The initial and final hearing levels of patients with sudden deafness were investigated using the hearing distribution as a parameter to elucidate the clinico-pathological feature of sudden deafness.
The hearing distribution was obtained by calculating the moving average values from the values of the frequency distribution (audiohistogram).
The pure-tone hearing levels of 407 cases with sudden deafness, who visited Kitasato University Hospital within four days after the onset were investigated at each frequency of 250-8000Hz. Three peaks, at normal hearing level, ca 70dB level and out of scale level, were observed in the hearing distribution of the initial and final audiograms. From the analysis of the hearing distribution of the hearing-improved and unimproved cases, it was revealed that the peaks were formed inevitably.
The relation between the pathological features of sudden deafness and the peaks in the hearing distribution was discussed.

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Main pathological change of Sudden deafness (SD) has been regarded as damage of the inner ear partition and it is supposed to be multiple and complex. Recently evoked otoacoustic emissions (EOAEs) have been expected as an objective test of the inner ear function assessment. Prognostic estimations of SD cases were studied with EOAEs in 73 cases which were evaluated by means of pure tone audiometry and EOAEs once a week as a rule during the treatment. The cases were classified into four (complete, prominent, partial recovery and no change) groups according to the degree of pure tone hearing improvement. The complete recovery group was compared to the partial recovery group. In the complete recovery group consisted of 24 cases, the minimun detectable levels of each components (fast and slow) of EOAEs improved with a slight delay from the recovery of pure tone hearing levels. Some of them showed a little improvement even after the fixation of hearing levels. The slow component showed striking recovery than that of the fast component. In contrast, in the partial recovery group consisted of 23 cases, changes of the minimum detectable levels of EOAEs showed no uniform tendency. The slow component frequently showed the absence and/or fading out. The conclusion was as follows, 1) the minimum detectable levels of EOAEs improved with a slight delay from the recovery of pure tone hearing levels, 2) the slow component was more sensitive to the inner ear damage, 3) the existence of the slow component in an early stage of the illness and quick recovery of the minimum detectable level to below that of the fast component suggested a good chance of the complete hearing recovery, 4) prognostic estimation of SD with EOAEs was successful with this tendency, 5) it is not possible to predict the prognosis of SD only with the initial EOAE result.

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Viral infections are assumed to play an important etiologic role in sudden deafness but most evidence so far has been circumstantial. Correlating the cochlear locations and symptomes of sudden deafness, it is assumed that lesions of stria vascularis, primary neurons and tectorial membrane are able to accout for sudden onset and reversibility of the perceptive deafness.
The survey of the previous reports on the experimental viral labyrinthitis suggests that paramyxoviruses such as mumps and Sendai viruses are the candidate of etiologic agents because of selective involvement of stria vascularis in a rather localized segment of the cochlea.
Serological studies of the patients revealed that seroconversion was most frequent in 5 viral infections, e. g. mumps, rubeola, varicella-zoster, CMV and influenza B.
In addition to primary viral infection, reactivation of herpes virus family is deemed as another possibility of sudden deafness.
Detection of HSV-1 and varicella-zoster virus DNA or RNA in the human spiral ganglia appears a supportive evidence for reactivation of those viruses.

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To investigate the role of pathology of the stria vascularis in sudden deafness, microvascular change and atrophy of the stria vascularis were examined by histological observation in guinea pig temporal bones with experimental endolymphatic hydrops. Blood cell sludge and vasoconstriction accompanied with strial atrophy were observed in the vessels of the lateral cochlear wall of the inner ear with endolymphatic hydrops exposed to noise, suggesting the development of the inner ear circulatory disturbance. Furthermore, circulatory disturbance of the stria vascularis induced by thrombi and microsphere caused strial atrophy and slight collapse or fluctuation of the Reissner's membrane. These results suggest the possibility that the pathological findings of sudden deafness such as strial atrophy, circulatory disturbance in the stria vascularis and endolymphatic hydrops might be closely related each other.

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We compared the results of two epidemiological surveys of idiopathic sudden sensorineural hearing loss (sudden deafness) conducted by the Research Committee of the Japanese Ministry of Health and Welfare. The incidence of patients with sudden deafness was high between 30 and 49 years of age in 1972, whereas it was high between 50 and 59 years of age in 1987. When we calculated the incidence of sudden deafness in the overall population, this disorder was found to be more frequent in people between 50 to 59 years of age both in 1972 and 1987. However, the incidence of sudden deafness per population was more frequent in people from 50 to 75 years of age in 1987 than in 1972. In 1972, sex distribution was significantly higher in men than women (909 males vs 765 females, P<0.01). In 1987, there were more women than men although the difference was not significant (730 males vs 760 females).
We also performed a case control study of sudden deafness. It was found that sudden deafness occurred more frequently in people who had fatigue and in people who caught a cold within one month before the onset of sudden deafness.

