Chloroquine gestational use in systemic lupus erythematosus: assessing the risk of child ototoxicity by pure tone audiometry

The objective of this study was to assess child chloroquine ototoxicity after its use during the gestational period in systemic lupus erythematosus (SLE). Nineteen children over four years old were evaluated: nine were exposed to chloroquine diphosphate (CDP) during gestation and 10 were born from mothers that did not take this drug before conception or anytime during pregnancy (CONTROL). Pure tone audiometry was performed in all children and high and low frequency threshold means were compared to evaluate the hearing status. All nine mothers taking CDP were exposed to this drug at least during the first trimester of pregnancy (56% during the whole gestational period) and the mean time of CDP use was 6.1 + 2.9 months. No significant difference was found in children of CDP and CONTROL groups regarding age (7.6 + 4.4 versus 12.3 + 7.2 years; P 0.10, respectively) and gender (P 0.65). Pure tone high frequency thresholds, which are the first to be affected by ototoxic drugs, presented within normal limits in children exposed or not to CDP (8.5 + 5.0 versus 7.4 + 3.6 dBHL; P 0.55, respectively). Likewise, the mean hearing thresholds at low frequencies were also similar in both groups (11.4 + 4.5 versus 11.9 + 3.0 dBHL; P 0.66). In conclusion, child in utero exposure to chloroquine diphosphate does not seem to induce hearing impairment as measured by pure tone audiometry, reinforcing its safe use during pregnancy of lupus patients.

Intratympanic Steroids for Treatment of Sudden Hearing Loss after Failure of Intravenous Therapy

OBJECTIVE: We sought to describe our experience with intratympanic steroid treatment of sudden sensorineural hearing loss after failure of intravenous steroid treatment.

STUDY DESIGN AND SETTING: We conducted a nonrandomized prospective clinical trial. Fifty patients presenting with sudden onset idiopathic hearing loss were treated intravenously over five days. After this period, patients with treatment failure (18 cases) were offered intratympanic steroid treatment. Nine patients refused, whereas the other nine patients received three weekly injections of methylprednisolone. Recovery of hearing was reported as improvement of more than 15 dB in pure tone average.

RESULTS: Intratympanic steroid treatment improved hearing loss in five patients (55%). This is significant compared with those patients who refused intratympanic treatment, who showed no further improvement ( P < 0.05). No serious adverse effects were observed.

CONCLUSION: Intratympanic steroids significantly improve the recovery outcome of sudden hearing loss that had not recovered after intravenous steroid treatment.

SIGNIFICANCE: Intratympanic steroids are an effective and safe therapy in sudden sensorineural hearing loss cases that are refractory to standard treatment.

Intratympanic Steroid Perfusion for Refractory Sudden Sensorineural Hearing Loss

OBJECTIVE: Patients with sudden sensorineural hearing loss (SSHL) can benefit from systemic steroid therapy. Unfortunately, some patients are not candidates for steroid therapy due to concern over possible complications. Furthermore, not all patients will benefit from steroid administration. This study evaluates the potential benefits and safety of treating patients with SSHL refractory to oral steroids with intratympanic steroid therapy.

METHODS: A retrospective case review was performed on all patients who presented with sudden sensorineural hearing loss refractory to oral steroid therapy during the past year. Seventeen patients were identified. All patients underwent intratympanic steroid administration, via MicroWick placement and/or round window catheter placement.

RESULTS: Nine patients with sudden sensorineural hearing loss showed an improvement with intratympanic steroid therapy, consisting of MicroWick placement with dexamethasone drop (Decadron) administration for 1–2 weeks and/or round window catheter placement with steroid perfusion. Only one of the patients presenting with hearing loss present for greater than 8 weeks benefited from intratympanic therapy. Complications were few and included tympanic membrane perforation, chronic otitis media, dysequilibrium, and dysguesia.

CONCLUSIONS: Intratympanic steroid therapy can be beneficial in treating patients with sudden sensorineural hearing loss refractory to oral steroid use. EBM rating: C.

