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Changes in otoacoustic emissions and auditory brain stem response after cis-platinum exposure in gerbils
Changes in otoacoustic emissions and auditory brain stem response after cis-platinum exposure in gerbils KATHLEENC.Y. SIE, MD, and SUSANJ. NORTON,PhD,Seattle, Washington Ototoxicity associated with cis-platinum administration commonly presents as hearing loss and tinnitus. The hearing loss is usually an irreversible, high-frequency sensorineural loss. Histologic studies in humans and animals suggest that the outer hair cells (OHCs) are most susceptible to cis-platinum. Evoked otoacoustic emissions (EOAE), as a measure of outer hair cell function, are potentially useful in following ototoxic insults involving OHCs. Distortion-product otoacoustic emissions (DPOAE) test frequency-specific regions of the cochlea and therefore may be particularly well suited for monitoring ototoxic injuries. We measured distortion product otoacoustic emissions, at f2 = 2, 4, 6, 8, 10, and 12 kHz, in gerbils after a single large dose of cis-platinum. Animals treated with saline served as controls. The findings were compared to auditory brain stem evoked response (ABR) thresholds, using tone pips of the same frequencies. The DPOAE and ABR thresholds were measured before treatment and again 2, 5, and 14 days after drug administration. The changes in DPOAE were compared with the changes in ABR. No treatment effect was noted in the 2day group. Animals treated with cis-platinum demonstrated significant elevation of DPOAE and ABR thresholds compared with control animals at 5 and 14 days. There was no significant difference between the threshold changes in the 5-and 14-day groups. (Otolaryngol Head Neck Surg 1997; 116:585-92.)
C/s-platinum
is an antineoplastic agent with known ototoxic effects. 1-5 It is used in the treatment of testicular, ovarian, and head and neck squamous cell malignancies in adults. Children receive cis-plafinum for the treatment of central nervous system tumors, neuroblastoma, and osteosarcoma. It is usually administered in a single dose over several hours or in smaller doses over 2 to 5 days. The dose is generally repeated every 3 to 4 weeks. Although nephrotoxicity has been the main
From the Children's Hospital and Medical Center, Seattle, and the Department of Otolaryngology-Head and Neck Surgery, University of Washington (Drs. Sie and Norton). Support provided by NIDCD T32 DC 00018 and K08 DC00011(SJN), NIH. Presented at the Annual Meeting of the American Academy of Otolaryngology-Headand Neck Surgery, Kansas City, Mo., Sept. 22-26, 1991. Reprint requests: Kathleen C. Y. Sie, Division of OtolaryngologyHead and Neck Surgery CH-62, Children's Hospital and Medical Center, 4800 Sand Point Way NE, Seattle, WA 98105. Copyright © 1997 by the American Academy of OtolaryngologyHead and Neck Surgery Foundation, Inc. 0194-5998/97/$5.00 + 0 2311173191
dose-limiting side effect, that has been effectively managed with concomitant use of diuretics and intravenous hydration. Unfortunately, the regimen used to ameliorate nephrotoxicity has not changed the ototoxic effects of cis-platinum. 6 The reported incidence of hearing loss associated with cis-platinum administration in adults ranges from 4% to 50%. 2,7-11 However, if ultra-high frequency audiometry is used, the incidence of threshold changes may be as great as 100%. 12 The ototoxic effect in adults is characterized as an irreversible, progressive, bilateral high-frequency sensorineural hearing loss associated with tinnitus. 2,8,1],13 Transient changes in threshold and unilateral losses have also been described. 2,13 The degree of hearing loss seems to be associated With cumulative dose, method of administration, previous cranial radiation, and age of the patient, with younger and older patients more commonly affected. 3,4,8,1°,13,14 In adults, the hearing loss is usually moderate, with thresholds in the 15 to 40 dB HL range. 2 The symptoms and audiologic findings in patients with cis-platinum ototoxicity are most consistent with a cochlear process, which is more pronounced in the basal turn. Ultrastructural examination of human temporal bones has shown that the primary site of the cis-plat-
585
