The role of high-frequency audiometry in early detection of ototoxicity

Early transtympanic administration of rhBDNF exerts a multifaceted neuroprotective effect against cisplatin-induced hearing loss

BACKGROUND AND PURPOSE

Cisplatin-induced sensorineural hearing loss is a significant clinical challenge. Although the potential effects of brain-derived neurotrophic factor (BDNF) have previously been investigated in some ototoxicity models, its efficacy in cisplatin-induced hearing loss remains uncertain. This study aimed to investigate the therapeutic potential of recombinant human BDNF (rhBDNF) in protecting cells against cisplatin-induced ototoxicity.

EXPERIMENTAL APPROACH

Using an in vivo model of cisplatin-induced hearing loss, we investigated the beneficial effects of transtympanic administration of rhBDNF in a thermogel solution on hearing function and cochlear injury, using electrophysiological, morphological, immunofluorescence and molecular analyses.

KEY RESULTS

Our data showed that local rhBDNF treatment counteracted hearing loss in rats receiving cisplatin by preserving synaptic connections in the cochlear epithelium and protecting hair cells (HCs) and spiral ganglion neurons (SGNs) against cisplatin-induced cell death. Specifically, rhBDNF maintains the balance of its receptor levels (pTrkB and p75), boosting TrkB-CREB pro-survival signalling and reducing caspase 3-dependent apoptosis in the cochlea. Additionally, it activates antioxidant mechanisms while inhibiting inflammation and promoting vascular repair.

CONCLUSION AND IMPLICATIONS

Collectively, we demonstrated that early transtympanic treatment with rhBDNF plays a multifaceted protective role against cisplatin-induced ototoxicity, thus holding promise as a novel potential approach to preserve hearing in adult and paediatric patients undergoing cisplatin-based chemotherapy.

Adverse Audio-Vestibular Effects of Drugs and Vaccines Used in the Treatment and Prevention of COVID-19: A Review

(1) Background: The purpose of this article is to review pharmacological treatments for COVID-19 (currently approved by the EMA (European Medical Agency) and FDA (Food and Drug Administration)) and highlight their potential audio-vestibular side-effects as an ototoxic adverse reaction. (2) Methods: Review of the available literature in the scientific databases PubMed, ResearchGate, Scopus, and ScienceDirect, and in summaries of product data sheets. (3) Results: In accordance with EBM (evidence-based medicine) the treatment of COVID-19 by using lopinavir/ritonavir, chloroquine and hydroxychloroquine, azithromycin, favipiravir, amantadine, oseltamivir, and ivermectin is no longer recommended for patients suffering from COVID-19 due to a lack of clinical data, publications, and recommendations. There were 39 publications and 15 summaries of product characteristics (as other sources of data) which were also used in this analysis. Adverse events could be permanent or disappear over time. Following treatment for COVID-19, the most frequent adverse audio-vestibular reactions reported in clinical trials and publications in the area of audiology and otorhinolaryngology were: dizziness, blurry vision with dizziness, nasopharyngitis, dysgeusia, and tinnitus. As far as vaccines are concerned, dizziness as an ototoxic effect was uncommon and occurs only in hypersensitive people who experience anaphylactic shock. (4) Conclusions: The ototoxicity of the drugs discussed here does not have as severe symptoms as the drugs used in the treatment of COVID-19 in 2020 (e.g., hydroxychloroquine), and relates mainly to disorders of the vestibulocochlear system. However, there is still a need to monitor ototoxic side-effects because of potential interactions with other ototoxic drugs. Many of the drugs approved by EMA and FDA are new, and not every side-effect is known.

Ototoxic effects of antineoplastic drugs: a systematic review

INTRODUCTION

Platinum-based chemotherapeutics play an important role in the treatment of cancer at different levels and are the most cited ototoxic agents when scientific evidence is analyzed.

OBJECTIVE

To present scientific evidence based on a systematic literature review, PRISMA, in order to systematize information on the ototoxic effects of using antineoplastic drugs.

METHODS

For the selection of studies, the combination based on the Medical Subject Heading Terms (MeSH) was used. The Medline (Pubmed), LILACS, SciELO, SCOPUS, WEB OF SCIENCE and BIREME databases were used, without restriction of language, period, and location. Evaluation of the quality of the articles was carried out, which included articles with a minimum score of 6 in the modified scale of the literature. The designs of the selected studies were descriptive, cohort, and cross-sectional, which were related to the research objective.

RESULTS

Three articles were included in this systematic review. The ototoxicity caused by cisplatin alone varied from 45% to 83.3%, while that caused by the use associated with carboplatin varied from 16.6% to 75%. There was a significant variation in the cumulative doses of these antineoplastic agents, both in isolated and in combination. Auditory changes, especially at high frequencies, were evident after completion of treatment.

CONCLUSION

Auditory changes after the use of platinum-based antineoplastic drugs were found, however, there was an important heterogeneity regarding the frequency of ototoxicity and the cumulative dose of the drugs used.

Extended high-frequency audiometry in healthy adults with different age groups

Background

It was well-documented that extended high-frequency (EHF, above 8 kHz) hearing test could be more sensitive comparing with the conventional measurement on frequency below 8 kHz, regarding the early prediction of auditory damage in certain population. However, hardly any age-specific thresholds of EHF in population with normal hearing ability were observed. This study aims to monitor the age-dependent hearing thresholds at EHF (from 9 to 20 kHz) in healthy hearing population.

Methods

A total of 162 healthy participants (from 21 to 70 years) with normal conventional pure tone audiograms were recruited and separated into five groups by age. Conventional pure tone average was performed with frequencies from 0.25 to 8 kHz under air conduction and from 0.25 to 4 kHz under bone conduction. EHF audiometry from 9 to 20 kHz was determined under air conduction.

Results

The effects of aging on hearing were evident at frequencies above 4 kHz. The hearing thresholds of EHF were less than 26 dB HL before 30 years-olds. Hearing abilities in EHF were deteriorated starting from the 31 ~ 40 group and were most obvious in the 51 ~ 60 group and the 61 ~ 70 group with the maximum thresholds of 75 dB HL. Sensitivity of EHF was inversely proportional to the frequency within each age group, and to age among groups. Subjects under 30 years old were totally responsive up to 16 kHz, and 52.2% could respond to 20 kHz. Meanwhile, no responsiveness was recorded to 20 kHz in the 51 ~ 60 group and even to 18 kHz in the 61 ~ 70 group. No gender differences in hearing threshold was observed within each age group, except an obvious decline at frequencies of 4, 6, 8, and 9 kHz in male participants of the 41 ~ 50 group.

