Motor Speech Disorders (Dysarthria Types & CAS)
A free preview, open without an account: the whole outline, its audio edition, and 7 key terms to check your recall.
Motor SpeechFull outline, free
On this page
Dysarthria vs. Apraxia of Speech
| Feature | Dysarthria | Apraxia of Speech (AOS) |
|---|---|---|
| Nature | Neuromuscular execution disorder | Motor planning/programming disorder |
| Errors | Consistent; distortions predominate | Distortions and distorted substitutions; consistency is debated (ASHA lists inconsistency; other criteria describe errors as relatively consistent in type and location) |
| Rate | Often slow or rapid (type-dependent) | Slow with trial-and-error groping |
| Prosody | Abnormal (type-specific) | Disrupted; equal stress pattern |
| Automatic speech | Equally affected | Better than volitional speech |
| Error pattern | Imprecise production from reduced strength, speed, range, or coordination | Errors increase with word length/complexity |
| Nonspeech oral movements | Often impaired | May be intact (dissociation) |
High-Yield: AOS is a PLANNING disorder, not a muscle weakness disorder. Hallmarks: slow rate with lengthened sounds and pauses, sound distortions and distorted substitutions, syllable segmentation with equalized stress, groping, and more errors as length and complexity rise; automatic speech is often easier. Error consistency is debated: ASHA lists inconsistent errors, while other criteria describe errors as relatively consistent in type and location.
Dysarthria Types (Mayo Classification)
| Type | Lesion Site | Key Features | Associated Conditions |
|---|---|---|---|
| Flaccid | LMN (cranial/spinal nerves) | Hypernasality, breathy voice, nasal emission, muscle atrophy, fasciculations | Myasthenia gravis, Guillain-Barré, Bell's palsy, progressive bulbar palsy |
| Spastic | UMN (bilateral) | Strained-strangled voice, slow rate, hypernasality, reduced range | Bilateral stroke, pseudobulbar palsy, spastic CP |
| Ataxic | Cerebellum | Irregular articulatory breakdowns, excess and equal stress, scanning speech, "drunken" quality | Cerebellar stroke, MS, Friedreich's ataxia, alcohol toxicity |
| Hypokinetic | Basal ganglia (substantia nigra) | Monopitch, monoloudness, reduced stress, short rushes of speech, breathy voice, festinating speech | Parkinson's disease |
| Hyperkinetic | Basal ganglia | Involuntary movements affect speech; variable; voice stoppages; excess loudness variations | Huntington's disease, dystonia, chorea, Tourette's |
| Unilateral UMN | UMN (unilateral) | Imprecise consonants, harsh voice, slow rate; generally mild | Unilateral stroke |
| Mixed | Multiple systems | Combined features | ALS (flaccid + spastic), MS, Wilson's disease |
High-Yield: ALS = mixed flaccid-spastic dysarthria. Parkinson's = hypokinetic dysarthria. Ataxic dysarthria features "scanning speech" with excess and equal stress.
Childhood Apraxia of Speech (CAS)
ASHA's 3 Consensus Features:
- Inconsistent errors on consonants and vowels in repeated productions
- Lengthened and disrupted coarticulatory transitions between sounds/syllables
- Inappropriate prosody (especially equal stress or lexical stress errors)
Additional CAS Characteristics:
- Limited consonant and vowel inventory
- Vowel errors (unusual in pure articulation disorders)
- Groping/silent posturing
- Increased errors with length and complexity
- Gap between receptive and expressive language (receptive >> expressive)
- Difficulty with volitional oral movements (may co-occur with oral apraxia)
- Repetition of single syllables (/papapa/) may be near normal while sequenced syllables (/pataka/) break down; this AMR/SMR contrast points to planning rather than weakness
CAS Treatment:
- DTTC (Dynamic Temporal and Tactile Cueing): Integral stimulation ("watch me, listen to me, do what I do")
- ReST (Rapid Syllable Transition Treatment): Targets smooth transitions
- PROMPT (Prompts for Restructuring Oral Muscular Phonetic Targets): Tactile-kinesthetic cues
- Frequent, high-repetition practice, with the session schedule set from the child's response and checked with data
- Principles of motor learning: practice amount and distribution, practice variability, and feedback type and frequency, each adjusted to the child
- Treatment approaches, target selection, and dosage for CAS are covered in Speech Sound Disorders: Intervention
High-Yield: CAS is diagnosed by behavioral speech features, NOT by neurological testing. Do NOT diagnose CAS based on non-speech oral motor difficulties alone.