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inum ototoxicity is the outer hair cells (OHCs) of the basal and middle turns of the cochlea. The supporting cells and the stria vascularis are generally preserved. Changes in spiral ganglion cells have also been reported in the basal turn, where OHC damage is most extensive. 2 Wright and Schaefer 15 also examined temporal bones from patients treated with cis-platinum and found changes in the myelinated fibers of the basal turn. It is unclear whether these changes were acute ototoxic effects or degenerative changes because the temporal bones studied were from older patients. Distortion product otoacoustic emissions (DPOAEs) are cochlear responses to two simultaneous stimuli of a known frequency relationship. The stimuli are referred to as f! and f2; fl is lower than f2. There are many "distortion products" that occur at mathematically predictable frequencies due to the nonlinearities of the cochlea. The greatest response in humans and rodents is seen at 2fl-f2, the cubic distortion tone. Considerable data indicate that DPOAEs can provide information regarding the functional status of OHCs. 16,17 With evidence that cis-platinum preferentially affects OHC function, it is hypothesized that DPOAEs would change with cis-platinum treatment. If DPOAEs are affected by cis-platinum, they may be a useful clinical tool for monitoring cis-platinum ototoxicity. The main purpose of this experiment was to establish cis-platinum ototoxicity in gerbils, so that they can be used to study developmental differences in ototoxicity. Gerbils are common laboratory rodents that undergo postnatal auditory development. Most investigators have used guinea pigs (reviewed by Schweitzer18), whose auditory systems are mature at birth. In the present study, DPOAEs and auditory brain stem evoked response (ABR) thresholds were measured in adult gerbils before and after each received a single large dose of cis-platinum, and in age-matched controls before and after normal saline. DPOAEs and ABRs were measured 2, 5, and 14 days after drug administration. Changes in DPOAE thresholds were compared with changes in ABR thresholds in response to stimulus frequencies between 2 and 12 kHz. METHODS Animals
A breeding colony of Mongolian gerbils, Meriones unguiculates, was maintained in the University of Washington vivarium. The protocol for this study was approved by the Institutional Animal Care and Use Committee in compliance with the "Guide for the Care and Use of Laboratory Animals" (NIH publication 8023, revised 1978). All animals had free access to food and water. The cages were checked daily for new litters. The pups were
considered one day of age on the day they were first noted. Thirty-one animals, from 6 to 8 weeks of age, were included. At this age, gerbils are young adults and their auditory responses are mature. Treatment
Each animal received cis-platinum (10 mg&g subcutaneously) or an equivalent volume of normal saline subcutaneously. Cis-platinum (cis-dichlorodiammine platinum II) was dissolved in sterile water (1 mg/1 cc) within 15 minutes before injection. The animals were randomly divided into six groups, in which DPOAEs and ABRs were measured 2, 5, or 14 days after drug or saline administration. Animals were observed for gross signs of wasting; those that became cachetic were euthanized. Distortion product otoacoustic emissions and auditory brain stem responses (details provided below) were measured on anesthetized animals before and after drug administration. Removal of the pinna and lateral external auditory canal was necessary to allow adequate ear probe placement. Anesthesia
Animals were premedicated with atropine sulfate (about 400 mcg/kg intramuscularly). Anesthesia was induced with ketamine hydrochloride (75 mg&g) and xylazine (5 mg/kg) intramuscularly before surgical procedures and measurement of DPOAEs and ABRs. The animals were able to breathe spontaneously under this technique. The foot-withdrawal reflex of each was checked every 20 minutes to assess the level of anesthesia. Additional doses of ketamine and xylazine, in increments of one third the original dose, were given to suppress the foot-withdrawal reflex. Each animal's core body temperature was maintained at 37 ° to 38 ° C using a thermocoupled warming blanket and rectal probe. DPOAE
