Apraxia of Speech, also known as Acquired Apraxia of Speech (AOS) is a neurogenic motor speech disorder characterized by an impaired ability to plan and program the movements required for accurate speech production. It is not due to muscle weakness or language confusion, but rather a breakdown in translating correctly formulated words into finely coordinated articulatory gestures. Individuals with AOS know what they want to say, but their speech comes out with distorted sounds, groping attempts to position the articulators (tongue, lips, jaw), and errors in sequencing sounds and syllables. Speech can be slow and halting, with abnormal prosody (intonation and stress) that makes the person sound monotonic or choppy.
Apraxia of speech most often occurs in adults after brain damage (e.g. stroke) and can present alongside aphasia, though it is a distinct disorder – in pure AOS, language comprehension and word selection are intact, but the person struggles to consistently produce the desired sounds. There is also a recognized degenerative form called Primary Progressive Apraxia of Speech (PPAOS), where motor speech planning gradually deteriorates due to neurodegenerative disease.
1. Stroke or Focal Brain Injury: The most common cause of acquired apraxia of speech is a stroke (cerebrovascular accident) in the dominant (usually left) hemisphere of the brain. Lesions in the left inferior frontal lobe (Broca’s area) or deep frontal structures like the anterior insula are strongly associated with AOS; for instance, studies have found that virtually all stroke patients with AOS have damage to the superior precentral gyrus of the insula, a region crucial for articulatory planning. Traumatic brain injury or surgical trauma affecting speech-motor cortex can similarly result in apraxia of speech if key motor planning areas are disrupted.
2. Neurodegenerative Disease: Apraxia of speech can develop as a symptom of progressive neurological conditions. In some patients with primary progressive aphasia or corticobasal degeneration, AOS is the initial or sole manifestation of the disease, gradually worsening over time. This progressive apraxia reflects degeneration of the neural networks for speech sequencing (for example, in fronto-insular pathways). Unlike stroke-induced AOS, which appears suddenly and may improve with therapy, PPAOS is insidious and related to underlying diseases (like Alzheimer’s or frontotemporal lobar degeneration) that have a genetic or idiopathic basis. In both cases, the neurological origin lies in damage to the speech motor programming centers of the brain.
Effective management of apraxia of speech requires careful assessment and targeted intervention by SLPs. Clinically, it is critical to differentiate AOS from aphasia or dysarthria, as treatment approaches differ. An SLP will perform a motor speech examination, observing hallmark signs such as inconsistent consonant and vowel errors (e.g. saying a word correctly one time and incorrectly the next), visible groping or trial-and-error articulatory movements, and disproportionately worse errors on longer or more complex words. Identifying these features confirms the diagnosis and guides therapy planning.
Treatment for AOS is typically intensive and employs articulatory-kinematic techniques – in practice, this means the patient repeatedly practices specific words or phrases with careful cueing to shape the articulator movements, gradually rebuilding motor plans for speech. Research evidence supports the use of such motor-drill therapy, often combined with rate/rhythm control methods, to improve speech accuracy. Throughout therapy, the SLP continually monitors the patient’s progress on speech intelligibility and carries out differential diagnosis (ensuring that any language deficits are also addressed separately from the motor speech work). In cases of severe or progressive apraxia, SLPs may introduce augmentative and alternative communication (AAC) tools (like communication boards or speech-generating devices) to support the person’s ability to convey messages as traditional speech therapy continues. With dedicated intervention, many individuals with apraxia of speech can regain a functional level of spoken communication, though ongoing practice is often needed to maintain improvements.
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Ballard, K. J., Wambaugh, J. L., Duffy, J. R., et al. “Treatment for Acquired Apraxia of Speech: A Systematic Review of Intervention Research.” Journal of Speech, Language, and Hearing Research 58, no. 5 (2015).
Botha, H., Utianski, R. L., Whitwell, J. L., et al. “Disrupted Functional Connectivity in Primary Progressive Apraxia of Speech.” NeuroImage: Clinical 18 (2018).
