顔面神経減荷手術―Bell麻痺を中心に―

Abstract

Bell’s palsy is one of the most common causes of facial nerve paralysis, usually on one side of the face, that has no known underlying cause. The natural course of this disease is generally favorable, and approximately 70% of patients recover completely without treatment. The pathogenesis of Bell’s palsy involves herpes simplex virus infection, inflammatory changes, secondary edema, and entrapment neuropathy in the narrow fallopian canal. Steroids and adjunctive antiviral agents are the treatment of choice. However, approximately 10% of patients do not respond to conservative treatment and experience profound denervation leading to severe sequelae. The treatment strategy for severe paralysis is acceleration of recovery by preventing further worsening of nerve degeneration in the early phase of the incident. Facial nerve decompression surgery is indicated in cases of Bell’s palsy suspected to have a poor prognosis, usually within 2 weeks of onset. Since Ballance and Duel first reported decompression of the facial nerve at the distal mastoid segment in 1932, several treatment procedures have been proposed; however, there only very low quality evidence exists, based on which an informed decision could not be made as to whether an operation would be helpful or harmful for patients with Bell’s palsy. Currently, most patients are treated medically, and decompression surgery is rarely undertaken. Decompression more than 2 weeks after the onset of paralysis is particularly rare because the surgical procedure is unlikely to facilitate nerve regeneration. However, the history of, the evidence for, and the procedure of facial nerve decompression surgery are still interesting for neuro-otologists who have to treat patients with severe Bell’s palsy, therefore those must be described in detail.