Auditory Tones and Foot-Shock Recapitulate Spontaneous Sub-Threshold Activity in Basolateral Amygdala Principal Neurons and Interneurons

In quiescent states such as anesthesia and slow wave sleep, cortical networks show slow rhythmic synchronized activity. In sensory cortices this rhythmic activity shows a stereotypical pattern that is recapitulated by stimulation of the appropriate sensory modality. The amygdala receives sensory input from a variety of sources, and in anesthetized animals, neurons in the basolateral amygdala (BLA) show slow rhythmic synchronized activity. Extracellular field potential recordings show that these oscillations are synchronized with sensory cortex and the thalamus, with both the thalamus and cortex leading the BLA. Using whole-cell recording in vivo we show that the membrane potential of principal neurons spontaneously oscillates between up- and down-states. Footshock and auditory stimulation delivered during down-states evokes an up-state that fully recapitulates those occurring spontaneously. These results suggest that neurons in the BLA receive convergent input from networks of cortical neurons with slow oscillatory activity and that somatosensory and auditory stimulation can trigger activity in these same networks.

Gentamicin-induced ototoxicity and nephrotoxicity vary with circadian time of treatment and entail separate mechanisms

The aminoglycoside antibiotic gentamicin can cause both ototoxicity and nephrotoxicity, the severity of which varies with circadian time of daily treatment. However, it is not yet resolved if such drug-induced adverse effects are independent or interdependent phenomena. Two groups of 9 female Sprague-Dawley rats (200-250 g), each housed separately and entrained to a 12 h light (06:00-18:00 h) - 12 h dark cycle, received a daily subcutaneous injection of 100 mg/kg gentamicin. One group was treated at the beginning of the activity span, 2 Hours After Lights On (HALO), and the other at the beginning of the rest span, 14 HALO. Global toxicity was gauged by both body weight loss relative to the pre-treatment baseline and number of deaths. Ototoxicity, i.e., hearing loss, was assessed by changes in auditory brainstem response (ABR) for pure tone stimuli of 8, 16, 24, and 32 kHz before and after 2 and 4 weeks of gentamicin treatment. Renal toxicity was evaluated by changes in urinary N-acetyl-β-glucosaminidase (NAG)/creatinine (CR) concentration ratio before and after each week of treatment. In a complementary substudy of separate but comparable 2 and 14 HALO groups of rats, blood samples were obtained before and 30, 60, 120, and 240 min post-subcutaneous injection of 100 mg/kg gentamicin. Number of animal deaths was greater in the 2 (4 deaths) than 14 HALO (1 death) group, mirroring more severe initial (first two weeks of treatment) body weight losses from baseline, being more than 2-fold greater in animals of the 2 than 14 HALO group. Ototoxicity progressively worsened during the treatment; although, the extent of hearing loss varied according to circadian time of treatment across all frequencies (p < 0.05), particularly the 24 and 32 kHz ones (both p < 0.005), both at the 2 and 4 week assessments. At 32 kHz after 4 weeks of gentamicin dosing, the 2 HALO group showed an average 42 dB hearing loss, while the 14 HALO group exhibited only an average 10 dB loss. ABR response latencies were longer for the 2 than 14 HALO rats. The time course of nephrotoxicity differed from that of ototoxicity. The mean urinary NAG/CR ratio peaked after the first week of treatment, averaging 13.64-fold greater than baseline for the 2 HALO-treated animals compared to 7.38-fold greater than baseline for the 14 HALO-treated ones. Ratio values declined thereafter; although, even after the second week of dosing, they remained greater in the 2 than 14 HALO group (averaging 8.15-fold greater and 2.23-fold greater than baseline, respectively). Pharmacokinetic analysis of the blood gentamicin values revealed slower clearance, on average by ∼25% (p < 0.001), in the rats of the 14 than 2 HALO group (x ± S.E.: 3.22 ± 0.49 and 4.53 ± 0.63 mL/min/kg, respectively). The study findings indicate robust difference of the time course in rats of both treatment groups of gentamicin-induced ototoxicity and nephrotoxicity, supporting the hypothesis these organ toxicities are independent of one another, and further suggest the observed treatment-time differences in gentamicin adverse effects may be more dependent on local cell, tissue, or organ circadian (chrono) pharmacodynamic than (chrono) pharmacokinetic mechanisms.

