Objective: To present a patient with segmental dystonia and sequential bilateral deep brain stimulation (DBS) in the internal pallidum (GPi) and the subthalamic nucleus (STN).

Background: Traditionally, dystonia is treated with stimulation in the GPi. In a randomized double-blinded protocol, DBS electrodes were implanted bilaterally in both the STN and the GPi. The protocol is described previously by Schjerling et al, 2013[1].

Method: A now 59-year-old woman with idiopathic isolated segmental dystonia, affecting the neck, shoulder and right arm, had a DBS operation in June 2013 with electrodes implanted bilaterally in both STN and GPi. Disease duration was 23 years, she was treated before surgery with botulinum toxin, clonazepam, anticholinergics, pethidine and oxycodone. Genetic analysis revealed no pathogenic variations in TOR1A/DYT1, CGH1/DYT5a or SGCE/DYT11. MRI of the brain was normal. Videos were recorded before surgery, 1 year after surgery with ongoing STN-DBS and approximately 2.5 years after surgery with ongoing GPi-DBS. Pre- and postoperatively the patient was rated using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Short Form Survey 36 (SF-36).

Results: Preoperatively the patient scored 25 on TWSTRS severity score and 32 on total BFMDRS. With STN-DBS approximately 1 year after surgery, TWSTRS severity score was 18 and total BFMDRS 8. Stimulation was changed to GPi. After approximately 2.5 years after DBS operation and 1.5 years with GPi-DBS, TWSTRS severity score was 12 and total BFMDRS 2. SF-36 improved significantly with both STN-DBS and GPi-DBS. STN-DBS had immediate effect on symptoms, GPi-DBS more insidious improvement. During STN-DBS, the patient suffered from dyskinesias. Contrary, GPi-DBS caused parkinsonian symptoms with hypophonia and slight bradykinesia. At long-term follow-up the patient prefer GPi-DBS. Long term effect has subsided slightly, TWSTR severity scale 9, total BFMDRS 10.5.

Conclusion: Both objectively and subjectively both GPi and the STN are effective and safe targets in this case, which highlights differing effects and side-effects with stimulation in these two targets. STN-DBS may be considered a safe and effective alternative to GPi-DBS in isolated segmental dystonia.

References: [1] Schjerling L et al. J Neurosurg 2013;119(6):1537-1545.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/alternating-bilateral-deep-brain-stimulation-in-the-internal-pallidum-and-subthalamic-nucleus-in-isolated-segmental-dystonia-a-case-report/