A robotic neck brace to characterize head‐neck motion and muscle electromyography in subjects with amyotrophic lateral sclerosis

OBJECTIVE: This paper presents the first study where a dynamic neck brace was used to characterize the head motion of ALS patients while concurrently recording the surface electromyography (EMG) of the neck muscles. METHODS: Eleven ALS patients and 10 age‐matched healthy controls consented and participated in an experiment. Each participant was asked to perform three single‐plane motions of the head‐neck that included flexion–extension in the sagittal plane, lateral bending in the coronal plane, and axial rotation in the transverse plane. Each motion was performed in a cycle and was repeated five times at self‐selected speeds. RESULTS: During single‐plane flexion–extension under gravity, compared to healthy peers, ALS patients showed a shorter duration to reach the maximum flexion and an earlier EMG onset in the neck extensors starting from the neutral. The brace measures in activation of the neck muscles in ALS patients were well correlated with clinically measured scores, such as the ALSFRS‐r and the FVC. The activation duration of sternocleidomastoid, used to rotate the head, correlated well with the ALSFRS‐r and FVC in ALS patients during axial rotation. INTERPRETATION: The ability to synchronously activate a pair of muscles to execute single‐plane motions in ALS patients seems to have been compromised due to the disease and potentially results in head drop. The neck brace measures can be adapted in the clinic to complement self‐reporting in ALS patients and used to assess the head drop and progress of the disease.