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Analysis of post-stroke speech Background

F. A. Cameron | Professor C. Mackenzie, Supervisor Speech & Language Therapy, School of Psychological Sciences & Health

Dysarthria is a motor speech disorder (MSD), where impaired control of the speech apparatus compromises naturalness and intelligibility of speech. It is associated with neurological disorders such as Parkinson’s disease, Multiple Sclerosis and is a common long term outcome arising from stoke. While there is information available concerning the characteristic features of speech in dysarthria, there is a paucity of data pertaining specifically to the speech of the post-stroke dysarthria (PSD) population (Mackenzie, 2011).

Aim To determine the most commonly occurring speech features in PSD, by means of auditory-perceptual analysis of conversational samples.

Method In order to address the identified dearth of PSD speech descriptors, it was necessary to determine an appropriate auditory-perceptual rating scale by which to identify and describe the characteristics of our cohort’s speech; reliability of any such scale was also identified. Duffy’s (2012) MSD rating scale, after Darley, Aronson and Brown’s (1969) Mayo Clinic Classification System, was determined most suited for the purposes of the present study.

Participants Number: 18 Mean age: 53.9 (SD, 8.5; range, 30–63) Time post infarct: 3-48 months Composition: 14 males, 4 females Neurological data: varied topography reported, where present

Data Set    

Recording: DVD, auditory and visual Duration: three minutes Speech sample: conversational Participants: client and researcher  Researcher: MM, an SLT, common to all recordings

Adequate/corrected vision and hearing First language English Dysarthria diagnosed by referring SLT

auditory-perceptual scale, where each parameter was attributed a score of 0 – 4 (0 = normal, 1 = mild, 2 = moderate, 3 = marked, 4 = severely deviant). Inter-rater agreement was calculated and considered sufficient to embark upon rating of the PSD sample: 64% exact agreement for all three raters, 99% exact for two of three listeners.

Rating sessions: Extensive auditory perceptual training was embarked upon prior  Toward ensuring continuity of perceptual understanding two sample recordings were revisited at beginning of each session. to rating the PSD cohort (approx. 2 weeks), toward refining  Constant listening environment and equipment used. and aligning understanding of Duffy’s (2012) MSD rating scale parameters. Perceptual training consisted of individual and  Dependent on complexity, between two and three participants group listening and discussion sessions between experienced were rated each session. raters: CM and MM and inexperienced rater: FC, considering:  Perceptual parameters were clustered and considered  3 minute sample recordings of clients demonstrating varied systematically: each cluster was considered as a whole, levels of dysarthria severity/combinations of deviant speech. with listening attuned to those perceptual parameters within the present cluster.  Elsevier’s online MSD support resource On occasion, when a particular parameter could not be rated (https://evolve.elsevier.com/) confidently, it was necessary to break down the cluster and Subsequently, additional samples were independently rated on consider constituent parameters independently. the 46 task specific parameters that constitute Duffy’s (2012) The recording was listened to as many times as required.

Results 31 deviant parameters were observed within the PSD sample. Illustrated are the ten most frequently reported parameters and the extent to which they were evident, and those factors that demonstrated the most severe impairment.

Most Frequently Impaired Parameters Intelligibility* Naturalness Imprecise consonants* Monoloudness* Monopitch* Hypernasality* Weak (nasalised) pressure consonants Inappropriate speech rate* Irregular articulatory breakdowns* Breathy voice (continuous)

100% 100% 88.9% 83.3% 83.3% 72.2% 72.2% 66.7% 61.1% 55.6%

*parameters identified by other PSD studies

Most Severely Impaired Parameters Naturalness Intelligibility Imprecise consonants Monoloudness Monopitch Weak (nasalised) pressure consonants Hypernasality Breathy voice (continuous) Excess and equal stress Inappropriate Speech Rate Intra-rater agreement calculated via random selection of 1/3 of the sample, and re-rated on all parameters: exact agreement, 82.97%; to within one scale value 96.38%.

Conclusions On the basis of the present study, reduced intelligibility and naturalness, imprecise consonants, monoloudness, monopitch, hypernasality, weak (nasalised) pressure consonants, inappropriate speech rate, irregular articulatory breakdowns and breathy voice (continuous) are identified as PSD speech characteristics. When considered in the context of Darley, Aronson and Brown’s (1969) dysarthria classifications, these parameters do not align with any current classification. Importantly, while Darley, Aronson and Brown’s (1969) classifications correlate lesion location to dysarthria type, recent research indicates that PSD may not demonstrate such a direct correlation, raising the question whether the present system of classification is suitable for the PSD population (Mackenzie, 2011). This may have therapy implications regarding how we approach treatment and, as such, warrants further investigation. Comparing our results to four previous studies that addressed PSD speech, consonant imprecision is the only deviant factor identified by all studies. Several other parameters identified by these studies were observed as familiar to ours, but inconsistently*. Caution should, however, be exercised when making comparisons due to variations in sample

Darley, F. L., Aronson, A. E., & Brown, J. R. (1969). Differential diagnostic patterns of dysarthria. Journal of Speech, Language and Hearing Research, 12(2), 246. Duffy, J. R. (2012). Motor Speech Disorders: Substrates, Differential Diagnosis and Management 3rd edition. St Louis, Elsevier Mosby

type and study design: contrary to other neurological conditions, stroke is not typically associated with one primary area and it is evident that lesion location in these studies, is varied. Future, larger scale research, will allow examination of PSD profiles in relation to lesion location. Higher levels of intra- as opposed to inter-rater agreement are consistently reported throughout the literature. It is proposed that this indicates that while an individual may hold a stable idea of what a parameter implies, this may not marry with the understanding of colleagues. Despite careful pre-rating training, one re-rated sample of ‘harsh’ voice produced a four scale value disagreement due to a non-stable perception of the parameter’s definition. It is proposed that when experienced raters come to consider the sample, there will be disagreement between their rating of this parameter, and that of the inexperienced rater. It is believed that with contextual experience and growing confidence, understanding of this parameter evolved from strongly held and naïve initial perceptions. As such, caution should be exercised when considering the results of the current rating process.

Mackenzie, C. (2011). Dysarthria in stroke: A narrative review of its description and the outcome of intervention. International journal of speech-language pathology, 13(2), 125-136. Wirz, S., & Mackenzie Beck, J. (1995). Assessment of voice quality: the vocal profiles analysis scheme, pp39-55. In Wirz, S (ed.). Studies in disorders of communication: Perceptual approaches to communication disorders. London : Whurr

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