Dysarthria in stroke: A narrative review of its description and the outcome of interventionCatherine MackenzieUniversity of Strathclyde, Glasgow, UK Correspondence: Professor Catherine Mackenzie, School of Psychological Sciences and Health, University of Strathclyde, Southbrae Drive, Glasgow G13 1PP, UK. c.mackenziestrath.ac.ukKey words: dysarthria; stroke; managementRunning head: dysarthria in strokeAbstractDysarthria is a frequent and persisting sequel to stroke and arises from varied lesion locations. Although the presence of dysarthria is well documented, for stroke there are scant data on presentation and intervention outcome. A literature search was undertaken to evaluate a) the features of dysarthria in adult stroke populations relative to the conventional Mayo system for classification, which was developed from diverse pathological groups, and b) the current status of evidence for the effectiveness of intervention in dysarthria caused by stroke. A narrative review of results is presented.The limited data available indicate that regardless of stroke location, imprecise articulation and slow speaking rate are consistent features, and voice disturbances, especially harshness, and reduced prosodic variation are also common. Dysarthria is more prevalent in left than in right hemisphere lesions. There is a need for comprehensive, thorough analysis of dysarthria features, involving larger populations, with stroke and other variables controlled and with appropriate age-referenced control data. There is low level evidence for benefits arising from intervention in stroke related dysarthria. Because studies involve few participants, without external control, and sometimes include stroke with other aetiologies, their results lack the required weight for confident evidence-based practice. IntroductionDysarthria is a neuro-motor disorder which results from abnormalities in speed, strength, steadiness, range, tone, or accuracy of movements required for the control of speech (Duffy, 2005). The speech impairments of dysarthria relate to articulation, phonation, respiration, nasality and prosody, and affect intelligibility, audibility, naturalness, and efficiency of spoken communication. Severity ranges from absence of speech (anarthria) or complete unintelligibility to mild changes which may be evident only to the speaker or by detailed speech evaluation. In contemporary usage dysarthria does not encompass speech disorders which are caused by structural abnormalities, such as cleft palate or glossectomy. It is also distinguished from apraxia of speech, which though of neurological origin, is conceptualised as a disorder of speech motor planning or programming (Duffy, 2005). Dysarthria is reported to be the most frequently acquired speech and language disorder (Enderby & Emerson, 1995). The significance of stroke as a cause of dysarthria is evident by 22% of a 1276 speech-language pathology (SLP) dysarthria case audit series having stroke aetiology (Duffy, 2005). While there has been a fair volume of research into dysarthria in progressive disease and its treatment, notably Parkinsons disease, dysarthria in stroke tends not to receive specific attention in published texts and reports, despite its frequency. In the SLP literature, dysarthria is normally described with reference to a set of diagnostic categories (the Mayo system, Darley, Aronson & Brown, 1975), within which stroke is combined with other aetiologies. Also there has been little controlled evaluation of any intervention approach in the dysarthric stroke population. No randomised controlled trials have been identified for stroke or other non-progressive dysarthria (Sellars, Hughes & Langhorne, 2005). As with diagnostic descriptions, in treatment studies stroke has often been included with other aetiological groups, such as traumatic brain injury and progressive disorders, and even participants with communication disorders other than dysarthria. Speech-language pathologists (SLPs) who work with adults will often encounter dysarthria in the context of stroke. A synthesis of the literature on the presentation of dysarthria in adult stroke and the current evidence base for intervention is thus relevant. In view of the lack of focus on stroke dysarthia in the SLP literature, some background context is first provided, regarding the prevalence of dysarthria in stroke, variables affecting diagnosis and description, and the course of dysarthria in stroke. The prevalence of dysarthria in stroke populationsDysarthria results from varied stroke lesion locations and its presence may have no localizing value (Kumral & Bayulkem, 2003; Melo, Bogousslavsky, van Melle & Regli, 1992). In prospective studies of large first stroke series, lesions were supratentorial in over 60% of cases (Kumral, Celebisoy, Celebisoy, Canbaz & Calli, 2007; Urban et al., 2006). Infratentorial lesions producing dysarthria were largel