In vivo detection of microglial activation in frontotemporal dementia

Using positron emission tomography and (11)C(R)-PK11195, a marker of "peripheral benzodiazepine sites" that is upregulated on activated microglia during progressive tissue pathology, we show increased binding of (11)C(R)-PK11195 in frontotemporal lobar degeneration in the typically affected frontotemporal brain regions. This implies the presence of an active glial response reflecting progressive neuronal degeneration. It also suggests that increased (11)C(R)-PK11195 binding, previously demonstrated for Alzheimer's disease, may occur independently from increased amyloid plaque formation, given that it is not a characteristic feature of frontotemporal lobar degeneration.