To determine whether primary dystonia patients with DYT1 mutation benefit from deep brain stimulation (DBS) surgery even with 10 or more years between onset of symptoms and surgery.

Several factors have been postulated to be associated with response to DBS, including disease duration prior to surgery. 

We performed a retrospective review of dystonia patients with GAG deletion in TOR1A, with greater than 10-year disease duration prior to DBS.  Preliminary analysis identified nine individuals with information regarding pre and post-operative Burke-Fahn Marsden Dystonia Rating Scale (BFMDRS) motor score and medication.  Six subjects were female.  Average age at onset was 9.9 ± 3.0(7-17) years.  Average age at DBS surgery was 41.3 ± 14.3(24-59) years; average duration between dystonia onset and surgery was 31.4 ± 14.6(14-52) years.  All cases targeted bilateral internal pallidum (GPi-DBS).

Average pre-operative BFMMS was 35.9 ± 17.6(8-70.5).  Average post-operative BFMMS was 16.1 ± 13.5(1.5-40.5).  Average decrease was 19.8 ± 15.4(5-52.5), reflecting an average BFMMS percentage improvement of 59.0 ± 29.9(11.0-87.9).   Post-operative BFMMS was performed at an average of 12 months from surgery.  While BFMMS was not necessarily performed at date of last follow-up, sustained benefit was documented in eight cases.  Mean length of follow-up was 4.1 ± 3(1-10) years.  All cases had post-operative medication reduction; two stopped all dystonia medications.  None had lead fracture or hardware malfunction; one had superficial infection. 

Our results in this relatively large cohort of DYT1 cases to undergo surgery in adulthood suggest that late presentation to DBS is still associated with significant improvement in motoric scores and medication reduction.  Thus, even for DYT1 patients with late diagnosis or other rationale for DBS delay, DBS may still be an effective treatment modality.  Further analysis of longer term outcomes is underway.  Comparison with cases that underwent surgery within ten years of disease duration is also underway.