Evidence for intraaxonal spread of Listeria monocytogenes from the periphery to the central nervous system

Rhombencephalitis due to Listeria monocytogenes is characterized by progres sive cranial nerve palsies and subacute inflammation in the brain stem. In this paper, we report observations made on mice infected with L. monocytoge nes. Unilateral inoculation of bacteria into facial muscle, or peripheral p arts of a cranial nerve, induced clinical and histological signs of mainly ipsilateral rhombencephalitis. Similarly, unilateral inoculation of bacteri a into lower leg muscle or peripheral parts of sciatic nerve was followed b y lumbar myelitis. In these animals, intraaxonal bacteria were seen in the sciatic nerve and its corresponding nerve roots ipsilateral to the bacteria l application site. Development of myelitis was prevented by transsection o f the sciatic nerve proximally to the hindleg inoculation site. Altogether, our results support the hypothesis that Listeria rhombencephalitis is caus ed by intraaxonal bacterial spread from peripheral sites to the central ner vous system.