Neuropathologic features of Parkinson's, Huntington's, and Alzheimer's diseases.

Some of the similarities and differences between the neuropathology of Parkinson's disease, Huntington's disease, and Alzheimer's disease have been reviewed, and the relationship between the three diseases has been discussed. Although interconnected and reciprocally innervated structures are affected in PD and HD, they appear less closely related than in PD and AD. Different neurotoxins may play a part in their pathogenesis, as also suggested from other evidence. Neuropathologic features of PD, HD and AD are entirely compatible with a role for neurotoxins in their pathogenesis, but do not by themselves make a strong case for a neurotoxic hypothesis. However, additional neuropathologic studies of experimental neurotoxins may further strengthen arguments in favor of a neurotoxic etiology, as the MPTP animal model is doing for Parkinson's disease. Such experimental studies along with further molecular biological and other sophisticated new methods may open the way for exciting new developments in the near future.