A survey of Italian cases of dystonia treated by deep brain stimulation

Aim. The aim of this study was to report on Italian cases of dystonia treated by deep brain stimulation up to the end of 2005. Methods. Retrospective survey. Presentation of data collection among all Italian neurosurgical institutions. Results. Seven out of 123 Italian neurosurgical centres were enrolled. Sixty-nine patients were operated. According to different classification criteria, cases were grouped as follows: 37 primary and 32 secondary dystonia; 61 generalized and 8 focal dystonia; 16 patients aged at onset <2 years, 22 aged 3-12 years, 14 aged 13-20 years, 17 aged >20 years. Primary dystonia (DYT) mutation 1 was identified in 21% of primary generalized dystonia. Age at surgery was <15 years in 21.7% of cases (N.=15). Mean time between clinical onset and surgery was 17 years. Globus pallidus internus (GPi) was chosen for implantation in all cases. Type of anesthesia, method of target localization, lead and implanted pulse generator (IPG) model differed among centres. Surgical complications occurred in 19% of patients, but at a higher rate (33%) in the pediatric subgroup. Stimulation parameters varied among centres, but the main scheme was 90-120 Ìs and 130 Hz. Follow-up duration ranged from 3 to 84 months (longer than 24 months in 50% of patients). Mean Burke-Fahn-Marsden scale (BFM) improvement was 42% for both severity and disability score, ranging from 0% to 92%. Improvement of at least 50% in BFM severity score has been reached by 45% of primary and 37% of secondary dystonia. Clinical results were better in the DYT1 subgroup, with 60% of cases improving more than 50%. Among secondary dystonia, the drug-induced group had very good results too. On the contrary delayed surgery and presence of comorbidity were negatively correlated to the outcome. Conclusion. In this series, primary generalized dystonia has a better outcome, especially if associated to DYT1 mutation. Among secondary dystonia, the drug-induced group has very good results. Correlation analysis of time to surgery and associated comorbidity suggests that earlier surgery is advisable.