“Silent event-related” fMRI reveals reduced sensorimotor activation in laryngeal dystonia

Objective: To study with fMRI the pattern of sensorimotor activation in patients with spasmodic dysphonia (laryngeal dystonia) compared to healthy controls. Methods: The authors performed fMRI measurements during vocal motor tasks in 12 patients with laryngeal dystonia and compared them with those of 12 healthy volunteers. Patients were scanned before (pre) and after (post) treatment with local injections of botulinum toxin (BTX). They examined two different motor tasks: simple vocalization inducing dystonia and whispering without appearance of dystonic symptoms. To avoid movement artifacts with oral motor tasks, the authors used a silent event-related fMRI approach involving noncontinuous sampling with no data acquisition during task performance. Results: They found reduced activation of primary sensorimotor as well as of premotor and sensory association cortices during vocalization in patients with laryngeal dystonia pre-BTX. This was partly observed also during the asymptomatic whispering task. BTX treatment did not result in reversal of reduced cortical activation. Conclusion: fMRI signal is reduced in sensorimotor cortices associated with movement of the affected body part in laryngeal dystonia, supporting a dystonic basis for this voice disorder.