Cerebral degenerations producing dementia: importance of neuropathologic confirmation of clinical diagnoses.

Dementia is a major public health concern with our increasing elderly population and currently affects more than three million Americans at an annual cost of $50 billion. The marked overlap in symptomatology between Alzheimer's disease and other primary parenchymal degenerations makes antemortem diagnosis based on clinical assessment tentative at best, with error rates of 25% commonly reported. Accurate diagnosis is of vital importance in order to improve our understanding of these illnesses, evaluate potential therapies, and provide appropriate genetic counseling to family members. Direct neuropathologic examination at autopsy is currently the only reliable method for assuring accurate diagnosis, and should be undertaken in all demented patients. To illustrate the importance of these principles, we present three patients who were clinically diagnosed with Alzheimer's disease, and subsequently found to have other dementing illnesses by careful postmortem neuropathologic examination.