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At least 505 records · Page 28Linked to original sources
PubMed2003

Localized pericochlear hypoattenuating foci at temporal-bone thin-section CT in pediatric patients: nonpathologic differential diagnostic entity?

PURPOSE: To evaluate the prevalence of localized hypoattenuating areas in the cochlear otic capsule at temporal-bone thin-section computed tomography (CT) in pediatric patients and correlate the findings with clinical information. MATERIALS AND METHODS: Temporal-bone thin-section CT images obtained in 73 patients aged 0-9 years (20 Austrian, 53 Finnish; 36 female and 37 male patients) were evaluated for the presence of localized hypoattenuating foci in the region of the fissula ante fenestram of the otic capsule. Clinical information collected for all patients was also evaluated. The data were analyzed with a logistic regression model. RESULTS: Hypoattenuating areas in the region of the fissula ante fenestram were observed in 23 of 73 patients (32%). Hypoattenuating foci were substantially more prevalent in patients younger than 3 years than in those 3 years or older (odds ratio, 0.14; 95% CI: 0.04, 0.52; P =.001). The prevalence did not differ between sexes or according to clinical diagnosis. Only three of the 23 patients with hypoattenuating foci had clinical findings suggestive of otosclerosis, and none had osteogenesis imperfecta. After adjustment for age and sex, the finding was more prevalent among the Finnish patients (odds ratio, 5.4; 95% CI: 1.19, 24.52; P =.02) than among the Austrian patients. CONCLUSION: Hypoattenuating areas in the region of the fissula ante fenestram in the otic capsule at thin-section CT are prevalent among children younger than 3 years in the absence of clinical evidence of otosclerosis or osteogenesis imperfecta and appear in children up to 9 years old.

Child↗
PubMed2006

Defective carbohydrate metabolism in mice homozygous for the tubby mutation.

Tub is a member of a small gene family, the tubby-like proteins (TULPs), with predominant expression in neurons. Mice carrying a mutation in Tub develop retinal and cochlear degeneration as well as late-onset obesity with insulin resistance. During behavioral and metabolic testing, we found that homozygous C57BL/6J-Tub(tub) mice have a lower respiratory quotient than C57BL/6J controls before the onset of obesity, indicating that tubby homozygotes fail to activate carbohydrate metabolism and instead rely on fat metabolism for energy needs. In concordance with this, tubby mice show higher excretion of ketone bodies and accumulation of glycogen in the liver. Quantitation of liver mRNA levels shows that, during the transition from light to dark period, tubby mice fail to induce glucose-6-phosphate dehydrogenase (G6pdh), the rate-limiting enzyme in the pentose phosphate pathway that normally supplies NADPH for de novo fatty acid synthesis and glutathione reduction. Reduced G6PDH protein levels and enzymatic activity in tubby mice lead accordingly to lower levels of NADPH and reduced glutathione (GSH), respectively. mRNA levels for the lipolytic enzymes acetyl-CoA synthetase and carnitine palmitoyltransferase are increased during the dark cycle and decreased during the light period, and several citric acid cycle genes are dysregulated in tubby mice. Examination of hypothalamic gene expression showed high levels of preproorexin mRNA leading to accumulation of orexin peptide in the lateral hypothalamus. We hypothesize that abnormal hypothalamic orexin expression leads to changes in liver carbohydrate metabolism and may contribute to the moderate obesity observed in tubby mice.

Acetate-CoA Ligase↗
PubMedDate not supplied

Cochlear dysfunction in patients with mitochondrial myopathy.

The present study investigates cochlear function in a group of 11 patients suffering from mitochondrial myopathy with normal or near normal audiometric pure tone thresholds, in most of whom diagnosis was histologically confirmed. A complete ENT, neurologic and audiological work-up, including transiently evoked otoacoustic emissions, was performed in all patients in order to estimate cochlear function. Compared to control subjects, most patients had absent otoacoustic emissions (OAE) in spite of normal hearing, indicating cochlear dysfunction. These findings suggest that subclinical involvement of the cochlea is quite common in patients with mitochondrial myopathy. Damage of the cochlea can be explained on the grounds of its increased metabolic rate, resulting in failure of the stria vascularis and the outer hair cells. Otoacoustic emissions might provide a useful tool in the clinical work-up and follow-up of these patients.

Adult↗
PubMedDate not supplied

A glucocorticoid reduces adverse effects of adenovirus vectors in the cochlea.

