Posterior cortical atrophy: an exemplar for renovating diagnostic formulation in neuropsychiatry.

Neurodegenerative dementias represent among the most clinically and pathologically complex syndromes in neuropsychiatry. Phenomenologically protean, and often initially presenting with subtle subsyndromal characteristics, neurodegenerative behavioral syndromes can manifest with an assortment of cognitive, mood, personality, and comportmental changes, often alloyed with elementary neurologic (e.g., motor) signs. A range of pathogenic mechanisms (e.g., amyloid plaques, Pick bodies, etc) typically underlie corresponding clinical syndromes. However, overlap in both clinical expression and histopathologic comorbidities frequently exist among cortical and subcortical neurodegenerative disorders. Moreover, secondary central nervous system pathologies (e.g., cerebrovascular disease) commonly coexist with neurodegenerative processes, further complicating clinical phenomenology-based nosologic categorization. Evolving insight into the etiologic mechanisms of neurodegenerative dementias, and correspondingly improving potential for intervention, require more precise differentiation among dementia subtypes and comprehensive identification of contemporaneous neurodegenerative processes. Increasing appreciation of this diagnostic complexity is prompting the need for renovation of existing diagnostic schemas. We address these issues by reviewing the atypical dementia type known as posterior cortical atrophy. We then use posterior cortical atrophy as an exemplar for renovating neuropsychiatric diagnostic classification to better account for the layered complexity of clinical and pathologic domains needing to be characterized to accurately and completely diagnose neuropsychiatric disturbances.