Intrathecal 2-hydroxypropyl-β-cyclodextrin decreases neurological disease progression in Niemann-Pick disease, type C1: a non-randomised, open-label, phase 1-2 trial

BACKGROUND

Niemann-Pick disease, type C1 (NPC1) is a lysosomal storage disorder characterised by progressive neurodegeneration. In preclinical testing, 2-hydroxypropyl-β-cyclodextrins (HPβCD) significantly delayed cerebellar Purkinje cell loss, slowed progression of neurological manifestations, and increased lifespan in mouse and cat models of NPC1. The aim of this study was to assess the safety and efficacy of lumbar intrathecal HPβCD.

METHODS

In this open-label, dose-escalation phase 1-2a study, we gave monthly intrathecal HPβCD to participants with NPC1 with neurological manifestation at the National Institutes of Health (NIH), Bethesda, MD, USA. To explore the potential effect of 2-week dosing, three additional participants were enrolled in a parallel study at Rush University Medical Center (RUMC), Chicago, IL, USA. Participants from the NIH were non-randomly, sequentially assigned in cohorts of three to receive monthly initial intrathecal HPβCD at doses of 50, 200, 300, or 400 mg per month. A fifth cohort of two participants received initial doses of 900 mg. Participants from RUMC initially received 200 or 400 mg every 2 weeks. The dose was escalated based on tolerance or safety data from higher dose cohorts. Serum and CSF 24(S)-hydroxycholesterol (24[S]-HC), which serves as a biomarker of target engagement, and CSF protein biomarkers were evaluated. NPC Neurological Severity Scores (NNSS) were used to compare disease progression in HPβCD-treated participants relative to a historical comparison cohort of 21 NPC1 participants of similar age range.

FINDINGS

Between Sept 21, 2013, and Jan 19, 2015, 32 participants with NPC1 were assessed for eligibility at the National Institutes of Health. 18 patients were excluded due to inclusion criteria not met (six patients), declined to participate (three patients), pursued independent expanded access and obtained the drug outside of the study (three patients), enrolled in the RUMC cohort (one patient), or too late for the trial enrolment (five patients). 14 patients were enrolled and sequentially assigned to receive intrathecal HPβCD at a starting dose of 50 mg per month (three patients), 200 mg per month (three patients), 300 mg per month (three patients), 400 mg per month (three patients), or 900 mg per month (two patients). During the first year, two patients had treatment interrupted for one dose, based on grade 1 ototoxicity. All 14 patients were assessed at 12 months. Between 12 and 18 months, one participant had treatment interrupted at 17 months due to hepatocellular carcinoma, one patient had dose interruption for 2 doses based on caregiver hardship and one patient had treatment interrupted for 1 dose for mastoiditis. 11 patients were assessed at 18 months. Between Dec 11, 2013, and June 25, 2014, three participants were assessed for eligibility and enrolled at RUMC, and were assigned to receive intrathecal HPβCD at a starting dose of 200 mg every 2 weeks (two patients), or 400 mg every two weeks (one patient). There were no dropouts in this group and all 3 patients were assessed at 18 months. Biomarker studies were consistent with improved neuronal cholesterol homoeostasis and decreased neuronal pathology. Post-drug plasma 24(S)-HC area under the curve (AUC_8-72) values, an indicator of neuronal cholesterol homoeostasis, were significantly higher than post-saline plasma 24(S)-HC AUC_8-72 after doses of 900 mg (p=0·0063) and 1200 mg (p=0·0037). CSF 24(S)-HC concentrations in three participants given either 600 or 900 mg of HPβCD were increased about two fold (p=0·0032) after drug administration. No drug-related serious adverse events were observed. Mid-frequency to high-frequency hearing loss, an expected adverse event, was documented in all participants. When managed with hearing aids, this did not have an appreciable effect on daily communication. The NNSS for the 14 participants treated monthly increased at a rate of 1·22, SEM 0·34 points per year compared with 2·92, SEM 0·27 points per year (p=0·0002) for the 21 patient comparison group. Decreased progression was observed for NNSS domains of ambulation (p=0·0622), cognition (p=0·0040) and speech (p=0·0423).

INTERPRETATION

Patients with NPC1 treated with intrathecal HPβCD had slowed disease progression with an acceptable safety profile. These data support the initiation of a multinational, randomised, controlled trial of intrathecal HPβCD.

FUNDING

National Institutes of Health, Dana's Angels Research Trust, Ara Parseghian Medical Research Foundation, Hope for Haley, Samantha's Search for the Cure Foundation, National Niemann-Pick Disease Foundation, Support of Accelerated Research for NPC Disease, Vtesse, Janssen Research and Development, a Johnson & Johnson company, and Johnson & Johnson.

Distortion product otoacoustic emissions: An objective technique for the screening of hearing loss in children treated with platin derivatives

In order to develop a sensitive audiometric protocol for identifying ototoxicity in children, a retrospective study of 16 children treated with cisplatin and/or carboplatin was performed. Audiometric testing was done by means of pure-tone threshold audiometry (PTA), high-frequency audiometry (HFA), and distortion product otoacoustic emissions (DPOAEs). Cisplatin caused a sensorineural high-frequency hearing loss in the study group compared to the controls (p < 0.01). Sixty-six percent of the cisplatin patients had a grade 2 or 3 ototoxicity. However, ototoxicity was not found in the patients treated with carboplatin. An excellent correlation was found between DPOAE levels and results obtained by audiometry (r = 0.82). Patients exposed to cisplatin are at significant risk for the development of drug-induced sensorineural hearing loss. Because of the several advantages of DPOAEs (noninvasive, objective, rapid, easy to use, sensitive) this method should be added in the audiological follow-up in infants and toddlers.

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.

Use of auditory brainstem responses for the early detection of ototoxicity from aminoglycosides or chemotherapeutic drugs

Effective objective HF (high-frequency) testing methodology provides for the early detection of ototoxic hearing loss because it typically progresses from high to low frequencies. Such early detection is considered necessary to prevent hearing loss from progressing into the frequency range important for understanding speech. Objective tests must be reliable, sensitive to hearing change, and time efficient. Auditory brainstem responses (ABRs) appear well suited to this task; however, current ABR techniques have limitations. Conventional clicks stimulate middle (1-4 kHz) rather than high frequencies (>8 kHz). Responses to HF tone bursts require considerable recording time. We hypothesized that using HF band-limited clicks (HF clicks) could overcome these limitations. Two different HF clicks, with bandwidths of 8-14 kHz were used to elicit ABRs. The current study compared responses among these stimuli. The results demonstrate the reliability of HF-click responses and of tone bursts presented in trains.

Organic solvent exposure and hearing loss in a cohort of aluminium workers

OBJECTIVES

Organic solvent exposure has been shown to cause hearing loss in animals and humans. Less is known about the risk of hearing loss due to solvent exposures typically found in US industry. The authors performed a retrospective cohort study to examine the relationship between solvent exposure and hearing loss in US aluminium industry workers.

