The clinical features of functional dysphonia.

OBJECTIVE: This report aims to study the prevalence of features of laryngeal muscle tension in a population of patients with functional dysphonia (FD) and nondysphonic control subjects. STUDY
DESIGN: Prospective control-blinded, cross-sectional study.
METHODS: We reported on a prospective control-blinded, cross-sectional study of the prevalence of the six features described by Van Lawrence and the six features incorporated in the Morrison-Rammage classification. A senior laryngologist and senior speech pathologist independently rated sound-free, random-sequence video laryngoscopies of 51 patients with FD and 52 nondysphonic control subjects. Assessments were made of the presence or absence of the 12 laryngoscopic features of laryngeal dysfunction, and an overall rating made of the vocal technique as "normal" or "abnormal."
RESULTS: More than 60% of the control population demonstrated 1 or more of the 12 features of hyperfunction. There was no significant difference in the prevalence of the six Van Lawrence features, the six Morrison-Rammage features, or the total number of abnormal features between patients with FD and control subjects. On overall assessment, both assessors noted a high prevalence (50% and 36%, respectively) of abnormal vocal technique in the control population. There was no statistical difference in the total number of abnormal features observed between patients with FD and control subjects. Positive predictive value calculations showed that the presence of a clinical feature, at best, presented a 75% chance of correctly identifying a patient with FD and, at worst, a 50% chance.
CONCLUSION: The laryngoscopy features commonly associated with FD are frequently prevalent in the nondysphonic population and fail to distinguish patients with FD from normal subjects.