Clinical Presentation and Evolution of Isolated Focal and Segmental Dystonia in Adults – 20 Years’ Experience from a Botulinum Toxin Clinic

Background and Objectives: Isolated dystonia generally occurs due to genetic causes, and the pattern and distribution may change over time. Botulinum toxin is the first-line treatment in those with isolated focal and segmental dystonia. We aimed to describe the clinical profile and evolution of adult patients with isolated focal and segmental dystonia presenting for treatment in our botulinum neurotoxin (BoNT) clinic, and the response to treatment, over 20 years. Methods: We retrospectively reviewed the medical records of patients with isolated focal and segmental dystonia who had at least two visits in our BoNT clinic. The clinical features at presentation and during follow-up, muscles injected for each type of dystonia, the self-reported benefit with BoNT, and adverse effects were analyzed. Results: Five hundred seventy-eight patients with isolated dystonia were injected and had at least one additional follow-up. Five hundred seventeen (89.4%) had focal dystonia, and 61 (10.6%) had segmental dystonia. Cervical dystonia was the most common type. Spread to other regions was seen in 81 (14%) of patients. Those with blepharospasm as initial presentation tended to have the highest occurrence (27.3%) of spread to other parts. The mean response to BoNT was around 68%. The presence of a sensory trick and the absence of tremor were found to be predictors of good outcomes with BoNT. Conclusions: Isolated focal and segmental dystonia in adults has a good prognosis, with the majority responding well to BoNT and the dystonia remaining confined to the initially affected body part. Our study provides evidence for the response to BoNT therapy in a real-world scenario, outside of a clinical trial setting.