METHODS

A cohort of 1319 workers aged 35 years or less at inception was followed for 5 years. Linkage of employment, industrial hygiene and audiometric surveillance records allowed for estimation of noise and solvent exposures and hearing loss rates over the study period. Study subjects were classified as "solvent exposed" or not, on the basis of industrial hygiene records linked with individual job histories. High frequency hearing loss was modelled as both a continuous and a dichotomous outcome.

RESULTS

Typical solvent exposures involved mixtures of xylene, toluene and/or methyl ethyl ketone (MEK). Recorded solvent exposure levels varied widely both within and between jobs. In a multivariate logistic model, risk factors for high frequency hearing loss included age (OR = 1.06, p = 0.004), hunting or shooting (OR = 1.35, p = 0.049), noisy hobbies (OR = 1.74, p = 0.01), baseline hearing level (OR = 1.04, p<0.001) and solvent exposure (OR = 1.87, p = 0.004). A multivariate linear regression analysis similarly found significant associations between high frequency hearing loss and age (p<0.001), hunting or shooting (p<0.001), noisy hobbies (p = 0.03), solvent exposure (p<0.001) and baseline hearing (p = 0.03).

CONCLUSION

These results suggest that occupational exposure to organic solvent mixtures is a risk factor for high frequency hearing loss, although the data do not allow conclusions about dose-response relationships. Industries with solvent-exposed workers should include such workers in hearing conservation programs.

Potential Ototoxicity of Aluminum in Hemodialysis Patients

OBJECTIVES/HYPOTHESIS

Aluminum (Al) is a neurotoxin in both human and animal models. Al accumulation is usually observed in patients with end-stage renal disease (ESRD). To clarify whether Al also exhibits toxic effects on the specified neural organ of inner ear, we recruited hemodialysis (HD) patients to investigate the effect of serum Al level on the auditory physiology.

STUDY DESIGN

Forty patients in maintenance HD as well as 40 age-matched healthy subjects without hearing complaints were enrolled. The auditory function tests, including pure-tone audiometry (PTA), distortion-product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR) were performed in all subjects. The serum Al levels determined within 3 months of auditory tests were used for analysis.

RESULTS

High-frequency hearing impairment was the predominant auditory dysfunction in HD patients who showed worse high-tone hearing level on PTA and diminished amplitudes of DPOAEs at 3 K and 4 K as compared with the controls (P < .001). Age was a significant factor determining the auditory dysfunction in both HD patients and control subjects. After age correction, serum Al level correlated reversely with the amplitude of DPOAEs-2 K (P = .002), but not with amplitudes of DPOAEs-3 K, -4 K, hearing levels on PTA, or wave latencies on ABR.

CONCLUSION

High-frequency hearing impairment is a common presentation in HD patients. Serum Al level correlates reversely with the amplitude of DPOAEs-2 K but not those of DPOAEs-3 K, -4 K, hearing levels on PTA, and wave latencies on ABR. Possibly, the correlation between the Al level and the high-frequency OAE results was obscured by the significantly diminished amplitudes of DPOAEs-3 K, -4 K in ESRD patients. These results implicate that the effect of Al is mainly of cochlear origin rather than of retrocochlear origin.

Relationship Between Cisplatin Administration and the Development of Ototoxicity

Purpose

To determine the auditory toxicity associated with dose- and schedule- intensive cisplatin/gemcitabine chemotherapy in non–small-cell lung carcinoma patients.

Patients and Methods

Patients were treated with gemcitabine followed by cisplatin according to an interpatient dose-escalation scheme. Patients were randomly assigned to receive treatment once a week for 6 weeks or once every 2 weeks for 4 weeks. The following cohorts of patients were treated with a reversed schedule once every 2 weeks, in which cisplatin was followed by gemcitabine. The dose-intensity of cisplatin was equal in both schedules. Audiometric evaluations were obtained for each ear at several frequencies. Mean hearing loss after cisplatin treatment was computed for each dose level at each tested frequency in each ear at baseline and subsequent follow-up audiometry. Pure tone averages (PTAs) were also calculated. The pharmacokinetics of cisplatin was determined to study the correlation among the maximum drug concentration, the area under the curve of unbound platinum, and the development of ototoxicity.

Results

A total of 328 audiograms were analyzed. At the higher frequencies, a more severe hearing impairment was recorded. Most patients showed a decrease in hearing thresholds at dosages above 60 mg/m2 cisplatin at the higher frequencies. PTAs at 1, 2, and 4 kHz show a mean hearing loss of 19 dB after cisplatin administration at dosages above 90 mg/m2. Threshold shifts at 8 and 12.5 kHz after cisplatin administration were experienced at dosages above 60 mg/m2.

Conclusion

Hearing loss after cisplatin therapy occurs mainly at high frequencies and at cisplatin dosages more than 60 mg/m2. It is more pronounced when cisplatin is given once every 2 weeks.

Predicting cisplatin ototoxicity in children: the influence of age and the cumulative dose

The aim of this study was to determine the risk factors for high-frequency hearing loss in children treated with cisplatin. We scored off-treatment pure-tone audiograms from 153 children (age 6 months to 18 years) who had completed cisplatin therapy (40-200 mg/m(2)/cycle) for germ cell tumours, hepatoblastoma, neuroblastoma or osteosarcoma. The risk of developing bilateral moderate to severe high-frequency hearing loss was significantly related to the age at treatment (P<0.001), and individual and cumulative cisplatin dosages (both P<0.005). Logistic regression showed that children younger than 5 years were at a greater risk of sustaining cisplatin ototoxicity than children older than 15 years, controlling for individual and cumulative doses of cisplatin (Odds Ratio (OR)=21.17, 95% Confidence Interval (CI): 2.48-180.94). Age at treatment and the cumulative dose of cisplatin were the two most important risk factors in predicting moderate to severe high-frequency hearing loss in children treated with cisplatin.

Aminoguanidine reduces cisplatin ototoxicity

Cisplatin is known to cause high-frequency neurosensory hearing loss. While reactive oxygen species have been shown to play a role, reactive nitrogen species have been implicated, but not proven to be involved, in cisplatin ototoxicity. The purpose of the present study was to investigate the role of nitric oxide (*NO) in cisplatin ototoxicity by administering aminoguanidine (AG), a relatively specific inhibitor of inducible nitric oxide synthase (iNOS), in conjunction with cisplatin. Rats were injected with cisplatin, AG, or both. Auditory brainstem evoked responses (ABR) were measured before and 3 days after cisplatin administration. The cochlear tissue was then assayed for *NO and malondialdehyde. Cisplatin alone caused significant ABR threshold shifts at all stimuli tested, whereas AG alone caused no shifts. There was a significant reduction in threshold shift for clicks and 16 kHz tone bursts (but not 32 kHz) when AG was given with cisplatin. The malondialdehyde concentration (but not the *NO concentration) in the AG/cisplatin group was significantly lower than that of the cisplatin group. This suggests that AG reduces cisplatin ototoxicity by directly scavenging hydroxyl radicals. The iNOS pathway may play a role in the generation of free radicals and hearing loss resulting from cisplatin administration, but this conclusion was not supported by our data.

