Interferon anti-viral system in Bell's palsy.

Thirty-two consecutive Bell's palsy patients were examined clinically and virologically. All the patients were assayed for serum interferon (IFN) levels at onset of the disease and most of them had repeated IFN assays during the course of the disease. In 15 patients the peripheral blood mononuclear cells (PBMC) were also evaluated for the presence of an anti-viral state (AVS). In viral infections, blood IFN levels are invariably increased, and the PBMC are usually in an AVS. Twenty-three patients (72%) had increased serum IFN values or were in an AVS. The mean serum IFN level was 95 U/ml (normal less than or equal to 16 U/ml) during the first 3 days following onset of the disease, declining later to normal values from the seventh day onwards. No patient had increased antibody titers to herpes simplex and varicella-zoster viruses. The increased blood IFN levels and the AVS of blood cells are compatible with an acute viral infection. It is concluded that the etiology of Bell's palsy is most likely an acute viral infection, possibly due to an unidentified or unusual virus, or to reactivation of a latent virus.