Gene transfer using a recombinant adenovirus is a powerful tool for research and clinical applications, but its cytotoxicity and immune response limit its use, especially when repeated application of the vector is necessary. This study investigated the effects of dexamethasone (DEX)-induced immunosuppression on the outcome of adenovirus gene transfer in guinea pig inner ears. Animals received DEX for 29 days. Their inner ear was inoculated with 5 micro l of adenovirus vector twice, on days 5 and 26. Auditory brainstem response was measured on days 1, 8 and 29. The animals were sacrificed on day 29, and reporter gene expression was evaluated. In control animals that received no DEX, postinoculation threshold shifts and lesions in the organ of Corti were observed and reporter gene expression was absent. In contrast, DEX-treated ears were largely protected, and transduction of inner ear cells was readily apparent. These data demonstrate that immunosuppressive treatment can reduce the negative consequences of repeated adenovirus-mediated gene therapy.

Adenoviridae Infections↗
PubMedDate not supplied

A cochlear cell line as an in vitro system for drug ototoxicity screening.

Aminoglycoside antibiotics, loop diuretics, antineoplastic agents and other commonly used pharmacological drugs are ototoxic. Understanding of the cellular and molecular mechanisms underlying drug ototoxicity, however, has been hampered by the limited availability of inner ear tissues and drug side effects on laboratory animals. Immortalized cell lines derived from the auditory sensory organ, sensitive to ototoxic drugs and growing in environments that can be systematically manipulated, would facilitate the research directed at elucidating these mechanisms. Such immortalized cell lines could also be used to discover novel therapeutic agents for preventing drug-induced sensorineural hearing loss. Here, we report a conditionally immortalized organ of Corti-derived epithelial cell line, which shows evidence of activation of apoptosis when exposed to known ototoxic drugs. This cell line may be an excellent in vitro system to investigate the cellular and molecular mechanisms involved in ototoxicity and for screening of the potential ototoxicity or otoprotective properties of new pharmacological drugs.

Aminoglycosides↗
PubMed2006

Diagnostics of the cochlear amplifier by means of distortion product otoacoustic emissions.

Distortion product otoacoustic emission (DPOAE) growth functions reflect the active nonlinear cochlear sound processing when using a primary-tone setting which accounts for the different compressions of the two primaries at the DPOAE generation site and hence provide a measure for objectively assessing cochlear sensitivity and compression. DPOAE thresholds can be derived from extrapolated DPOAE input/output (I/O) functions independently of the noise floor and consequently can serve as a unique measure for reading DPOAE measurements. The thus-estimated DPOAE thresholds exhibit a close correspondence to behavior audiometric thresholds and thus can be used for reconstructing an audiogram, i.e., a DPOAE audiogram. The DPOAE I/O functions' slope increases with cochlear hearing loss and thus provides a measure for assessing recruitment. Hence, DPOAE I/O functions can give more information for diagnostic purposes than those of DP grams, transiently evoked OAEs (TEOAEs), or auditory brain stem responses (ABRs). DPOAE audiograms can be applied in pediatric audiology to assess cochlear dysfunction in a couple of minutes. In newborn hearing screening, they are able to detect transitory sound-conductive hearing loss and thus can help to reduce the rate of false-positive TEOAE responses in the early postnatal period. Since DPOAE I/O functions are correlated with loudness functions, DPOAEs offer the possibility of basic hearing aid adjustments, especially in infants and children. Extrapolated DPOAE I/O functions provide a tool for a fast automated frequency-specific and quantitative evaluation of hearing loss.

Audiometry, Evoked Response↗
PubMedDate not supplied

Effect of dextran on gentamicin-induced ototoxicity.

The effect of low-molecular-weight dextran (DX) on gentamicin (GM)-induced ototoxicity was examined in guinea pigs. GM (100 mg/kg) was administered intramuscularly for 10, 12 and 14 days with or without DX. Cochlear damage was evaluated by compound action potential thresholds and surface preparation after fixation with osmium tetroxide. The percentage of missing outer hair cells was significantly increased by combined administrations of GM with DX. However, there was no significant difference in blood urea nitrogen levels in guinea pigs with or without DX. When aminoglycoside antibiotics and DX are administered together, attention should be paid not only to nephrotoxicity but also to ototoxicity.

