gms | German Medical Science

Objective: Some patients with essential tremor experience habituation to chronic ventral intermediate (Vim) thalamic deep brain stimulation (DBS), leading to loss of sustained tremor control over weeks to days after an adjustment. The aim of this study was to investigate whether the distance of the active contact of the stimulation electrode to the dentate-rubro-thalamic tract (DRTT) is correlated to the recurrence of the tremor.

Method: 6 patients with essential tremor and chronic thalamic DBS were included in this retrospective study. DRTTs were determined by Diffusion Tensor Imaging (DTI) in 12 hemispheres and the distance between the active contact and the tract was measured. The correlation between these distances and the occurence of habituation effects were analysed.

Results: In patients with better and sustained tremor alleviation the distance between the active contact of the electrode was smaller (mean: 2,9mm; standard deviation: 2.2mm) compared to patients who experienced habituation of the tremor (mean: 6,1 mm; standard deviation: 3,9 mm). In one patient, suffering from unilateral habituation the electrode was stereotactically re-positioned towards the DRTT. After 12 months follow-up the tremor was more and persistently supressed.

Conclusions: Closer distances of the active contacts to the DRTT seam to alleviate tremor more pronounced and more sustained than greater interspaces. Potentially, habituation of the tremor to chronic DBS could be avoided. Further studies including more patients are mandatory to confirm our preliminary results.