Asymmetric muscle activation pattern found in patients with cervical dystonia during cervical flex-ion movement – a pilot study

Starting point: Cervical dystonia is a common form of focal dystonia, resulting in neck pain and the development of asymmetric neck and head postures. These abnormal postures contribute to muscular impairment, muscle imbalances, and, as a result, alteration in movement patterns. This study aimed to compare the asymmetry of cervical muscle activation pattern during cervical flexion movements between individuals with cervical dystonia and healthy young subjects.Methods: Eight individuals with cervical dystonia and eight healthy participants participated in this study. We recorded muscle activation from five pairs of cervical muscles (sternocleidomastoid, scalene, trapezius, suprahyoid, and infrahyoid) using surface electromyography. Normalized cross-correlation was used to analyze the symmetry of bilateral muscle activation.Results: The results showed significant differences in muscle activation symmetry between the cervical dystonia group and healthy subjects. Notably, patients with cervical dystonia exhibited less symmetric activation in the trapezius and sternocleidomastoid muscles compared to healthy controls (p < 0.01 and p < 0.05, respectively). Additionally, the trapezius muscle on the dystonic side lacked coordination with other cervical muscles, unlike in healthy individuals who displayed better coordination. Conclusions: These findings underline the challenges faced by individuals with cervical dystonia in achieving symmetric activation and coordination of cervical muscles. Evaluating cervical muscle activation symmetry may be a valuable approach for assessing motor impairments in these patients.