Long-term outcomes of bilateral pallidal stimulation for primary generalised dystonia.

Objectives: Bilateral pallidal stimulation is an established surgical management for patients with primary generalised dystonia (PGD). The aim of this study was to present our long-term experience of bilateral pallidal stimulation in patients with PGD.

Methods: The study population is composed of 12 patients diagnosed with of PGD (six patients with DYT-1 positive PGD and six patients with DYT-1 negative PGD). The patients were operated under general anaesthesia with no intraoperative target refinement by means of microrecording. The stereotactic technique was based on a combination of the indirect targeting technique relative to the midcommisural point coordinates and direct image-guided MRI target refinement. The formal objective assessment included the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). The BFMDRS assessment was performed before and after it annually up to five years when bilateral pallidal stimulation was switched on and compared to baseline scores. Baseline BFMDRS scores and subsequent follow-up BFMDRS scores were compared with the use of a Wilcoxon signed-rank test for matched pairs. A two-tailed probability level of 5% (p<0.05) was considered significant.

Results: At the last follow-up visit, in patients with DYT-1 positive PGD the mean preoperative functional and motor scores of the BFMDRS decreased from 14.0 and 63.75 to postoperative scores of 5.75 (p=0.068) and 22.0 (p=0.066), respectively. In patients with DYT-1 negative PGD the mean preoperative functional and motor scores of the BFMDRS decreased from 13.0 and 46.5 to postoperative scores of 5.25 (p=0.066) and 22.75 (p=0.068), respectively. The hardware-related complications affected seven patients.

Conclusions: Our results indicate that bilateral pallidal stimulation is an effective treatment for patients with DYT-1 positive and DYT-1 negative PGD. The most common hardware-related complication (DBS lead breakage) in our series was associated with the slippage of the connector to the cervical area. To prevent this complication after changing the surgical technique (suturing and placing the connector in parietal region) we did not observe these complications. Unilateral IPG failure resulted in the development of severe status dystonicus.