Objective: Recent reports on the occurrence of bradykinetic symptoms like freezing, postural instability and micrographia after chronic DBS of the GPi in patients with dystonia however stimulated a discussion on alternative targets. Here, we report on the unusual occurrence of dyskinesias upon chronic pallidal stimulation.

Background: The globus pallidus internus (GPi) is regarded as an established and safe target for deep brain stimulation (DBS) in dystonia.

Methods: A 74-year-old man with segmental dystonia including blepharospasm, orofacial dystonia and aerophagia underwent bilateral stereotactic implantation of DBS electrodes in the GPi. A stereotactic CT scan confirmed the accuracy of lead placement. Eleven years later during effective chronic DBS for dystonia he experienced gradual onset of hyperkinetic involuntary movements movements mainly concerning his arms but also his trunk.

Results: Detailed assessment in various conditions showed that off DBS resulted in an increase of both choreatic hyperkinesias and dystonia. The Burke-Fahn- Marsden Dystonia Rating Scale (BFMDRS) decreased from 15 to 28. DBS with higher frequency (130 Hz) and low amplitude stimulation improved both dystonia and hyperkinesias, on DBS at higher voltages (2,0 V) resulted in further improved dystonia but in parallel resulted in increased hyperkinesias. As a compromise between optimal stimulation for dystonia and hyperkinesias we finally choose a bipolar stimulation with a low amplitude (0,4- 0,6 V) at 130 Hz and a pulse width of 210 used

Conclusions: Chronical pallidal DBS in long term might be accompanied not only by bradykinetic symptoms but also in the rare case by hyperkinesias. Such an occurrence requires complex reassessment of stimulation programming.

WSSFN Interim Meeting, Mumbai, September 3-6, 2015.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/development-of-hyperkinesias-after-long-term-pallidal-stimulation-for-dystonia/