Conclusions

Hearing thresholds at EHF from 9 to 20 kHz were more sensitive than at frequencies below 8 kHz for hearing measurement, and aging inversely affected hearing ability at EHF in healthy population. Hearing thresholds at EHF deteriorated with age and raising frequency, while the upper frequency limit decreased with aging.

Graphical abstract

Drug-Induced Ototoxicity: Diagnosis and Monitoring

Ototoxicity diagnosis and management has historically been approached using a variety of methods. However, in recent years a consensus on useful and practical approaches has been developed through clinical guidelines of the American Speech Language Hearing Association, the American Academy of Audiology, and multiple clinical trials published in peer-reviewed literature. Some of the guidelines and approaches are used to detect and monitor ototoxicity, while others are used to grade adverse events. Some of the audiologic measures are primary, while others are adjunct measures and may be tailored to the specific needs of the patient or clinical trial. For some types of monitoring, such as drug-induced tinnitus or dizziness, validated paper survey instruments can be both sensitive and easy for fragile patients. This review addresses the characteristics of some of the most common clinical ototoxins and the most common methods for detecting and monitoring ototoxicity in clinical practice and clinical trials.

Hearing loss in adult patients with Fabry disease treated with enzyme replacement therapy

INTRODUCTION

Data on prevalence, natural history, and effect of enzyme replacement therapy (ERT) on hearing loss (HL) in Fabry disease (FD) are scarce.

METHODS

This is a retrospective study with cross-sectional and longitudinal analyses. Low and high-frequency HL in the Dutch FD cohort was studied in four groups: classical and non-classical FD patients with or without ERT. To study effects of ERT, longitudinal data, corrected for age and gender according to ISO-1999 guidelines, were analyzed with mixed models.

RESULTS

In the cross-sectional analysis, 107 FD patients (41 males), median age 47.6 years (18.8-80.6) were analyzed. At baseline, i.e., before start of ERT, HL was present in 18 patients (16.8 %), of whom four had bilateral sensorineural HL. HL was more often present in patients with the classical phenotype than non-classical patients (p < 0.01). Likewise, males had more often HL than females. Compared to the general population, FD patients show a median HL of 8.2 dB at low frequencies (p < 0.01) and 29.5 dB at ultra-high frequencies (p < 0.01). Longitudinal analyses (n = 91) revealed that ERT treated patients show a similar rate of decline, not significantly different from healthy controls.

CONCLUSION

Adult FD patients, especially classical affected males, show impaired hearing. Longitudinal analyses during ERT in these patients demonstrates a decline of HL similar to healthy controls, but HL present before initiation of therapy cannot be reversed. Whether early therapy can prevent hearing loss is unknown.

Diagnostic dilemmas in Fabry disease: a case series study on GLA mutations of unknown clinical significance

Fabry disease' (FD) phenotype is heterogeneous: alpha-galactosidase A gene mutations (GLA) can lead to classical or non-classical FD, or no FD. The aim of this study is to describe pitfalls in diagnosing non-classical FD and assess the diagnostic value of plasma globotriaosylsphingosine. This is a case series study. Family 1 (p.A143T) presented with hypertrophic cardiomyopathy (HCM), absent classical FD signs, high residual alpha-galactosidase A activity (AGAL-A) and normal plasma globotriaosylsphingosine. Co-segregating sarcomeric mutations were found. Cardiac biopsy excluded FD. In family 2 (p.P60L), FD was suspected after kidney biopsy in a female with chloroquine use. Males had residual AGAL-A, no classical FD signs and minimally increased plasma globotriaosylsphingosine, indicating that p.P60L is most likely non-pathogenic. Non-specific complications and histology can be explained by chloroquine and alternative causes. Males of two unrelated families (p.R112H) show AGAL-A <5%, but slightly elevated plasma globotriaosylsphingosine (1.2-2.0 classical males >50 nmol/l). Histological evidence suggests a variable penetrance of this mutation. Patients with GLA mutations and non-specific findings such as HCM may have non-classical FD or no FD. Other (genetic) causes of FD-like findings should be excluded, including medication inducing FD-like storage. Plasma globotriaosylsphingosine may serve as a diagnostic tool, but histology of an affected organ is often mandatory.

High-frequency hearing thresholds: effects of age, occupational ultrasound and noise exposure

PURPOSE

It has been suggested that high-frequency audiometry (HFA) could represent a useful preventive measure in exposed workers. The aim was to investigate the effects of age, ultrasound and noise on high-frequency hearing thresholds.

METHODS

We tested 24 industrial ultrasound-exposed subjects, 113 industrial noise-exposed subjects and 148 non-exposed subjects. Each subject was tested with both conventional-frequency (0.125-8 kHz) and high-frequency (9-18 kHz) audiometry.

RESULTS

The hearing threshold at high frequency deteriorated as a function of age, especially in subjects more than 30 years old. The ultrasound-exposed subjects had significantly higher hearing thresholds than the non-exposed ones at the high frequencies, being greatest from 10 to 14 kHz. This hearing loss was already significantly evident in subjects with exposure <5 years and increased with years of exposure and advancing age. The noise exposure group had significantly higher hearing thresholds than the non-exposed group at the conventional frequencies 4 and 6 kHz and at the high frequency of 14 kHz. After stratification for age, there was a significant difference between the two groups at 9-10 and 14-15 kHz only for those under 30 years of age.

CONCLUSION

Multivariate analysis indicated that age was the primary predictor, and noise and ultrasound exposure the secondary predictors of hearing thresholds in the high-frequency range. The results suggest that HFA could be useful in the early diagnosis of noise-induced hearing loss in younger groups of workers (under 30 years of age).

Behavioral hearing thresholds between 0.125 and 20 kHz using depth-compensated ear simulator calibration

OBJECTIVES

The purpose of this study was to obtain behavioral hearing thresholds for frequencies between 0.125 and 20 kHz from a large population between 10 and 65 yr old using a clinically feasible calibration method expected to compensate well for variations in the distance between the eardrum and an insert-type sound source. Previous reports of hearing thresholds in the extended high frequencies (>8 kHz) have either used calibration techniques known to be inaccurate or specialized equipment not suitable for clinical use.