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At the present time, there is no specific test for hearing loss related to immune disorders. Steroidresponsive sensorineural hearing loss (SNHL), however, can be diagnosed by the responsiveness of hearing to steroid therapy with predonisolone (PSL).
Although it is relatively uncommon, it is important to recognize steroid-responsive SNHL, since it is treatable.
In the present study, steroid-responsive SNHL was classified into three types (systemic, localized and syphilitic). The clinical findings in cases of each type were examined, and a method of early diagnosis for steroid-responsive hearing loss was proposed. The combined use of the herbal medicine Saireito with PSL facilitated the reduction of the maintenance dose and decreased side-effects.
Because there were discrepancies in the steroid-responsive hearing loss proposed by the author and the autoimmune sensorineural hearing loss described by McCabe, it was surmised that interracial differences may exist in hearing loss related to immune disorders.

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A total of 230 patients (232 ears) with traumatic perforation of the tympanic membrane, including 132 patients of direct injuries and 98 patients of indirect injuries, visited the Department of Otolaryngology, Iwate Medical University, during the past 11 years (1980-1990).
Of 230 patients, 98 patients with tympanic perforation due to indirect injuries were clinically studied in this paper.
The results were as follows:
1. As a cause, slapping was observed most freqently in 59 eras.
2. In 71 ears, the size of perforation was small, and these perforations were observed more freqently in the anterior-lower quadrant of the tympanic membrane.
3. The mean period for healing of a tympanic perforaion was in 26 days of the patients with a small tympanic perforation, and 37 days with a middle or large perforation. In most of cases, the perforation was healed spontaneously within 2 months.
4. Good hearing recovery was obtained in most cases. In 11 patients with bone conduction hearing loss hearing recovery to normal range was obtained after healing of their tympanic membrane perforation.

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The combined approach of lateral tympanotomy with reconstruction of defective posterosuperior wall of the external auditory canal was performed in 150 ears, regardless to the complications' of cholesteatoma. The following findings were obtained.
1) Satisfactory prognosis was confirmed in 90% of the total cases operated on, and this technique was considered to heve a wide indication.
2) Occlusion of the anterior tympanic isthmus along a ventilating route, caused either by granulation or cholesteatoma, was found in all cases with poor prognosis during the exploratory reoperations. Thorough anterior tympanotomy should, therefore, be made in order to prevent possible postoperative ventilatory failure.
3) Cartilage plate was considered more suitable for the reconstructive material than a piece of cortical bone, because the reconstructive operations were easily done with the combination of cartilage plate and fibrin glue, whereas an interstice was even tually developed between a piece of cortical bone and the external auditory canal.
4) Recurrence of cholesteatoma was observed postoperatively in 3 of 27 cases of cholesteatoma in the pars tensa. Accordingly, the indication of this technique should be deliberately considered for the surgical treatment of cholesteatoma in the pars tensa.

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Forty two ears with tympanosclerosis, operated on from 1982 to 1992, were examined. Patients' age ranged from 12 to 72 years, (49.7 years on the average). There were 6 males and 36 females. Thirty seven ears showed more than medium perforation of tympanic membrane and only 2 ears showed otorrhea. Dry tympanic membrane was noted in the others.
Sclerotic tissue was located in the tympanic membrane (35 ears, 83%), on the malleo-incudal joint (31 ears, 74%), and around the oval window (17 ears, 40%). Sclerotic tissue around the oval window was connected to that of the malleo-incudal joint. The long process of the incus was missing in 10 ears or 24%. The superstructures of the stapes, all but one, were present. Tympanoplasty type I was performed in 19 ears, type III with ossicular reconstruction in 22 ears, and type IV with ossicular reconstruction in one ear.
During postoperative follow up, tympanic membrane perforation was encountered in only two patients. An air-bone gap closure of less than 20dB was achieved in 18% of 17 ears with sclerotic tissue around the oval window and 72% of others 25 ears, or 50% of all patients.
Sclerotic tissue around the oval window severely affected the postoperative air-bone gap, but had no effect on pre-and postoperative bone conduction.

