Objective: Investigate the use of injection guidance techniques and their impact on patient outcomes in the routine management of cervical dystonia (CD) with botulinum neurotoxin type A (BoNT-A).

Background: The use of guidance techniques is often recommended by experts to improve proper muscle selection and effectiveness of BoNT-A injections.

Methods: INTEREST IN CD2 (NCT01753349) is an observational study of CD subjects treated with BoNT-A. Use of injection guidance techniques was recorded at each visit (more than 1 technique could be used) and clinical outcomes were assessed using the change from baseline/first injection (V1) to end of cycle/next injection (V2) in Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score.

Results: Of the 974 subjects assessed at V1 341 (35%) had been injected with the assistance of a guidance technique, and 633 (65%) without. Within the guided subgroup, electromyography was the most common guidance technique (309 subjects); 33 used ultrasonography; 3 electrostimulation, and 1 computer tomography guidance. The proportion of injections using guidance techniques remained unchanged from V1 (341/975, 35%) to V2 (328/963, 34%). Of note, the use of guidance techniques was proportionately higher in subjects new to BoNT-A versus those previously injected (V1: 43% vs 34%; V2: 41% vs 33%). Considering the 5 most commonly injected muscles at V1, guidance was used more frequently for injections into the levator scapulae (42%) and semispinalis capitis (41%) versus splenius capitis (34%), trapezius (29%) and sternocleidomastoid (28%). The use of injection guidance had little impact on the change from V1 to V2 in TWSTRS total scores: -1.9±7.8 points in the group using a guidance technique, and -2.0±7.7 in the group not using a guidance technique.

Conclusions: These results suggest that injection guidance is used in less than half of routine BoNT-A injections for CD, and seems to have little impact on patient outcomes as measured by TWSTRS. Guidance techniques are more commonly used for patients not previously treated with BoNT-A and for deeper and/or smaller neck muscles that may be harder to locate.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/injection-guidance-use-in-the-management-of-cervical-dystonia-with-botulinum-toxin/