Language disorders in neurodegenerative diseases

The goal of this chapter is to discuss neuroanatomy of normal language function, and review clinical evaluation and management of progressive aphasias. Systematic use of neuroimaging, laboratory work up, and pharmacological, neuromodulatory, and nonpharmacological interventions including speech-language therapy, and psychosocial remediation will be reviewed. Based on recent neuroimaging studies, language network is studied based on neuroanatomically distinct ventral and dorsal pathways. These pathways contribute to lexical and phonological/syntactic processing respectively. Gradual impairment in these pathways, in the absence of significant decline in other cognitive networks will result in syndromes of primary progressive aphasia (PPA). Meticulous evaluation of word comprehension, fluency and grammaticality, repetition, naming, reading and writing, helps with further subtyping PPA. Following formulation of the clinical syndrome, structural and functional neuroimaging (topographical or progression biomarkers) are helpful tools to further specify the clinical phenotype as a guide to determine the underlying neuropathological process. Currently analysis of the cerebrospinal fluid and amyloid positron emission tomography (PET) can help with diagnosis of the neuropathological process (etiologic or state biomarkers). Based on diagnosis of the underlying neuropathology decision regarding appropriate pharmacological intervention will be possible. Comprehensive management of PPA involves utilization of both pharmacological and non-pharmacological intervention which include speech-language therapy, and psychosocial remediations.