Long term safety and efficacy of unilateral deep brain stimulation of the thalamus for parkinsonian tremor

The objective was to investigate the long term safety and efficacy of unila teral deep brain stimulation (DBS) of the VIM nucleus of the thalamus in Pa rkinson's disease. Twelve patients with Parkinson's disease underwent unilateral DBS of the th alamus for medication resistant tremor between 1994 and 1997. Patients were evaluated with the motor section of the unified Parkinson's disease rating scale (UPDRS) in the medication on state at baseline, 3 months, 12 months, and yearly thereafter. Three patients were lost to follow up. Nine patient s had follow up evaluations greater than 24 months and were included in the analyses. The last postsurgical follow up occurred on average 40.0 (SD 17. 2) months after surgery. Tremor scores were significantly improved with sti mulation on at the long term follow up compared with baseline. There was no significant change in UPDRS motor scores at long term follow up compared w ith baseline. There was no significant change in any stimulus parameters fr om 3 months to the long term follow up. Two patients had asymptornatic intr acerebral haemorrhages and one patient had a subcutaneous haematoma over th e implantable pulse generator site. Stimulus related adverse reactions were mild and easily controlled with changes in stimulus parameters. Two patien ts had replacement of the implantable pulse generator due to normal battery depletion, one patient had lead repositioning due to migration, and one pa tient had the lead extension wire replaced due to erosion. In conclusion, unilateral DBS of the thalamus has long term efficacy for tr eatment of tremor due to Parkinson's disease.