1) The unilateral deafness was found in 12.1% of all the patients of sensori-neural deafness. 2) There were several audiometric patterns such as gradual sloping form, flat form, rising form and dip form. 3) The total deafness mostly occurred in childhood, and the other types of deafness occurred in young adults, the fourth and fifth decades of age. 4) By recruitment test, Békésy audiometer, speech audiometer, speech audiometer, tone decay test and electrocochleography, the lesions were estimated as peripheral in most of the cases, but the retrolabyrinthine type was also encountered. 5) With a long-term follow-up for more than 2 years, progressive sensori-neural hearing loss and fluctuating sensori-neural hearing loss were found. 6) HLA was examined and HLA-AW33 was slightly dominant.
A statistical analysis was made on 233 cases of unilateral perceptive deafness whose causes were unknown in 4 years between 1973 and 1976. The following results were obtained. 1) The rate of occurrence was found in 0.8% of the out-patients, in 5.4% of perceptive deafness, and in 41.7% of unilateral perceptive deafness of known and unknown causes. 2) The male cases were 52.8% and female 47.2%. 3) The age of occurrence was 5-9 years old in the total deaf group, and there was a peak of the occurrence at the young age groups. In the other groups, there was the two-phase distribution of occurrence with one peak at the young age of 5-9 years and the other at the age of around 30. 4) The possibility of a heredity factor was found in 9% and slightly frequent in females. 5) There was no characteristic audiogram in those who were suspected to have a hereditary deafness. 6) The heredity pattern was not simple. 7) Regarding the hearing patterns, more than half were of the total deaf, while high tone hearing loss came to next in number. 8) The most of patients with unilateral perceptive deafness which occurred in their young ages did not have tinnitus or dizziness. 9) There were cases whose hearing loss were altered or improved.
The clinical histories, results of auditory and vestibular examinations of 75 cases, mostly adults, with unilateral sensori-neural deafness of obscure etiology were discussed, and their clinical pictures were presented. Fourty-six cases (61.3%) indicated sensory hearing loss and had many past histories as intrinsic or extrinsic factors such as hypertension, head injury, gastric ulcer, allergy, gynecological surgery, Streptomycin injection, and diabetes mellitus. Five cases (6.7%) indicated sensory and retrocochlear hearing loss simultaneously, 11 cases (14.7%) indicated retrocochlear hearing loss, and 13 cases (17.3%) were unclassified. Some cases with retrocochlear hearing loss of obscure etiology showed probabilities of cerebellopontine angle arachnitis and 46.7% of the patients complained of vertiginous symptoms, and 46.6% showed canal parasis in bithermal caloric examination. Further investigations will be necessary about anatomical and morphological differences in the cases of obscure etiology.
During 7 years since 1971, 97 preschool children of unilateral sensorineural hearing loss with normal hearing contralaterally were either screened out by the hearing screening tests for nursery-school children, or found by the consultations at the Children's Medical and Welfare Center. Seventy-nine children attended for interviews and further examinations. Among 6, 825, preschool children, 10 cases of unilateral sensorineural hearing loss were screened out. Neither sexual nor affected-ear difference was observed. In 57 percent out of 79 patients, the disorder was discovered by their parents before their school age. Etiology was unknown in 89 percent, though about half of them had any suspicious factor in their history. Mumpus was the cause in 8 percent. In other 2 cases (3 percent), the rapid onset of hearing impairment appeared after high fever and earache. Eighty-one percent of them showed severe hearing loss. In 21 percent of the children, the hearing loss was progressed. Caloric test showed canal paresis of the affected ears in 24 percent of the patients. One third of them were in the progressive hearing loss group. No abnormality was discovered by X-ray tomography in the canal paresis group.
This paper reported 126 children with unilateral deafness in whom one ear had normal hearing and the other had total deafness with unknown causes. The results of this investigation were as follows: 1) Unilateral total deafness was found in 16.4% of 770 cases of sensorineural deafness, and 63.0% of 200 cases of unilateral severe hearing loss above 60dB. 2) No differences between boys and girls, and also betweenn right and left ear. 3) The age which child was first noticed to be deaf was between 5 and 6 years. 4) The majority of unilateral deafness was formed in cases that “child has always worn an earphone of telephone to the same ear” and “the affected ear was picked up by the preschool screening test”. 5) Hereditary unilateral deafness was found in 7 cases. The similar audiograms to the patients in each family pedigree were obtained in 6 out of 7 cases.
Fifty patients with “juvenile unilateral severe sensori-neural hearing loss” treated in the authers' clinic during 7 years from 1971 to 1977 were studied. By investigating their clinical histories and the results of hearing and caloric tests, the following findings were obtained. 1) 51% of the patients showed canal paresis of the affected side by Hallpike's caloric test, though few patients complained of vertigo. 2) Regarding to the etiologic factors, the cases with the past history of mumpus and measles showed a high incidence. The patients with mumpus history showed more unilateral hearing loss than “juvenile bilateral hearing loss with obscure etiology”. 3) Four cases showed hereditary problems. 4) In some cases, labyrinthitis due to otitis media and malformation of the labyrinth could not be excluded as the causative pathologic factors. 5) In this investigation “juvenile unilateral severe sensori-neural hearing loss” was characterized by “childrens specifity” rather than a specific pathologic factor.
Electrocochleography was performed on nine patients with unilateral sensorineural hearing loss due to unknown cause. They were tested with trapstympanic promontory electrodes using 0.5, 1, 2, 4, 8kHz tone pip as acoustic stimuli. Electrocochleographic audiograms consisted of the sound pressure level for 0.5μV of CM and AP response were obtained. The AP wave form was also investigated, and aural reflex was tested with reduction of CM amplitude at 0.5kHz. The following pathologic lesions were identified: the cochlea (sensory) in 4 cases, the auditory nerve (neural) in 1 case, the brain-stem in 2 cases, the cochlea and auditory nerve in 1 case and the auditory nerve and brain-stem in 1 case.
A 44-year-old woman who had fluctuating sensoryneural hypoacusis in her left ear without vertigo was reported. The hearing loss fluctuated beetween 40 and 60dB in all frequencies during about 1 year. Audiometric evaluations revealed that the lesion of this hearing impairment might be in the inner ear. Transtympanic electrocochleographies (ECochG) were performed both at the early stage and at 8 months after the onset when the hearing loss was fixed at 40dB. At the early stage, the prolongation of N1-latency, increasing of SP/AP ratio and a wide N1 waveform were observed in ECochG. These findings which were commonly observed in Ménière's disease induced a conclusion that insufficiency of the stria vascularis and endolymphatic hydrops mentioned earlier by Williams, resulted in a reversible fluctuating hearing loss.
A 47-year-old male at first examination to have any one of sudden deafness of the right ear, or gouty inner ear disorder, however, was thought Ménière's disease because of the fluctuating hearing loss these diseases were denied. It was finally confirmed that an aneurysma of the right anterior cerebellar artery by vertebral angiography and this was thought to cause the fluctuating hearing loss. After operation the hearing loss was improved and the hearing remained stationary at 36dB on an average. Vertiginous attack, tinnitus, dull pain of the right head and spastic sensation of the right face also disappeared. Electrocochleographic study showed a steeper input-output function curve of AP on 24 days after the initial examination. Even when the pure tone audiogram showed no response, CM with low voltage was recorded but no AP was recorded. These findings seemed to suggest that the cochlear nerve would be more affected than the cochlear hair cells. The polarity of SP maintained a negative dominant deflection. After the operation, AP wave form became broard. This finding was similar to the broad AP recorded in cases of tumor in the posteriocranial fossa.