An immunological concept for bell's palsy — Experimental study

Bell's palsy is considered by many authorities to be an ischemic paralysis. The mechanism is thought to be a primary vasoconstriction of the vasa nervorum supplying the facial nerve within the fallopian canal and a secondary ischemia induced by the bony canal. The factor precipitating the vasospasm is the proclivity of certain individuals toward segmental arteriolar spasm. In our work.on experimental ischemic facial paralysis, another explanation for the etiology of Bell's palsy presented itself. We observed that dogs sensitized to horse serum showed a greater paralytic response and more marked histopathologic changes after the intrafallopian injection of saline than non-sensitized dogs. Subsequent investigations using a more potent antigen seemed to strengthen the idea that the experimental paralysis we have accomplished in these dogs is the result of an immunologic or hypersensitivity reaction. In these experiments using adequate control dogs, the animals were sensitized with intravenous horse serum and with a Freund's. adjuvant — horse serum mixture. The presence of horse serum antibodies was demonstrated in the serum of three dogs. The fallopian canal was injected with a combination of solutions: saline solution, Ringer's solution, distilled water, horse serum and the dog's serum. At the end of two weeks, the degree of paralysis was recorded, the nerve was removed and was sent for histopathologic examination. The significant degree of paralysis and the major histopathologic changes were seen in the sensitized dogs injected with saline or Ringer's solution or horse serum. The mechanism of the paralysis is postulated to be an initial antigenantibody reaction with a complement fixation, a degranulation of mast cells producing vasoactive components, an increased capillary permeability, edema, vasospastic phenomenia, and subsequent trophic changes in the nerve. In addition, the edematous neuropathy is severely affected by the compression of the nerve by the bony canal wall. We suggest that these events observed experimentally may be related to the changes seen in Bell's palsy, and Bell's palsy is caused by a localized immunologic or hypersensitivity reaction.