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Cholesterol granuloma with blue ear drums is considered to be related to progressive otitis media with effusion. We investigated the surgical indication and hearing prognosis of 5 cases of cholesterol granuloma that were observed for more than 1 year.
All subjects fulfilled the following criteria.
1) The tympanic membrane was blue and revealed cholesterol crystals in the middle ear effusions.
2) CT scan findings showed a soft tissue density after elimination of effusion.
The surgical indication was made when the aditus was blocked on CT scan findings.
After the removal of the effusion, improvement of low frequency hearing was not better than middle and high frequencies.
The operative methods included mastoidectomy, posterior tympanotomy and tube insertion. There was black mastoid and aditus block noted but the ossicular chain was intact.
Postoperative hearing showed air-bone gap in low frequency tones. We thought the hearing disturbance of low frequency was caused by increased stiffness of the ossicular chain.

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Although ossicular abnormalities can frequently be seen in clinical practice, familial congenital ossicular malformations are rare. We report a daughter (11-year-old) and her father (44-year-old) with bilateral congenital ossicular malformations.
Their auricles and external auditory canals were normal, and they had no other anomalies in general. Tympanotomy disclosed a bony fusion of the head of the malleus and the body of the incus, defect of the long process of the incus and deformity of the head of the stapes in each ear in both patients. Interposition between the handle of the malleus and the crura of the stapes with the body of the incus was performed. In 4 ears, postoperative hearing improvement about 40dB was achieved in the following 5 years.
A review of the literature suggested that familial congenital ossicular malformations may be inherited as autosomal dominant traits. Our cases showed familial, bilateral and same malformations which affected both sexes. So these findings suggested inheritance of autosomal dominant traits in the present cases.

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A pattern of audiogram and duration before treatment are considered to be important factors affecting the prognosis of idiopathic sudden sensorineural hearing loss. We studied 73 cases with horizontal audiogramic pattern on the first examination visiting our hospital within 5 days after the onset. We evaluated the prognosis using recovery rate in this study, and compared the recovery rate among cases which were classified by the difference of days before the first examination after onset, age, the mean hearing level between 250Hz and 8000Hz or each frequency. There was a statistically significant difference in recovery rate between patients with the mean hearing level under 70dB and those above 70dB on the initial examination. The hearing in the cases completely recovered tended to improve within 10 days after the onset. In conclusion we considered that we could predict the prognosis of idiopathic sudden sensorineural hearing loss with the horizontal audiogramic pattern by investigating both the initial mean hearing level and the time course of hearing within 10 days after the onset.

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Seven patients with traumatic perilymphatic fistula caused by an earpick were reported. Averaged age of these patients was 27.1 years and 6 out of 7 patients were female. In most of the patients, traumatic perilymphatic fistula was developed when a child ran against a patient who was cleaning the ear canal with an earpick. Vertigo, dizziness and dysequilibrium were most common chief complaints in these patients, while hearing loss, tinnitus, plugged sensation of the ear and ear pain were also observed in most of the patients. A perforation was observed in the posterior-superior and/or -inferior quadrants of the tympanic membrane in each patient. Pure-tone audiometry revealed mixed hearing loss with various degree of hearing level. Six out of 7 patients showed spontaneous nystagmus directed to the unaffected side. Fistula test was positive in all patients. The patients underwent the closure of perilymphatic fistula and ossicular reconstruction, and hearing loss was recovered in 4 out of 7 patients.
The diagnostic and therapeutic problems for traumatic perilymphatic fistulas caused by an earpick were discussed.

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Three cases of steroid responsive sensorineural hearing loss are reported. They were all female and have no known systemic diseases.
The value of fibrinogen, CRP and ESR were higher than normal range in one of 3 cases whose data were measured. Those data fluctuated according to the hearing loss with steroid treatment. The cause of high fibrinogen, CRP and ESR is unknown but could be due to inflammatory changes including autoimmune mechanism.
The measurement of fibrinogen, CRP and ESR was one of the important parameters to observe steroid effectiveness for the hearing loss and to reduce the dose of steroid in a steroid responsive sensorineural hearing loss.

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The relationship between click evoked otoacoustic emission (EOAE) and distortion product otoacoustic emission (DPOAE) was investigated. The subjects were 42 normal-hearing ears which showed the pure-tone hearing level of 20dB or less at all 7 frequencies between 125Hz and 8kHz.
The EOAE was elicited by non-linear clicks of 82±1dBSPL produced from the Otodynamic Analyser ILO88D (Version 3.51) and the FFT analysis of the EOAE wave was conducted. Three parameters such as total echo power (TEP), highest peak power (HPP) and frequency area peak power (FAPP) in 6 frequency areas were analyzed.
The DPOAE was recorded by the Otodynamic Analyser ILO92 (Version 1.31). The F₂/F₁ ratio was fixed between 1.18 and 1.20, and the DP level at 2F₁-F₂was investigated at 14 F₂points between 708Hz and 6299Hz. The stimulus intensity of primaries was fixed to 70dBSPL at F1 and 60dBSPL at F₂, respectively. Three parameters such as total DP level, highest DP level and DP levels at individual F₂points were analyzed.
The results obtained were as follows;
1) When the relationship between TEP in EOAE and total DP level in DPOAE was investigated, a highly positive correlation was found between them (r=0.82).
2) The HPP in EOAE and the highest DP level in DPOAE also showed the positive correlation (r=0.60).
3) When the FAPPs in 6 frequency areas of EOAE and the DP levels at 14 F₂ points of DPOAE were compared, they showed the highest positive correlations in corresponding frequency areas.
4) The results obtained in this study suggested the possibility that both the EOAE and the DPOAE were derived largely from the similar generation mechanisms within the cochlea.

