Invasion of cranial nerves and brain stem by herpes simplex virus inoculated into the mouse tongue.

Herpes simplex virus type 1 (HSV) of a highly or slightly neuropathogenetic strain was inoculated into the tongues of mice. After appropriate survival times, the animals were killed and portions of the facial and trigeminal nerves as well as the brain stem were examined with virus isolation and immunocytochemistry for the presence of HSV. Both virus strains were demonstrated in the geniculate and trigeminal ganglia and in the CNS portion of the facial and trigeminal nerves, as well as in various brain stem areas including the trigeminal tract and nucleus, the facial and hypoglossal nuclei, and nuclei in the reticular formation. The results indicate that HSV is transported to the CNS by efferent and afferent axons of the tongue and subsequently via transneuronal passage to various brain stem nuclei. These findings provide an anatomic basis for a putative relationship between HSV and cranial nerve dysfunction.