Synapse density related to cerebral blood flow and symptomatology in frontal lobe degeneration and Alzheimer's disease

In order to evaluate the functional significance of synaptic pathology, synaptic density was quantitated and related to clinical symptomatology and regional cerebral blood flow (rCBF) in 8 patients with frontal robe degeneration of non-Alzheimer type (FLD) and 19 patients with Alzheimer's disease (AD), Synaptic density was measured in all layers of prefrontal and parietal cortex. The clinical picture of FLD was dominated by a frontal lobe syndrome with changes in personality and behavior, while AD was dominated by temporoparietal symptoms. This parallels the finding of frontal rCBF reductions in FLD patients and temporoparietal reductions in AD patients. Synaptic density was significantly decreased in both FLD and AD, with a regional severity which closely correlated with that of the degeneration, symptomatology and rCBF deficit. The results suggest that synaptic pathology is a likely cause of clinical symptoms and regional metabolic decrement in dementia.