Dysarthria
Dysarthria is a motor speech disorder caused by muscle weakness or incoordination affecting respiration, phonation, articulation, resonance, and prosody.
What Dysarthria is
Dysarthria is a collective term for a group of neurogenic motor speech disorders that result from weakness, paralysis, incoordination, or altered muscle tone affecting the muscles used for respiration, phonation, resonance, articulation, or prosody. It is distinct from apraxia of speech, which is a motor planning disorder, and from aphasia, which is a language disorder. The Mayo Clinic classification system (Darley, Aronson, & Brown 1969) identified six primary types — flaccid, spastic, ataxic, hypokinetic, hyperkinetic, and mixed — each with characteristic perceptual features that map back to the neurologic site of lesion. Dysarthria can occur across the lifespan and is most common in progressive neurological disease (ALS, Parkinson's, multiple sclerosis) and stroke.
Prevalence
Dysarthria is the most common acquired motor speech disorder. It affects an estimated 70% of patients with Parkinson's disease, 30% of stroke survivors, and close to 100% of advanced ALS patients (Duffy 2019).
Diagnostic criteria and defining features
- Motor speech impairment attributable to weakness, incoordination, or altered tone of speech musculature
- Perceptual features consistent with one of the Mayo Clinic dysarthria types
- Neurological basis documented through imaging, EMG, or clinical examination
- Impact on at least one of: respiration, phonation, articulation, resonance, prosody
- Distinguishable from apraxia of speech and aphasia on motor speech examination
Criteria summarised from DSM-5-TR, ICD-11, and ASHA practice guidance. Always cross-reference against the diagnostic manual of record before using in a report.
Clinical presentation
The clinical presentation of dysarthria varies widely with aetiology. A patient with Parkinson's disease typically shows hypokinetic dysarthria — reduced loudness, monopitch, imprecise articulation, and variable rate. A patient with ALS shows progressive mixed flaccid-spastic dysarthria with tongue fasciculations, hypernasality, and progressive intelligibility loss. Stroke-related dysarthria is often unilateral upper motor neuron in type and presents as mild to moderate articulatory imprecision and slurred speech with intact phonation. The Frenchay Dysarthria Assessment and the Darley perceptual rating system are the standard clinical probes. Intelligibility at the single-word and connected-speech level is the functional outcome variable that matters most to patients and families.
“The daughter who says "mom's speech gets worse after 4pm" is describing the fatigue pattern of myasthenia or bulbar ALS. The diurnal pattern of dysarthria is diagnostic before any imaging reaches the chart.”
How language sample analysis contributes
A connected-speech language sample is essential for documenting dysarthria severity and tracking change. Record a 3-minute picture description and a 3-minute monologue, transcribe with intelligibility rating at the word level, and compute PCC, words per minute, and an overall intelligibility score using the Speech Intelligibility Test or a sentence-level rating scale. In progressive disease, monthly sampling documents decline and guides AAC transition decisions. In acute stroke or traumatic brain injury populations, sampling at admission, discharge, and follow-up documents recovery and treatment effect.
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Free tools for Dysarthria
PCC Calculator
Free interactive Percent Consonants Correct (PCC) calculator for speech-language pathologists. Enter the consonants attempted and produced correctly from a 50- to 100-utterance connected-speech sample and get the PCC percent plus the Shriberg & Kwiatkowski (1982) severity band (mild, mild-moderate, moderate-severe, severe). Built for SLP intake, IEP eligibility, treatment-progress tracking, and graduate phonological-assessment training. Mobile-friendly, client-side, no sign-up.
Open toolSpeech Intelligibility by Age Calculator
Free interactive speech intelligibility calculator for speech-language pathologists. Enter a child age and the observed unfamiliar-listener intelligibility percent from a connected-speech sample, and the tool returns the typical / borderline / refer flag against the pooled Coplan & Gleason (1988), Flipsen (2006), and Hustad et al (2021) age expectations. Built for SLP intake, well-child visits, EI eligibility, and parent counselling. Mobile-friendly, client-side, no sign-up.
Open toolCAPE-V Voice Rating
Free interactive CAPE-V (Consensus Auditory-Perceptual Evaluation of Voice) rating tool for speech-language pathologists, voice clinic laryngologists, and voice-therapy trainees. Rate the six perceptual parameters — Overall Severity, Roughness, Breathiness, Strain, Pitch, and Loudness — on the 100 mm visual analog scale as published by Kempster et al. (2009) and get instant severity classification (within normal limits, mild MI, moderate MO, severe SE) anchored to the Kempster printed-form bands. Built for voice clinic intake, voice therapy progress visits, pre- and post-laryngology surgical follow-up, and SLP graduate training in voice evaluation. Mobile-friendly, client-side, no sign-up.
Open toolRelated disorders
Aphasia
Aphasia is an acquired language disorder caused by brain injury, most commonly stroke, affecting expression, comprehension, reading, and writing in varying combinations.
LifespanVoice Disorder
A voice disorder is an impairment in vocal quality, pitch, loudness, or endurance that interferes with communication or the speaker's occupational or personal life.
LifespanDysphagia (Swallowing Disorder)
Dysphagia is a swallowing disorder caused by neurological, structural, or functional impairment that can lead to malnutrition, dehydration, or aspiration pneumonia.
References
- Duffy, J. R. (2019). Motor Speech Disorders: Substrates, Differential Diagnosis, and Management (4th ed.). Elsevier.
- Darley, F. L., Aronson, A. E., & Brown, J. R. (1969). Differential diagnostic patterns of dysarthria. JSHR, 12(2), 246–269.
- Enderby, P., & Palmer, R. (2008). Frenchay Dysarthria Assessment (2nd ed.). Pro-Ed.