Glutamate-aspartate transporter (GLAST), a powerful glutamate uptake system, removes synapticallyreleased glutamate from a synaptic cleft and facilitates re-use of glutamate as a neurotransmitter recycling system. When the function of GLAST is disturbed, glutamate is no longer absorbed from the synaptic cleft. Excessive glutamate thus deposited in the cleft eventually spreads to the surroundings and causes excitotoxicity to the neural tissue. The present study was conducted to disclose the role of GLAST on postnatal hearing in GLAST deficient mouse. As a result, threshold of auditory brainstem response (ABR) was higher in GLAST deficient mouse than in wild mouse at 6 or 9 months after birth, although there was no such difference at 3 months. Histological examinations showed that the hair cells, especially the inner hair cells (IHCs), sporadically disappeared and the number of spiral ganglion cells (SGCs) reduced at 9 months in GLAST deficient mouse. We speculated that in GLAST deficient mouse, glutamate excessively deposited in the synaptic cleft may have leaked to the surroundings and induced degeneration of the IHCs and SGCs. From these findings, dysfunction of GLAST can be a cause of progressive sensorineural hearing loss of unknown origin.
To examine the effects of p38 mitogen activated protein kinase (MAPK) on acoustic injury, specific inhibitors of p38 MAPK (SB203580, SB202190) were given to albino guinea pigs immediately prior to exposure to a 2 kHz pure tone of 120 dB SPL for 10 minutes. The amplitude of distortion product otoacoustic emissions (DPOAEs) and the threshold of compound action potential (CAP) were measured before, immediately after and one week after the acoustic overexposure. The p38 MAPK inhibitors significantly ameliorated the cochlear dysfunction one week after the acoustic overexposure. These results suggest that p38 MAPK inhibitors possess protective effects against acoustic injury.
The 18p- syndrome which is caused by partial or total deletion of the short arm of chromosome 18 presents multiple clinical features ranging from severe malformations in compatible with life, to mild physical abnormalities. There has been no report describing the temporal bone histopathology in the 18p- syndrome. This case is the first reported temporal bone histopathology in the 18p- syndrome. The female stillborn infant delivered at 25 weeks' gestation was applicable to the severe form of this syndrome. The histopathologic findings demonstrated relatively mild malformation of the ossicles, facial nerve and cochlea. Because of mild aural anomalies in the severe form of 18p- syndrome, and because of few clinical reports involving deafness, the possibility of severe aural anomalies or profound deafness associated with 18psyndrome seems to be slight, though this conclusion needs further investigation on cases of this syndrome.
Recently, penicillin resistantStreptococcus pneumoniae (PRSP) and β-lactamase-negative ampicillinresistantHaemophilus influenzae (BLNAR) have been increased among children with acute otitis media. These resistant bacteria were becoming less susceptible to commonly prescribed oral antibacterial drugs. We studied clinical effect and utility of surgical management that bacteria were isolated 91 patients with acute otitis media between April 2001 and March 2002. In addition, we investigated the effectiveness of cefditoren pivoxil (CDTR) for three major bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis) in all bacteria isolated from the outpatients with acute otitis media. InHaemophilus influenzae, especially, we conducted gene level studies using PCR to identify resistant gene. The clinical effect on all bacteria was 72.5%. Myringotomy was effective more than conservative treatment for acute otitis media. Three major bacteria wereStreptococcus pneumoniae (30 strains, 30%), Haemophilus influenzae (24 strains, 24%) andMoraxella catarrhalis (7 strains, 9%). The Streptococcus pneumoniae strains included PSSP 16 (53%), PISP 10 (33%), and PRSP 4 (13%). TheHaemophilus influenzaestrains included BLNAS 9 (38%), Low-BLNAR 13 (54%), and BLNAR 2 (8%). The clinical effects of CDTR in patients with PSSP, PISP, and PRSP was 67%, 80%, and 100%. The clinical effects of CDTR in patients with BLNAS, Low-BLNAR and BLNAR was 100%, 77%, and 50%.
