Inner ear morphology of experimental perilymphatic fistula.

The inner ear pathology of experimental perilymphatic fistula (EPLF) is described. EPLF was produced by injecting artificial perilymph into the subarachnoid space, or by suctioning 4 microL of perilymph through one of the round window membranes of the guinea pig. The animals were either killed immediately, or were kept alive for 3 weeks to 3 months. The conventional celloidin embedding method was employed for morphologic study. Vestibular function of the animals was tested by observing spontaneous nystagmus and positional nystagmus after the experiment. The caloric test was also performed. Various pathologic changes of the membranous labyrinth were observed. In the cochlea these included rupture or collapse of Reissner's membrane, bulging of Reissner's membrane, loss of hair cells, and compression of the organ of Corti. Pathology of the otolithic organs and semicircular canals mainly consisted of collapse of the membranous labyrinth. Clinical symptoms in patients with perilymphatic fistula (PLF) are explained, based on our experimental findings. Electronystagmography (ENG) of EPLF animals showed either no caloric response or, with a longer duration, caloric irregularity. Prolonged unsteadiness in patients may be due to "floating" labyrinth.