Childhood Apraxia of Speech: The Praxis Differential Diagnosis

Childhood apraxia of speech (CAS) is a favorite Praxis 5331 item because it forces a differential diagnosis: the exam gives you a case and asks whether it's apraxia, dysarthria, or a phonological disorder. Get the three hallmark features down and these questions become free points.

What CAS actually is

CAS is a neurological speech sound disorder of motor planning and programming. The child knows the word and has adequate strength and tone — the breakdown is in sequencing the movements. That's the key contrast with dysarthria, which is a weakness/tone problem, and with phonological disorder, which is a linguistic rule problem.

ASHA's three consensus features

1. Inconsistent errors on consonants and vowels across repeated productions of the same word.
2. Lengthened and disrupted coarticulatory transitions between sounds and syllables.
3. Inappropriate prosody, especially in lexical or phrasal stress — often equal stress across syllables.

Supporting signs: groping/silent posturing, vowel distortions, errors that increase with word length and complexity, a large gap between receptive and expressive language, and better automatic speech than volitional speech.

The differential table to memorize

• CAS — inconsistent errors, groping, prosodic disturbance, normal strength, errors worsen with length.
• Dysarthria — consistent errors, weakness or abnormal tone, imprecise consonants, hypernasality, breathy or strained voice, drooling. Non-speech function is also impaired.
• Phonological disorder — consistent, rule-governed pattern errors; normal prosody; no groping.
• Severe articulation disorder — consistent distortions, normal prosody and rate.

Full dysarthria types and their perceptual signatures are in the motor speech guide.

Assessment

There's no single confirmatory test. Expect the correct answer to be a combination:

• Repeated trials of the same word to document inconsistency (Dynamic Evaluation of Motor Speech Skill, Inconsistency subtest of the DEAP).
• Diadochokinetic tasks — sequenced /pʌtʌkʌ/ is far more revealing than repeated /pʌ/.
• Words of increasing length ("play, playing, playground") to elicit breakdown.
• Oral mechanism exam to rule out weakness.
• Hearing screening and language testing — always part of a defensible workup.

Do not diagnose CAS from a single-word articulation test. If an answer choice is "administer the GFTA-3 and diagnose," it's wrong.

Treatment principles

CAS treatment follows principles of motor learning, not phonological rules:

• High-frequency, intensive practice — many short sessions beat one long weekly session.
• Many repetitions of few targets, chosen for functional power.
• Blocked/massed practice early, moving to random and variable practice for generalization.
• Reduce feedback frequency over time and shift from knowledge of performance to knowledge of results.
• Multisensory cueing — tactile, gestural, visual (PROMPT, DTTC — Dynamic Temporal and Tactile Cueing).
• Movement sequences, not isolated phonemes. Non-speech oral motor exercises are not supported and are a classic distractor.
• AAC as a bridge for severely unintelligible children — it supports, not replaces, speech development. See the AAC guide.

Common exam traps

• Choosing oral motor exercises for any motor speech disorder.
• Diagnosing CAS in a 2-year-old with limited output — insufficient data; the label requires volitional speech attempts.
• Confusing "inconsistent" with "variable severity" — CAS inconsistency is across repetitions of the same target.
• Forgetting that CAS commonly co-occurs with language and literacy deficits, so the plan should address them.

Practice the differential in question form with our motor speech question set, then check timing under pressure on a full practice test.