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.