Role of p19ink4d in the pathogenesis of hearing loss

This study aimed to investigate the p19 expression in cisplatin-treated rats and the role of p19 in the degeneration of inner ear cells. It also searched for p19 gene alterations in patients with profound sensorineural deafness. P19ink4d is essential for the postmitotic maintenance of hair cells. It is presumed that a mutation in the functional homolog of p19 or a disturbance in its regulated expression can be the underlying cause of hearing loss. Experiments were conducted on male and female Sprague-Dawley rats (aged 6-7 weeks, 280-320 g) with thresholds of auditory brainstem responses <30 dB in the sound pressure level, and signs of middle ear infection were used for the experiment. For clinical evaluation, 400 children (age less than 13 years) from unrelated families with severe or profound sensorineural hearing loss (SNHL) were recruited at the second Xiangya Hospital of Central South University between 2005 and 2013, and genomic DNA for deafness gene analysis was obtained from peripheral blood samples of the patients and their lineal relatives. It was found that the p19 expression increased over time in the inner ear cells after cisplatin administration, but the p19 mRNA and protein levels significantly decreased in rats with manifested hearing loss induced by cisplatin. However, no mutation existed within the coding exons of p19 in the patients with profound sensorineural deafness. To conclude, the results support the concept that p19 may play an important role in the ototoxic effects of cisplatin and is probably involved in the pathogenesis of hearing loss.

Atrial natriuretic peptide modulates auditory brainstem response of rat

CONCLUSION

These findings suggest that Atrial natriuretic peptide (ANP) exhibits an inhibitory effect on auditory brainstem response (ABR) and is involved in the neuromodulation of the auditory nervous system.

OBJECTIVES

ANP may alter electrophysiological properties of the cochlea and play a role in auditory action.

METHODS

This study was undertaken to examine and clarify the role of ANP in the rat auditory system using ABR audiometry. The mean ABR thresholds and the latencies for wave II at the ABR threshold altered at given frequencies throughout the study.

RESULTS

Intra-arterial infusion of ANP (0.1 mg/kg, 4 mg/kg, and 8 mg/kg; bolus injection) resulted in a significant increase in ABR thresholds. A significant shift in the ABR wave II latency was observed at lower frequency (1 kHz and 2 kHz). There was a little change in latency at 20 kHz. Increased amount of ANP significantly altered the ABR in rats.

Continuous topical drug delivery using osmotic pump in animal cochlear implant model: Continuous steroid delivery is effective for hearing preservation

CONCLUSIONS

Continuous topical drug delivery using an osmotic pump is an effective supplementary technique for hearing preservation after cochlear implantation, as demonstrated in a guinea pig model.

OBJECTIVE

To evaluate the effect of continuous topical steroid delivery via an osmotic pump in an animal cochlear implant model.

METHODS

Twenty-three guinea pigs were used for the study. The animals were divided into three groups: control group (n = 8), simple topical dexamethasone delivery group (sDEXA group, n = 7) and continuous topical dexamethasone delivery group (cDEXA, n = 8). The hearing thresholds of all animals were measured by pre-operative auditory brain stem responses (ABRs) at 2, 8, 16, 24, and 32 kHz. ABRs were re-evaluated after cochlear implantation, and the animals were sacrificed for hematoxylin and eosin staining.

RESULTS

The ABR threshold at 1 week post-operatively was significantly lower in the cDEXA group than in the control and sDEXA groups at most frequencies. Threshold shifts from baseline were statistically smaller in the cDEXA group than in the control and sDEXA groups at all frequencies. Histological analysis revealed decreased numbers of multi-nucleated giant cells and thinner histiocyte layers.

Hearing preservation using topical dexamethasone alone and associated with hyaluronic acid in cochlear implantation

CONCLUSION

Topical dexamethasone associated with hyaluronic acid in cochlear implant surgery demonstrated a statistically significant difference in the preservation of low-frequency thresholds when compared with topical dexamethasone alone and a control group. Topical dexamethasone alone was not superior in hearing preservation when compared to the control group.

OBJECTIVE

To compare the effects of topical dexamethasone alone and associated with hyaluronic acid intraoperatively in hearing preservation in cochlear implantation.

METHODS

Eighteen severely to profoundly hearing-impaired adult patients with measurable hearing were divided into three groups preoperatively: cochlear implantation as a control group (group 1), cochlear implantation using topical dexamethasone intraoperatively (group 2), and cochlear implantation using topical dexamethasone associated with hyaluronic acid intraoperatively (group 3). Preimplant and postimplant low-frequency pure-tone averages (PTAs) were calculated from unaided audiograms at 125, 250, and 500 Hz.

