Olfactory centres in Alzheimer's disease: olfactory bulb is involved in early Braak's stages

In Alzheimer's disease (AD), neurofibrillary tangles spread from the entorh inal cortex to the limbic system, then to neocortical areas, according to t he Braak's stages. Olfaction is impaired in early stages of AD. The aim of this study was to describe the pathology of the cortical olfactory centres in relation to Braak's stages determining the earliest site of pathology. W e examined 15 control and 15 AD cases. The primary olfactory cortices were involved in more advanced Braak's stages, while olfactory bulbs were damage d in very early (i.e. Braak's stage 0 or 1) stages. These results are suppo rting the fact that olfaction might be an early marker in AD and argues aga inst the hypothesis that AD pathology is spreading through the olfactory sy stem. NeuroReport 12:285-288 (C) 2001 Lippincott Williams & Wilkins.