Bunina bodies in neurons of the medullary reticular formation in amyotrophic lateral sclerosis.

To determine how often Bunina bodies (BBs) appear in the medullary reticular formation (MRF) in amyotrophic lateral sclerosis (ALS), we microscopically examined 20 serial sections of MRFs from each of nine autopsied ALS cases, which had BBs in the lower motor neurons, including those of cranial motor nuclei. In 1 of them, the pontine tegmentum was examined in the same way. In 8 cases one to several BB-containing neurons in the MRF were seen. The case in which the pontine tegmentum was also investigated exhibited several neurons with BBs in this region. Some of the BBs in the MRFs were confirmed by electron microscopy. Thus, this study demonstrates the common appearance of BBs, although the number is small, in the MRF, indicating that pathological processes that undermine the lower motor neurons in ALS in some way also affect neurons other than motor neurons in this condition.