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. Ann Neurol 2004;56:894–897