Central Pathology in Patients with Spasmodic Dysphonia

Objective: Spasmodic dysphonia (SD) is a rare, primary focal dystonia that develops spontaneously, usually in mid-life. It is characterized by loss of voluntary control of vocal fold movements during speech production. This loss is due to involuntary, spasmodic contraction of laryngeal muscles. SD is a task-specific disorder that impairs conversational phonation, whereas emotional vocal expressions such as laughter and crying usually remain intact. Furthermore, SD patients rarely experience intervals during which they are completely asymptomatic, although symptoms may fluctuate in severity. The pathophysiology of SD is poorly understood. Therefore, management of the disorder is aimed toward symptom relief rather than cure. Current treatments include voice therapy, botulinum toxin injections, and surgery. Surgical treatment options include thyroplasty, myomectomy, thyroarytenoid neurectomy, and recurrent laryngeal branch nerve denervation. Researchers have proposed a central neurological basis for SD through techniques including fMRI and PET scans, postmortem histological studies, and diffusion tensor imaging. Small clusters of inflammation in the reticular formation surrounding the tractus solitarius, spinal trigeminal and ambiguus nuclei, inferior olive, and pyramids have been identified in SD patients compared to healthy controls. Reduced activations of the primary sensorimotor have been identified, as well as the premotor and sensory association. The purpose of this study was to examine whether patients with spasmodic dysphonia have an increased prevalence of central nervous system (CNS) pathologies detected on routine MRI.

Methods: Approximately 750 patient charts were screened to identify 100 SD and 200 control patients. The otologic control groups consisted of patients with otological complaints and normal voices, and the laryngologic control group consisted of patients with structural vocal fold lesions and dysphonia but with no evidence of dystonia. Each set of controls was age-matched to the SD cases. Multiple variables were collected, including but not limited to past medical and surgical history, social history, laryngeal EMG, and MRI scan results. Researchers performed analysis to determine whether a correlation exists between the location and severity of central pathology and the clinical presentation and outcomes.

Results and Conclusion