AN INVESTIGATION OF ACUTE FACIAL PARALYSIS IN ANIMALS INDUCED BY EXPOSURE OF THE TYMPANIC MEMBRANE TO COLD-AIR

The goal of this investigation was to test the hypothesis that tympani c membrane exposure to cold air is a cause of acute facial palsy. A se ries of acute invasive experiments and a series of chronic noninvasive experiments were conducted in both cats and dogs, In the acute studie s, stimulation was applied intracranially to the facial nerve root thr ough a stereotaxically placed microelectrode and recordings of compoun d action potentials obtained extracranially from the facial nerve. Ner ve conduction was monitored continuously during the application of col d air to the tympanic membrane, Nerve conduction disturbances were obs erved in all animals tested (8), and reduction in compound action pote ntial amplitude ranged from 33% to 96%, Histologic analysis of the int ratemporal portion of the facial nerve was performed in the animal exh ibiting the greatest block in conduction, representative of a near-tot al paralysis, Axon swelling, demyelinization, and degeneration (Bungne r's bands) without inflammation were apparent along the entire tympani c membrane segment, Interstitial swelling of nerve endoneurium was als o present at the second genu and vertical segment, In the chronic stud ies, animals were exposed to cold air and monitored daily for facia I paralysis after recovery from anesthesia, None of the animals demonstr ated any detectable behavioral facial paralysis.