Comparison of ABR stimuli for the early detection of ototoxicity: conventional clicks compared with high frequency clicks and single frequency tonebursts

Effective objective testing methodology is needed for early detection of the effects of ototoxicity on hearing in patients. The requirements for such testing include responses that are: 1) reliable across test sessions; 2) sensitive to ototoxic change ( > 8 kHz), and 3) recordable in a time-efficient manner. Auditory brainstem responses (ABR) appear well suited to this task however, conventional clicks stimulate primarily mid-frequencies (1-4 kHz) and high frequency tonebursts require too much time. We hypothesized that delivery of a band of high frequencies (a high frequency "click"), would elicit reliable and useful ABRs. In the current study, flat and sloped HF (high frequency) clicks with a bandwidth of 8-14 kHz were used. The purpose was to compare brainstem responses elicited by tonebursts, two HF clicks and conventional clicks. The results show that the reliability of responses to the HF clicks were comparable to the tonebursts and further, both HF clicks produced responses slightly larger than tonebursts.

Audiologic monitoring for potential ototoxicity in a phase I clinical trial of a new glycopeptide antibiotic

This study describes audiologic methodology and results for evaluating potential ototoxicity in a phase I clinical trial of a new glycopeptide. This study was conducted under good clinical practices, which are regulated by the US Food and Drug Administration (FDA) (21 Code of Federal Regulations), and input from the FDA was sought prior to study implementation. Healthy, normal volunteers underwent extensive medical and audiologic assessments as part of this phase I dose- escalation study of dalbavancin, a new glycopeptide, to assess potential side effects. Audiologic monitoring included air-conduction thresholds in the conventional (0.25-8 kHz) and high-frequency (10-16 kHz) ranges. At baseline, subjects were also tested using word recognition, bone conduction testing if indicated, and tympanometry. Full testing was to be repeated if any subject met the American Speech-Language-Hearing Association (ASHA) 1994 criteria for ototoxic change. However, no subjects demonstrated ototoxic change after receiving dalbavancin, nor were any false-positive results obtained.

A case of sensorineural deafness following ingestion of Ecstasy

Ecstasy is a substance of abuse commonly associated with the dance scene and taken by many young people. A brief history of Ecstasy and its side-effects is given. A case of ototoxicity is presented, as an additional side-effect to the long list of complications caused by Ecstasy.

Evoked otoacoustic emissions--an approach for monitoring cisplatin induced ototoxicity in children

OBJECTIVES

Cisplatin chemotherapy is associated with an increased risk of ototoxic changes. The incidence of hearing loss after the 1st cisplatin-infusion session is only scarcely mentioned in the international literature. With increasing survival rates, prevention and/or early detection of ototoxicity are important for providing management options. The predictive value of pure-tone audiometry in early detection of ototoxicity has been questioned, particularly in the higher frequencies. Otoacoustic emissions appear to be more sensitive to cochlear insult than the conventional pure-tone audiometry. The aims of our study was (a) to define the extent of hearing damage in children after the 1st cisplatin-infusion session (50 mg/m(2)); and (b) to compare the efficacy of otoacoustic emissions (transient evoked otoacoustic emissions, distortion-product otoacoustic emissions) with that of pure-tone audiometry as methods of audiological monitoring.

METHODS

Baseline audiometric (0.25-8 kHz) and otoacoustic emission testing (transient evoked otoacoustic emissions, distortion-product otoacoustic emissions) was conducted in 19 children, 12 of whom met the criteria for inclusion in the final study. Comparisons were performed between baseline measurements and those recorded after the 1st cisplatin course. Transient evoked otoacoustic emissions were analyzed in terms of emission level and reproducibility as a function of frequency (0.8-4 kHz). Distortion-product otoacoustic emissions were obtained as DP-grams and I/Q functions at 4,6 and 8 kHz. The DP-gram amplitude, the dynamic range and the detection thresholds from the I/Q functions were determined for each child.

RESULTS

Threshold changes from baseline were founded to be statistically significant from 4-8 kHz in 50% of the children (P<0.01). Transient evoked otoacoustic emissions revealed a significant decrease in the emission level and in the reproducibility at the highest frequency tested (4 kHz, P<0.01), reflecting the results seen in pure-tone audiometry. Distortion-product otoacoustic emissions demonstrated a significant threshold shift, a reduced dynamic range and a decreased amplitude in the frequencies >3 kHz (P<0.05). Furthermore, DP-gram amplitude also reduced significantly at 3 kHz (P<0.05) without any similar change in pure-tone audiometry.

CONCLUSIONS

A significant high-frequency hearing loss is identified in children even after one low-dose cisplatin-infusion session. As ototoxicity screening tools DP-grams were extremely sensitive and superior to pure-tone audiometry and/or transient evoked otoacoustic emissions. Their use is recommended for regular monitoring of cochlear function, aiming in prevention of permanent damage. Some suggestions for reducing the potential for cisplatin ototoxicity (chemoprotective agents, gene therapy, inhibition of apoptosis) are also discussed.

High-frequency (8 to 16 kHz) reference thresholds and intrasubject threshold variability relative to ototoxicity criteria using a Sennheiser HDA 200 earphone

OBJECTIVE

The first purpose of this study was to determine high-frequency (8 to 16 kHz) thresholds for standardizing reference equivalent threshold sound pressure levels (RETSPLs) for a Sennheiser HDA 200 earphone. The second and perhaps more important purpose of this study was to determine whether repeated high-frequency thresholds using a Sennheiser HDA 200 earphone had a lower intrasubject threshold variability than the ASHA 1994 significant threshold shift criteria for ototoxicity.

DESIGN

High-frequency thresholds (8 to 16 kHz) were obtained for 100 (50 male, 50 female) normally hearing (0.25 to 8 kHz) young adults (mean age of 21.2 yr) in four separate test sessions using a Sennheiser HDA 200 earphone.

RESULTS

The mean and median high-frequency thresholds were similar for each test session and increased as frequency increased. At each frequency, the high-frequency thresholds were not significantly (p > 0.05) different for gender, test ear, or test session. The median thresholds at each frequency were similar to the 1998 interim ISO RETSPLs; however, large standard deviations and wide threshold distributions indicated very high intersubject threshold variability, especially at 14 and 16 kHz. Threshold repeatability was determined by finding the threshold differences between each possible test session comparison (N = 6). About 98% of all of the threshold differences were within a clinically acceptable range of +/-10 dB from 8 to 14 kHz. The threshold differences between each subject's second, third, and fourth minus their first test session were also found to determine whether intrasubject threshold variability was less than the ASHA 1994 criteria for determining a significant threshold shift due to ototoxicity. The results indicated a false-positive rate of 0% for a threshold shift > or = 20 dB at any frequency and a false-positive rate of 2% for a threshold shift >10 dB at two consecutive frequencies.