RESULTS

The mean changes in the low-frequency PTA comparing postoperative against preoperative thresholds were 28.03 ± 6.77 dB in group 1, 30 ± 14.53 dB in group 2, and 7.23 ± 6.12 dB in group 3. There was statistical difference when comparing group 3 with groups 1 and 2 using one-way ANOVA (p = 0.002) followed by Scheffé post hoc test.

Disparities in auditory physiology and pathology between C57BL/6J and C57BL/6N substrains

C57BL/6 inbred mice are frequently used as models in auditory research, mostly the C57BL/6J and C57BL/6N substrains. Genetic variation and phenotypic disparities between these two substrains have been extensively investigated, but conflicting information exists about differences in their auditory and vestibular phenotypes. Literature-based comparisons are rendered difficult or impossible because most auditory publications do not designate the substrain used. We therefore evaluated commercial C57BL/6N and C57BL/6J mice for their baseline auditory brainstem response (ABR) thresholds at 3 months of age as well as their susceptibility to noise exposure and aminoglycoside antibiotics. Both substrains have similar thresholds at 4 and 12 kHz, but C57BL/6N show significantly higher baseline thresholds at 24 and 32 kHz. Because of these elevated thresholds, the N substrain is unsuitable as a model for drug ototoxicity, which primarily affects high frequencies. Exposure to 2-20 kHz broadband noise for 2 h at 110 dB produced significantly higher threshold shifts in the J substrain. These results suggest caution in the selection of C57BL/6 substrains for auditory research and indicate the need to specify substrains, age and the breeding source in all publications.

Myosin VIIa and otoferlin in cochlear inner hair cells have distinct response to ototoxic exposure

CONCLUSION

Ototoxic gentamicin exposure does not disrupt the expression of myosin VIIa in the inner hair cells (IHCs) of mice, whereas gentamicin ototoxicity causes altered expression of otoferlin in IHCs, as well as parallel hearing threshold shifts.

OBJECTIVE

To explore whether myosin VIIa and otoferlin in IHCs have different responses to gentamicin ototoxicity.

METHODS

Lower dose treatment (100 mg/kg): adult C57 mice were continuously injected intraperitoneally with gentamicin once a day for 14 consecutive days. Dose-dependent gentamicin treatment: mice were injected intraperitoneally with differing doses (100, 200, and 300 mg/kg) once a day for 2 consecutive days. The hearing thresholds were detected by auditory brainstem response (ABR). Immunostaining and Western blotting were utilized to measure the manner of expression of myosin VIIa and otoferlin in IHCs.

RESULTS

Lower dose treatment: There were no significant differences among the control (day 0), and 4, 7, and 14 days after the ototoxicity exposure (p > 0.05). Dose-dependent gentamicin treatment: There were no significant differences among the control, 100, 200, and 300 mg/kg groups after the ototoxicity exposure (p > 0.05). In contrast, we found an altered expression of otoferlin in IHCs among the control (day 0), and 4, 7, and 14 days of exposure, when the mice were exposed to gentamicin ototoxicity (p > 0.05).

Exposure to low levels of jet-propulsion fuel impairs brainstem encoding of stimulus intensity

Jet propulsion fuel-8 (JP-8) is a kerosene-based fuel that is used in military jets. The U.S. Armed Services and North Atlantic Treaty Organization countries adopted JP-8 as a standard fuel source and the U.S. military alone consumes more than 2.5 billion gallons annually. Preliminary epidemiologic data suggested that JP-8 may interact with noise to induce hearing loss, and animal studies revealed damage to presynaptic sensory cells in the cochlea. In the current study, Long-Evans rats were divided into four experimental groups: control, noise only, JP-8 only, and JP-8 + noise. A subototoxic level of JP-8 was used alone or in combination with a nondamaging level of noise. Functional and structural assays of the presynaptic sensory cells combined with neurophysiologic studies of the cochlear nerve revealed that peripheral auditory function was not affected by individual exposures and there was no effect when the exposures were combined. However, the central auditory nervous system exhibited impaired brainstem encoding of stimulus intensity. These findings may represent important and major shifts in the theoretical framework that governs current understanding of jet fuel and/or jet fuel + noise-induced ototoxicity. From an epidemiologic perspective, results indicate that jet fuel exposure may exert consequences on auditory function that may be more widespread and insidious than what was previously shown. It is possible that a large population of military personnel who are suffering from the effects of jet fuel exposure may be misidentified because they would exhibit normal hearing thresholds but harbor a "hidden" brainstem dysfunction.

