gms | German Medical Science

Objective: STN-DBS is a well-established treatment for motor complications in Parkinson's disease (PD). The average improvement of motor symptoms amounts to 50-70%. In this respect the dorsolateral aspect of the subthalamic nucleus is considered as optimal target for stimuation. If subthalamic deep brain stimulation (STN-DBS) results in poor symptom control or adverse side effects at low stimulation threshold surgical lead revision for optimal placement must be discussed as a treatment option

Methods: 9 subjects with PD (Øage 63.7 Hoehn&Yahr St. Ø3.0) were investigated for electrode revision due to poor clinical benefit (reduction of 14.9 points in UPDRS III ( = 33.8% motor benefit) or inacceptable adverse effects. Surgical revision was considered if the primary electrodes were placed outside the dorsolateral aspect of the STN (>2mm) using MRI-CT analysis (SureTune & Elekta). Surgical techniques included explantation and reimplantation in two or one sessions or leaving initial leads in place if they had some clinical benefit.

Results: 15 electrodes were revised (6 bilateral, 3 unilateral). Main clinical indication were inadequate improvement with persistent rigidity, fluctuations and freezing (5 patients) and unbearable stimulation side effects (e.g. dysarthrophonia, ataxia, hypomania, hypersexuality). Mean vector distance between best active contacte pre-/postrevision was 4.28mm (range 8.4 – 1.6mm). The mean UPDRS-III improvement after revision Stim-On/Meds-Off were additional 17.7 points compared to the Stim-On/Meds-Off state before electrode revision (range 28 - 12, p-value 0.001). Resulting overall improvement of motor symptoms after lead revision by 41,6 points (67 %). Adverse effects of stimulation improved markedly especially hypomania and speech disturbances.

Conclusion: Unsatisfactory stimulation outcome or low-threshold adverse effects of STN-DBS can indicate unfavourable electrode position(s). If malpositioning is confirmed by MRI or MRI-CT-fusion an electrode revision may be a promising procedure according to this case series. Our findings suggest that a lead replacement aiming at the dorsolateral part of the STN is improving motor symptoms in STN-DBS poor-responders. The ideal surgical technique, single or two steps is depending on the patients' clinical needs and on surgical aspects such as primary trajectories and ideal target accessibility.