Prospective studies were performed to evaluate short-term tympanostomy tube insertion in comparison with myringotomy to treat infants and children with acute otitis media. Insertions of the Grommet type tympanostomy tube were performed under local anesthesia. The results were as follows: 1. Among 150 cases, 65 cases were evaluated after a short-term tympanostomy tube insertion and 69 cases were also evaluated after myringotomy. Sixteen cases could not be evaluated. 2. We evaluated the duration of antibiotic administration, the duration for the cessation of aural discharge, the duration for the normalization of the tympanic membrane, recurrence of acute otitis media and occurrence of injection of the tympanic membrane. 3. Significant difference was recognized for duration of antibiotic administration, recurrence of acute otitis media and occurrence of injection of the tympanic membrane. Regarding these points, short-term tympanostomy tube insertion was more effective than myringotomy in this series. Regarding duration until the normalization of the tympanic membrane, myringotomy was more effective than the short-term tympanostomy tube insertion. 4. Based on this study, we conclude that the short-term tympanostomy tube insertion is useful for treatment of acute otitis media in infants and children. 5. By the short-term tympanostomy tube insertion, the duration of antibiotic use may be shorten, and it may reduce the development of resistant bacteria.
Forty ears with auditory ossicular malformations without deformities of the external meatus, were treated at the Department of otolaryngology, Hokkaido University Hospital over a 15-year period. The pathological conditions were classified according to the surgical findings. The classification results were as follows. Absence of the incudo-stapedial (I-S) joint was seen in 19 ears (47.5%), fixation of the malleus and/or incus in 2 ears (5%), fixation of the stapes in 9 ears (22.5%), and absence of oval window was seen in 4 ears (10%). Ossicular reconstructions were performed in 36 ears and exploratory tympanotomy without ossicular reconstruction was performed in the other 4 ears. The modified type method was performed in 15 ears and the modified type IV method was performed in 8 ears. The small-fenestra stapedectomy was performed in 10 ears and the total or partial stapedectomy was performed in 3 ears. We also evaluated hearing results in 30 ears more than six months after the operation. Hearing improvement after the operation was observed in 93. 3%(28 ears) of the cases.
Seventy five patients underwent gaze, positional and positioning nystagmus tests in order to determine the origin of nystagmus after middle ear surgery. Nystagmus after surgery was observed in 44 (59%) out of 75 cases. The rates of detected nystagmus in the positional and positioning nystagmus tests were about twice as much as that in the gaze nystagmus test. Nystagmus before surgery was observed in 22 (28%) out of 75 cases, and nystagmus after surgery was observed in 21 (95%) out of these 22 cases. Nystagmus after surgery was observed in 23 (43%) out of 53 cases in which nystagmus before surgery was not observed. The rates of detected nystagmus after surgery in cases with manipulation of the ossicle or with mastoidectomy used by a surgical drill were higher than those without them. There were some cases when postoperative nystagmus occured due to general or local anesthesia. These results suggest that nystagmus after middle ear surgery could be caused by vestibular irritation due to chronic otitis media, manipulation of the ossicle, vibratory effects of the surgical drill and general and local anesthesia.
Two cases that presented stapedial suprastructure detached from the footplate are reported. The first patient was a 28-year-old male from South Asia with bilateral severe hearing impairment. Pre-operative examination indicated a fixation of the ossicles in the right ear and detachment in the left. He received surgery for three times in his both ears and hearing was improved to mild degree. The left stapes was characterized by the separation of anterior and posterior crus from the footplate. It was speculated that there was a dysembryoplasia in the first and the second branchial arches. The other case was a 30-year-old Japanese female with bilateral mixed hearing loss associated with decalcification of the temporal bone, blue sclera, previous fracture in the elbow and hereditary similarity. This was a case of osteogenesis imperfecta, known as van der Hoeve syndrome, which often shows bony fragility with possible involvement of the middle ear. The surgery was successful. The stapedial suprastructure was easily removed due to the separation from the footplate. It is suggested that this separation was induced by bony fragility.