The effect of systemic administration of desmopressin on cochlear function in guinea pigs

CONCLUSIONS

Systemic desmopressin (dDAVP) administration in guinea pigs for up to 2 weeks induced only minor or no significant changes in cochlear sensitivity, suggesting that other factors may be required to induce the cochlear dysfunction that is usually associated with endolymphatic hydrops.

OBJECTIVES

To investigate the effects of chronic systemic administration of dDAVP, a synthetic analog of vasopressin, on cochlear sensitivity in guinea pigs.

METHODS

dDAVP was administered subcutaneously via a mini-osmotic pump, at a rate of 0.2 ng/kg/min (low-dose group) or 2.0 ng/kg/min (high-dose group) for up to 2 weeks. Cochlear responses (compound action potentials) and distortion product otoacoustic emissions (DPOAEs) were measured. Example specimens were scanned using X-ray micro-tomography (micro-CT).

RESULTS

Compared with the control group, the low-dose dDAVP group showed a significant threshold increase in response to a 2 kHz tone-burst after 2 weeks of treatment, and also a decrease in the amplitude of the DPOAE after 1 week of treatment. However, individual results were variable and the high-dose dDAVP group showed no significant change compared to the control group. In the micro-CT images, two of four ears in the low-dose group showed mild hydrops, but no hydrops was found in the three ears sampled from the high-dose group.

Irreversible damage to auditory system functions caused by perinatal hypothyroidism in rats

We examined the effect of perinatal hypothyroidism on auditory function in rats using a prepulse inhibition paradigm. Pregnant rats were treated with the antithyroid drug methimazole (1-methyl-2-mercaptoimidazole) from gestational day 15 to postnatal day 21 via drinking water at concentrations (w/v) of 0 (control), 0.002 (low dose), or 0.02% (high dose). Rats from methimazole-treated mothers were tested at ages 1, 6, and 12months using techniques to examine prepulse inhibition and startle response. The startle stimulus consisted of 40ms of white noise at 115dB, whereas the prepulse, which preceded the startle stimulus by 30ms, consisted of 20ms of white noise at 75, 85, or 95dB. When the prepulse intensity was 75 or 85dB, the high-dose group showed decreased prepulse inhibition percentages compared with the control and low-dose groups. The reduced percentages of prepulse inhibition did not return to control levels over the 12-month study period. In contrast, no differences in prepulse inhibition were observed among the three dose groups when prepulse intensity was 95dB. Moreover, the high-dose group displayed excessive reaction to auditory startle stimuli compared with the other groups. Reductions in plasma free thyroxine and body weight gain were observed in the high-dose group. We conclude that perinatal hypothyroidism results in irreversible damage to auditory function in rats.

Relationship between changes in the cochlear blood flow and disorder of hearing function induced by blast injury in guinea pigs

The auditory system is the most susceptible to damages from blast waves. Blast injuries always lead to varying degrees of hearing impairment. Although a disorder of the cochlear blood flow (CoBF) has been considered to be related to many pathological processes of the auditory system and to contribute to various types of hearing loss, changes in the CoBF induced by blast waves and the relationship between such changes and hearing impairment are undefined. To observe the changes in the cochlear microcirculation after exposure to an explosion blast, investigate the relationship between changes in the CoBF and hearing impairment and subsequently explore the mechanism responsible for the changes in the CoBF, we detected the perfusion of the cochlear microcirculation and hearing threshold shift after exposure to an explosion blast. Then, an N-nitro-L-arginine-methyl ester (L-NAME, NO synthase inhibitor) solution and artificial perilymph were applied to the round window (RW) of the cochlea before the blast exposure, followed by an evaluation of the CoBF and hearing function. The results indicated that the changes in the CoBF were correlated to the strength of the blast wave. The cochlear blood flow significantly increased when the peak value of the blast overpressure was greater than approximately 45 kPa, and there was no significant change in the cochlear blood flow when the peak value of the blast overpressure was less than approximately 35 kPa. Following local administration of the NO synthase inhibitor L-NAME, the increase in the CoBF induced by the blast was inhibited, and this reduction was significantly associated with the hearing threshold.

