Apraxia of Speech (AOS)
Problem with the motor programming of speech movements
What does AOS co-occur with?
Often co occurs with aphasia and dysarthria.
-also oral and limb apraxia
What is AOS almost always due to?
Left cerebral hemisphere damage
4 steps in speaking:
- Speaker conceptualizes what is going to be said. This is where the message is determined.
- Speaker formulates the message through selecting semantic, syntactic, morphological, phonological structures for the message.
- The Motor Speech Programmer programs/plans the movements necessary to produce the needed phonemes. It activates a plan for the motor execution needed.
- This program is sent to through the nervous system to produce muscle movement/motor execution.
If difficulties occur in step 2
the result may be aphasia
If difficulties occur in step 3
the result may be apraxia
If difficulties occur in step 4
the result may be dysarthria
Motor Speech Programmer (MSP)
Located in the parietal-frontal lobes and related subcortical circuits responsible for programming: • Duration of movement • Amplitude of movement • Acceleration • Deceleration • Time to peak velocity • Timing of speech events.
Areas primarily involved with the MSP
- Pre-motor area (Broca’s area)
- Supplemental motor area
- basal ganglia and cerebellar circuits
- Parietal lobe somatosensory cortex and supramarginal gyrus
- basal ganglia (putamen and caudate nucleus)
Primary site of lesion for AOS
left posterior frontal lobe (Broca’s area, insula, and basal ganglia)
Non speech characteristics of AOS
- Right sided weakness and spasticity
- Babinski reflex and hyperactive stretch reflexes
- limb apraxia (left side prominent due to right side hemiparesis/hemiplagia)
Primary etiologies of AOS
(that affect the left hemisphere)
Patient complaints of AOS
Can’t pronounce words correctly even though they know what they want to say
Clinical findings for AOS: Oral Mechanism Exam
Without dysarthria; gag reflex, chewing, swallowing, pathological oral reflexes should be WNL
Clinical findings for AOS: Non Verbal Oral Apraxia (NVOA)
Problems with involuntary movements of non verbal oral structures during performance of volitional tasks
Clinical findings for AOS: Auditory processing skills
Auditory processing skills are WNL however with DAF more severe breakdowns occur than with normal speakers
Clinical findings for AOS: Speech
- Use voluntary speech tasks (conversation, narratives, reading)
- Sequencing of syllables (SMRs, multisyllabic words)
- Increase morphological complexity of words (endear/ing/ly)
- Listen for false articulatory starts
- Watch for groping of articulators
- For more severe AOS try to elicit any speech responses
- Primary articulation error is distortion especially on blends
- Rate and prosodic problems
- Fluency due to attempts to correct errors
Most important diagnostic criteria for AOS
- Slowed rate of speech
- Consistent predictable sound errors (distortions)
- Prosodic abnormalities