Frontal lobe degeneration of non-Alzheimer type. Structural characteristics, diagnostic criteria and relation to other frontotemporal dementias.

Frontal lobe degenerative dementias, the second largest degenerative dementia group after Alzheimer's disease, is dominated by frontal lobe degeneration of non-Alzheimer type. It is classified in a group also containing Pick's disease, progressive aphasia and dementia in motor neuron disease. Frontal lobe degeneration of non-Alzheimer type is clinically marked by frontal lobe symptoms and frontotemporal reduction of blood flow. From a histopathological point of view it is characterized by gliosis, microvacuolation, neuronal atrophy-loss and 40-50% loss of synapses in three superficial cortical laminae of the frontal convexity and anterior temporal cortex, while the deeper laminae are little or not changed. The structural changes of Alzheimer's disease including amyloid, Levy body dementia and Pick's disease are entirely lacking. A strong heredity points to a genetic cause as yet undefined.