Atrophy and sponginess of the mammillary bodies with neuronal sparing: not only inactive Wernicke's encephalopathy.

Two cases are reported in which old anoxic/ischemic damage to the Ammon's horns was associated with atrophy and sponginess of the mammillary bodies but with sparing of the neuronal perikarya. The lesions were unilateral in one case and bilateral in the other. The changes in the mammillary bodies closely resembled those seen in inactive Wernicke's encephalopathy but they were considered to be due to transneuronal atrophy following loss of hippocampal afferent fibres. Consequently, this condition may present a problem in diagnostic neuropathology. However, there was no reactive astrogliosis in these cases and this may serve to distinguish this condition from inactive Wernicke's encephalopathy in which gliosis is always present and often prominent.