Pneumolabyrinth in perilymphatic fistula: report of three cases.

In three patients with perilymphatic fistula, exploratory tympanotomy revealed air bubbles emerging through the ruptured round window membrane. Review of the literature disclosed three case reports in which air was demonstrated in the labyrinth in association with perilymphatic fistula. Experimental evidence that air could enter the labyrinth through a defect of the round window membrane was described in two articles. In our patients, the perilymphatic fistula was produced by implosive force. When a perilymphatic fistula was produced by implosive force, or in the case of a pre-existing perilymphatic fistula, we assume, air may enter the scala tympani through the defect of the round window membrane if the middle ear pressure rises beyond a certain limit. Sudden onset of deafness and reversibility of hearing in perilymphatic fistula could be attributable to the presence of air bubble in the scala tympani--pneumolabyrinth--which might disturb propagation of the traveling wave of the basilar membrane.