and effective treatment modalities for intractable post-traumatic tremor. Stimulation of the ZI may have some advantages over the Vim target in this population. Long-term follow-up is required to determine if clinical benefit is maintained without the development of tolerance. A randomized controlled trial will be conducted to compare the efficacy of ZI stimulation alone, VIM stimulation alone, and simultaneous stimulation.