DESIGN

Hearing thresholds were measured from 352 human subjects between 10 and 65 yr old having clinically normal-hearing thresholds (<20 dB HL) up to 4 kHz. An otoacoustic emission probe fitted with custom sound sources was used, and the stimulus levels individually tailored on the basis of an estimate of the insertion depth of the measurement probe. The calibrated stimulus levels were determined on the basis of measurements made at various depths of insertion in a standard ear simulator. Threshold values were obtained for 21 frequencies between 0.125 and 20 kHz using a modified Békésy technique. Forty-six of the subjects returned for a second measurement months later from the initial evaluation.

RESULTS

In agreement with previous reports, hearing thresholds at extended high frequencies were found to be sensitive to age-related changes in auditory function. In contrast with previous reports, no gender differences were found in average hearing thresholds at most evaluated frequencies. Two aging processes, one faster than the other in time scale, seem to influence hearing thresholds in different frequency ranges. The standard deviation (SD) of test-retest threshold difference for all evaluated frequencies was 5 to 10 dB, comparable to that reported in the literature for similar measurement techniques but smaller than that observed for data obtained using the standard clinical procedure.

CONCLUSIONS

The depth-compensated ear simulator-based calibration method and the modified Békésy technique allow reliable measurement of hearing thresholds over the entire frequency range of human hearing. Hearing thresholds at the extended high frequencies are sensitive to aging and reveal subtle differences, which are not evident in the frequency range evaluated regularly (≤8 kHz). Previously reported gender-related differences in hearing thresholds may be related to ear-canal acoustics and the calibration procedure and not because of differences in hearing sensitivity.

Clinically accurate assessment and grading of ototoxicity

OBJECTIVES/HYPOTHESIS

To design a grading scale and audiologic protocols to better reflect clinical impact than the currently widely used classifications.

STUDY DESIGN

Retrospective.

METHODS

Audiologic studies from 130 patients receiving cisplatin chemotherapy were analyzed. Pure-tone audiograms were evaluated using the newly proposed grading criteria, Brock criteria, and Common Terminology Criteria for Adverse Events (CTCAE). The resulting grades were then compared to recommended audiologic interventions. Auditory brainstem response (ABR) data and data on incidences of conductive hearing loss from other multi-institutional studies that the author participated in were compared to data from this cohort.

RESULTS

Although the newly proposed, Brock, and CTCAE ototoxicity grades were significantly related to audiologist recommendations for assistive devices (P < .0001), the newly proposed criteria were more specific and allowed better delineation of different patients into distinct subgroups requiring either FM system (grade 2a) or hearing aid (grade 2b or higher). Multi-institutional data review indicated significant problems with ABR evaluations and separating out conductive hearing losses from ototoxicity.

CONCLUSIONS

The newly proposed grading system needs to be paired with specific recommendations regarding audiologic monitoring protocols as well as active participation by the audiologists implementing the protocol to provide clinically accurate assessment and grading of ototoxicity.

Auditory filter shapes and high-frequency hearing in adults who have impaired speech in noise performance despite clinically normal audiograms

Some individuals complain of hearing difficulties in the presence of background noise even in the absence of clinically significant hearing loss (obscure auditory dysfunction). Previous evidence suggests that these listeners have impaired frequency resolution, but there has been no thorough characterization of auditory filter shapes in this population. Here, the filter shapes of adults (n = 14) who self-reported speech recognition problems in noise and performed poorly on a sentence-in-noise perception test despite having clinically normal audiograms were compared to those of controls (n = 10). The filter shapes were evaluated using a 2-kHz probe with a fixed level of 30, 40, or 50 dB sound pressure level (SPL) and notched-noise simultaneous maskers that were varied in level to determine the masker level necessary to just mask the probe. The filters of the impaired group were significantly wider than those of controls at all probe levels owing to an unusual broadening of the upper slope of the filter. In addition, absolute thresholds were statistically indistinguishable between the groups at the standard audiometric frequencies, but were elevated in the impaired listeners at higher frequencies. These results strengthen the idea that this population has a variety of hearing deficits that go undetected by standard audiometry.

High frequency audiometric study in cancer-cured patients treated with cisplatin

Hearing loss has been described in patients undergoing chemotherapy, given the ototoxic nature of these drugs. An audiological investigation is relevant in such cases.

Aim

to assess audibility thresholds at high frequencies in individuals with cancer that was treated successfully with cisplatin and its associations, to verify possible hearing loss as a side effect of therapy. Site and date of the study: Campinas, Sao Paulo, in 2006.

Material and Method

Ten volunteers aged between 5 and 27 years were assessed by a clinical history, otoscopy, and conventional and high frequencies audiometry in this clinical and experimental study.

Results

A kappa coefficient statistical analysis revealed significant differences between ears in 50% of 14 frequencies that were evaluated. Eight participants presented hearing losses, which started at 1 kHz, increasing markedly at 6 kHz and above. Fisher's Exact Test revealed a significant association only with the dose and the right ear at high frequencies.

Conclusion

It is possible that the hearing loss detected in this study is at least partially due to the ototoxicity of antineoplastic drugs; such loss may occur even after treatment is interrupted. We suggest that a protocol for audiological follow-up of patients undergoing chemotherapy should be created.

Hearing loss due to concurrent daily low-dose cisplatin chemoradiation for locally advanced head and neck cancer

BACKGROUND AND PURPOSE

Cisplatin-based chemo-irradiation (CRT) is increasingly used for head and neck squamous cell carcinoma (HNSCC). We aimed to assess hearing deterioration due to low-dose cisplatin chemoradiation and to compare the observed hearing loss with hearing loss in our previously described high-dose cisplatin CRT cohort.

MATERIALS AND METHODS

A prospective analysis of hearing thresholds at low and (ultra)-high frequencies obtained before and after treatment in 60 patients. Patients received low-dose cisplatin (6mg/m(2), daily infusions, 20-25 days) with concomitant accelerated radiotherapy (70Gy).

