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
- insula
- 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
Tumors
Trauma
Stroke
(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
