Pure apraxia of speech associated with infarction in premotor cortex (P3.199)

Objective: NA Background: Apraxia of speech (AOS) is an articulation disorder distinct from dysarthria and aphasia as a disorder of motor speech planning, also called aphemia in its most severe form. Various lesions have been associated with AOS in studies that are limited in precise localization due to variability in size and type of pathology. We present a case of pure AOS and discuss lesion evidence in support of dPMC in speech planning and coordination. Design/Methods: A 60-year-old right-handed man presented with sudden onset of slurred speech with right face and arm weakness. MRI of the brain showed acute infarction in left dorsal premotor cortex and left motor cortex. Initially mute, he slowly recovered with a severely “garbled” speech with delayed initiation, slow rate, halting output along with groping oral movements with silently voiced phonemes, segmentation of syllables, sound distortions, distorted substitutions, trial-and-error articulatory movements, decreased coordination of the respiratory-phonatory subsystems, irregular rhythm and stress, final consonant deletions, phonemic substitutions, articulation errors especially with the fricative phonemes, as well as consonant clusters, and increased difficulty with increased length and complexity of utterances were all present in his output. Confrontational naming, auditory comprehension, repetition, grammar, syntax, reading, and writing was normal. Results: dPMC is an integral part of the dorsal stream in the dual-stream model of speech processing, where the speech signals from posterior temporal lobe are translated into articulatory representations in the dPMC by the maintenance of sublexical representations in an active state during the performance of the task like phonetic discrimination i.e. “sound to action”. The role of dPMC is further supported by hierarchical state feedback control model as the controller. Conclusions: AOS is a distinct articulation disorder. By virtue of its connections, dPMC plays a crucial role in speech planning and processing. A lesion in dPMC can lead to pure AOS. Disclosure: Dr. Patira has nothing to disclose.