Muckle-Wells syndrome: a treatable cause of congenital sensorineural hearing loss

Muckle-Wells syndrome (MWS) is a rare autosomal dominant condition with variable expression. It is a subset of auto-inflammatory diseases characterised by recurrent inflammatory crises and is associated with chronic recurrent urticaria, sensorineural deafness, periodic arthritis and secondary amyloidosis. The diagnosis of MWS is a clinical one with sufferers classically presenting in childhood with a moderate fever and non-pruiginous urticaria. We describe a case of a six-year-old girl who was successfully diagnosed and treated with Anakinra. Muckle and Wells originally described this syndrome in 1962; however, only recently was it discovered to be genetically linked to chromosome 1q44 and subsequently to missense mutations in the CIAS1/NALP3/PYPAF1 gene. Since then, treatment has evolved and it remains one of few treatable causes of congenital profound sensorineural hearing loss.

Effect of the ketamine/xylazine anesthetic on the auditory brainstem response of adult gerbils

The auditory brainstem response (ABR) is a test widely used to assess the integrity of the brain stem. Although it is considered to be an auditory-evoked potential that is influenced by the physical characteristics of the stimulus, such as rate, polarity and type of stimulus, it may also be influenced by the change in several parameters. The use of anesthetics may adversely influence the value of the ABR wave latency. One of the anesthetics used for e ABR assessment, especially in animal research, is the ketamine/xylazine combination. Our objective was to determine the influence of the ketamine/xylazine anesthetic on the ABR latency values in adult gerbils. The ABRs of 12 adult gerbils injected with the anesthetic were collected on three consecutive days, or a total of six collections, namely: pre-collection and A, B, C, D, and E collections. Before each collection the gerbil was injected with a dose of ketamine (100 mg/kg)/xylazine (4 mg/kg). For the capture of the ABR, 2000 click stimuli were used with rarefaction polarity and 13 stimuli per second, 80 dBnHL intensity and in-ear phones. A statistically significant difference was observed in the latency of the V wave in the ABR of gerbils in the C and D collections compared to the pre-, A and E collections, and no difference was observed between the pre-, A, B, and E collections. We conclude that the use of ketamine/xylazine increases the latency of the V wave of the ABR after several doses injected into adult gerbils; thus clinicians should consider the use of this substance in the assessment of ABR.

Time-frequency analysis of transient-evoked otoacoustic emissions in children exposed to carboplatin chemotherapy

The aims of this study were to characterize and quantify time-frequency changes in transient-evoked otoacoustic emissions (TEOAEs) recorded in children diagnosed with retinoblastoma who were receiving carboplatin chemotherapy. A signal processing technique, the wavelet transform (WT), was used to analyze TEOAE waveforms in narrow-band frequency components. Ten children (aged 3-72 months) diagnosed with unilateral or bilateral retinoblastoma were enrolled in the study. TEOAEs were acquired from the children with linear sequences of 70 dB peak equivalent SPL clicks. After WT analysis, TEOAE energy, latency and normalized energy in the narrow-band frequency components were compared before and during carboplatin chemotherapy treatment (average dose 1693 mg/m2). On a group basis, no significant differences (p>0.05) in the TEOAE energy, latency or normalized energy before and after carboplatin treatment were observed. There were decreases in normalized energy on an individual basis in 10 out of 18 ears in the sample. Exposure to carboplatin chemotherapy did not cause significant changes in TEOAE energy, latency and normalized energy during treatment. However, long-term monitoring of hearing with measurements of TEOAEs is warranted, given the risks of delayed hearing loss in some children receiving carboplatin chemotherapy.

Assessment of the ototoxicity of docusate sodium (colace) in a guinea pig animal model

OBJECTIVE

Docusate sodium (Colace) is an off-label ceruminolytic agent used to soften ear wax and relieve ear canal obstruction. At present, its effect on hearing in the presence of tympanic membrane (TM) perforation is not clear. The present study aimed to assess the safety of ototopic docusate sodium on hearing in the presence of TM perforation.

STUDY DESIGN

A prospective, randomized, controlled trial in a guinea pig animal model.

MATERIALS AND METHODS

Ten guinea pigs underwent bilateral myringotomy. In each animal, one ear received docusate sodium, serving as the experimental ear, and the other received normal saline as the control. Auditory brain response (ABR) was performed at baseline and then 1, 7, and 14 days following the application.

RESULTS

At day 14 following application, there was no significant change in ABR thresholds at 8, 12, 16, 20, or 25 kHz.

