A preliminary study of perceptual diversity in adductor spasmodic dysphonia

The purpose of this study was to determine if speech language pathologists could reliably identify different perceptual variants of adductor spasmodic dysphonia (ADSD) using a classification system proposed by Bastian (2009). Audio samples of sustained vowel phonation, sentence production, passage reading, and conversation were pre-recorded from 16 patients with a primary diagnosis of spasmodic dysphonia. Four speech language pathologists specializing in voice disorders listened to the audio samples and identified the ADSD variant, the presence of co-occurring tremor, and overall severity of the voice disorder. Re-rating of half of the audio samples was conducted two weeks later. Inter-judge reliability for the diagnosis of ADSD variants was fair (©§ = 0.25). All four judges agreed on variant 19% (3/16) of the time, three judges agreed 62% (10/16) of the time, and two judges 19% (3/16) of the time. Inter-judge reliability agreement for identifying co-occurring tremor was fair (©§ = 0.35). All four judges agreed on the presence of co-occurring tremor 44% (7/16) of the time. Three judges agreed 50% (8/16) of the time. Inter-judge reliability for assessing overall severity was moderate (©§ = 0.41). Four judges agreed on overall severity 38% (6/16) of the time. Three judges agreed 19% (3/16) of the time. Two judges agreed 38% (6/16) of the time. Judges disagreed on overall severity 6% of the time (1/16). Further analysis revealed three sources of diagnostic discrepancies: 1) the co-occurrence of multiple perceptual characteristics that correspond to multiple variants, 2) the ambiguity in identifying co-occurring tremor, 3) misidentification of perceptually similar characteristics. Relevant spectrographic evidence was presented. Clustering and categorizing perceptual characteristics were proposed as a more reasonable approach to capture perceptual variation of ADSD to optimize clinical diagnosis and acoustic research.