RESULTS

Audiometry up to 16kHz was performed before therapy and 31 days (median) post-treatment. The total incidence of ototoxicity in CTCAEv3.0 was 31% in audiograms up to 8kHz, and 5% of ears tested qualified for HAs due to treatment. The mean hearing loss at speech frequencies was 2.6dB (SD 5.7) and 2.3dB (SD 9.2) at PTA 1-2-4kHz air-conduction and bone-conduction, respectively. The mean hearing loss at ultra-high frequencies (PTA AC 8-10-12.5kHz) was 9.0dB (SD 8.1). Low-dose cisplatin CRT caused less acute hearing loss (CTCAE 31%), compared to high-dose cisplatin CRT (CTCAE 78%).

CONCLUSIONS

Low-dose cisplatin chemo-irradiation for HNSCC is a relatively safe treatment protocol with respect to ototoxicity.

Estudo audiometrico de alta fraquência em pacientes curados de câncer tratados com cisplatina

Alterações auditivas têm sido encontradas em pacientes submetidos à quimioterapia devido à ototoxicidade, daí a importância da investigação audiológica nesses casos. OBJETIVO: Avaliar os limiares de audibilidade nas altas freqüências em indivíduos curados de câncer, tratados com cisplatina e associações, para verificar possível perda auditiva como seqüela do tratamento. Local e data do estudo: Campinas - SP, em 2006. MATERIAL E MÉTODO: Roteiro de anamnese, otoscópio e audiômetro. Dez voluntários, entre 5 a 27 anos, foram submetidos a anamnese; meatoscopia; audiometria tonal convencional e de altas freqüências. Forma de Estudo: Clínico experimental. RESULTADOS: O kappa ponderado evidenciou diferença significativa entre as orelhas em 50% das 14 freqüências avaliadas. Oito participantes apresentaram perda auditiva. O acometimento iniciou-se em 1 kHz, com crescimento acentuado a partir de 6kHz. O Teste Exato de Fisher evidenciou associação significativa apenas para dose e orelha direita nas altas freqüências. CONCLUSÃO: É possível que as perdas auditivas detectadas devam-se, pelo menos parcialmente, à ototoxicidade dos antineoplásicos utilizados, a qual pode ocorrer mesmo após a interrupção do tratamento. Sugere-se estabelecer protocolo de acompanhamento audiológico no tratamento quimioterápico.

Extended high-frequency audiometry and noise induced hearing loss in cement workers

BACKGROUND

It has been suggested that extended high-frequency audiometry (EHFA) might be more sensitive than conventional audiometry in detecting early signs of hearing impairment. However, this technique has not been adequately tested in an occupational environment. We therefore investigated the usefulness of this method in noise-exposed workers.

METHODS

We compared conventional frequency audiometry (0.25-8 kHz) and EHFA (9-18 kHz) in 184 noise-exposed and 98 non-noise-exposed workers.

RESULTS

Both methods showed significantly higher threshold levels (P < 0.05) in noise-exposed workers for most of the tested frequencies; however, the differences were more marked for EHFA, especially in young exposed workers. Significant differences in the EHF range were detected also in the subgroup of noise-exposed workers with normal findings at conventional audiometry. Stepwise regression analysis showed that in 21- to 40-year-old workers the noise effect was largely predominant at both conventional audiometry and EHFA, whereas in older subjects the noise effect was predominant up to 6 kHz frequency, the effect of age being significantly greater at higher frequencies.

CONCLUSIONS

These data indicate that EHFA is more sensitive than conventional audiometry in detecting noise induced hearing loss. However, hearing loss in the EHF range seems an age-dependent phenomenon with progression into the lower speech range frequencies with increasing age. These changes seem to be accentuated in the early years by noise exposure, suggesting that EHFA could represent a useful preventive measure in young exposed workers.

Audiologic testing and molecular analysis of 12S rRNA in patients receiving aminoglycosides

BACKGROUND

Pathogenic mutations in the mitochondrial genome are associated with a wide variety of maternally inherited human diseases including sensorineural hearing loss (HL). A specific mutation, m.1555A>G in the mitochondrial 12S rRNA gene, is associated with predisposition to aminoglycoside ototoxicity and HL. Mutation screening in this gene has been recommended before use of aminoglycosides as a preventative strategy to reduce the risk of ototoxicity.

OBJECTIVE

To study the incidence of mutations in the 12S rRNA gene in patients being treated with aminoglycosides and its correlation with ototoxicity.

METHODS

Patients undergoing treatment with aminoglycosides were prospectively enrolled in this study (n = 27). Total dosage administered and therapeutic levels of the antibiotic were noted. All patients underwent high-frequency pure-tone audiometry pre- and posttherapy and sequencing of the 12S rRNA gene. In addition, 12S rRNA gene was also sequenced in 50 controls to characterize population specific polymorphisms.

RESULTS

Five of 27 patients suffered from HL involving the high frequencies: four mild and one moderate. Only one of the five patients with ototoxicity harbored two sequence alterations in 12S rRNA of uncertain pathogenicity. The m.1555A>G and m.961delTInsCn mutations were not detected.

CONCLUSIONS

High-frequency pure-tone audiometry is critical for detection of aminoglycoside-induced HL. In the Swiss population, screening for mutations in the 12S rRNA gene, before the initiation of aminoglycoside therapy, is not supported by this limited study. A larger multicenter and multicultural study is warranted to more definitively address this critical clinical issue.

A benefit-risk assessment of ofloxacin otic solution in ear infection

Ofloxacin is a fluoroquinolone antibacterial with potent bactericidal activities and the topical otological preparation of this drug has been clinically utilised since the late 1980s. The rate of eradication with ofloxacin ranges from 83.3% to 100% for all pathogens commonly isolated from middle ear effusions in cases of otitis media and otitis externa. Despite the significant length of its usage, emergence of resistant pathogens has been rarely encountered in clinical trials; only two strains of Pseudomonas aeruginosa have been documented with decreased susceptibility to ofloxacin following the use of the otic solution.Ear infections, including otitis externa, chronic suppurative otitis media and otorrhoea associated with tympanostomy tubes, are common problems in clinical practice. The potential complications associated with ear infection can be otological, extratemporal, or even psychosocial. They are sometimes fatal and the effect can be long-lasting and detrimental. The use of an effective topical antibacterial with high cost-effectiveness is definitely warranted. As regards various clinical aspects, including overall success rate, symptomatic relief of otalgia and otorrhoea, ofloxacin otic solution was found to be more effective than comparator agents, be it a topical antibacterial, a systemic antibacterial or combination drugs. The systemic absorption of fluoroquinolones is minimal after topical application. Ofloxacin otic solution 0.3% has been shown to have a low rate of adverse drug reactions. Adverse reactions to ofloxacin otic solution were generally mild. The lack of ototoxic effect from ofloxacin eardrops, even in the concentration higher than 0.3%, has been demonstrated in animal studies. In the clinical setting, no increase in bone-conduction threshold has been shown after the treatment of topical ofloxacin otic solution. There have not been any reports of ototoxicity with ofloxacin otic solution since its approval. To conclude, ofloxacin otic solution 0.3% is clinically effective in the treatment of otitis externa and chronic suppurative otitis media in particular with respect to the overall cure rate, relief of otalgia and otorrhoea. It is well tolerated, with minimal adverse effects. It is not associated with any ototoxicity both experimentally and clinically.

