Suppression of post-caloric nystagmus in experimental perilymph fistula

Albino guinea pigs (n = 28) were used to establish an animal model of the p erilymph Fistula (PLF) bq suctioning 2-4 mu l of perilymph via the left rou nd window membrane. At times, varying from 1-3 weeks post-operatively, 9 an imals bad no caloric response, 5 had a weak caloric response and none had p ost-caloric nystagmus (PCN). The remaining 14 animals had caloric irregular ity in lesioned cars: 12 of these (87%) also did not have PCN. Morphologica l study of the latter revealed an intact contour of the membranous labyrint h in the lateral semicircular duct and partial collapse of the utricular wa ll, a condition called the "floating labyrinth". We therefore believe that effective suppression of PCN in the experimental PLF is due to failure in s hort-term adaptation, caused by lesions in the peripheral vestibular organs . such as the floating labyrinth.