Vestibular loss as a contributor to Alzheimer's disease.

Alzheimer's disease is a complex disorder whose etiology is still controversial. It is proposed that vestibular loss may contribute to the onset of Alzheimer's disease, which initially involves degeneration of cholinergic systems in the posterior parietal-temporal, medial-temporal, and posterior-cingulate regions. A major projection to this system emanates from the semicircular canals of the vestibular labyrinth, with vestibular damage leading to severe degeneration of the medial-temporal region. The vestibular loss hypothesis is further supported by the vestibular symptoms found in Alzheimer's patients as well as in various diseases that are major risk factors for Alzheimer's disease.