Objective: Describe a case of unilateral globus pallidus internus (GPi) deep brain stimulation (DBS) for refractory dystonia after subthalamic nucleus (STN) DBS on a Parkinson Disease (PD) patient.

Background: A small subset of STN-DBS patients experiences troublesome dyskinesia despite optimal programming and medication adjustments. Few cases reported the efficacy of simultaneous stimulation of both the GPi and STN to control it.

Method: Description of clinical case and therapeutic approach.

Results: A 65-year-old man with a 20-year-long history of idiopathic PD was submitted to bilateral STN-DBS surgery 4 years earlier due to severe motor fluctuations and presence of severe off and on dystonia. Bilateral stimulation was initiated with right STN: monopolar, 2-C+, 1.0V, 60us, 130Hz; left STN: monopolar, 10-C+, 1.8V, 60us, 130Hz; preoperative LEDD was 800 mg and postoperative was 549 mg. Following STN-DBS, control of motor symptoms was achieved during the first two years but declined thereafter. He experienced gradual recurrence of motor fluctuations, disabling and painful left hemibody on-dystonia affecting his gait and facial dystonia. In off-state, he presented a bilateral akinetic-rigid syndrome (55 on the UPDRS-III score) with left hemibody off-dystonia (13/120 on the Burke-Fahn-Marsden (BFM) Dystonia Rating Scale). In on-state, the akinetic-rigid syndrome improved but with worsening of the dystonia (24 on the BFM). Multiple attempts to optimize medication, adjust stimulation contacts and parameters failed to improve bothersome dystonia and the patient underwent rescue GPi-DBS. Right GPi stimulation was able to control akinetic-rigid syndrome without induced left hemibody dystonia. Stimulation parameters at discharge were: left STN, monopolar, 10-C+, 2V, 60μs, 130Hz; right GPi, monopolar, 2-C+, 2.5V, 60μs, 130Hz. Postoperative LEDD was 850 mg. Significant benefit was observed up until at least 18 months post-op.

Conclusion: Bilateral rescue GPi-DBS combined with STN-DBS has proven effective in few cases reports of persistent or severe dyskinesia after STN-DBS in PD patients. In this case, unilateral GPi-DBS with contralateral STN-DBS effectively improve dystonic symptoms and improved quality of life of our patient without adverse effects. This provides a proof of concept that STN-DBS may be paired with contralateral GPi-DBS, however, summary patient series are required to verify the significance of rescue GPi-DBS therapy.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/gpi-dbs-for-refractory-dystonia-4-years-after-stn-dbs-on-a-parkinsons-disease-patient/