Cervical Dystonia Severity Assessment with 3D Motion Analysis and MRI

This investigation assessed the utility of 3D motion analysis, in conjunction with radiological imaging (MRI, magnetic resonance imaging) and clinical assessment, to objectively measure head/neck motion and tremor in patients with cervical dystonia (CD). It also investigated the relationship between head/neck muscle volume and head/neck motion and posture in patients with CD. Nineteen CD patients participated in this study (age: 56.3 +/- 14.4 yrs). Subjects were clinically assessed, completed MRI and 3D movement analysis. The following movements were recorded by a Vicon system (OMG, England) with 8 MX cameras (100 Hz): relaxed posture, and head/neck range of motion in the sagittal (flex/ext), frontal (lateral flex/ext) and transverse planes (rotation). A body builder program was used to extract head/neck motion relative to the thorax and to assess tremor. MRI imaging of the Sternocleidomastoid, Splenius Capitus, Semispinalis Capitus and Levator Scapulae muscles (right and left) were captured and used to estimate muscle volumes based on the principle of summation of truncated cones. Data demonstrates that the Vicon system can record tremor associated with CD. This tremor is in the order of 1 to 2 mm with a dominant frequency at 4 Hz in the sagittal and transverse planes. Data analysis showed that muscle volume asymmetry was not associated or correlated with head-neck posture adopted by the subjects. In conclusion, 3D motion analysis can identify movement abnormality and tremor in CD and may prove valuable in identifying neck musculature for botulinum toxin treatment. There was an association between muscle volume asymmetry and head/neck posture for a subgroup of the patients, but not for the group as a whole. It may be that these two methods measure different aspects of CD severity which is known to be strongly influenced by differing rates of development prior to treatment.