Background Mutations of the THAP1 gene were recently shown to underlie DYT6 torsion dystonia. Little is known about the response of this dystonia subtype to deep brain stimulation (DBS) at the internal globus pallidus (GPi).
Methods Retrospective analysis of the medical records of three DYT6 patients who underwent pallidal DBS by one surgical team. The Burke–Fahn–Marsden Dystonia Rating scale served as the primary outcome measure. Comparison is made to 23 patients with DYT1 dystonia also treated with GPi-DBS by the same team.
Results In contrast with the DYT1 patients who exhibited a robust and sustained clinical response to DBS, the DYT6 patients exhibited more modest gains during the first 2 years of therapy, and some symptom regression between years 2 and 3 despite adjustments to the stimulation parameters and repositioning of one stimulating lead. Microelectrode recordings made during the DBS procedures demonstrated no differences in the firing patterns of GPi neurons from DYT1 and DYT6 patients.
Discussion Discovery of the genetic mutations responsible for the DYT6 phenotype allows for screening and analysis of a new homogeneous group of dystonia patients. DYT6 patients appear to respond less robustly to GPi-DBS than their DYT1 counterparts, most likely reflecting differences in the underlying pathophysiology of these distinct genetic disorders.
Conclusions While early results of pallidal DBS for DYT6 dystonia are encouraging, further research and additional subjects are needed both to optimise stimulation parameters for this population and to elucidate more accurately their response to surgical treatment.
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Funding This study was supported in part by the Bachmann-Strauss Foundation for Dystonia and Parkinson's disease (RLA, LJO, SBB, RSP) as well as the Dystonia Medical Research Foundation (TF).
Competing interests RLA and MT receive occasional teaching honoraria from Medtronic Inc.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the institutional review boards of Beth Israel Medical Center and Mount Sinai School of Medicine.
Provenance and peer review Not commissioned; externally peer reviewed.
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