CONCLUSIONS

This study verified that the output of high-frequency audiometers at 0 dB HL using Sennheiser HDA 200 earphones should equal the 1998 interim ISO RETSPLs from 8 to 16 kHz. Further, because the differences between repeated thresholds were well within +/-10 dB and had an extremely low false-positive rate in reference to the ASHA 1994 criteria for a significant threshold shift due to ototoxicity, a Sennheiser HDA 200 earphone can be used for serial monitoring to determine whether significant high-frequency threshold shifts have occurred for patients receiving potentially ototoxic drug therapy.

Auditory sensori-neural alterations induced by salicylate

Early after the development of aspirin, almost 150 years ago, its auditory toxicity has been associated with high doses employed in the treatment of chronic inflammatory diseases. Tinnitus, loss of absolute acoustic sensitivity and alterations of perceived sounds are the three auditory alterations described by human subjects after ingestion of large doses of salicylate. They develop over the initials days of treatment but may then level off, fluctuate or decrease, and are reversible within a few days of cessation of treatment. They may also occur within hours of ingestion of an extremely large dose. Individual subjects vary notably as to their susceptibility to salicylate-induced auditory toxicity. Tinnitus may be the first subjective symptom, and is often described as a continuous high pitch sound of mild loudness. The hearing loss is slight to moderate, bilaterally symmetrical and affects all frequencies with often a predominance at the high frequencies. Alterations of perceived sounds include broadening of frequency filtering, alterations in temporal detection, deterioration of speech understanding and hypersensitivity to noise. Behavioral conditioning of animals provides evidence for mild and reversible hearing loss and tinnitus, similar to those observed in humans. Anatomical examinations revealed significant alterations only at outer hair cell lateral membrane. Electrophysiological investigations showed no change in endocochlear resting potential, and small changes in the compound sensory potentials, cochlear microphonic and summating potential, at low acoustic levels. Measures of cochlear mechanical responses to sounds indicated a clear loss of absolute sensitivity and an associated broadening of frequency filtering, both of a magnitude similar to audiometric alterations in humans, but at extremely high salicylate levels. Otoacoustic emissions demonstrated changes in the mechano-sensory functioning of the cochlea in the form of decrease of spontaneous emissions and reduced nonlinearities. In vitro measures of isolated outer hair cells showed reduction of their fast motile responses which are thought to be at the origin of cochlear absolute sensitivity and associated fine filtering. Acoustically evoked neural responses from the eighth nerve to the auditory cortex showed reversible and mild losses of absolute sensitivity and associated broadening of frequency filtering. There is no evidence of a direct alteration of cochlear efferent innervation. Evidence was obtained for decreases in cochlear blood supply under control of autonomous innervation. Spontaneous neural activity of the auditory nerve revealed increases in firings and/or in underlying temporal synchronies. Similar effects were found at the inferior colliculus, mostly at the external nucleus, and at the cortex, mostly at the anterior and less at the secondary auditory cortex but not at the primary auditory cortex. These changes in spontaneous activity might underlie tinnitus as they affect mostly neural elements coding high frequencies, can occur without a loss of sensitivity, are dose dependent, develop progressively, and are reversible. Biochemical cochlear alterations are poorly known. Modifications of oxydative phosphorylation does not seem to occur, involvement of inhibition of prostaglandin synthesis appears controversial but could underlie changes in blood supply. Other biochemical alterations certainly also occur at outer hair cells and at afferent nerve fibers but remain unknown.

Extended High-Frequency Ototoxicity Induced by the First Administration of Cisplatin

The ototoxicity induced by cisplatin results in high-frequency hearing loss. The sound-pressure thresholds at extended high frequencies of 8 to 20 kHz were measured in 12 patients with head and neck cancer before and after the first administration of cisplatin. Ototoxicity was defined statistically by the newly introduced regression-line analysis. This analysis revealed that the threshold of 1 of the 12 patients increased evenly from 8 to 10 kHz, and the damage to the hearing system of this patient was permanent. The reasons for such a low rate of ototoxicity might be the long-term administration of low doses of cisplatin and the addition of fosfomycin.

Late toxicity following curative treatment of testicular cancer

Cisplatin appears to be the major cause for long-term toxicity in patients treated for testicular cancer. Long-term side effects consist mainly of nephrotoxicity, ototoxicity, and neurotoxicity as well as gonadal damage. Following standard-dose chemotherapy approximately 20% to 30% of patients will be affected by long-term side effects, although not all these side effects will cause an impaired quality of life. Several strategies have been or currently are being evaluated to reduce acute and long-term complications including the introduction of equally effective, but less toxic regimens, or the use of cytoprotective agents such as amifostine. Secondary acute myeloid leukemia and secondary myelodysplastic syndrome probably represent the worst possible long-term complications of cancer therapy in those patients who originally were cured of their primary testicular cancer. Therapy-related solid tumors are mainly associated with the use of radiation therapy and the risk for developing a therapy-related solid tumor is increased approximately two to three times compared to the general population. In contrast, therapy-related leukemias are predominantly associated with chemotherapy, particularly with the use of topoisomerase-II inhibitors and alkylating agents. In general, the cumulative incidence of therapy-related leukemia following treatment of germ cell cancer is low. It is approximately 0.5% and 2% at 5 years of median follow-up for patients receiving etoposide at cumulative doses< or = 2 g/m(2) and >2 g/m(2), respectively. The risk-benefit analysis in patients with testicular cancer clearly favors the use of current treatment regimens including high-dose chemotherapy. However, even the acceptably low number of therapy-related long-term complications should encourage the search for equally effective but less toxic therapies. This review will highlight important available data about therapy-related toxicity and particularly, therapy-related malignancies following cisplatin-etoposide-based chemotherapy.

Evaluation of organic solvent ototoxicity by the upper limit of hearing

To clarify the effects of organic solvents on hearing, we measured the upper limit of hearing in 93 male workers exposed to organic solvents in 7 factories that produced plastic buttons or baths. Medical examinations, environmental monitoring (i.e., concentration in breathing-zone air), and biological monitoring (i.e., concentration in urine) of the organic solvents were also done. Although the organic solvent concentrations in the environmental monitoring were lower than the occupational exposure limit, the upper limit of hearing was reduced in workers who were exposed for 5 y or more. This reduction was dose-dependent and was related to styrene concentrations in breathing-zone air and mandelic acid concentrations in urine. Even individuals who had normal medical examinations showed a reduced upper limit of hearing. The upper limit of hearing may serve as an early detection indicator of health effects in workers constantly exposed to styrene.

[Mefloquine and ototoxicity: a report of 3 cases]

We report these cases of high-frequency sensorineural hearing loss and tinnitus, following malaria prophylaxis with mefloquine (Lariam). Only one patient had partial remission of hearing loss after suspension of the treatment. In the remaining two cases the symptomatology remained unchanged. None of the patients reported improvement of tinnitus. Our experience suggests that a routine audiologic evaluation, before and after prophylactic use of antimalarial drugs, is important to monitor potential hearing deficit.

