Differential diagnosis of spasmodic dysphonia: A kinematic perspective

Although originally considered an hysterical functional disorder, spasmodic dysphonia (SD) appears to be a heterogeneic symptom complex that is associated with several neurological diseases. Perceptual, acoustic, and electromyographic studies have not clearly differentiated the underlying pathologies that result in spasmodic phonatory dysfunction. Kinematic analysis of documented laryngeal examinations during phonation and respiration indicates that particular different movement disorders affect laryngeal function and are associated with spasmodic phonatory characteristics. The particular features of dystonia, tremors, myoclonus, and progressive supranuclear pathology should be recognized, since they may present with disease focal to the laryngeal muscles. Other movement disorders may also be associated with spasmodic phonatory abnormalities, but are less likely to be focal. Treatment of SD signs and symptoms is more likely to be successful and assessments of treatment more likely to be meaningful if the underlying pathophysiology of spasmodic phonatory behavior is identified.