To characterize the locations of pain in patients with cervical dystonia (CD), and to assess what factors predict pain reduction following botulinum toxin injection.

Pain is a common symptom in CD patients. Botulinum toxin injected every 3 months is the mainstay of treatment and has been shown to reduce levels of pain.

We conducted an open-label, single-center observational study of CD patients who report pain and who are receiving botulinum toxin treatment. On the day of the injection (in the untreated state), patients filled out a survey evaluating primary and secondary sites of pain as indicated on a diagram, and Pain Numeric Rating Scale assessing average pain over the past 24 hours. Two weeks later, they filled out a follow-up survey (in the treated state) to evaluate whether location and pain intensity changed. We used univariate linear regression to analyze what factors associated with pain improvement.

52 patients participated in the study, and 40 completed both surveys. Most patients reported pain over the posterior musculature, especially in the areas overlying superior trapezius and levator scapulae. 21 of 40 (52.5%) patients reported improvement of pain intensity by ≥30% in the primary site. The mean improvement in pain intensity was 30.4% (SD=32.4%), with a mean improvement on Numeric Rating Scale of 2.13 (SD=2.02). 68% of patients received injections into their primary site of pain. There was no clear effect of age, sex, muscles injected, nor TWSTRS motor subscale on the degree of pain improvement. The locations of pain remained relatively stable in the post-treatment state.

We confirmed that botulinum toxin may be effective for treatment of pain related to CD. We generated a heatmap of the typical locations of pain in CD. There was a trend towards superior pain improvement in those patients who received injections into their primary site of pain.