Twenty-nine patients with unilateral severe sensori-neural hearing loss were studied in the light of preservation of semicircular canal function. Most ears were incidentally found to be deaf at the age of 3 to 13, but 4 adult ears became deaf after mumps infection. Twenty-five out of 29 were total deafness and other 4 had residual hearing at 254 and 500Hz. Twenty-four ears had good response to 2ml ice water, but three ears revealed vestibular hypofunction. Serological studies using complement fixation and hemagglutination inhibition tests were done to clarify the etiologies of the deafness with preserved semicircular canal function, and these tests revealed no specific cause of the unilateral deafness. The conclusion of this study was that pathology of the severe unilateral sensori-neural deafness in children was in general in the cochlea and that most of the cases preserved the semicircular canal function.
During the period between August 1973 and May 1978, 42 children under 10 years of age with unilateral total deafness, were treated in Fukuoka University Hospital. Etilogy of unilateral total deafness was not determined in most cases, but among these 42 cases, it was found that 10 cases (23.8%) became certainly and 11 cases (26.2%) possibly deaf unilaterally after mumps.
Three cases with fluctuating hearing loss were discussed, and the threshold shift by torsion of the neck was remarkable when hearing was good. But, the threshold shift was absent when the hearing was not good.
Three experiments were made on the effect of stimulus rise time on the latency of the most prominent positive deflection of the auditory brainstem response. In the experiment 1, tone bursts of fixed intensity and duration were presented at various rise times of 1 to 9 msec. The latency of the response increased with an increase in the stimulus rise time. In the experiments 2 and 3, tone bursts and pips with a rise of a given slope were presented at various rise times of 0.5-1 to 5-10 cycles. The response latency was almost invariable in the change of the stimulus rise time. The results suggested that the appearance of the response was mainly attributed to the initial 0.5-1 cycle of the stimulus tones. The successive part of the stimulus seemed not to take part in evoking the response so far as the initial part was intensive enough to elicite the response.
Electrically and acoustically evoked brain stem responses were compared in guinea pigs. Electrical stimulation of the cochlea was made by two electrodes, one to the scala tympani of the basal turn, and the other to the scala media of the third turn. Six hundred consecutive responses were averaged by a computer. Responses evoked by the direct stimulations of the cochlear, vestibular and facial nerves were respectively recorded by the same procedure. Electrical stimulation of the cochlea could evoke a response with successive five to six waves within 8 msec, of which the fourth wave was most prominent and stable. This response was similar to that one elicited by auditory stimuli. Direct stimulation of the cochlear nerve could evoke the same pattern of the response. On the other hand, stimulations of the vestibular and facial nerves could evoke definitely different responses, or even could evoke nothing.
Three cases in a family with hereditary unilateral deafness with malformations of the internal ear is reported. The proband is a 12-year-old girl, and her audiogram revealed unilateral deafness of the right ear. Her mother (38-year-old) has also deafness of the right ear. Caloric vestibular tests of the mother and daughter showed normal response. The patient's maternal grandfather has been deaf in the right ear since his youth. There was a consanguineous marriage, and the maternal grandfather was cousin of grandmother. X-ray of the temporal bones of the mother and daughter showed stenosis of the internal auditory canal and aplasia of the cochlea.