Pathophysiology of language, speech and emotions in neurodegenerative disease.

Studying neurodegenerative diseases has greatly expanded our knowledge of language, speech and emotion as these diseases can affect areas not typically seen with stroke or tumor. Newer imaging techniques such as voxel based morphometry), fluorodeoxyglucose (F18) positron emission tomography and functional magnetic resonance imaging have allowed localization of these deficits and a greater understanding of the language network targeted by these progressive neurodegenerative illnesses. This review illustrates these important points by describing five syndromes, using clinical cases and then noting the anatomy, typical pathology, and proposed pathophysiology. The syndromes are Progressive Nonfluent Aphasia, Semantic Dementia, Logopenic Aphasia, Primary Progressive Apraxia of Speech and Dysprosody of Speech. Clinicians recognizing these syndromes using the associated clinico-anatomic patterns will lead to more accurate diagnosis and improved patient counseling and management. Further, patients may be included in appropriate clinical trials when their doctors are aware of the most likely pathology.