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.

Intratympanic therapy for Ménière's disease. High-concentration gentamicin with round-window protection

Many therapeutic options exist for the management of patients with Ménière's disease. In the last few years, the use of intratympanic gentamicin has been investigated as an alternative treatment to vestibular nerve section or labyrinthectomy. In humans, the concentration of gentamicin used for intratympanic treatment of vertigo ranges from 10 mg/mL to 40 mg/mL, and the number of doses from 2 to 14, with a total administered amount between 6 and 2.400 mg. Here lower doses of gentamicin were used, usually had the lowest incidence of hearing loss, but more injections were needed to ablate vestibular function. The purpose of this study was to evaluate the acute and chronic ototoxic effects of intratympanic high-concentration gentamicin after having obliterated the round-window niche with connective tissue in 11 subjects' ears with Ménière's disease. Intratympanic gentamicin was administered according to a predetermined and fixed schedule consisting of two doses of 0.5 mL gentamicin solution, injected once a week with a drug concentration of 80 mg/mL. The total dose of gentamicin was < or = 80 mg. The charts of the patients were surveyed in accordance with the 1995 AAO-HNS guidelines. Three patients had recurrence of vertigo between 3 and 6 months after the second injection and went on to one additional dose of gentamicin. At 2 years follow-up, 10 patients (91%) had complete and 1 (9%) substantial control of vertigo; 3 subjects (27%) had hearing decreased. Tinnitus disappeared or decreased in 3 patients (27%); eight subjects (73%) reported their aural pressure abolished or decreased. The present study demonstrates that in patients with Ménière's disease, 0.5 mL gentamicin solution, with a concentration of 80 mg/mL (total dose < or = 80 mg), injected intratympanically once a week after having obliterated the round-window niche, permits complete or substantial control of vertigo in two-thirds of cases after two doses and in all subjects after three doses. This vertigo control rate is compared to that observed after vestibular nerve section. Hearing results are not different from those with natural control, with endolymphatic sac surgery, and with vestibular nerve section.

Topical ofloxacin versus systemic amoxicillin/clavulanate in purulent otorrhea in children with tympanostomy tubes

Acute otitis media (AOM) in children with tympanostomy tubes in place typically presents with otorrhea (draining ear). Because therapy is not standardized, various topical and systemic antibiotics of unproven efficacy and safety have been used in this indication. This study compared the safety and efficacy of ofloxacin otic solution, 0.3% (OFLX) with that of Augmentin oral suspension (AUG) in pediatric subjects 1-12 years of age with tympanostomy tubes and acute purulent otorrhea. Subjects were randomized to receive 10d of OFLX, 0.25 ml topically bid, or of AUG, 40 mg/kg per day. Audiometry was performed in subjects > or =4 years of age. Overall cure rate for clinically evaluable subjects was 76% with OFLX (n = 140) and 69% with AUG (n = 146; P = 0.169). Overall eradication rates for OFLX and AUG were similar for Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis and were superior with OFLX for Staphylococcus aureus and Pseudomonas aeruginosa (P<0.05 for both). OFLX had a greater overall pathogen eradication rate (96% vs. 67%; P<0.001). Treatment-related adverse event rates were 31% for AUG and 6% for OFLX (P<0.001). Neither treatment significantly altered hearing acuity. Topical ofloxacin 0.3% otic solution 0.25 ml bid was as effective and better tolerated than systemic therapy with Augmentin oral suspension 40 mg/kg per day in treating AOM in children with tympanostomy tubes.

Aging and high-frequency hearing sensitivity

As part of a large population-based study of hearing and aging, ultra high-frequency (9-20 kHz) threshold measures are reported for 3396 participants grouped by age (48-59 years, n = 1233; 60-69 years, n = 1031; 70-79 years, n = 851; 80-92 years, n = 281). Ultra high-frequency (UHF) thresholds were higher for older age groups. The percentage of unmeasurable responses also was significantly higher for older age groups and for higher frequencies in the UHF range. The observed age effects remained significant after adjusting for gender. In general, UHF thresholds were significantly higher for men compared to those for women at lower UHF frequencies (9-14 kHz), but were not significantly different by gender for the highest UHF frequencies (16, 18, and 20 kHz). After accounting for hearing loss at traditional audiometric frequencies (250-8000 Hz), the age effect still remained; even for comparable degrees of sensorineural hearing loss, participants in older age groups evidenced higher UHF thresholds.

Analysis of risk factors for cisplatin-induced ototoxicity in patients with testicular cancer

This study evaluates the degree and relevance of persisting ototoxicity after cisplatin-based standard-dose chemotherapy for testicular cancer, with emphasis on identification of potential factors for an increased risk of this late sequel. Hearing thresholds of 86 patients with a median age of 31 years (range 21-53 years) and a median follow-up time of 58 months (range 15-159 months) were assessed by conventional pure-tone audiometry. Interviews were conducted evaluating the patients' history with special regard to audiological risk factors, as well as circumstances of ototoxic symptoms. Details concerning treatment and patient variables were extracted retrospectively from the patients' charts. An additional screening programme assessed current body functions, blood parameters and other late toxicities. Symptomatic ototoxicity persisted in 20% of patients (59% tinnitus, 18% hearing loss, 23% both), while 10% had experienced completely reversible ototoxic symptoms for a duration of 1-18 months after treatment. Symptoms were bilateral in 81% of patients. Hearing thresholds were compatible with cisplatin-induced hearing loss in 42% of audiograms performed. Subjective (history) and objective (audiogram) findings were not always consistent. The following statistically significant risk factors for ototoxicity were established: high cumulative dose of cisplatin (P < 0.0001); history of noise exposure (P = 0.006). Additionally, high doses of vincristine (P = 0.001) seemed to result in reversible ototoxic symptoms. No other independent risk factors were identified. In conclusion, persisting ototoxicity represents a clinical sequel for approximately 20% of testicular cancer patients treated at standard dose but may affect more than 50% of patients receiving cumulative doses of cisplatin > 400 mg m(-2). Previous noise exposure may also result in a threefold increased risk for cisplatin ototoxicity. Future studies should use these risk factors as important stratification criteria for trials aiming at the evaluation and prevention of cisplatin-induced ototoxicity.