CONCLUSION

In guinea pigs with perforated TMs, docusate sodium does not seem to cause ototoxicity. Future clinical studies are required.

Development and validation of a cisplatin dose-ototoxicity model

BACKGROUND

Cisplatin is effective in the treatment of several cancers but is a known ototoxin resulting in shifts to hearing sensitivity in up to 50-60% of patients. Cisplatin-induced hearing shifts tend to occur first within an octave of a patient's high frequency hearing limit, termed the sensitive range for ototoxicity (SRO), and progress to lower frequencies. While it is currently not possible to know which patients will experience ototoxicity without testing their hearing directly, monitoring the SRO provides an early indication of damage. A tool to help forecast susceptibility to ototoxic-induced changes in the SRO in advance of each chemotherapy treatment visit may prove useful for ototoxicity monitoring efforts, patient counseling, and therapeutic planning.

PURPOSE

This project was designed to (1) establish pretreatment risk curves that quantify the probability that a new patient will suffer hearing loss within the SRO during treatment with cisplatin and (2) evaluate the accuracy of these predictions in an independent sample of Veterans receiving cisplatin for the treatment of cancer.

STUDY SAMPLE

Two study samples were used. The Developmental sample contained 23 subjects while the Validation sample consisted of 12 subjects.

DATA COLLECTION AND ANALYSIS

Risk curve predictions for SRO threshold shifts following cisplatin exposure were developed using a Developmental sample comprised of data from a total of 155 treatment visits obtained in 45 ears of 23 Veterans. Pure-tone thresholds were obtained within each subject's SRO at each treatment visit and compared with baseline measures. The risk of incurring an SRO shift was statistically modeled as a function of factors related to chemotherapy treatment (cisplatin dose, radiation treatment, doublet medication) and patient status (age, pre-exposure hearing, cancer location and stage). The model was reduced so that only statistically significant variables were included. Receiver-operating characteristic (ROC) curve analyses were then used to determine the accuracy of the risk curve predictions in an independent Validation sample of observations from over 62 treatment visits obtained in 24 ears of 12 Veterans.

RESULTS

Only cumulative cisplatin dose and pre-exposure hearing were found to be significantly related to the risk for hearing shift. The dose-ototoxicity risk curve predictions developed from the Developmental sample yielded area under the ROC curve accuracy estimates of 0.85 when applied to an independent Validation sample.

CONCLUSIONS

Cumulative cisplatin dose in combination with pre-exposure hearing provides an indication of whether hearing will shift in the SRO in advance of cisplatin administration. The validated dose-ototoxicity risk curves described herein can be used before and during treatment to anticipate hearing loss. While having such a tool would not replace serial hearing testing, it would be of great benefit to an ototoxicity monitoring program. It would promote relevant pretreatment counseling. Furthermore, for those found to be at risk of SRO shifts within the speech frequencies, the oncology treatment plan could incorporate anticipated dosing adjustments that could stave off the impact that ototoxicity might bring.

Distortion-product otoacoustic emissions: a useful test for monitoring ototoxicity induced by pegylated interferon and ribavirin treatment in patients with chronic hepatitis C

Pegylated-interferon (peg-IFN) and ribavirin combination therapy for the treatment of hepatitis C virus (HCV) infection is well known to be associated with significant adverse effects. Several studies have investigated a possible auditory pathway involvement during IFN therapy, but a method to monitor the potential auditory involvement during treatment has not yet been described. The aim of this study is to evaluate possible modifications of the outer hair cell (OHC) function in HCV patients receiving peg-IFN and ribavirin combination therapy. Thirteen adult HCV patients (8 F/5 M, mean age 52∓12 years) treated with peg-IFN and ribavirin combination therapy underwent Pure Tone Audiogram and Distortion Product Otoacoustic Emission (DPOAE) tests. We compared mean auditory thresholds (PTA) and mean DPOAE amplitude before, at month 3 during, and at the end of treatment (T0, T3, and Tend, respectively), and 3 months after treatment discontinuation (Tfu). No significant differences were found in hearing levels at the different time points analyzed. During treatment, three patients developed tinnitus, which in 2 cases resolved spontaneously after the end of therapy. Compared to T0 (19.5±0.83), a statistically significant DPOAE increase at T3 (30±1,26) and Tend (28.6±2.16) was found (p<0.05 at both time points), while DPOAEs returned to pre-treatment levels at Tfu (19.3±1.3). In our group, none of the patients reported a permanent auditory impairment, excluding one patient with persistent tinnitus. Peg-IFN could produce an increase of motility of the OHCs by means of intracellular pathways. DPOAE test could be considered a new method for monitoring ototoxicity induced by IFN. On the basis of recent literature and our audiological results, physicians should be aware of the possible ototoxic effects of peg-IFN, requiring appropriate surveillance, and the patient should be informed of the potential side effects of IFN therapy on the auditory pathway.

