The outer hair cell (OHC) is believed to play an important role for the normal function of the cochlea, and the cochlear amplification is believed to be based on the OHC electromotility. Recently, various studies such as the measurements of the electromotility and mechanical properties of the OHC and the estimation of the force production of the cell using OHC models have been done to clarify the mechanism of the cochlear amplification. In these reports, although the elastic properties of the cell have been well analyzed, the longitudinal viscoelastic properties of the cell, which may affect the basilar membrane vibration, have not been characterized yet. Therefore, in this study, first, the cell was held at cuticular plate by an elastic probe and at a basal part of the lateral wall by a glass pipette, and the cell was stretched to the longitudinal direction and the force generated in the cell was measured. Then, by adapting a three parameter Voigt model, which includes a spring with stiffness k1 in series with a Voigt element containing a spring with stiffness k2 and a dashpot characterized by η, to the measurement results, an attempt was made to evaluate the viscoelastic properties of the OHC. The results are as follows: 1. When the OHC is stretched by the glass pipette, a large force is generated instantaneously and then gradually relaxed. 2. Analyzing the measurement results using the three parameter Voigt model, the stiffness parameters of the OHC k1, k2 and the viscous parameter η in the model are (0. 98±0. 68)×10-3 N/m, (1.0±1.0)×10-3 N/m and (17±13)×10-3 N·s/m, respectively. Based on this model, adaptation and relaxation characteristics of the OHC are estimated, and the adaptation and relaxation times are obtained to be 24sec and 9. 1sec, respectively. 3. It can be said that OHCs show much stronger viscoelastic behavior than erythrocytes and leukocytes.
The distribution of NOergic neurons in the auditory nuclei of the brain stem was studied with NADPHdiaphorase (NADPH-d) histochemical method and nitric oxide synthases (NOSs) immunohistochemical method. The NADPH-d and brain NOS (bNOS) positive neurons were predominantly found in the lateral superior olivary nucleus (LSO), the medial nucleus of trapezoid body, the dorsal cortex, the external cortex and the commissure of the inferior colliculus (DCIC, ECIC and CoIC), and only a small proportion of the neurons in the central nucleus of the inferior colliculus, and the medial division and nucleus suprageniculatus of the medial geniculate body were reactive for NADPH-d and bNOS. The neuropil and neuronal terminals expressing NADPH-d activity and bNOS immunoreactivity were most abundant in the LSO, DCIC, ECIC, CoIC and the dorsal nucleus of the lateral lemniscus. The double staining of NADPH-d and bNOS showed that NADPH-d activity fully accounted for bNOS immunoreactivity in all of observed NADPH-d positive neurons and neuropil, and thus it was clear that NADPH-d activity is a direct marker for bNOS in the auditory nuclei of the brain stem of the rat. From these results, it may be concluded that NO, which is produced by bNOS, appears to play an emportant role in regulating auditory processing and acoustico-motor reflex.
The auditory pathways in the mammalian CNS have ipsi- and contralateral components, therefore the auditory cortex receives stimuli from both ears. This work was carried out to observe the effect of the stimulation side in primary auditory cortex of Japanese monkeys. Three Japanese monkeys (Macaca fuscata) weighing 4-7 kg, were anesthetized with ketamine, xylazine and Nitrous oxide. A craniotomy was performed and electrodes were inserted in order to reach the auditory areas. White noise and pure tones were presented by a dynamic earphone. The stimuli had a linear rise time of 10 msec, a plateau of 20 msec and a falling phase of 10 msec. Varnish-coated tungsten microelectrodes were used to record single unit activity, and post stimulus time histograms and tuning curves were constructed. After the recording, the animals were perfused and parvalbumin staining was done to confirm that the units recorded in this study were located in primary auditory cortex (AI and R). The results revealed that the side of unilateral stimulus (ipsilateral or contralateral) did not influence the best frequency of the AI and R neurons. As there are several cross-overs in the auditory system, the each hemisphere receives the hearing information from both ears. The results of this study are compatible with the hypothesis that there are strong connections between the zones of different areas with the same best-frequency, and the auditory center has a simple systems to process various and complicated auditory informations.