Low-dose intratympanic gentamicin and the treatment of Meniere's disease: preliminary results

The most disabling symptom for most patients with unilateral Meniere's disease is vertigo. Eradication of the diseased end organ is effective in eliminating the vertigo. Labyrinthectomy remains the "gold standard"; unfortunately, residual hearing is sacrificed to obtain this end. The purpose of this study is to evaluate low-dose intratympanic gentamicin for the control of vertigo and for the preservation of hearing. A single dose of gentamicin (10-80 mg) was injected into the middle ear space of 23 patients with unilateral Meniere's disease as an office procedure. Eighty-four percent of the patients had no episodes of vertigo during the last 6 months of follow-up. Pure tone average and word discrimination scores were unchanged as a group. Ninety-five percent of patients had a hearing loss at 6 and 8 kHz that averaged 7.5 dB. Caloric function was reduced in 93%. Low-dose intratympanic gentamicin is a safe, simple, office procedure that is effective in controlling the definitive vertiginous episodes in most patients with unilateral Meniere's disease. Control of vertigo can be obtained with preservation of hearing.

Sensorineural hearing loss in children

Hearing loss in infants and children may be sensorineural, conductive, or mixed. Severity varies from mild to profound. Educational initiatives aimed at children, parents, and primary health care providers could help prevent needless permanent hearing impairment. Effective programs aimed at education and hearing conservation among children and adolescents are overdue. The causes of sensorineural hearing loss, the concept of multidisciplinary team evaluation, and measurement of hearing are discussed. Advances in genetics of hearing loss are reviewed.

Onset of ototoxicity in the cat is related to onset of auditory function

Cats are altricial mammals; they are born deaf and undergo rapid maturation of the auditory periphery late in the first and throughout the 2nd week of life. Previous studies, using multiple aminoglycoside administration over several days or weeks, have indicated that there is a reduction in the degree of ototoxicity in young animals provided the drug is administered prior to the onset of auditory function. In order to provide a more precise relationship between the degree of ototoxicity and auditory development, we used a single administration of Kanamycin (KA) and the loop diuretic ethacrynic acid (EA), as the co-administration of these drugs is known to produce a rapid and profound hearing loss in adult animals. Thirty kittens were administered with KA and EA at ages that varied from 2 to 16 days after birth (DAB) using a fixed dose per kilogram body weight sufficient to profoundly deafen adult animals. All animals made an uneventful recovery from the procedure. At 26 DAB, tone-pip-evoked auditory brainstem responses (ABR) were recorded from each animal in order to establish the extent of the hearing loss. The degree of hearing loss was compared with normal ABR audiograms recorded from 6 age-matched control animals. All animals treated with KA/EA at 9 DAB or older had a profound hearing loss similar to adult animals. Animals treated between 2 and 8 DAB exhibited severe high-frequency hearing losses. The extent of the loss was correlated with age (r = 0.63) and body weight (r = 0.72) such that hearing loss tended to spread towards lower frequencies as age and/or weight increased. All animals exhibited bilaterally symmetrical hearing losses which remained relatively stable over monitoring periods of up to 6 months following the drug treatment. These findings imply that the onset of ototoxicity is related, at least in part, to the onset of auditory function in the kitten. The rapid onset of deafness following this procedure makes it a useful technique in the study of both ototoxicity and cochlear development.

High-frequency toneburst-evoked ABR latency-intensity functions in sensorineural hearing-impaired humans

The latency-intensity functions (LIFs) of ABRs elicited by high-frequency (8, 10, 12, and 14 kHz) toneburst stimuli were evaluated in 20 subjects with confirmed 'moderate' high-frequency sensorineural hearing loss. Wave V results from clicks and tonebursts revealed all intra- and intersession data to be reliable (p > 0.05). Linear regression curves were highly significant (p < or = 0.0001), indicating linear relationships for all stimuli analyzed. Comparisons between the linear regression curves from a previously reported normal-hearing subject group and this sensorineural hearing-impaired group showed no significant differences. This study demonstrated that tonebursts at 8, 10, and 12 kHz evoked ABRs which decreased in latency as a function of increasing intensity and that these LIFs were consistent and orderly (14 kHz was not determinable). These results will contribute information to facilitate the establishment of change criteria used to predict change in hearing during treatment with ototoxic medications.

Mid-frequency hearing loss and reduction of acoustic startle responding in rats following trichloroethylene exposure

Modification of auditory evoked startle responding using prepulse inhibition was used to examine the effects of trichloroethylene (TCE) exposure on auditory thresholds. Rats were exposed by inhalation to 0, 1500, or 3000 ppm TCE for 18 hours per day, 5 days a week for 3 weeks. Auditory thresholds for 5 and 20 kHz tones were measured before exposure and at 1, 3, and 6 weeks postexposure. In addition, hearing thresholds for 5 and 35 kHz tones were examined at a 5-week postexposure time-point. Results indicated that hearing thresholds for 20 kHz but not for 5 or 35 kHz prepulses were significantly increased in rats exposed to 3000 ppm TCE. These findings demonstrate a selective hearing loss in the 20 kHz range by short-term, high-level TCE exposure. With respect to effects on startle responding per se, the present study also found that compared to controls, TCE-exposed rats failed to show an increase in baseline startle with repeated testing. This difference could not be attributed to differences in body weight and was persistent throughout the postexposure period.

