Frequency of different subtypes of cervical dystonia: a prospective multicenter study according to Col-Cap concept.

Patients with cervical dystonia (CD) may present with head and/or neck movements in the coronal, sagittal or transverse plane. According to the Col-Cap concept, CD postures are classified in torti-, latero-, ante- and retrocollis/caput patterns. The frequency of these different subtypes has to be evaluated. Between January and June 2019, we examined 306 patients (55.5 ± 13.1 years, 67% female) with CD according to the Col-Cap concept. They were all treated with botulinum toxin. This prospective study took place in seven different movement disorder centers. The most common primary form was torticaput (49%), the second most common was laterocaput (16.7%). All other subtypes were less than 10% of the study population. Pure forms were observed in 16.3% of patients only. Torticaput was combined in 46% with laterocaput, and in 20.7% with retrocaput. Laterocaput was combined mainly with torticaput (45.1%), laterocollis (33.2%) or retrocaput (23.5%). Shift forms were found in 14.7%, but diagnosed only in 3.9%. On average, the patients had 2.51 (± SD 1.09) subtypes each. Tremor was observed in 55.6%. The mean number of injected muscles was 4.4 (SD 1.6). The most often injected muscles were splenius capitis (83%), sternocleidomatoideus (79.1%), and upper trapezius (58.5%). This is the first multicenter study to examine the frequency of different subtypes of CD according to the Col-Cap concept. The caput subforms are more common than the cervical types, with torticaput as the most common one. Shift forms were diagnosed less often than described. Pure forms are very rare, combinations of 2-6 subtypes are common (83.7%). Sternocleidomatoideus, splenius capitis and trapezius muscles were still injected most often, but the muscles rarely injected in the past such as levator scapulae (48.7%), obliquus capitis inferior (35.3%) and longissimus (16.7%) were considered quite often. Since optimal therapy results depend on the injection of the right muscles, the correct classification should optimize the treatment outcome.