A bacteriological study on acute suppurative otitis media in children was performed to detect major athogens, altered penicillin-binding protein genes from penicillin-resistant Streptococcus pneumoniae (PRSP), and serotypes of pneumococcal isolates. Sixty-seven children under 10 years of age were examined. Approximately half of the subjects were under two years old. One hundred and twelve strains were isolated from nasopharyngeal swabs and 39 strains from middle ear discharge. Major pathogens detected in 45 cases, 68.9% of them were Streptococcus pneumoniae. Of these, 83.9% were not sensitive to Penicillin G. By using the polymerase chain reaction (PCR) method, altered penicillin-binding protein genes were found in 82.6% of the Streptococcus pneumoniae, all of which were either penicillin-insensitive Streptococcus pneumoniae (PISP) or PRSP. Streptococcus pneumoniae with serotypes 19F or 23F were predominantly insensitive to Penicillin G.
Streptococcus pneumoniae and Haemophilus influenzae are leading pathogens of acute otitis media (AOM), and there are recent reports indicating increasing resistance of these bacteria to penicillin and other β-lactams. In this study, we examined the detectable bacteria of middle ear and nasopharynx of 331 children with AOM, under 10 years of age, in Sendai City. The resistance of S. pneumoniae to penicillin and other β-lactams was identified by the polymerase chain reaction (PCR). Of the strains of Streptococcus pneumoniae, penicillin insensitive (PISP) and penicillin resistant S. pneumoniae (PRSP) were identified in 12%-16% and 23-31%, respectively. Similarly, of the strains of H. influenzae, 3% were found to be β-lactamasepositive and 8% were found to be β-lactamase-negative ampicillin resistant (BLNAR). These percentages of resistant strains in the S. pneumoniae and the H. influenzae are increasing compared with those reported in 1996.
The classical term of congenital cholesteatoma has generally been used since Derlacki and Clemis proposed in 1965. However, many questions were recently raised up regarding the terminology that it develops behind the intact tympanic membrane in a patient without previous history of aural infections, because children are likely to have middle ear infection. We retrospectively investigated clinical findings of 10 cases of congenital cholesteatoma, which showed no association with the tympanic membrane, compared to those of 30 cases of acquired cholesteatoma. As a result of otoscopic, X-ray and surgical findings, the followings can be added to the modified terminology: 1. Cholesteatoma is likely located in the tympanic isthmus. 2. It has no relation to the tympanic membrane even though a white mass can be observed behind it. 3. No to little pathologic changes are observed in the middle ear mucosa. 4. The degree of mastoid pneumatization is likely good.
Primary middle ear surgery was performed on 493 ears from January 1988 to September 1998 at Kagawa Medical University. One hundred sixty-five ears with chronic otitis media (COM) followed more than six months after the operation were analyzed. Type I tympanoplasty with mastoidectomy was performed in 83 ears, modified type III with mastoidectomy in 8 ears, and type I tympanoplasty without mastoidectomy in 5 ears. Ordinary myringoplasty was performed in 33 ears, and simple method with fibrin glue in 36 ears. At six months after the operation, the graft success rate for each operation group was 89.2%, 87.5%, 80%, 81.8%, and 72.2%, respectively, and the rate of hearing improvement was 92%, 71.2%, 75%, 84.6%, and 92.3%, respectively. The graft success rate in cases with mild inflammation tended to be higher, but not significant, in the group of tympanoplasty with mastoidectomy compared with the group which underwent tympanoplasty without mastoidectomy and ordinary myringoplasty, whereas the rate of postoperative otorrhea was not significantly different between both groups. Further analysis is necessary to determine the role of mastoidectomy on COM.
Since middle ear reconstruction began to be widely performed a number of different assessments of hearing results has been proposed. The criteria of Clinical Otology Japan (1987) is commonly used in Japan otherwise the post-operative air bone gap is used as a success rate in foreign countries. In this paper we proposed a new concept of “Achievement Rate” as a hearing assessment which is represented “post-operative hearing gain/pre-operative air bone gap”. This parameter simply means the closing rate of the pre-operative air bone gap and also how much the surgeon contribute to the patient within the extent of pati ent's sensory neural ability. Employing this method we made a retrospective study of 373 ears, tympanoplasty without ossiculoplasty in 27 ears, type 1 in 181 ears, type 3 in 151 ears, type 4 in 77 ears. This study suggested that “Achievement Rate” is related to the post-operative air bone gap and postoperative hearing gain neither to pre-operative air conduction threshold nor pre-operative air bone gap. It was concluded that “Achievement Rate” might be usefful for concrete prediction of the post-operative hearing level and analysis of the operative efficacy.
