Using a wearable, automated measure system, we propose a simple method to rate cervical dystonia (CD) motor severity.

Rating scales (TWSTRS2, CDIP58) have been recommended for use in CD. These methods are reliable and used frequently in research. The TWSTRS2 measures disability, severity and pain but excludes key aspects of CD, e.g. tremor. It can also be cumbersome to apply regularly in clinical practice. An easy-to-use, objective method of measuring dystonia severity and movement is lacking. An objective system like this would also have the advantage of allowing comparisons to be made on the effect of therapy on CD.

We used a small, wearable device integrating an accelerometer and gyroscope to measure the range of motion (ROM), velocity and smoothness of movement to capture the degree of motor severity in cervical dystonia. An initial pilot study was performed on four controls and two patients with CD. Patients with CD were measured just before toxin treatment.

The protocol takes 30 seconds per participant, using two sensors attached by straps- one for the head and one across the chest as a control. A mobile application was used for recording data. A MATLAB script was used for data processing.

Cervical flexion (ROM), rotation asymmetry (ROM) and movement velocity are parameters separating patients from controls. The log dimensionless jerk (LDJ; a measure of smoothness of movement) was the most sensitive test differentiating patients and volunteers.

Smoothness of movement is a sensitive indicator of disease severity in CD. The equipment is cheap, can be easily applied in dystonia clinics and may prove to be a more sensitive marker of disease change than the commonly used rating scales. In patients reporting poor response to treatment that is not reflected in rating scales (e.g., tremulous CD)- this device can be valuable in quantifying the extent of disability.