We investigated hearing levels of 55 children aged 7-16 with cerebral palsy by pure tone audiogram or COR test. Hearing examination in 40 cases. Two cases of 15 hearing impaired children needed fitting of hearing aid. Diagnostic categories of cerebral palsy in 55 children were 9 athetoid without history of Rh incompatibility, 18 quadriplegia, 19 diplegia, 3 hemiplegia, 4 mixed, 1 ataxic, and 1 unknown group. Hearing impairment was detected in 33.3% of the athetoid and the quadriplegia group, and in 13.63% of the diplegia and the hemiplegia group. This difference was statistically significant (P<0.05). Mentally retarded children had no precise response to pure tone stimuli. And some cases with quadriplegia also needed COR test, although they have normal IQ level. This result suggested that hearing test result was affected by characteristic personality of cerebral palsy (especially quadriplegia) which is immature and dependent reactions to outer stimulations. Therefore COR was very useful hearing test for children with severe mental retardation or cerebral palsy.
Acoustic distortion product (DP) measure in the ear canal was evaluated as an objective and quantitative cochlear function test. Two primaries of iso-intensity and fixed frequency ratio (f2/f1=1.2) were set at 52 frequency combinations, and DP emissions at 2f1-f2 were mesured. Results were evaluated as the “DP audiogram” (DP level plots against f2 frequencies). In normal hearing human ears without obvious middle ear abnormality, DP signals were clearly identified at 10 to 35dB above noise levels, throughout a wide frequency range (0.5 to 10kHz for f2). On the other hand, DP generation in ear with cochlear dysfunctions were disturbed in various degrees. Considering excellent similarities between Békésy audiogram and “DP audiogram”, it is concluded that the DP measure is highly frequency specific. This test can provide invaluable information about fine distribution of cochlear pathology, especially that of outer hair cell system, along the cochlear partition. It might be a major breakthrough in the evolution of cochlear function tests.
Automatic measuring system of synchronous evoked otoacoustic emissions (se-OAE) was developed, and sound pressure level and phase of the output components, which had the same frequency as the stimulus, in normal subjects were measured precisely. Then, the extraction of se-OAE components from the measurement results was attempted by applying vector analysis to the measurement results, and the characteristics of se-OAE were evaluated by the aid of Nyquist plot of the se-OAE components. The following conclusions were obtained. (1) Periodical fluctuation of the measured sound pressure level and phase were dominant in the lower frequency region (f<1.2kHz). (2) Sound pressure level and phase fluctuated on a large scale in the frequency regions where spontaneous OAEs (s-OAEs) were detected, but in some frequency regions where s-OAEs were not detected, their large fluctuation was also observed. (3) Nyquist plot clarified that the rotational velocity of the se-OAE components (dφse/dt or dΔφ/dt) was proportional to the amplitude of the se-OAE components. (4) Frequency interval when Nyquist plot drew a circle was nearly 70Hz, and this value was independent of the amplitude of the se-OAE components and of the existence of s-OAE. (5) The basic characteristics of the measured sound pressure level, which revealed both dip and peak, only peak and only dip, were almost the same as each other, with the exception of the phases of the se-OAE components.
Epidemiological studies of acute profound deafness by sending questionaires to the Japanese hospitals which have more than 200 beds including university hospitals were done between January 1 and December 31, 1987. In the first questionare, the number of patients with deafness who received treatment in 1987 was estimated as follows; 1) sudden deafness in 13, 900-19, 600 patients, 2) idiopathic bilateral perceptive deafness in 800-2, 000, 3) perilymphatic fistula in 200-310, 4) mumps deafness in 200-400, 5) ipsilateral profound deafness in 2, 000-3, 000. In the second questionare, informations regarding three types of deafness, sudden deafness, idiopathic bilateral perceptive deafness and perilymphatic fistula were obtained individually in order to elucidate the clinical manifestations of these diseases. The results were as follows; 1) In sudden deafness, i) the number of patients consulted doctors in early stage have been increased in comparison with those in 15 years ago, ii) prognosis of profound deafness was poor, iii) vertigo was accompanied in one third of the patients. It was found that the prognosis of slight to moderate deafness without vertigo was better than those with vertigo. 2) In idiopathic bilateral perceptive deafness, the number of diagnostically confirmed cases was small. The age distribution study showed that the incidence was higher in teenagers and people over 40 years. 3) Perilymphatic fistula can be confirmed only exploratory tympanotomy, and the number of diagnostically confirmed cases was extremely small.
We attempted to suppress the tinnitus with the use of electrical promontory stimulation (EPS) using Promontory Stimulator (Cochlear Co.). In 59 patients, hearing acuity was normal or profoundly impaired. The causes of tinnitus were an idiopathic sudden deafness, a hearing loss with hair cell damage, ototoxicity, a noise induced hearing loss, labyrinthitis, Meniere disease, acoustic neuroma and unknown origin. Reduction of tinnitus were obtained in 41 of 62 (66.1%). Of these, EPS was most effective in cases of an idiopathic sudden deafness (85.7%; 12/14), followed by Meniere disease (83.3%; 5/6), ototoxicity or a noise induced hearing loss (80.0%; 8/10), unknown origin (76.9%; 10/13), labyrinthitis (71.4%; 5/7). The effect was hardly found in patients with acoustic neuroma (8.3%; 1/12). Seventeen patients reported residual inhibition and it's duration ranged from several hours to a few weeks. Our results suggest that tinnitus due to cochlear lesions can be suppressed by EPS. This technique may be useful for differentiation of tinnitus of the cochlear lesions from the retrocochlear lesions.
Low-frequency sensorineural hearing loss (SNHL) of various extent developed in 14 of 963 patients who underwent microvascular decompression for hemifacial spasm. Surgical records revealed that all of them had excessively short recurrent perforating arteries (RPA), so that the artries were stretched during surgery. Occlusion of RPA is suspected to cause a lateral brain stem infarction and resulted in low-frequency SNHL. Only 4 of the 14 patients, however, noticed ipsilateral roarling tinnitus. These 4 patients had short RPA surrounding the entry zone of nerves VII and VIII, and showed Horner's syndrome. These findings suggest that the lesion of these 4 patients situated in the region near the cochlear nucleus and dorsolateral to the inferior olivary nucleus. We suspect that involvement of the proximal cochlear nerve and its nucleus may cause roaring tinnitus, but involvement of more distant neural structures may cause no roaring tinnitus.