Which of the following best represents etiologies that can cause AOS in adults?

• A. Left hemisphere stroke and traumatic brain injury
• B. Parkinson's disease and Huntington's disease
• C. Alzheimer's disease and chronic headaches
• D. Hearing loss and visual impairment

Answer: (A)

AOS in adults is most often caused by damage to the left hemisphere's motor planning network for speech. Left hemisphere injuries, such as stroke or traumatic brain injury, frequently affect areas like the inferior frontal gyrus and insula that are crucial for planning and sequencing the precise movements used in speech. When these planning networks are compromised, it leads to the hallmark features of apraxia of speech: effortful, uneven articulation and disrupted speech motor programming.

The other possibilities don’t fit as cleanly. Parkinson’s and Huntington’s diseases involve broader motor control problems and often produce dysarthria due to execution and coordination issues, not the planning/programm ing disruption seen in AOS. Alzheimer’s disease and chronic headaches may impact communication but are not primary etiologies of AOS. Hearing or visual impairments affect perception or overall communication but do not cause the motor planning deficits characteristic of AOS.