[Does pure-tone audiometry provide inferences for a vascular cause of sudden deafness?]

The theory that sudden hearing loss is caused by some form of vascular catastrophe has not been confirmed by pathological evidence, but it agrees with a number of clinical observations. But there are several pieces of experimental and clinical evidence that cast serious doubt upon a vascular hypothesis, especially the considerable variability in site and degree of cochlear and vestibular impairment. A review of the vascular anatomy of the inner ear makes it clear that many clinically observed audiometric patterns and associated partial vestibular deficits in idiopathic sudden hearing loss cannot be explained by assigning a site of presumed vascular occlusion. We investigated 166 pure tone audiograms of patients with idiopathic sudden hearing loss by using the statistical method of cluster analysis, which allow an explanation based on the vascular anatomy. Three types of audiograms could be found which differed not in shape but in the degree of hearing loss. None of them can be explained by the vascular anatomy. The three groups of audiograms with different degrees of hearing loss allowed investigations of the influence of age, sex, vestibular disturbance and vascular disease. Men are more often affected, the degree of the hearing loss is not dependent on age, vestibular disturbance, vascular disease, diabetes or smoking. The prognosis for sudden hearing loss is independent of all the investigated parameters. Our findings support the conclusion that a vascular hypothesis cannot adequately explain the clinical findings in idiopathic sudden hearing loss.