Systemic immunity influences hearing preservation in cochlear implantation

HYPOTHESIS

To determine whether a systemic immune response influences hearing thresholds and tissue response after cochlear implantation of hearing guinea pigs.

METHODS

Guinea pigs were inoculated with sterile antigen (Keyhole limpet hemocyanin) 3 weeks before cochlear implantation. Pure-tone auditory brainstem response thresholds were performed before implantation and 1 and 4 weeks later. Dexamethasone phosphate 20% was adsorbed onto a hyaluronic acid carboxymethylcellulose sponge and was applied to the round window for 30 minutes before electrode insertion. Normal saline was used for controls. Cochlear histology was performed at 4 weeks after implantation to assess the tissue response to implantation. To control for the effect of keyhole limpet hemocyanin priming, a group of unprimed animals underwent cochlear implantation with a saline-soaked pledget applied to the round window.

RESULTS

Keyhole limpet hemocyanin priming had no significant detrimental effect on thresholds without implantation. Thresholds were elevated after implantation across all frequencies tested (2-32 kHz) in primed animals but only at higher frequencies (4-32 kHz) in unprimed controls. In primed animals, dexamethasone treatment significantly reduced threshold shifts at 2 and 8 kHz. Keyhole limpet hemocyanin led to the more frequent observation of lymphocytes in the tissue response to the implant.

CONCLUSION

Systemic immune activation at the time of cochlear implantation broadened the range of frequencies experiencing elevated thresholds after implantation. Local dexamethasone provides partial protection against this hearing loss, but the degree and extent of protection are less compared to previous studies with unprimed animals.

Effect of low-level laser treatment on cochlea hair-cell recovery after acute acoustic trauma

We investigated the effect of low-level laser radiation on rescuing hair cells of the cochlea after acute acoustic trauma and hearing loss. Nine rats were exposed to noise. Starting the following day, the left ears (NL ears) of the rats were irradiated at an energy output of 100 to 165 mW/cm(2) for 60 min for 12 days in a row. The right ears (N ears) were considered as the control group. Frequency-specific hearing levels were measured before the noise exposure and also after the 1st, 3rd to 5th, 8th to 10th and 12th irradiations. After the 12th treatment, hair cells were observed using a scanning electron microscope. Compared to initial hearing levels at all frequencies, thresholds increased markedly after noise exposure. After the 12th irradiation, hearing threshold was significantly lower for the NL ears compared to the N ears. When observed using an electron microscope, the number of hair cells in the middle turn of the NL ears was significantly larger than that of the N ears. Our findings suggest that low-level laser irradiation promotes recovery of hearing thresholds after acute acoustic trauma.

A comparison of the effects of isoflurane and ketamine anesthesia on auditory brainstem response (ABR) thresholds in rats

The auditory brainstem response (ABR) is an acoustically evoked potential commonly used to determine hearing sensitivity in laboratory animals. Both isoflurane and ketamine/xylazine anesthesia are commonly used to immobilize animals during ABR procedures. Hearing threshold determination is often the primary interest. Although a number of studies have examined the effect of different anesthetics on evoked potential waveforms and growth functions, none have directly compared their effect on ABR hearing threshold estimates. The present study used a within-subject comparison and typical threshold criteria, to examine the effect of isoflurane and ketamine/xylazine on ABR thresholds for clicks and pure-tone stimuli extending from 8 to 32 kHz. At comparable physiological doses, hearing thresholds obtained with isoflurane (1.7% in O(2)) were on average elevated across a broad frequency range by greater than 27 dB compared to ketamine/xylazine (ketamine HCl, 50mg/kg; xylazine, 9 mg/kg). This highly significant threshold effect (F(1,6) = 158.3403, p = 3.51 × 10(-22)) demonstrates a substantial difference between general anesthetics on auditory brainstem sensitivity. Potential mechanisms and implications for ABR threshold determination under anesthesia are discussed.