Neural Mechanisms of Swallowing Dysfunction and Apraxia of Speech in Acute Stroke

Abstract

Speech and swallowing utilize overlapping anatomy and are thus inherently related processes. We sought to identify common neural mechanisms between risk of swallowing dysfunction and apraxia of speech (AOS). This was a retrospective analysis using data from a prospectively collected cohort. Left hemisphere stroke patients (68 subjects) tested with the Apraxia Battery for Adults II, a swallow screen, and MRI were included in the study. Main outcome measure was the presence of AOS or aspiration risk after stroke. We identified a significant association between AOS measures and increased aspiration risk (defined by failed swallow screen; p=0.04; OR 5.2). Lesions in pars opercularis of Broca's area (BA 44) were associated with both AOS (p=0.044; OR 9.7) and increased aspiration risk (p=0.04; OR 5) but deficits rarely co-occurred in the same cases. Lesions in left premotor cortex (BA 6) were not significantly associated with increased aspiration risk (p=0.06; OR 3.3) but were significantly associated with AOS (p=0.008; OR 7). Impaired swallowing function was also associated with lesions in Wernicke's area (BA 22; p=0.05; OR 3.5) and pars triangularis (BA 45; p=0.02; OR 6.8). AOS and risk of aspiration are associated in patients with acute left hemisphere stroke. Acute infarct in the pars opercularis of Broca's area is associated with both deficits, though they rarely co-occur in the same individual. The co-occurrence of AOS and risk of aspiration likely reflects dependence on closely related neural structures.