Which neuroanatomical regions are most commonly implicated in adult AOS?

• A. Left hemisphere premotor cortex and insula, with involvement of adjacent planning areas.
• B. Right hemisphere occipital lobe.
• C. Cerebellum only.
• D. Frontal lobe lesions in either hemisphere with no insular involvement.

Answer: (D)

Adult apraxia of speech arises mainly from disruption of the left-hemisphere network that plans and programs speech movements. The most commonly implicated regions are the left premotor cortex and the left insula, with involvement of nearby planning areas such as the inferior frontal gyrus and the supplementary motor area. Damage to these areas disrupts the sequencing and coordination required for precise articulatory movements, leading to slow, halting, and distorted speech with inconsistent errors that reflect impaired motor planning rather than a primary weakness or a pure language deficit.

Why the other patterns aren’t as typical: right hemisphere occipital lobe damage isn’t a motor-planning culprit for speech, cerebellar-only involvement is more associated with coordination problems rather than the planning of complex speech sequences, and frontal lesions in either hemisphere without insular involvement don’t consistently produce the characteristic left-dateralized speech planning disruption seen in adult AOS.