Differentiation of cochlear pathophysiology in ears damaged by salicylate or a pure tone using a nonlinear systems identification technique

Mongolian gerbils were exposed to either alpha-ketoglutarate, salicylate, or an 8-kHz pure tone. Cochlear microphonic (CM) was recorded from the round window in response to 68 and 88 dB SPL Gaussian noise. A nonlinear systems identification technique provided the frequency-domain parameters of a third-order polynomial model characterizing cochlear mechano-electric transduction (MET). A series of physiologic indices were derived from further exploration of the model. Exposure to the 8-kHz pure tone and round window application of salicylate resulted in different changes in the polynomial parameters and physiologic indices even though the threshold shifts were similar. A general reduction of CM magnitude was found after the tone exposure, and an increase at low-mid frequencies was demonstrated in the salicylate group especially at the lower signal level. The slope of the MET curve was reduced by the acoustic overstimulation. The root or the operating point of the MET was shifted in opposite directions after the two treatments. Sound-pressure levels that saturate MET expanded in the tone exposure group and narrowed in the salicylate group. The signal level also had effects on these indices.

Antiviral therapy in a child with pediatric human immunodeficiency virus (HIV): case study of audiologic findings

Over the past decade, much research has been conducted to determine the auditory consequences of human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). This research, primarily using adult patients, has focused on the involvement of the central auditory nervous system (CANS). Measures of auditory evoked potentials, particularly the auditory brainstem response (ABR), can document changes in the CANS as the disease progresses and during treatment with antiviral therapies such as zidovudine (AZT) and didanosine (ddI). This case study presents the audiologic findings for a child with HIV infection. Evaluations were performed over a 2-year period prior to the initiation of antiviral therapy and following treatment. Audiologic measures included behavioral audiometry, tympanometry, otoacoustic emissions, and ABR latency/intensity functions and rate studies. Findings indicated a gradual shortening of all ABR component latencies following the initiation of antiviral therapy. In addition, a high-frequency hearing loss was detected during the final evaluation subsequent to 19 months of treatment with AZT and ddI.

Familial hearing loss and cisplatin therapy

Familial high-tone hearing loss in males is a recessive trait often unrecognized. Cisplatin chemotherapy may be associated with hearing loss. A review was made of audiograms in 85 patients with testicular carcinoma prior to cisplatin chemotherapy to determine the extent of preexisting familial hearing loss. Clinical histories defined patients exposed to high noise levels and other common causes of hearing loss. Audiometric findings were classified according to normal hearing or mild, moderate, and severe hearing impairment. Pretreatment audiograms were normal in 51 patients and abnormal in 19 patients with histories of high-level noise exposure, and in 15 patients with high-frequency hearing loss there was no history of noise exposure, ear infection, or other potential causes of hearing loss. These last 15 patients were judged to have recessive familial hearing loss. Awareness of familial hearing loss is important in male patients in whom cisplatin chemotherapy is planned. Pretreatment hearing assessment, including audiograms, is recommended for such male patients.

Transient-evoked otoacoustic emissions in children after cisplatin chemotherapy

Little is known about cisplatin ototoxicity in pediatric patients. Measurement of otoacoustic emissions is a rapid, reproducible, objective method of evaluating hearing. We examined whether transient-evoked otoacoustic emissions in pediatric patients exposed to cisplatin in the past correlated with audiographic findings. Twelve patients were entered into the study (mean age at treatment 7.8 years, mean cumulative dose 442.5 mg/mm2, mean 7.1 doses). Hearing at 3000 Hz was preserved in 82.6% of patients. In the higher frequencies significant sensorineural hearing loss was noted: 43.5% at 4 kHz; 81.0% at 6 kHz; and 90.5% at 8 kHz. Transient-evoked otoacoustic emissions were measurable in 11 of 12 patients. Middle ear disease accounted for abnormal otoacoustic emission seen in three patients (1 with effusion, 2 with significant negative middle ear pressure). When the middle ear was normal, a statistically significant correlation was seen between the transient-evoked otoacoustic emissions reproducibility and pure-tone threshold (correlation coefficient = -0.69, p = 0.008). Increased hearing loss was also associated with young age at first dose of cisplatin (p = 0.044), high number of chemotherapy cycles (p = 0.042), and high cumulative dose (p = 0.042).

Intrasubject reliability of high-frequency (9-14 kHz) thresholds: tested separately vs. following conventional-frequency testing

Retrospective analysis of hearing-threshold data from a multisite ototoxicity monitoring study identified an individualized range of predominantly high frequencies (> 8 kHz) that appeared to be highly sensitive to early threshold changes caused by ototoxicity. This suggested the potential for a limited-frequency monitoring protocol that could be conducted rapidly without compromising sensitivity to ototoxicity. Such testing would require high-frequency thresholds to be obtained independently, that is, without prior testing at conventional frequencies (0.25-8 kHz). This study was conducted to determine the test-retest reliability of isolated threshold testing in a "target" frequency range of high frequencies (9, 10, 11.2, 12.5, and 14 kHz) that represented a shortened ototoxicity monitoring test. Twenty normal-hearing subjects were evaluated over five sessions. During each session, subjects were tested in each of two conditions: (1) conventional frequencies (0.25-8 kHz) tested first, followed by target frequencies; and (2) target frequencies tested alone (isolation condition). Depending on test frequency, reliability of high-frequency thresholds was either unchanged or improved in the isolation condition. Although these results cannot be generalized to ill hospitalized patients, who may also have pre-existing hearing loss, they lay the groundwork for development of a time-saving limited-frequency test to monitor for ototoxicity in these patients.

[Hearing loss caused by high dose carboplatin therapy]

BACKGROUND

Carboplatin is regarded as a non-ototoxic or low-grade ototoxic chemotherapeutic agent.

METHOD

We report on three patients with a recurrence of testicular cancer after cisplatin chemotherapy who suffered hearing loss after subsequent high-dose carboplatin therapy.

RESULTS

Audiometry demonstrated carboplatin-induced hearing loss primarily in the mid-range and high frequencies up to 45 dB at 3 kHz and up to 55 dB at 8 kHz. In two of three patients, transitory-evoked otoacoustic emissions were absent after carboplatin therapy.

CONCLUSION

Following first-line cisplatin chemotherapy, salvage treatment with high-dose carboplatin can generate hearing loss in the middle and high frequencies.

