The results of all these studies when taken together allow us to conclude that Borrelia burgdorferi and oral spirochetes can persist in the brain and  in analogy to Treponema pallidum, can cause dementia, cortical atrophy and amyloid deposition. Exposure to bacteria or to their toxic products, host responses similar in nature to those observed in AD may be induced. Bacteria and/or their degradation products may initiate a cascade of events leading to cell death, neurodegeneration and amyloid deposition in AD. As a consequence may cause cortical atrophy, amyloid deposition and dementia.