Differentiation of adductor-type spasmodic dysphonia from muscle tension dysphonia by spectral analysis.

OBJECTIVES: To determine the utility of spectral analysis in the differentiation of adductor-type spasmodic dysphonia (AdSD) from muscle tension dysphonia (MTD).

STUDY DESIGN: Prospective blinded study.

METHODS: Forty-seven samples of AdSD-connected speech spectrograms from 27 subjects and 17 samples of MTD-connected speech spectrograms from 15 subjects were selected from clinical charts and de-identified. These spectrograms were reviewed independently and blindly by two speech language pathologists experienced in spectrography. The speech language pathologists designated the spectrogram as consistent with AdSD and MTD, and these designations were compared with actual clinical diagnoses.

RESULTS: The ability to differentiate AdSD from MTD with spectral analysis was 94% for rater #1 and 98% for rater #2. No MTD subjects were incorrectly diagnosed as having SD (100% specificity).

CONCLUSIONS: This study suggests that experienced speech language pathologists can distinguish AdSD from MTD with a high degree of sensitivity and specificity based on spectral analysis. Spectral analysis is especially useful in cases where perceptual analysis and clinical evaluation alone are insufficient.