A 13-year-old boy complained of a left hearing loss after a head injury sustained when skiing 3 weeks previously. A pure-tone audiogram revealed a left conductive hearing loss and right high frequency sensorineural hearing loss. Results of tympanogram and acoustic reflex of the left ear showed Ad-type tympanogram and inverted response to ipsilateral stimulation with no response to contralateral stimulation and these suggested a disruption of the ossicular chain. Computed tomographic examination of the left temporal bone revealed the dislocation of the malleus and incus suggesting the disruption of the malleoincudal joint. Seven months after the initial examination, his left conductive hearing loss had recovered to an average airbone conduction gap of 5 dB and a normal acoustic response to ipsilateral stimulation, indicating recovery of the ossicular conduction.
Otological complications such as ear anomalies, recurrent otitis media and hearing loss in Turner syndrome are well known; however, clinical states of the otological disorders are still unclear. To clarify the clinical states, 20 cases of Turner syndrome aged 8-40 were examined clinically and audiometrically. Clinical differences between cases with total X-chromosome deficit (45, X) and combination of cell lines (mosaicism) were also analyzed. Nine of 20 cases (45%) had a history of middle ear disorders. Pure tone audiometry revealed conductive hearing loss in 4 of 40 ears (10%) and high frequency sensory neural hearing loss in 14 of 40 ears (35%). Cases aged 20 or more showed a decreased hearing threshold and the hearing deteriorated with age. No correlations were found between middle ear disorders and progressive hearing loss. Seven of 10 cases with the karyotype 45, X demonstrated hearing loss. 5 and 2 of 10 cases had a history of otitis media and cholesteatoma, respectively. On the other hand, 3 of 10 cases with the mosaicism karyotype demonstrated hearing loss and only 2 of 10 cases had a history of middle ear infections. All cases aged over 30 developed hearing loss regardless of gene deletion type. In conclusion, Turner syndrome women frequently suffer from otitis media disturbance and sometimes develop sensorineural hearing loss after puberty. The findings emphasize the importance of regular otological examination for woman with Turner syndrome.
A number of intrinsic and extrinsic factors have been considered to have an intricate association with age-related change in hearing. Age-related change in hearing thresholdsvaries among individuals considerably, and part of the variation can be explained by the presence/absence of potential causes. The objective of the present study is to investigate the independent contributions of aging and generalized diseases to hearing threshold deterioration, considering potential confounding factors. Subjects and method: Of 1534 participants in a population-based study, 1347 subjects aged between 41 and 82 years who adequately completed detailed questionnaires for the present analysis and completed puretone audiometry were selected. Confirmed hearing loss was classified into six types: average threshold equal or greater than 40 dBHL of thresholds at 3 low frequencies in the better ear [type 1] or the worse ear [type 2]; that of thresholds at 3 high frequencies in the better ear [type 3] or the worse ear [type 4]; and that of thresholds at 4 speech range frequencies in the better ear [type 5] or the worse ear [type 6]. Statistical analysis according to sex was performed in order to identify factors associated with the 6 types of hearing loss using a multiple logistic regression model in which the independent variables were age, hypertension, hyperlipidemia, diabetes mellitus, ischemic heart disease, renal disease, liver disease, ear disease, smoking habit, and occupational noise exposure. Results: Age (odds ratio [OR] per 10 years=1.17, 1.12, 1.17, 1.17, 1.28, and 1.15 for types 1, 2, 3, 4, 5, and 6, respectively, in males, and OR=1.27, 1.11, 1.17, 1.14, 1.13, and 1.13 for types 1, 2, 3, 4, 5, and 6, respectively, in females), presence of diabetes mellitus (OR=2.29, 3.67, and 2.42 for types 2, 5, and 6, respectively, in males and OR=3.03 for type 3 in females), presence of ischemic heart disease (OR=3.80 for type 1 in males) and presence of renal disease (OR=5.90 for type 1 in females) showed a significant statistical association with hearing loss. Conclusion: Diabetes mellitus, ischemic heart disease, and renal disease may each adversely affect hearing preservation. Aging may, however, still be considered an independent risk factor of hearing impairment.