Loss of spiral ganglion cells as primary manifestation of aminoglycoside ototoxicity

Although pulmonary infections caused by Pseudomonas aeruginosa can hardly be eradicated in patients with cystic fibrosis (CF, the most common genetic disease among Caucasians), these patients are mainly treated with intravenous and nebulized tobramycin. Long-term treatment with tobramycin, however, may induce ototoxic effects. We assessed the clinical histories and postmortem temporal bones of six patients with CF for signs of this ototoxicity. Four bones showed typical manifestations of ototoxicity induced by aminoglycosides (AGs): loss of hair cells in the lower turns, and degeneration of ganglion cells. Six bones revealed no loss or scattered loss of hair cells, however, degeneration of the spiral ganglion cells was observed. This suggests that degeneration of the spiral ganglion may occur as a primary manifestation in some cases of ototoxicity due to aminoglycosides. Recent reports have shown that trophic factors (neurotrophins and acidic fibroblast growth factor) interacting with hair cells and the spiral ganglion protect the inner ear from damage. It may be that disturbances in supply of such trophic factors caused degeneration of ganglion cells without loss of hair cells in the cases we studied.

Ototoxic effects of supradose cisplatin with sodium thiosulfate neutralization in patients with head and neck cancer

OBJECTIVE

To assess the incidence and magnitude of ototoxicity in patients undergoing an experimental targeted chemoradiation protocol incorporating extremely high-dose intra-arterial cisplatin therapy with systemic sodium thiosulfate neutralization for the treatment of advanced carcinomas of the head and neck.

DESIGN

Inception cohort study.

SETTING

University-based, tertiary care referral center for advanced head and neck malignant disease.

PATIENTS

The first 70 patients with advanced carcinomas of the head and neck consecutively entered in the protocol.

INTERVENTION

Patients received up to 4 weekly courses of intra-arterial cisplatin (150 mg/m2 per infusion), together with systemic sodium thiosulfate and external beam radiation (68-70 Gy). Audiometric analysis was performed before the initiation of therapy, and subsequent to the second and fourth cisplatin infusions.

MAIN OUTCOME MEASURES

Audiometric thresholds. Ototoxicity was defined as an increase in pure-tone threshold of 15 dB at 1 frequency or 10 dB at 3 frequencies, between 250 and 4000 Hz.

RESULTS

The incidence of ototoxicity was 25% at 150 mg/m2, 50% at 300 mg/m2, 64% at 450 mg/m2, and 60% at 600 mg/m2. Hearing at frequencies of 2000 Hz or less was minimally or not affected. Previous hearing loss did not appear to affect the incidence of ototoxicity. A plateau of hearing loss at 60-dB hearing level, as noted by other authors, was not observed. There were no cases of debilitating tinnitus or of vestibular loss.

CONCLUSIONS

Ototoxicity did occur but was largely confirmed to the higher frequencies. Hearing losses resulting from this chemoradiation protocol were not sufficiently severe to alter its application.

Radiotherapy enhanced ototoxicity of cisplatin in children

We reviewed and re-examined 31 children (6 months-14 years at the time of diagnosis), who had been treated for a neoplasm in Turku University Central Hospital between 1989 and 1994. The children were divided into 3 groups according to the site of the neoplasm and the type of therapy. Group I included 13 children, operated on for an intracranial tumor and received postoperative radio- and cisplatin-based chemotherapy. Group II included 14 children operated on for intracranial tumors and treated with radiotherapy, but not given chemotherapy. Group III included 4 children suffering from extracranial malignancies and they had received chemotherapy including cisplatin. The children in Group I had significantly worse hearing thresholds in the middle- and high-frequency range than children in Groups II and III. In a precise analysis of the different factors, no single dose of cisplatin, inner ear irradiation dose or totally to the central nervous system (CNS) received irradiation dose correlated to the detected hearing loss. However, multiple linear correlation analyses suggest a combined effect of radiotherapy plus cisplatin resulting in a high frequency hearing loss. This is in accordance with earlier random case reports, and supports the idea that radiotherapy should be considered cautiously in children treated with cisplatin for intracranial malignancies.

Acute massive gentamicin intoxication in a patient with end-stage renal disease

A 65-year-old man with end-stage renal disease on continuous ambulatory peritoneal dialysis accidentally received an acute massive overdose of gentamicin as a treatment of peritonitis. The patient developed acute vestibular dysfunction and hearing loss following the overdose. His serum gentamicin had reached the extremely toxic level of 220 microg/mL. To remove the gentamicin, the patient received hemodialysis and hemoperfusion immediately. This was followed by two more courses of hemodialysis during the following 2 days. The gentamicin level was brought down to 10 microg/mL after the third hemodialysis. Moderate and persistent high-frequency hearing loss was documented with serial audiograms. The patient made a gradual but incomplete recovery from the vestibular dysfunction. The complications of gentamicin toxicity and its management are discussed with respect to our patient.

Hearing loss in children with brain tumors treated with cisplatin and carboplatin-based high-dose chemotherapy with autologous bone marrow rescue

Carboplatin is less ototoxic than cisplatin, but ototoxicity may occur with carboplatin at higher doses. We evaluated hearing in children with brain tumors treated with conventional dose cisplatin followed by high-dose carboplatin. Children under 6 years of age, newly diagnosed with brain tumors, were treated after surgery with cisplatin, Etoposide, cyclophosphamide, and vincristine, followed by consolidation with carboplatin, ThioTEPA, Etoposide, and autologous bone marrow rescue. Hearing was assessed before and after consolidation, utilizing standard audiometric techniques. Seven of the 11 evaluable patients developed high-frequency sensorineural hearing loss after induction therapy. Hearing deteriorated after consolidation in five patients, with pure tone threshold shifts of up to 65 dB between 2,000 and 8,000 Hz. Of these five patients, audiological abnormalities were documented in four prior to consolidation, one received cranial irradiation after consolidation, and all five received aminoglycoside antibiotics for at least 2 weeks, with toxic drug levels in four. Three patients have subsequently required hearing aids. Significant ototoxicity is common in these patients. Ototoxicity related to consolidation therapy is likely due to the high dose of carboplatin used, prior cisplatin therapy, aminoglycosides, and, in one patient, cranial irradiation. Audiological assessment is essential in children treated with dose-intensive chemotherapy regimens containing cisplatin and carboplatin for identification and rehabilitation of ototoxicity.

Ototoxicity of aminoglycoside drugs in tuberculosis treatment

The possible ototoxic effect of kanamycin, streptomycin and a standard anti-TB drug combination, used in the treatment of 92 TB patients (7-71 years old), was examined by measuring the highest audible electric bone conduction frequency before and after treatment, using an Audimax 500 audiometer. At the so-called "safe" levels of drug administration it was found that kanamycin was markedly ototoxic, streptomycin very slightly ototoxic and the standard anti-TB drug combination had practically no ototoxic effect. Furthermore, it was found that none of these drugs were gender specific. Lastly, the possible effects of ageing on highest audible bone conduction frequency is discussed.

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.

Cisplatin in children: hearing loss correlates with iris and skin pigmentation

Pigmentation is reported to affect cisplatin-induced ototoxicity in adult humans. The hearing loss is worse in people with brown irises, than in those with blue irises. We assessed the hypothesis that cisplatin-treated children with dark irises suffer more deterioration in auditory thresholds than do those with less pigmentation. For the 19 children whose data met the requirements of this observational retrospective study, we found a weak correlation (Spearman's r = 0.50; p < 0.05) of high frequency hearing loss (at 4000 Hz) and pigmentation. Blue or hazel-eyed children averaged 2.9 dB worsening at 4000 Hz, in contrast to 14.2 dB worsening for brown or black-eyed children. Pigmentation may account for some of the individual susceptibility to cisplatin ototoxicity. We suggest that iris colour be included in future reports of cisplatin-related hearing loss.