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The frequency selectivity evaluated by psychophysical tuning curve (PTC) was investigated in 12 cases of unilateral cochlear deafness (CD) of unknown cause and 13 cases of surgically proven unilateral acoustic neuroma (AN).
Test tones were pure-tones of 1-2 seconds duration with the intensity of 5dB above the hearing threshold at 1000Hz and 4000Hz which were produced from a pure-tone audiometer (RION AA-67N). Masking tones were continuous pure-tones at 500Hz, 800Hz, 1500Hz and 2000Hz for 1000Hz testing, and at 2000Hz, 3000Hz, 6000Hz and 8000Hz for 4000Hz testing. These masking tones were produced from a pure-tone audiometer (RION AA-61BN) and were presented by the simultaneous masking method. The PTC in each ear was drawn from the minimal masking levels at 4 masking frequencies and test tone's level. The angle at tip region (tip angle) of PTC was adopted to be the quantitative parameter to investigate the frequency selectivity in this study.
The results obtained were as follows;
1) The tip region of PTC was sharp and the slope of PTC in high frequency side was steeper than that in low frequency side in normal-hearing ears (unimpaired ears of the subjects).
2) The intersubject variance of tip angle of PTC was relatively small in normal-hearing ears.
3) The tip angle of PTC slightly widened as the elevation of hearing threshold at test frequency even in normal-hearing ears. This result suggested that the frequency selectivity could slightly be deteriorated as the elevation of hearing threshold even in normal-hearing ears.
4) When the relationship between the hearing threshold at test frequency and the tip angle of PTC was analyzed, the slope of the regression line in CD and AN ears was steeper than that in normal-hearing ears. This result suggested that the frequency selectivity in CD and AN ears could more apparently be deteriorated as the elevation of hearing threshold than that in normal-hearing ears.
5) Based upon these results, it was concluded that the analysis of the tip angle of PTC enabled us to quantitatively evaluate the frequency selectivity in the individual ear.

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In order to study the correlation between amplitude of the summating potential (SP) and the cochlear microphonics (CM), electrocochleograpy was performed in 23 adults with normal hearing, 26 patients with low tone sensorineural deafness, 10 patients with high tone deafness, and 34 patients with Meniere's disease. The particular correlation was not always observed between SP and CM amplitude in various inner ear conditions. In patients with Meniere's disease whose hearing disturbance were reversible, high correlation was observed between SP and CM amplitude at 0.5 and 1kHz. In these cases, it was speculated that the endolymphatic hydrops would influence the cochlea from basal turn to apical turn, and CM amplitude at 0.5 and 1kHz and SP amplitude would be increased.

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The fluid pathway inside the nerve fascicles was examined along with endoneurial vascular permeability using the tracer technique in the rabbit facial nerve. Fluorescent substances such as sodium fluorescein (M. W. 376) and fluorescein labeled dextran (M. W. 40, 000) were injected intravenously or into the nerve trunk, and then localized by fluorescence microscopy.
The tracers penetrated into endoneurium as well as epineurium and perineurium after intravenous injection and spread along the endoneurium following injection into the nerve fascicles. No penetration into nerve fibers was observed. Furthermore, in the endoneurium red connective tissue fibers characteristic of collagen fibers were stained red with van Gieson Staining.
In this study, it was suggested that the endoneurial connective tissues constitute an extravascular fluid pathway within the nerve fascicles and that endoneurial collagen fibers seem to play an important role.

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Lately, it is reported that sudden deafness and the deafness followed by cisplatine treatment might be related to free radicals. However, the distribution of SOD (superoxide dismutase) in the rat inner ear is not elucidated. In this study the distribution of MnSOD (manganese superoxide dismutase) in the rat cochlea was revealed by immunohistochemical stain. The distribution pattern might suggest that the rich vascular areas were positively stained and MnSOD can be used as an induceble enzyme.

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