Management of Secondary Poor Response to Botulinum Toxin in Cervical Dystonia: A Multicenter Audit.

[BACKGROUND] Botulinum toxin A (BoNT-A) is an effective treatment for cervical dystonia. Nevertheless, up to 30% to 40% patients discontinue treatment, often because of poor response. The British Neurotoxin Network (BNN) recently published guidelines on the management of poor response to BoNT-A in cervical dystonia, but adherence to these guidelines has not yet been assessed.

[OBJECTIVES] To assess adherence to and usefulness of BNN guidelines in clinical practice.

[METHODS] We undertook a retrospective medical notes audit of adherence to the BNN guidelines in 3 United Kingdom tertiary neurosciences centers.

[RESULTS] Of 76 patients identified with poor response, 42 (55%) had a suboptimal response and, following BNN recommendations, 25 of them (60%) responded to adjustments in BoNT dose, muscle selection or injection technique. Of the remaining 34 (45%) patients with no BoNT response, 20 (59%) were tested for immune resistance, 8 (40%) of whom showed resistance. Fourteen (18%) of all patients were switched to BoNT-B, and 27 (36%) were referred for deep brain stimulation surgery. In those not immune to BoNT-A, clinical improvement was seen in 5 (41%) after adjusting their dose and injection technique.

[CONCLUSION] Our audit shows that optimizing BoNT dose or injection strategy largely led to improvements in those with suboptimal response and in those reporting no response without resistance. It would be helpful to standardize investigations of potential resistance in those with no therapeutic response.