Minimal clinically important change in the Toronto Western Spasmodic Torticollis Rating Scale

Abstract Objectives To characterize the minimal clinically important change (MCIC) after treatment in cervical dystonia patients using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Methods Changes in the TWSTRS from an observational study of abobotulinumtoxinA in the routine management of cervical dystonia (NCT01314365) were analyzed using the Patient Global Impression of Change (PGIC) as anchor. Results For the overall population (N = 304, baseline TWSTRS-Total score 43.4 ± 19.4), the MCIC for the TWSTRS Total score was −11.9 (95%CI: −13.9, −10.0; p  Conclusions A 3-point change is the minimal clinically important change after treatment using TWSTRS as endpoint with higher cutoffs for greater baseline disease severity. For an average trial population (TWSTRS-total: 40–45), a 12-point decrease is clinically meaningful.