Sensorineural hearing loss in chronic ear surgery.

The author's series of 3000 consecutive operations of tympanoplasty from 1960 to 1975 were reviewed in regard to the occurrence of sensorineural hearing loss as a consequence of the surgical procedure. Worsening of bone conduction thresholds by 10 dB through the frequencies 500 to 4000 cps, or a 10% reduction in speech discrimination scores were considered significant. Whereas in transcanal tympanoplasty the incidence of cochlear damage was greater in ears when initially the ossiculare chain was incomplete, by contrast in combined approach tympanoplasty the risk was greater when the chain was intact initially. It was concluded that cochlear trauma was usually due to 1) the hydraulic effect of excessive stapes manipulation during the removal of disease, and 2) the development of a perilymph fistula. The unpredictable predisposing threat of cochlear fragility due to genetic and inflammatory factors was emphasized and the poor results of tympanoplasty in tympanosclerosis were underlined. The current methods of treating sensorineural hearing loss after tympanoplasty were enumerated and discussed. It was concluded that although those aimed at improving labyrinthine circulation had theoretical backing, there is as yet little experimental or clinical evidence to support the claims of their protagonists.