Acquired Apraxia of Speech
Apraxia of Speech (AOS) is a neurological speech disorder in which the ability to plan or execute the movements necessary for clear speech is impaired. This definition, originating from research by Duffy in 2013, describes AOS as a breakdown in the normal speech-making processes that involve precise timing and placement of speech muscles. In clinical discussions, this term is also known under other names, such as verbal apraxia or dyspraxia.
For our discussion, we'll focus on acquired AOS, which also shares many characteristics with progressive AOS, particularly in how it's assessed and diagnosed. Researchers, including Allison et al. (2020) and Ballard et al. (2014), have identified several key features for diagnosing AOS:
Distortions of phonemes and the addition of distorted substitutions,
A slower overall speech rate,
Clear segmentation of syllables with prolonged pauses within and between segments,
A tendency to place equal emphasis on adjacent syllables.
These characteristics underline the challenges in planning and programming speech movements, which tend to worsen with longer words and more complex syllable structures. Depending on the underlying cause and the time since its onset, AOS might improve, stabilize, or deteriorate.
AOS often coexists with other complications, depending on the brain area affected. These can include:
Aphasia, which affects understanding and forming language,
Dysarthria, where speech is difficult due to muscle weakness or coordination problems, often related to a stroke,
Nonverbal oral apraxia, making it hard to control facial muscles for non-speech actions,
Apraxia of swallowing, involving challenges with coordinating muscles needed for swallowing,
Limb apraxia, which is difficulty in making purposeful arm or leg movements,
Various levels of unilateral (usually right-side) weakness and spasticity.
Understanding these associated conditions is crucial as they impact the overall approach to managing and treating AOS.