To assess the occurrence of changing directionality in CD and the factors that influence change

The predictable patterning of muscle contractions is a characteristic feature of CD. Small case series report changes in patterning in ~1/3 of patients. Improved understanding of the presence of change in patterning and factors associated with change will improve counseling in CD patients. We hypothesize that non-focal CD [i.e. segmental] (NF-CD) is more likely to change patterning than focal (F-CD).

This is a 10-year retrospective chart review of CD patients receiving BTX within the past year. Exclusions included dystonia due to acquired etiologies and neurodegenerative conditions, incomplete medical records, and <1 year follow-up. Chi-square, t-tests and rank sum tests were used to compare characteristics between groups. The rate of change in BTX dosage reflects the average monthly increase or decrease in dose for each patient. P-values were adjusted using Sidak’s method.

31.5% (34/108) of CD patients had patterning changes. Gender, symptom onset age, presence of neck tremor, and duration of BTX injections did not differ in patients with static vs dynamic patterning. There was no difference in medication use between patients with F-CD and NF-CD; however patients with dynamic F-CD were more likely to use anticholinergics than static F-CD (40% vs 12%, p< .01). Patients with NF-CD were more likely to have changes in muscle patterning, (44% vs 23%, p<.05). Patients with pattern changes had a greater rate of change in BTX dosing over time (0.59 vs 0.20, p<0.01).

This is the largest study to date assessing CD patients and patterning change. The overall percentage of CD with pattern changes was similar to prior reports. Presence of dystonia in additional locations increases the likelihood of pattern changes. Patients with pattern changes are more likely to receive increased doses of BTX which may have cost implications.