Nothing to say, something to sing: primary progressive dynamic aphasia.

We describe a 76-year-old man (ADY) with dynamic aphasia in the setting of a degenerative frontal lobe dementia: primary progressive dynamic aphasia. He displayed a striking paucity of propositional speech despite intact speech production, and preserved singing and prosody. Vocal expression in the verbal and musical domains was investigated in a series of neuropsychological experiments based on novel language and musical tasks that were designed to establish the nature and specificity of the verbal output deficit. The features of the language disorder indicated that the speech output pathway was disrupted at the early stage of generation of a new pre-verbal message. In contrast, tests of musical output demonstrated that the generation of new musical ideas was unimpaired. The domain-specificity of dynamic aphasia may result from the disruption of specific cognitive processes necessary for the creation of verbal messages, as well as selective damage of brain regions involved in language production.