OBJECTIVE: To evaluate bilateral constant-current globus pallidus
internus (GPi) deep brain stimulation using an 8-contact lead.
METHODS: This prospective, open-label, single-center pilot study of 10
patients assessed the feasibility of delivering bilaterally
constant-current GPi deep brain stimulation with a novel 8-channel lead
to treat primary dystonia using standard scales as outcome measures.
RESULTS: Patients included 4 men and 6 women with a mean age of 35.8
years +/- 9.2 (range, 27-49 years). Mean age of onset was 18.5 years +/-
9.1 (range, 8-35 years), and mean disease duration was 17.3 years
(range, 7-27 years). All had primary dystonia (8 generalized dystonia, 1
segmental dystonia, 1 focal dystonia). The primary variable was
determined as 50% reduction in dystonia symptoms from baseline to the
6-month follow-up, as defined by the Burke-Fahn-Marsden Dystonia Rating
Scale. Six patients (60.0%) achieved >50% reduction in
Burke-Fahn-Marsden Dystonia Rating Scale score and were classified as
responders at the 6-month follow-up. Five of these 6 responders (83.3%)
sustained that response through the assessment at the end of the first
year. Constant-current stimulation was associated with significant
improvement in pain and quality of life in all patients. Nearly 84% of
the overall improvement occurred by the end of first month after
stimulation onset, documenting an early response to treatment. Axial
symptoms responded the best.
CONCLUSIONS: Constant-current GPi deep brain stimulation proved safe and
efficacious for treatment of primary dystonia. Motor scores improved by
54%, mostly within the first month. No phenotype-specific stimulation
could be achieved, despite the capability of the new lead to stimulate
specific loci within the GPi
