Factors influencing botulinum toxin response in cervical dystonia: a two-center GAS-based study

Botulinum toxin (BoNT) is first-line therapy for cervical dystonia (CD), yet treatment response is heterogeneous. Patient-centered outcomes may be better captured by Goal Attainment Scaling (GAS) than by examiner-rated motor scales. We aimed to identify clinical factors influencing BoNT response in CD using GAS.

We conducted a retrospective two-center study including adults with CD treated with BoNT between January 2011 and August 2025. Treatment response was assessed using GAS T-scores. The primary outcome was achieving GAS ≥ 50 after the first session; the secondary outcome was achieving GAS > 50 in at least one session during follow-up.

Eighty-seven patients were included (74.7% female; median age 68 years; median follow-up 4 years). Patients with focal cervical dystonia were significantly more likely to achieve a GAS score ≥ 50 after the first treatment session than those with non-focal forms (segmental, multifocal, or generalized dystonia; OR 5.667; 95% CI 1.853-17.326; p = 0.001). Failure to achieve a GAS score > 50 was significantly associated with the presence of other neurological disorders (OR 0.284; p = 0.020) or concomitant movement disorders (OR 0.211; p = 0.010). Ultrasound guidance was not associated with higher GAS scores.

Focal dystonia and absence of neurological comorbidities were associated with better BoNT response. Ultrasound guidance did not confer measurable benefit in this real-world cohort. GAS may support individualized treatment evaluation in CD.