Vestibular neuritis: etiopathogenesis.

Vestibular neuritis presents as sudden unilateral vertigo in the absence of hearing loss or neurologic involvement and is thought to be due to neurotropic viruses. Its morbidity is unknown and it affects both sexes equally, with the highest incidence at 40-50 years of age. The etiology of this condition has been ascribed to viral, bacterial and protozoan infections, as well as allergic and auto-immune causes. Inflammation of the vestibular nerve is followed by demyelination and loss of function, which is not always reversible. Higher plasma fibrinogen and CRP levels in the acute phase, longer BERA latency and I-III interval and increased gadolinium uptake in the vestibular nerve and Scarpa's ganglion on enhanced MRI confirm the inflammatory nature of the process. An animal model of vestibular neuritis using retroauricular inoculation of herpes simplex virus in mice, histologic findings in the temporal bone of individuals who had vestibular neuritis, and influenza A virus infection in cultured Schwann's cells suggest viral infection as the main aetiologic cause.