Exploration of cochlear function by otoacoustic emissions: relationship to pure-tone audiometry

The amplitudes, growth functions and detection thresholds of evoked otoacoustic emissions (EOE) were measured in 44 normally hearing subjects and 138 patients with two categories of cochlear dysfunctions: (a) acoustic trauma; and (b) presbycusis. Separate sets of experiments were also performed: (a) detection of stimulus frequency emissions; and (b) click EOE. EOE properties were studied around 2 kHz, 1 kHz and 0.75 kHz (+/- 0.1 kHz). A partial correlation and multivariate analysis was carried out to investigate the relationships between EOE properties and puretone auditory thresholds (from 0.25 to 8 kHz, half-octave steps). For each experiment and each frequency, only one highly significant correlation was found, linearly relating the n kHz EOE threshold with the hearing threshold at 2n kHz: there was a shift of about one octave between EOE amplitudes and audiometric data. This means that EOE thresholds give no direct information about the local cochlear state. A simplified model has been implemented, which assumes that EOE thresholds and amplitudes are proportional to the total number of residual active sites along the organ of Corti, i.e., to the total length of active basilar membrane towards the base of the cochlea. It is shown that this model accounts for the results revealed by the statistical analysis and closely fits the experimental data.

Age variation in the upper limit of hearing

The upper limit of hearing was measured in 6105 otologically normal ears of subjects ranging in age from 5 to 89 years. The results are as follows: in each age group from 5 to 59 years in both sexes, the upper limit of hearing showed an approximately normal distribution if a logarithmic scale was used for the upper limit of hearing axis. The mode of the distribution shifted to a lower frequency with increasing age. Over age 60 years, the distribution became much wider. Standard upper limit age curves were established by calculating 10th, 25th, 50th, 75th and 90th percentiles for each age group. From early childhood where no age variation was recognized in conventional audiometry, deterioration of the upper limit of hearing was already in progress. This deterioration was slight between ages 25 and 39 but at ages over 40 it was accelerated and led to so-called presbycousis. The upper limit of hearing was found to be one of the best parameters for showing the quantitative age-related changes in hearing.

Quantitative assessment of human cochlear function by evoked otoacoustic emissions

The amplitudes of evoked otoacoustic emissions (EOE) and their detection threshold were measured in 44 normal young adults and 118 patients with two categories of cochlear dysfunction, acoustic trauma and presbycusis. A different method was used for each category: detection of click EOE or of stimulus frequency emissions. A partial correlation and multivariate analysis was performed for both groups of results to investigate the relations between EOE threshold one pure tone audiometric thresholds (250 to 8000 Hz). Only one significant correlation was found, linearly relating EOE threshold and hearing threshold at 2 kHz (P less than 0.001), independently of the origin of cochlear dysfunction. It suggests that EOE threshold is not frequency-specific since the frequency of EOE at threshold was nearly always close to 1 kHz. A simple model is proposed, based on the assumption that EOE amplitudes and threshold are proportional to the total number of residual active sites in the organ of Corti, i.e. to the total length of active basilar membrane. It is shown that this model accounts for the results disclosed by the statistical analysis and fits the experimental data. It can be used for quantitatively predicting the residual cochlear activity of a patient. However, the EOE threshold is only sensitive to already important cochlear alterations and this parameter does not seem to allow a follow-up of early stages of cochlear dysfunction.

High-frequency audiometry. Response characteristics of the KH70 vibrator

Various response characteristics of the Präcitronic KH70 bone vibrator have been investigated in the frequency range 0.25 through 16 kHz. Masked threshold reproducibility is satisfactory throughout the frequency range. An occlusion effect is present only at frequencies at and below 1 kHz. Stimulus perception lateralizes to the occluded ear through 1 kHz and less consistently at successively higher frequencies. The KH70 does not satisfy the IEC 645 (1979) criterion for acoustic radiation for frequencies below 6 kHz, especially at the intermediate frequencies of 0.5, 1 and 2 kHz. With the restrictions inherent in the occlusion effect, this does not, however, interfere with threshold determination. The vibrator would thus seem suitable for clinical use through 16 kHz.

Ototoxicity of cis-platinum and its relationship to eye colour

The following hypothesis is presented: that the susceptibility of an individual patient to hearing loss as a result of cis-platinum administration can be predicted on the basis of eye colour. The rationale is that the melanin content of the inner ears is related to that of the eyes; dark eyes contain more melanin than light-coloured eyes; and melanin causes the accumulation of the ototoxic drug within the inner ear. Hence those with dark eyes will suffer greater damage to the hearing than those with pale eyes. An investigation that confirmed this hypothesis is reported. In addition to cochlear damage there is a significant likelihood of damage to the auditory nerve as a result of the treatment.

High-frequency air-conduction and electric bone-conduction audiometry. Comparison of two methods

Threshold values for 147 subjects (9-43 years old) were measured with a high-frequency (HF) air-conduction (AC) (Interacoustics AS 10 HF) and an electric bone-conduction (EBC) (Audimax 500) audiometer. In addition, the reproducibility of these methods was studied in another group of 24 subjects. The results confirmed the previous findings of Okstad et al. (1988) that the electric current (i) used as a stimulus in the Audimax 500 audiometer can be converted into decibels with a correction factor of 40 log (i) re 1 mA as Tonndorf & Kurman (1984) have proposed. However, an additive frequency-dependent correction is needed to obtain similar loudness sensation increases with these audiometers. Reproducibility with the EBC audiometer was better than with the AC audiometer, especially in the HF range.

High-frequency air-conduction and electric bone-conduction audiometry. Age and sex variations

208 subjects representing both sexes and five age groups (15-70 years) were examined to obtain age-related threshold values for high-frequency (HF) electric bone-conduction (EBC) audiometry. The measurements also included conventional pure-tone audiometry and air-conduction (AC) HF (8-18 kHz) audiometry. The measured EBC thresholds were comparable to the values obtained with AC audiometers, and were equal to ISO standards at the frequencies of 0.5-6 kHz. The 15- and 20-year-old groups' EBC thresholds at 8 kHz were equivalent to thresholds of 15-year-old people from a cross-sectional material in Northern Finland. Thresholds deteriorated as a function of age, particularly in the HF range. The males had poorer thresholds than the females, especially in the age groups of 40 and 60 years. This could be attributed mainly to their greater noise exposure. The EBC method is quite practical and reliable for routine clinical measurements, but the dynamic range of the audiometer limits its use to relatively young subjects.