Treatment for Dysarthria
- Lee Silverman Voice Treatment (LSVT LOUD): Hypokinetic dysarthria (Parkinson's); "Think loud!"
- Palatal lift/prosthesis: Flaccid dysarthria with velopharyngeal incompetence
- Rate control strategies: Pacing board, alphabet board, finger tapping
- Respiratory support: Expiratory muscle strength training (EMST), postural adjustments
- Prosodic training: Contrastive stress drills for monotone speech
Sources to Know
- ASHA Practice Portal: Dysarthria in Adults
- ASHA Practice Portal: Acquired Apraxia of Speech
- ASHA Practice Portal: Childhood Apraxia of Speech
- [ASHA (2007). Childhood Apraxia of Speech [Technical Report]](https://www.asha.org/policy/tr2007-00278/)
- Darley, Aronson & Brown (1969). Differential diagnostic patterns of dysarthria. JSHR
- Maas et al. (2008). Principles of motor learning in treatment of motor speech disorders. AJSLP
- Strand (2020). Dynamic Temporal and Tactile Cueing: a treatment strategy for childhood apraxia of speech. AJSLP
- Murray, McCabe & Ballard (2015). A randomized controlled trial comparing Rapid Syllable Transition Treatment and the Nuffield Dyspraxia Programme. JSLHR
- Ramig et al. (2018). Speech treatment in Parkinson's disease: randomized controlled trial. Mov Disord
- Duffy, J. R. (2020). Motor Speech Disorders: Substrates, Differential Diagnosis, and Management (4th ed.). Elsevier.
Reviewed: 2026-09
Key terms 7
- Apraxia of Speech (AOS)
- Motor speech planning/programming disorder with slow rate, distortions and distorted substitutions, syllable segmentation, groping, and prosodic disruption; error consistency is debated; NOT due to muscle weakness
- Flaccid dysarthria
- LMN damage causing hypotonia, breathy voice, hypernasality, nasal emission; seen in myasthenia gravis, bulbar palsy
- Spastic dysarthria
- Bilateral UMN damage causing hypertonia, strained-strangled voice, slow rate; seen in pseudobulbar palsy
- Ataxic dysarthria
- Cerebellar damage causing irregular articulatory breakdowns, excess and equal stress, "scanning speech"
- Hypokinetic dysarthria
- Basal ganglia damage (substantia nigra) causing monopitch, monoloudness, festinating speech; hallmark of Parkinson's disease
- CAS
- Childhood Apraxia of Speech: motor planning disorder with inconsistent errors, disrupted coarticulatory transitions, and inappropriate prosody
- DTTC
- Dynamic Temporal and Tactile Cueing: integral stimulation approach for CAS using multimodal cues and systematic cue reduction
End of the free preview
29 more audio guides work the same way
Every guide has chapters you can jump between, speed control and a spoken recall of the key terms, beside its full outline. A plan opens all 33 audio guides, all 49 outlines and 1,300+ original practice questions with a rationale for every answer. These 4 previews stay free.
See plans and prices- audio guides
- 33
- study outlines
- 49
- practice questions
- 1,300+
Related outlines
- Named Treatment Approaches (Comprehensive List)Receptive & Expressive Language
- Speech Sound Disorders: Intervention (Articulation, Phonology & CAS)Speech Sound Production
- Speech & Language Development Milestones (Birth to 5)Speech Sound Production
- Phonological Development (Processes, Suppression, Acquisition)Speech Sound Production
Disclaimer: Praxis is a registered trademark of Educational Testing Service (ETS). SLP Study Hub is not affiliated with or endorsed by ETS or ASHA. This outline is original educational content written for SLP Study Hub and aligned to the publicly available Praxis 5331 test blueprint.