Acoustic Stimulation↗
PubMed2003

Cross-sectional analysis of hearing threshold in relation to age in a large family with cochleovestibular impairment thoroughly genotyped for DFNA9/COCH.

Hearing threshold was analyzed for each frequency in relation to age in 88 members of a large Dutch family with cochleovestibular impairment caused by a P51S mutation in the COCH gene within the DFNA9 locus (chromosome 14q12-13). The participants in this study were 34 mutation carriers and 54 relatives without the mutation (control subjects). A sigmoidal dose-response curve with a variable slope was used to fit the mutation carriers' threshold-on-age data. Progression started at about 40 years of age and only lasted for some 20 to 25 years; the associated average progression was 2.9 dB/y for all frequencies. However, some hearing impairment was already present before, predominantly at the high frequencies. The mean thresholds in the young mutation carriers (< 33 years of age) were significantly higher (by 4 to 13 dB) than those in age-matched controls at 2 to 8 kHz. Presumably, mutation carriers have a congenital, stable offset threshold (10 to 29 dB) at these frequencies, and develop progression later in life.

Adult↗
PubMedDate not supplied

A reexamination of experimental type II collagen autoimmunity: middle and inner ear morphology and function.

Type II collagen autoimmunity has been reported to result in a number of middle and inner ear morphological and functional abnormalities. We investigated the immunological, electrophysiological, and anatomical effects of this autoimmune state in well-established Wistar-Furth rat models of type II collagen autoimmune arthritis. Seventeen animals immunized with bovine type II collagen were divided into short term (1-3 months postimmunization) and long term (9-11 months) groups. Thirty-three experimental ears were tested electrophysiologically and were compared to nine ears of unimmunized Wistar-Furth rats. No hearing loss was found in the immunized animals, except for four animals that showed middle ear abscess formation consistent with spontaneous, purulent otitis media. All immunized animals showed very significant serum and perilymph antibody titers to type II collagen. No morphological abnormalities of the external, middle, or inner ears could be identified in the noninfected experimental animals. These findings do not support previously reported observations that type II collagen autoimmunity results in ear disease.

Animals↗
PubMedDate not supplied

Speaking fundamental frequency of postlingually profoundly deaf adult men.

We investigated the speaking fundamental frequency (F0) of 21 postlingually profoundly sensorineurally deaf men. Results indicated that speaking F0 was significantly higher for the deaf group than for normal-hearing, age-matched men. Neither duration of profound deafness nor hearing aid usage affected speaking F0 values significantly. The findings of the present study provide a baseline for determining the effects of rehabilitation.

Adult↗
PubMed1990

Histopathologic study of the perilymph-suctioned labyrinth.

A small amount of perilymph was suctioned from the scala tympani through the round window membrane of guinea pigs. The animals either were killed immediately after the suctioning or were kept alive for 1 to 3 months. For morphologic study, the conventional celloidin embedding method was employed, and the temporal bones were serially sectioned. Various kinds and degrees of changes in the membranous labyrinth were observed: hydrops, collapse, and rupture. Loss of outer hair cells in the upper turns of the cochlea was noted in the 1- to 3-month recovery specimens. These findings are identical to those found in animals in which artificial perilymph was injected into the subarachnoid space in order to produce experimental perilymphatic fistula. After comparing morphologic changes of the membranous labyrinth following use of each method, we concluded that perilymph suctioning from the round window can be used as an animal model of perilymphatic fistula.

Animals↗
PubMed1994

Changes in cerebrospinal fluid pressure in daily life.

The purpose of the present study was to measure changes in cerebrospinal fluid pressure (CSF-P) during actions of daily life. A spinal tap was performed on 23 inpatients. During the procedure, the patients were requested to perform the following four actions: nose blowing with one side closed, nose blowing with both sides closed, breath holding, and sniffing. The CSF-P was recorded before and during these actions. Of these, nose blowing with both sides closed resulted in the greatest elevation of pressure. Three patients with perilymph fistula showed larger changes than the other 20 patients. Conversely, sniffing lowered the CSF-P in all cases. The present study suggests that daily physical actions cause significant elevations of CSF-P. Such changes may be responsible for the development of perilymph fistula.

Activities of Daily Living↗
PubMed1999

Cochlear function of guinea pigs with experimental chronic renal failure.

