Long term follow-up results of deep brain stimulation of the Globus pallidus interna in pediatric patients with DYT1-positive dystonia

Objectives: : Primary generalized dystonia (PGD) due to heterozygous torsin 1A (TOR1A) gene mutation (DYT1) is a childhood onset dystonia with rapid deterioration of symptoms, leading to severe disability in adolescence. Globus pallidus interna deep brain stimulation (GPi-DBS) has been shown to provide significant improvement in these cases. Methods: : This was a retrospective study of TOR1A mutation positive dystonia patients, conducted at a university hospital from 2006 to 2018. Burke-Fahn-Marsden Dystonia Rating Scale (BFM-DRS) was used to evaluate dystonia severity before and after surgery. Emergence of postsurgical parkinsonian symptoms was evaluated using the Unified Parkinson Disease Rating Scale (UPDRS) part III. Montreal Cognitive Assessment (MOCA) was applied to assess cognitive dysfunction. SPSS version 18 was used for data analysis. Results: : Eleven patients entered for analysis with an average age of 22.36 (+/- 3.35) years (range: 18-28). Seven patients (63.6 %) were female. Mean follow-up period was 8.72 (+/- 0.87). Difference between baseline and most recent BFM scores was significant (disability: 10.5 +/- 4.52 versus 2.09 (+/- 3.20), P: 0.001; severity: 48.45 (+/- 17.88) versus 9.36 (+/- 10.47), P<0.001). The mean MOCA and UPDRS III scores after 7-9 years of DBS were 27.18 (+/- 2.99), and 6.09 (+/- 4.15), respectively. Conclusion: : Our experience confirms that GPi-DBS in pediatric patients with DYT1 dystonia is overall successful, with significant and long-lasting positive effects on motor and cognitive functions. There was no prominent side effect in long-term follow up.