Abstract 2978: Size Matters, but so do Broca's Area and Anterior Temporal Cortex, in Recovering from Apraxia of Speech
Background: Apraxia of speech (AOS) is considered a deficit of motor planning and programming of speech articulation. In chronic stroke patients, the anterior insula has previously been associated with AOS using lesion overlap studies. However, the anterior insula association with AOS might be due to the typically large areas of infarction in patients with chronic AOS, as insula is infarcted in 94% of patients with stroke due to occlusion of the left middle cerebral artery. We hypothesized that the volume of infarct in chronic stroke patients would be significantly associated with AOS, and we sought to identify other regions that, when damaged, would cause deficits in motor speech programming after controlling for infarct volume.
Methods: We tested a series of 34 patients at least 6 months post onset of left supratentorial ischemic stroke with the Apraxia Battery for Adults II and obtained concurrent MRI. Patients received scores on 4 apraxia tests: Increasing Word Length Parts A and B, Repeated Trials (which scores errors in the repetition of the same polysyllabic word) and Inventory of Articulation (which scores characteristics of AOS observed during spontaneous speech, reading, and automatic speech). MRI (FLAIR sequences) were analyzed by a technician masked to apraxia results for presence or absence of ischemia in each of 11 Brodmann’s areas (BA) as well as the anterior and posterior insula. The technician also conducted volumetric analysis on each MRI; volumes were recorded (cm3). We identified associations between impaired apraxia measures and both areas of infarct and lesion volumes using age-adjusted linear regression models.
Results: There was a strong association between lesion volume and AOS, as measured by Inventory of Articulation (coefficient=1.48 more points (worse score) per 10 cc larger infarct; p=0.002) and Repeated Trials (coefficient=-0.91 (worse score) per 10 cc increase; p=0.008). After adjustment for both volume and age, lesions in BA 44 and 45 (Broca’s Area) were significantly associated with AOS, as measured by Inventory of Articulation (coefficient=12.07, p=0.009 for both BA 44 and 45). BA 20 and 38 lesions were also associated with AOS, as measured by Repeated Trials scores (coefficient= -22.7, p=0.008 for both). Additionally, there was a strong association between lesions in the posterior insula and Inventory of Articulation scores (coefficient= 3.23, p=0.007).
Conclusion: In chronic stroke patients, lesion size is highly correlated with AOS. Chronic damage to Broca’s Area and anterior temporal cortex (BA 38, 20), as well as posterior insula, is also associated with AOS, regardless of lesion size. These areas may be important for recovery of speech planning.
- © 2012 by American Heart Association, Inc.