[Sudden idiopathic hearing loss. Case reports in the course of ten years]

The authors present a retrospective case study of 132 subjects with sudden-onset hearing loss who had been observed during the course of 10 years. The results were compared with those available in the literature. These patients were divided into two subgroups based on age: over or under 40. The hearing loss was divided into 4 subgroups according to audiogram morphology. Then the presence, and entity, of any recovery in hearing was evaluated. There was no preference for sex while the greatest incidence was found in the VI and VII decade of life. The audiohistograms obtained when the patients were admitted to the hospital and 2 months later indicated an improvement in the hearing threshold localized above-all in the medium-low frequencies. This confirms a better evolution in those forms localized in the apex of the cochlea. The threshold of 60 dB HL is the dividing line between a totally favorable prognosis and a partially or totally unfavorable prognosis. This indirectly confirms that the intensity of the initial hearing damage is an important prognostic factor. From the morphological point of view the forms with the best evolution appear to be those with a flat or rising morphology. The forms with descending morphology do not present a favorable evolution although those with a threshold around 8000 Hz are worse than those with a threshold of 4000 Hz. As regards age no significant differences were found in the evolution of hearing loss between subjects under and over 40. In conclusion, the essential characteristics of sudden-onset hearing loss are as yet poorly defined. There are so many variables affecting the onset and evolution of hearing loss that it proves impossible to perform any statistically valid analysis which includes them all. To date the elements able to provide some degree of prognostic prediction are the audiogram morphology and the entity of the initial hearing loss.