EXTRACELLULAR FLUID PATHWAY INSIDE THE FACIAL-NERVE FASCICLES

The extracellular fluid pathway in the facial nerve and the diffusion of a tracer from the facial nerve to other cranial nerves was examined in the rabbit. Sodium fluorescein solution was injected into either t he facial nerve fascicles or the epineurial connective tissue as a tra cer at the stylomastoid foramen and then localized by fluorescence mic roscopy. In the facial nerve, fluorescence was observed in the endoneu rium and external nerve sheath (epineurium and perineurium) through th e geniculate ganglion following injection into the nerve fascicles. Th e vestibular, trigeminal, and glossopharyngeal ganglia also showed flu orescence on the injection side in ganglion cells and intercellular co nnective tissues. The results suggested that the endoneurial connectiv e tissue constitutes a diffusion pathway inside the facial nerve fasci cles and that the extracellular fluid pathway from the facial nerve to these cranial ganglia may be related to the neural spread of inflamma tion or neoplastic metastasis.