Which brain regions are most relevant when imaging supports a neurodegenerative etiology for AOS?

• A. Left frontal speech planning regions.
• B. Right occipital cortex.
• C. Left hippocampus only.
• D. Brainstem pathways.

Answer: (A)

When imaging points to a neurodegenerative cause of apraxia of speech, the most relevant regions are the left frontal speech planning areas. These are the parts of the brain that organize and sequence the movements of speech before they’re produced, including the left inferior frontal gyrus (especially its opercular and triangular parts), the left precentral gyrus, the insula, and often the supplementary motor area. In conditions like primary progressive apraxia of speech, degeneration or reduced function in this left frontal network is what disrupts the planning of articulatory gestures, leading to the characteristic speech errors.

The other regions don’t fit as well with the typical profile of neurodegenerative AOS. The right occipital cortex is mainly about visual processing, not speech planning. The left hippocampus is tied to memory, not the motor planning of speech. Brainstem pathways are more about executing movements rather than organizing the motor plan, so they’re less diagnostic for a neurodegenerative AOS pattern.