Senile plaques and other senile changes in the brain of an aged American black bear.

A female American black bear (Euarctos ursus americanus) over 20 years old had shown epileptiform neurologic signs starting in March 1992 and was found dead unexpectedly 8 months later. At necropsy, pulmonary and intrabronchial hemorrhage was noted. In the brain, the leptomeninges exhibited slight thickening, and petechiae were evident in the hippocampus. Histopathologic examination of the brain revealed several senile changes: numerous senile plaques, amyloid deposition in cerebromeningeal arterioles, mineral deposition in the pallidum, and numerous corpora amylacea in the cerebellum.