Cortical synapse loss in progressive supranuclear palsy

Cortical synapse loss, the probable substrate of cognitive impairment in Al zheimer disease (AD), has not previously been evaluated in progressive supr anuclear palsy (PSP). Hypothesizing that synapse loss would be greater in d emented than non-demented PSP patients, we examined synaptophysin concentra tions in 8 cases of PSP (5 demented and 3 nondemented cases). We found a de crease in mean synaptophysin concentration in these 8 cases in frontal, tem poral, and parietal lobes, and in cerebellum, compared to the means in corr esponding lobes of 16 controls. The decreases were similar to those in 28 c ases of AD, but not as great. We determined synaptophysin concentration fro m motor cortex in only 4 of our PSP cases, 2 demented and 2 non-demented. T he average concentrations in these 4 cases were lower than in AD motor cort ex; both were lower than controls. When demented and non-demented PSP cases were compared, neocortical synaptophysin concentrations in non-demented PS P cases were lower than in demented cases. There appears to be a link betwe en AD and PSP, in that synapse loss is found in both. However, the basis an d significance of the prominent neocortical synapse loss in PSP, especially in non-demented subjects, remain to be explored.