Nystagmus induced by insertion of black ink into the stylomastoid foramen in rabbits (author's transl)

Abstract

The purpose of this paper is to present the results of insertion of 0.3 ml black ink into the stylomastoid foramen in 30 rabbits.In all animals, vestibular nystagmus lasting from 30 seconds to 20 minutes was elicited. As to the quick phase of the elicited nystagms, there were three groups of responses. In Group A (i i of 30 animals), after insertion of black ink, horizontal nystagmus to the inserted side lasting from 4 to 45 seconds were first observed and after this period, nystagmus to the opposite side lasting from 35 seconds to 20 minutes was elicited in 7 of 11 animals, and in one, the direction changed to vertical in nature. In Group B (14 of 30 animals), horizontal or oblique nystagmus to the opposite side of the insertion lasted from 40 seconds to 7 minutes and 45 seconds without changing direction. In Group C (5 of 30 animals), after the procedure, upwards vertical nystagmus lasting from 15 seconds to one minute and 35 seconds was first observed and after this period, in 4 of these 5 animals, oblique or horizontal nystagmus lasting from one to 8 minutes was elicited.Ten days after the above mentioned procedure, all animals were sacrificed. Macroscopically, the black ink inserted into the stylomastoid foramen flowed into the internal ear canal through the facial canal (Fig. 1) and optically and scanning electron microscopically, it was not found in the perilymphatic or endolymphatic spaces (Fig. 2)From this results, it was emphasized that nystagmus induced by insertion of black ink into the stylomastoid foramen in rabbits was not due to the stimulation of the endorgen in the labyrinth, but due to the stimulation of the vestibular nerve fibers.