Dynamic aphasia in progressive supranuclear palsy: a deficit in generating a fluent sequence of novel thought
Abstract
We report a patient (KAS) who presented with pure dynamic aphasia in the context of progressive supranuclear palsy (PSP). KAS had the hallmark propositional language impairment in the context of preserved naming, reading, repetition and comprehension skills. The severity of KAS's propositional language deficit was demonstrated to be comparable to other dynamic aphasic patients. Remarkably, despite virtually abolished propositional speech, KAS was unimpaired on word and sentence level generation tasks that required a single response. This dissociation was further investigated on two discourse level generation tasks that required the generation of multiple connected sentences. Quantitative production analysis and novelty measures demonstrated that her performance was extremely reduced and characterised by a lack of novel words and sentences and a tendency to perseverate. This pattern of performance suggests that there may be two subtypes of dynamic aphasia. Patients with the more documented first subtype have language-specific deficits, fail word and sentence level generation tests and have left inferior frontal gyrus lesions. Patients with the second subtype, like KAS, pass word and sentence level generation tests and fail disco...Continue Reading
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