Improving the Efficacy of Botulinum Toxin for Cervical Dystonia: A Scoping Review

Cervical dstonia (CD) is a chronic disorder with a significant detrimental impact on quality of life, requiring long-term treatment. Intramuscular injections of botulinum neurotoxin (BoNT) every 12 to 16 weeks have become the first-line option for CD. Despite the remarkable efficacy of BoNT as a treatment for CD, a significantly high proportion of patients report poor outcomes and discontinue the treatment. The reasons that drive sub-optimal response or treatment failure in a proportion of patients include but are not limited to inappropriate muscle targets and/or BoNT dosing, improper method of injections, subjective feeling of inefficacy, and the formation of neutralizing antibodies against the neurotoxin. The current review aims to complement published research focusing on the identification of the factors that might explain the failure of BoNT treatment in CD, highlighting possible solutions to improve its outcomes. Thus, the use of the new phenomenological classification of cervical dystonia known as COL-CAP might improve the identification of the muscle targets, but more sensitive information might come from the use of kinematic or scintigraphic techniques and the use of electromyographic or ultrasound guidance might ensure the accuracy of the injections. Suggestions are made for the development of a patient-centered model for the management of cervical dystonia and to emphasize that unmet needs in the field are to increase awareness about the non-motor spectrum of CD, which might influence the perception of the efficacy from BoNT injections, and the development of dedicated rehabilitation programs for CD that might enhance its effectiveness.

Automated summary

Cervical dystonia is a chronic disorder that significantly affects quality of life and requires long-term treatment. Although botulinum neurotoxin injections are highly effective, a substantial number of patients experience poor outcomes and discontinue treatment. Factors contributing to treatment failure include improper muscle targeting, dosing, injection technique, subjective inefficacy, and the development of neutralizing antibodies. This review identifies these factors and proposes potential solutions to improve treatment outcomes, such as using a new classification system for muscle targeting and employing kinematic or scintigraphic techniques for more accurate injections. A patient-centered model and increased awareness of the non-motor aspects of cervical dystonia, as well as the development of dedicated rehabilitation programs, may enhance the effectiveness of treatment.