Low-Frequency Deep Brain Stimulation for Dystonia: Lower is Not Always Better.

Background: It has been observed that low-frequency stimulation (LFS) may be effective for dystonia, and the use of LFS may alleviate the need for frequent battery changes in a subset of patients. The aim of this study was to analyze LFS as a strategy to treat deep brain stimulation (DBS) patients with various dystonias.

Methods: Subjects had to receive a minimum of 6 months of clinical follow-up at the University of Florida, and were required to have a minimum of 3 months on a LFS trial. Twenty-seven dystonia DBS patients were retrospectively analyzed from the UF-INFORM database.

Results: Thirteen subjects met inclusion criteria. Of the 13 subjects, all had bilateral internal pallidum (GPi) DBS, and five (38.5%) remained with at least one side on LFS settings at their last follow up (average follow up 24 months, range 6-46 months). Within the first 6 months, six (46%) subjects remained on LFS and seven (54%) were changed to high-frequency stimulation (HFS). Those who remained on LFS settings at 6 months were characterized by shorter disease durations than those on HFS settings. There were no significant differences in dystonia severity (Unified Dystonia Rating Scale and Burke-Fahn-Marsden Dystonia Rating Scale) at baseline between the two settings. The estimated battery life for LFS (79.9±30.5) was significantly longer than for HFS settings (32.2±13.1, p<0.001).

Discussion: LFS was ultimately chosen for 38.5% of all subjects. Although this study failed to yield solid predictive features, subjects on LFS tended to have shorter disease durations.