This study aimed to evaluate electrophysiologically the cochlear function of guinea pigs that underwent a five-sixths nephrectomy and, additionally, to explore the synergistic action between chronic renal failure (CRF) and noise. Cochlear potentials were recorded at 1, 2, and 3 months postoperatively. Slight changes in compound action potential and cochlear microphonics were seen at 1 month postoperative, while moderate and profound changes were seen at 2 and 3 months. Endocochlear potential showed no significant reduction. The results indicate that CRF may be an etiologic factor for cochlear dysfunction and that the hair cells seem likely to be a main site of the lesion. One-month-postoperative animals were exposed to a broadband noise. In contrast to control animals, the test animals demonstrated no recovery from the decrease in compound action potential and cochlear microphonics that occurred immediately after noise exposure. This suggests a synergistic interaction between CRF and noise.

Animals↗
PubMedDate not supplied

Ototoxicity: an argument for evaluation of the cochlea in safety testing in animals.

The cochlea is one of the more common targets for toxic effects, yet current toxicologic screening in animals does not routinely evaluate the cochlea as a potential target organ. Although histopathologic sections are routinely taken from the eye and the optic nerve and tract and most studies include at least 1 section through the nasal cavity and olfactory mucosa, the cochlea is not histopathologically examined in routine toxicity studies. Unfortunately, routine clinical examinations frequently miss ototoxicity because rodents and other species can lose most of their high-frequency hearing and still respond to most ambient noises. Ototoxicity as a deficiency in toxicologic screening can be remedied by using well-established histopathologic and behavioral methods or electrophysiologic methods, such as brain stem auditory evoked responses (BAERs). Once the equipment is in place, BAERs can be obtained quickly and easily for ototoxicity screening (approximately 15 minutes for paired testing of 2 rats and 30 minutes each for dogs). BAERs also can be used in virtually all mammalian species. Three or 4 probe frequencies (eg, 4, 8, 16, and 32 kHz), representing different areas of the cochlea, can be tested in a few minutes with subcutaneous electrodes under short-acting chemorestraint. Given the availability of several approaches to screening for ototoxicity and the importance of the auditory function in human health, safety tests of chemicals and drugs should include an effective screening test for ototoxicity.

Animals↗
PubMed1992

Abnormal auditory brainstem responses and cochlear pathology in rats induced by an exaggerated styrene exposure regimen.

Groups of 12 male 42-day-old rats were exposed to 0 or 800 ppm styrene vapors for 14 hr/day, 5 days/week for 3 weeks. Tone-pip auditory brainstem responses (ABRs) at 4, 8, 16, and 30 kHz were obtained after the last exposure. ABRs were minimally affected at 4 kHz and moderately to severely affected at 8, 16, and 30 kHz as indicated by waveforms which had a decreased amplitude and increased latency as compared to the controls. Missing outer hair cell(s) were evident in the basal and lower middle turns of the organ of Corti. Outer hair cell loss was least in the first row and greatest in the second and third rows. Occasional inner hair cells were also missing in regions of severe outer hair cell loss. The distribution of hair cell loss within the cochlea was consistent with the pattern of ABR alterations. These data document mid-frequency auditory dysfunction in styrene-exposed young adult rats with significant damage to the organ of Corti following an exaggerated styrene exposure regimen.

Animals↗
PubMed1991

Rapid protein test for perilymph fistula.

The existence of a perilymph fistula may be difficult to prove preoperatively or at surgery, except in obvious cases in which perilymph can be seen coming out of the inner ear around the stapes footplate or round window niche. Some surgeons doubt the common occurrence of spontaneous perilymph fistula. Most surgeons believe that a perilymph fistula is rare and is produced by some type of trauma and pressure change to the inner ear fluids. Analysis of fluid collected from the oval window area and round window niche may be a great help in confirming or disproving the diagnosis of perilymph fistula. After a myringotomy or tympanotomy, fluid collected in micropipets from the oval window or round window area is analyzed for protein concentration, using rapid protein indicator paper. The original technique was developed in the 1960's to analyze the inner ear fluid as a diagnostic procedure (i.e., diagnostic labyrinthotomy) in acoustic neuroma suspects. Normal perilymph has a protein content of approximately 200 mg %, which turns the indicator paper light green, whereas serum or transudate has a protein content of approximately 7000 mg %, which turns the indicator paper dark green. The protein concentration is determined by comparing the color of the indicator paper with the color developed by known protein standards. A middle ear tap may help avoid negative middle ear exploration for perilymph fistula and helps document the presence or absence of perilymph after the exploration.

Cochlear Diseases↗