Perceptual Classification of Motor Speech Disorders: The Role of Severity, Speech Task, and Listener's Expertise

Abstract

Purpose: The clinical diagnosis of motor speech disorders (MSDs) is mainly based on perceptual approaches. However, studies on perceptual classification of MSDs often indicate low classification accuracy. The aim of this study was to determine in a forced-choice dichotomous decision-making task (a) how accuracy of speech-language pathologists (SLPs) in perceptually classifying apraxia of speech (AoS) and dysarthria is impacted by speech task, severity of MSD, and listener's expertise and (b) which perceptual features they use to classify. Method: Speech samples from 29 neurotypical speakers, 14 with hypokinetic dysarthria associated with Parkinson's disease (HD), 10 with poststroke AoS, and six with mixed dysarthria associated with amyotrophic lateral sclerosis (MD-FlSp [combining flaccid and spastic dysarthria]), were classified by 20 expert SLPs and 20 student SLPs. Speech samples were elicited in spontaneous speech, text reading, oral diadochokinetic (DDK) tasks, and a sample concatenating text reading and DDK. For each recorded speech sample, SLPs answered three dichotomic questions following a diagnostic approach, (a) neurotypical versus pathological speaker, (b) AoS versus dysarthria, and (c) MD-FlSp versus HD, and a multiple-choice question on the features their decision was based on. Results: Overall classification accuracy was 72% with good interrater reliability, varying with SLP expertise, speech task, and MSD severity. Correct classification of speech samples was higher for speakers with dysarthria than for AoS and higher for HD than for MD-FlSp. Samples elicited with continuous speech reached the best classification rates. An average number of three perceptual features were used for correct classifications, and their type and combination differed between the three MSDs. Conclusions: The auditory-perceptual classification of MSDs in a diagnostic approach reaches substantial performance only in expert SLPs with continuous speech samples, albeit with lower accuracy for AoS. Specific training associated with objective classification tools seems necessary to improve recognition of neurotypical speech and distinction between AoS and dysarthria.

Differentiation of Motor Speech Disorders through the Seven Deviance Scores from MonPaGe-2.0.s

“…In the PD/ALS classifications, three out of ten patients from the PD group were misclassified as ALS (while only one of the ALS was misclassified as PD). A similar error rate was found in a previous study testing perceptual classification on a set of patients overlapping in part the PD and ALS cohorts included here [ 16 ]: perceptually, the patients with hypokinetic dysarthria in PD were perceptually classified with only 72% accuracy in a PD/ALS classification. Analysis of the deviant dimensions contributing to the correct classification of patients with PD shows here that two different main features contribute the most to characterize hypokinetic dysarthria in PD: the absence of deficit in the DDK task (vs. presence in AoS, ALS and SCA), and quasi-absence (or weak) deviance on the articulatory dimension (vs. Kennedy and Wilson).…”

“…In clinical practice, the diagnosis of MSD and of its subtypes is mainly based on an auditory-perceptual approach in association with the information about the underlying neuropathology. The accuracy and inter-judge agreement of perceptual classification is nevertheless quite low [ 11 , 12 , 13 , 14 , 15 , 16 ], where even the two main subtypes (AoS versus dysarthria) are often confounded. For instance, in [ 16 ], speech and language therapists have often misclassified AoS and confused it with mixed dysarthria.…”

“…The accuracy and inter-judge agreement of perceptual classification is nevertheless quite low [ 11 , 12 , 13 , 14 , 15 , 16 ], where even the two main subtypes (AoS versus dysarthria) are often confounded. For instance, in [ 16 ], speech and language therapists have often misclassified AoS and confused it with mixed dysarthria. As for the perceptual classification of subtypes of dysarthria, some subtypes seem to be easier to identify than others.…”

“…As for the perceptual classification of subtypes of dysarthria, some subtypes seem to be easier to identify than others. For instance, hypokinetic dysarthria is often better identified perceptually than other types of dysarthria [ 15 , 16 ], while identification of “mixed” subtypes of dysarthria is quite bad [ 13 , 16 ]. These observations indicate that only some perceptual features of impaired speech are stable within a MSD category and/or easy to identify by ear, while most features or combinations of features of MSD are variable.…”

Ataxic speech disorders and Parkinson’s disease diagnostics via stochastic embedding of empirical mode decomposition

“…The DAB model split SMD into two classes, apraxia and dysarthria, and dysarthria into five clusters, flaccid, spastic, ataxic, hypokinetic, and hyperkinetic. Patients often show a combination of the five subtypes (i.e., mixed dysarthria) independently of the final diagnosis, and no speech feature (or a set) has yet to be found discriminative of the different types [1,[12][13][14]. Furthermore, this clinical system relies entirely on subjective auditory-perceptual observations requiring advanced expert clinical training [10,13].…”