Neomycin-induced perception deafness following bladder irrigation in patients with end-stage renal disease

OBJECTIVE

To report a serious side-effect of intravesical instillations of neomycin in patients with end-stage renal disease.

PATIENTS AND METHODS

Three patients (two men and a woman, aged 51.71 and 54 respectively) with end-stage renal disease who had undergone bladder irrigation with neomycin sulphate solution suffered complete irreversible deafness, which was assessed by audiogram.

RESULTS

All three patients developed complete perception deafness after 3, 4 and 10 months, with characteristic changes in the audiogram. The severe progressive hearing loss was maximal in the high-frequency range. A high-pitched tinnitus was the first sign of impending hearing difficulty and two patients developed a spontaneous nystagmus.

CONCLUSION

In view of the doubtful efficacy and, most importantly, the risk of severe disabling side-effects such as ototoxicity, we recommend the avoidance of intravesical instillation with neomycin whenever possible.

The ototoxicity of 3,3'-iminodipropionitrile: functional and morphological evidence of cochlear damage

Previous reports have suggested that IDPN may be ototoxic (Wolff et al., 1977; Crofton and Knight, 1991). The purpose of this research was to investigate the ototoxicity of IDPN using behavioral, physiological and morphological approaches. Three groups of adult rats were exposed to IDPN (0-400 mg/kg/day) for three consecutive days. In the first group, at 9-10 weeks post-exposure, thresholds for hearing of 5.3- and 38-kHz filtered clicks were measured electrophysiologically and brainstem auditory evoked responses (BAERs) were also recorded to a suprathreshold broadband click stimulus. A second set of animals was tested at 9 weeks for behavioral hearing thresholds (0.5- to 40-kHz tones) and at 11-12 weeks post-exposure for BAER thresholds (5- to 80-kHz filtered clicks). A third group of animals was exposed (as above), and killed at 12-14 weeks post-exposure for histological assessment. Kanamycin sulfate was used as a positive control for high-frequency selective hearing loss. Surface preparations of the organ of Corti were prepared in order to assess hair cells, and mid-modiolar sections of the cochlea were used to examine Rosenthal's canal and the stria vascularis. Functional data demonstrate a broad-spectrum hearing loss ranging from 0.5 kHz (30 dB deficit) to 80 kHz (40 dB deficit), as compared to a hearing deficit in kanamycin-exposed animals that was only apparent at frequencies greater than 5 kHz. Surface preparations revealed IDPN-induced hair cell loss in all turns of the organ of Corti, with a basal-to-apical gradient (more damage in the basal turns) at the lower dosages. At higher dosages there was complete destruction of the organ of Corti. There was also a dosage-related loss of spiral ganglion cells in all turns of the cochlea, again with a basal-to-apical gradient at the lower dosages. These data demonstrate that IDPN exposure in the rat results in extensive hearing loss and loss of neural structures in the cochlea.

Ototoxicity of carboplatin: comparing animal and clinical models at the Hospital for Sick Children

Carboplatin was introduced to the paediatric population as an alternative chemotherapeutic agent in the management of various malignant neoplasms, including sarcomas of the head and neck, in the hope that it would have fewer side effects than pre-existing agents. While many investigators have considered the ototoxicity of this drug only incidentally, others have presumed it to be of negligible importance. A recent animal model of its use has demonstrated damage to the inner hair cells of the cochlea, particularly at the basal turn, with a corresponding high incidence of hearing loss. Similarly, 11 of 22 patients who received this agent at the Hospital for Sick Children over the past 2 years demonstrated a sensorineural hearing loss in the 4 to 12 kHz range. This complication occurred as early as after the first dose and was generally progressively worse with subsequent doses. Consequently, we recommend careful audiologic monitoring of children receiving this agent.

High-frequency audiometric monitoring strategies for early detection of ototoxicity

Therapeutic drugs such as the aminoglycoside antibiotics (AMG) and the chemotherapy agent cisplatin (CDDP) are known to cause irreversible hearing loss, typically affecting highest frequency hearing first with progression of loss to the lower frequency regions. Conventional (0.25-8 kHz) and high-frequency (9-20 kHz) serial hearing threshold monitoring was done in 123 hospitalized patients (222 ears) administered AMG or CDDP. Of ears showing a decrease in sensitivity corresponding with treatment, 62.5% demonstrated initial hearing loss solely in the high-frequency range, 13.5% first showed loss only in the conventional-frequency range, and 24.0% showed loss in both frequency ranges concurrently. Thus, if only high frequencies had been monitored, early change in auditory sensitivity would have been detected in 86.5% of these patients. Further analysis revealed a range of five frequencies, specific to each individual's hearing threshold configuration, in which initial ototoxicity appeared most likely to be detected. Testing only these five frequencies would have identified 89.2% of ears that showed change. The results of this study confirm the need to serially monitor auditory thresholds, especially in the high-frequency range, of patients receiving ototoxic drugs. A shortened five-frequency monitoring protocol is presented and suggested for use with patients unable to tolerate lengthy audiometric testing procedures.

Mid-frequency hearing loss in rats following inhalation exposure to trichloroethylene: evidence from reflex modification audiometry

The present experiments were undertaken to characterize the hearing loss associated with 1,1,2-trichloroethylene (TCE) exposure. Adult male Long-Evans (LE) rats were exposed to TCE via inhalation (whole body) for 6 h/day for 5 days. The concentration-effect function (0-4000 ppm) was determined 3 weeks post-exposure. Animals were tested for auditory thresholds to 4, 8, 16, 24, 32, and 40-kHz tones using reflex modification audiometry. In a separate experiment, the time course of effects was determined by monitoring 16-kHz thresholds prior to, 1 h following each of the 5 exposure days, and 5 days, 1, 2, 4, 8, and 12 weeks post-exposure. At 14 weeks, these same animals were tested for thresholds to 0.5, 1, 2, 4, 8, 16, 24, 32, and 40-kHz tones. Results indicate elevated thresholds (hearing loss) for the 4000 ppm group at 8 and 16 kHz of approximately 18 and 30 dB, respectively. Time-course data demonstrated a rapid onset, a 20-dB loss at 16 kHz after the fifth exposure day, and a 40-dB loss by 2 weeks that persisted up to 14 weeks post-exposure. These data demonstrate an atypical and persistent, mid-frequency hearing loss in rats following inhalation exposure to TCE.

