Ventral Intermediate Nucleus Versus Zona Incerta Region Deep Brain Stimulation in Essential Tremor

The ventral intermediate nucleus (VIM) is the target of choice for Essential Tremor (ET) deep brain stimulation (DBS). Renewed interest in caudal zona incerta (cZI) stimulation for tremor control has recently emerged and some groups believe this approach may address long-term reduction of benefit seen with VIM-DBS.

To compare clinical outcomes and DBS programming in the long-term between VIM and cZI neurostimulation in ET-DBS patients.

A retrospective review of 53 DBS leads from 47 patients was performed. Patients were classified into VIM or cZI groups according to the location of the activated DBS contact. Demographics, DBS settings, and Tremor Rating Scale scores were compared between groups at baseline and yearly follow-up to 4 years after DBS. Student t-tests and analysis of variance (ANOVA) were used to compare variables between groups.

Relative to baseline, an improvement in ON-DBS tremor scores was observed in both groups from 6 months to 4 years post-DBS (p < 0.05). Although improvement was still significant at 4 years, scores from month 6 to 2 years were comparable between groups but at 3 and 4 years post-DBS the outcome was better in the VIM group (p < 0.01). Stimulation settings were similar across groups, although we found a lower voltage in the VIM group at 3 years post-DBS.

More ventral DBS contacts in the cZI region do improve tremor, however, VIM-DBS provided better long-term outcomes. Randomized controlled trials comparing cZI vs VIM targets should confirm these results.