Objective: To study fast voluntary neck movements in patients with cervical dystonia (CD) before and after therapy with botulinum toxin type-A (BTX-A).
Methods: A selected sample of 15 patients with CD (with prevalent torticollis) and 13 age-matched control subjects performed both right and left rotational, and flexion and extension neck movements as fast as possible. Movements were recorded with a motion analysis system (SMART, BTS). Movement time, angular amplitude, and peak angular velocity were analyzed. In patients, rotational neck movements were pooled as "pro-dystonic" (toward the dystonic side) and "anti-dystonic" (toward the non-dystonic side). Results obtained in patients before BTX-A treatment were compared with those of control subjects. The effect of BTX-A treatment was evaluated by comparing movement performance before and after treatment.
Results: Before receiving BTX-A, patients performed pro- and anti-dystonic movements with lower peak angular velocity than control subjects. Pro-dystonic movements had a reduced angular amplitude. Anti-dystonic movements showed an abnormally long movement time. Flexion and extension movements required longer movement times, but the other kinematic variables were normal. After BTX-A injections, pro-dystonic movement amplitude and anti-dystonic movement peak angular velocity increased, whereas flexion and extension movements remained unchanged.
Conclusions: Before BTX-A injection patients with CD perform fast voluntary neck movements abnormally and BTX-A injections improved their peak velocity and amplitude.
Significance: Kinematic studies can detect specific neck movement disturbance in patients with CD, and can quantify both the severity of clinical picture and the effect of BTX-A injections in these patients.