The sensitivity to 3,3'-iminodipropionitrile differs for high- and midfrequency hearing loss in the developing rat

3,3'-Iminodipropionitrile (IDPN) has been demonstrated to produce a loss of hearing following both neonatal and adult exposures. Adult exposure induces a full spectrum hearing loss, whereas early postnatal exposure produces a high-frequency loss only. The purpose of this work was to delineate the period of development during which the rat becomes sensitive to the full ototoxic effects of IDPN. Primiparous Long Evans rats or their offspring were exposed to either saline or 300 mg/kg IDPN for three consecutive days. Ages of exposure were as follows: gestational days 15-17 or postnatal days (PND) 1-3, 5-7, 15-17, 20-22, 25-27, 30-32, 40-42, or 70-72. All animals were tested as adults for auditory thresholds to 5- and 40-kHz tones using reflex modification audiometry. Results demonstrate that adult-like susceptibility to IDPN was not reached until approximately PND 30-32. Early exposures (PND 5-22) to IDPN will induce a highfrequency selective hearing loss, sparing the lower frequency. Prenatal or early neonatal (PND 1-3) IDPN exposure resulted in a high degree of mortality (> 70%). The long period of time between the susceptible period for the high frequency (PND 5-7) and the lower frequency (PND 30-32) does not correspond to the basal to apical ontogenic profile of any one physiological or anatomical process. These data suggest either a unique site of action for IDPN in the cochlea or the possibility of two different mechanisms, one operating at early postnatal ages and one at later ages.

Effects of occupational exposure to organic solvents and noise on hearing

This study explored the effects of occupational exposure to solvents and noise on hearing. Interviews and hearing tests were conducted for printing and paint manufacturing workers. The experimental groups included unexposed (N = 50) workers and workers exposed to noise (N = 50), noise and toluene (N = 51), or an organic solvent mixture (N = 39). The risk of hearing loss was greater for the exposed groups than for the unexposed group. The adjusted relative risk estimates were four times greater [95% confidence interval (95% CI) 1.4-12.2] for the noise group, 11 times greater (95% CI 4.1-28.9) for the noise and toluene group, and five times greater (95% CI 1.4-17.5) for the solvent-mixture group. The findings suggest that exposure to the studied solvents had a toxic effect on the auditory system and that an interaction between noise and toluene took place. The audiological results of the noise and toluene group suggest a central auditory pathway involvement in the hearing losses observed.

High-frequency monitoring for early detection of cisplatin ototoxicity

Cisplatin can cause irreversible hearing loss initially detectable as impairment of high-frequency hearing with progression to lower frequencies. Many patients receiving cisplatin are too ill to tolerate lengthy audiometric testing. Therefore, a rapid and sensitive high-frequency monitoring strategy to detect cisplatin-induced ototoxicity is needed. Serial conventional (0.25 to 8 kHz) and high-frequency (> or = 8 kHz) threshold monitoring was performed in patients receiving cisplatin, resulting in 84% of ears showing hearing loss, of which 71% were detected first in frequencies of 8 kHz or greater. By analysis according to an individualized, specific high-frequency range, early identification of hearing loss occurred in 94% of ears showing change. This five-frequency procedure is a sensitive detector of ototoxicity and is proposed as an alternative monitoring protocol for patients receiving cisplatin who cannot tolerate extended testing.

Aminoglycoside ototoxicity in pediatric patients receiving long-term peritoneal dialysis

We evaluated 14 children on long-term peritoneal dialysis for ototoxicity associated with aminoglycoside (AG) therapy. Baseline evaluation of all patients and 7 controls included pure-tone audiometry (PTA) and click-evoked auditory brain stem response (ABR). Nine patients had repeat PTA and ABR evaluations and vestibular testing 1 year after study entry. Five patients had an additional assessment following intraperitoneal AG therapy. The baseline auditory function of the patients was significantly poorer than controls at 6.0 and 8.0 kHz by PTA (P < 0.05), whereas the results of ABR testing were not different. Of the 14 patients, 4 (28%) had hearing loss, 3 of whom had a history of intravenous AG therapy. In contrast, none of the patients who received intraperitoneal AG therapy only, or without a history of AG therapy, had hearing loss (P < 0.005). There was no evidence of progressive loss of hearing acuity with time or associated with intraperitoneal AG therapy. One patient had findings of vestibular dysfunction. We conclude that children receiving peritoneal dialysis are at risk of AG ototoxicity. While intraperitoneal administration of AG may be associated with less ototoxicity than intravenous administration, further study is necessary to verify this finding and close monitoring of AG levels remains mandatory irrespective of the route of administration. PTA rather than click-evoked ABR appears to be the best indicator of abnormal hearing acuity in this population.

Erythromycin associated hearing loss in a patient with prior cis-platinum induced ototoxicity

A case is reported of reversible sensorineural hearing loss associated with intravenous erythromycin treatment. Cis-platinum induced high frequency hearing loss developed nine months previously during treatment for stage IV papillary cystadenocarcinoma. Renal and hepatic function were normal; however, serum erythromycin levels were elevated. Clinical recovery promptly followed discontinuation of erythromycin.

Aminosidine (paromomycin) in the treatment of leishmaniasis imported into the United Kingdom

We report 11 patients with leishmaniasis from different endemic areas, treated in the UK with intravenous aminosidine alone or in combination with other drugs. Clinical and parasitological cures were achieved in all 7 patients from the Mediterranean zone who had visceral disease, with one relapse. Two of 4 patients with cutaneous or mucosal disease were cured; the other 2, from Iraq and Iran, did not respond. Toxic effects were high-tone deafness in 2 patients, one of whom had pre-existing renal impairment, and transient, mild elevation of serum creatinine in 3. Aminosidine is an effective, tolerable and relatively non-toxic alternative to existing antileishmanial drugs for the treatment of visceral leishmaniasis. Further studies will be needed to assess its place in cutaneous and mucosal disease.

Exposure to methyl mercury from birth to adulthood impairs high-frequency hearing in monkeys

Hearing deficits are a frequent consequence of both developmental and adult methyl mercury exposure in humans. However, a detailed characterization of these deficits has not been performed in either humans or animals. Cynomolgus monkeys (Macaca fascicularis) were dosed from birth to 7 years of age with 50 micrograms/kg/day of mercury as methyl mercuric chloride. Steady-state blood mercury levels during dosing were 0.6-0.9 ppm. When monkeys were 14 years old, pure tone detection thresholds were determined by a psychophysical procedure. Control monkeys exhibited thresholds at frequencies between 125 and 31,500 Hz comparable to previously published values for macaques. One methyl mercury-treated monkey exhibited normal detection thresholds at all frequencies. Three treated monkeys were impaired at the second highest frequency tested (25,000 Hz) and therefore were not tested at 31,500 Hz. The fifth treated monkey displayed severely elevated thresholds at middle frequencies (10,000-12,500 Hz), precluding testing at higher frequencies. These results indicate a selective high-frequency deficit in monkeys exposed to methyl mercury from birth to adulthood and not exposed to methyl mercury in the 7 intervening years before auditory testing. These findings extend previous results in this group of monkeys in which deficits in spatial and temporal visual function were observed.