Temporal bone fractures due to skull trauma often associate with facial palsy and inner ear disorders. For the management of sensorineural hearing loss, tinnitus, vertigo and/or dizziness, medical treatments are usually chosen and continued for long time until the symptoms stabilize as sequelae. In our abundant surgical experiences in the treatments of facial nerve paralysis due to temporal bone fracture we found middle ear pathologies such as ossicular dislocation, ossicular chain interruption and perilymphatic fistula frequently triggered the inner ear disorders. Successful surgical corrections of the middle ear pathologies brought dramatic improvements of the inner ear disorders. Based on the experiences we have come to the belief that otologists are responsible to treat surgically not only the facial nerve paralysis but also the middle ear pathologies which induce inner ear disorders. Two representative cases were reported. Case 1 was a 55-year-old female with a transverse fracture of the left temporal bone complaining of deafness, tinnitus, persistent dizziness and unsteadiness. From the findings of pure tone audiometry, tympanogram, left sided positional vertigo, loss of caloric nystagmus and coronal CT, ossicular dislocation and perilymphatic fistula were suspected. Transmastoid exploration of the middle ear revealed the incudostapedial dislocation and the perilymphatic fistula due to a fracture of the stapes foot plate. Following the surgical repair low tone hearing and tinnitus improved. Dizziness and unsteadiness disolved significantly. Case 2 was a 41-year-old male complaining of left facial palsy, deafness and tinnitus. He had a vertical temporal bone fracture and a sensorineural hearing loss of 35 dB in average. The coronal CT suggested a dislocation of the incus. Surgical decompression of the facial nerve together with correction of the ossicular dislocation and reconstruction of the ossicular chain brought immediate improvement of facial palsy and tinnitus. One year follow up examination confirmed normal facial nerve function and normal hearing without tinnitus. Based on the review of the cases and the literatures we conclude that the transmastoid middle ear exploration is advisable in the patients with inner ear disorders associated with temporal bone fracture if middle ear damage is suspected to induce the inner ear disorders.
Ninty-two patients receiving cochlear implantation showed excellent auditory performance. However, six patients had some kinds of subjective dizziness after surgery. Three patients had recurrent dizziness after surgery. Of these, two patients had paroxymal vertigo after surgery, and one patient had persisting dizziness before and after surgery and also CP. The two patients with paroxymal vertigo had normoresponse in the caloric test before surgery, and hyporesponse in the caloric test after surgery, indicating that cochlear implantation must be the cause of their vertigo. One patient with persisting dizziness before and after surgery attemped suicide. Her dizziness was assumed to be caused by depression and not by the surgery. These results suggest that informed consent is very important before surgery to patients with normo- or hyporesponse in the caloric test or with a mental disease.
Epitympanic retraction cholesteatoma is a rather frequently encountered variety of chronic otitis media in which the invagination of Schrapnell's membrane takes place in the attic with disturbed aeration. This disturbed aeration is caused by tubal occlusion or an inadequate ventilation of the middle ear as seen in longstanding secretory otitis media. A cholesteatoma is characterized by resolving the adjacent bony structure. In cases with extended cholesteatoma, the superior wall of the external auditory canal is involved, the scutum is often eroded. We report a case of cholesteatoma in which an unusual growth pattern was observed. In this case, the epitympanic retraction cholesteatoma has projected down straight to erode the superior wall of the external auditory meatus without a significant extension to the middle ear cleft.
A 49-year-old male suffered from hepatitis C complained of vertigo and hearing loss after the attack of abdominal and chest pain. During seven days his pure tone thresholds showed elevation of 10dB. Saxizon® hydrocortizone sodium succinate was given from the dose of 300mg and was tapered every 2 days to 100mg for 6 days. However, more elevation of 10dB was recorded. Saxizon ® was discontinued without further deterioration of hearing. Two month later, he was diagnosed as of mixed type of cryoglobulinemia, and we started the therapy with interferon (INF-α-2b). As a result, liver function and the serum immunoglobulin level were normalized, and hearing level was greatly improved.