Age variation in the upper limit of hearing and amplitude of eye accommodation in childhood and adolescence

The upper limit of hearing and amplitude of eye accommodation were examined, and their standard aging curves were established in order to evaluate their age-related changes in childhood and adolescence. The subjects were 2497 audiometrically and otologically normal ears and 2349 optometrically and ophthalmologically normal eyes ranging in age from 5 to 24 years in Japan. The upper limit of hearing was measured by the equipment made by us. The amplitude of eye accommodation was calculated at near point and far point measured by the ophthalmodynamometer. Both the upper limit of hearing and amplitude of eye accommodation became gradually less as age increased. The variability of the upper limit of hearing was less than that of the amplitude of eye accommodation. Standard aging curves were established in childhood and adolescence by calculating 10th, 25th, 50th, 75th and 90th centiles. There is no significant relationship between the upper limit of hearing and the amplitude of eye accommodation.

Changes of stapedius reflex and hearing threshold in patients receiving high-dose cisplatin treatment

The value of stapedius reflex (SR) measurement in the clinical management of the ototoxic side-effect of cisplatin was examined in 24 patients who had received a dose of 100-120 mg/m2. The main finding was a frequent but inconsistent deterioration of the SR threshold (SRT) at 3 and/or 4 kHz, usually with a moderate rise of the hearing threshold (HT) in the frequency range 3-8 kHz. A hearing loss exceeding 60 dB HL is detected with high probability as an SRT deterioration. None of the patients showed any influence on the SRT before the HT rise could be detected. The SR test cannot replace pure-tone audiometry for the identification of cisplatin ototoxicity. The pathological SR results observed in this study indicated a cochlear lesion. It was not possible to identify those patients most susceptible to ototoxic changes from the pretreatment results of the SR test.

Role of high-frequency audiometry in the early detection of ototoxicity. II. Clinical Aspects

As a supplement to a previous paper [Dreschler et al.: Audiology 1985; 24:387-395] high-frequency (HF) audiometry was applied to compare the ototoxic effects of two different drug administration protocols for cis-platinum (CDDP). In both subgroups, HF audiometry considerably enhanced the early detection of ototoxicity. Marked differences between treatments have been established both in the pattern of onset of the damage and in the relation between dose and damage severity. For subjects treated with platinum derivatives, the thresholds at 12 and 14 kHz prove to be especially important. The results suggest that for these subjects the measurement of only a single frequency may be considered: with a minimum of effort, most of the increased sensitivity for a complete HF audiogram can be obtained. Finally, the relation between threshold deteriorations above 8 kHz and threshold deteriorations in the conventional range of audiometric frequencies has been investigated.

The effects of occupational exposure to styrene on high-frequency hearing thresholds

Subchronic exposure to styrene has been reported to produce high-frequency hearing loss in rats. In humans, hearing thresholds for higher frequencies (greater than 8 kHz) are also more vulnerable to ototoxic drugs than those at lower frequencies. Since hearing loss at frequencies above 8 kHz does not seem to play a role in speech processing, hearing loss at frequencies above 8 kHz in workers exposed to styrene or other solvents might easily escape detection. Therefore, hearing thresholds were evaluated at frequencies up to 16 kHz in workers exposed to styrene and compared to those of a control group of unexposed workers. The airborne concentrations of styrene typically did not exceed 150 mg/m3 although individual exposures did, at times, reach higher values (up to 700 mg/m3). In accordance with the literature, an age-dependent increase in hearing thresholds at high frequencies was found. Compared to controls, workers exposed to styrene did not appear to demonstrate an aggravated age-dependent decrease in hearing high frequencies. A comparison, however, within the experimental group between the least exposed and the most exposed workers revealed a statistically significant difference on hearing thresholds at high frequencies.

High frequency audiometry in prospective clinical research of ototoxicity due to platinum derivatives

The results of clinical use of routine high frequency audiometry in monitoring the ototoxic side effects of platinum and its derivatives are described in this prospective study. After demonstrating the reproducibility of the technique, we discuss the first results of an analysis of ototoxic side effects in 75 patients (150 ears). Significant differences in the pattern of hearing loss were registered for the different platinum treatment groups (cisplatin 20 mg/m2, cisplatin 50 mg/m2, and carboplatin 350 mg/m2). In the groups receiving cisplatin 50 mg/m2 and carboplatin 350 mg/m2, 42% and 25%, respectively, of the investigated ears proved to be undamaged, versus 9% undamaged in the group receiving cisplatin 20 mg/m2 (p less than .01). Ototoxic hearing loss started mainly (46% to 70%) in the higher frequencies (10,000 to 18,000 Hz) and developed into a broader-range hearing loss (1,000 to 18,000 Hz) during treatment in 13% to 43% (p less than .01). The onset of hearing damage was influenced by the patient's age (p less than .001) and the existence of a troubled otologic history (p less than .05). The study demonstrates the important role of high frequency audiometry in early detection and monitoring of ototoxic damage.

High-frequency audiometry: comparison of electric bone-conduction and air-conduction thresholds

Thresholds have been measured with two commercially available high-frequency (HF) audiometers providing respectively air-conduction (AC) and electric bone-conduction (EBC) stimulation. Normative values for the latter have been obtained, and the reduction of HF sensitivity with both stimulus modes documented in two groups aged 50-59 and 70-79 years. EBC reproducibility is of the same order of magnitude as the AC signal through 14 kHz, while the dynamic range is limited to 50 dB. Lateralization of the EBC signal occurs up to at least 17 kHz. The logarithmic conversion factor of Tonndorf and Kurman [Ann. Otol. Rhinol. Lar. 93: 576-582, 1984] does not result in equivalent AC and EBC thresholds at all frequencies, but does provide similar loudness sensation increases. The 40 log (i) re 1 mA conversion factor must be adjusted with a frequency-dependent additive correction.

An abnormality in the human cochlear vasculature in a case of cis-platinum ototoxicity

The histopathological findings of a study of a human temporal bone are reported. The subject of this study was treated with cis-platinum in combination with bleomycin. High-frequency audiometry was performed pre- and post treatment. Microdissection for surface preparation was carried out after death. An unusual blood vessel in the cochlea was found. The possible cause of this vascular abnormality in the human cochlea is discussed.

Selected pathological findings in the human cochlea

Out of a material of 45 patients with known audiograms where the inner ears had been fixed with an aldehyde within 7 h after death, 4 cases were chosen for detailed morphological examination. The general findings in the ageing human cochlea are presented as well as the findings in the 4 specific cases.