After each animal had been anesthetized and the outer ear removed, the tympanic membrane was examined with an operating microscope; none of the animals had evidence of middle ear disease at the time of testing. All testing performed in a double-walled soundproof booth. Each animal was placed on a custom platform equipped with a head holder to maintain a fixed head position. After the animal was positioned and its temperature equilibrated, an ear probe was positioned in the bony meatus. The ear probe consisted of an Etymotic Research 10B microphone and two sound delivery tubes connected to ER-2 earphones. The two stimuli were produced by different channels of a Hewlett-Packard 8904A Multifunction Synthesizer,
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with f2:fl = 1.3; L1 = L2; and f2 = 2, 4, 5, 8, 10, and 12 kHz. Before each measurement, both channels were calibrated from 0.5 to 20 kHz with the microphone probe. The microphone output was displayed on a HewlettPackard 3561A Dynamic Signal Analyzer (DSA), and the tracing was used to check both the seal of the ear probe and the output of the sound delivery tubes. After calibration, DPOAE input-output (I/O) functions were generated with stimuli from 10 to 80 dB sound pressure level (SPL) on 5 dB increments for each f2 frequency. The cubic distortion tone (2fl-f2) was measured by the HP 3561A DSA with a fast-Fourier transform using a frequency span of 400 Hz centered at the 2fl-f2 frequency with a resolution of 6 Hz. The 2flf2 frequency was monitored, and the threshold was determined by the stimulus level at which the 2fl-f2 level was above the noise floor by at least 2 dB. The noise floor was measured by determining the root mean square seven points above and seven points below the cubic distortion tone; the measurement was taken in volts and converted to decibels SPL.
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Histology
Scanning electron micrographs of the basilar membrane were examined qualitatively. Four cochleas from two animals injected with a single dose of cis-platinum were examined after 5 days. Two control animals were also studied.
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After the DPOAEs were measured, ABRs were obtained with subdermal Grass pin electrodes that were placed over each external auditory meatus, with the ground in the left leg. The stimuli were tone pips at 2, 4, 6, 8, 10, and 12 kHz presented at 22.2 per second. Each tone pip had a 2-msec duration with a 1-msec linear rise and fall time. The ABRs were measured by averaging differential response signals from the electrodes. The signals were led to a Grass P15 preamplifier (x100), band-pass filtered between 30 Hz and 3 kHz, viewed on an oscilloscope, and further amplified for input to a 12-bit A to D converter. The responses within the first 10 msec after the stimulus offset were averaged over 512 stimulus repetitions by a Macintosh computer. Responses to tone pips at 80 dB SPL were measured; then the stimulus intensity was decreased in 5 dB intervals until Wave V could no longer be visually identified. The level at which Wave V was first identifiable and replicable was defined as the ABR threshold. ABRs were measured 5 dB below, at, and 5 dB above threshold. All responses were repeated to demonstrate replicability.
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Fig. 1. The upper graph shows the mean c h a n g e in ABR threshold as a function of stimulus frequency measured 2 days (diamonds), 5 days (triangles), and 14 days (circles) after cis-platinum administration. The lower graph shows the corresponding changes in m e a n DPOAE thresholds as a function of f2 frequency. Error bars represent one standard error of the mean. The changes in DPOAE thresholds tend to be of greater magnitude than the changes in ABR thresholds, though this is not statistically significant.
After the appropriate treatment and time interval, each animal was deeply anesthetized with ketamine (100 mg/kg) and xylazine (6.25 mg/kg). The animal was decapitated and the cochlea was immediately isolated from the temporal bone. The cochlea was perfused with glutaraldehyde 3% and sucrose 3% in 0.1 mol/L phosphate buffer and immersed in the fresh fixative overnight. The following day, the specimen was osmicated and the bony capsule, stria vascularis, Reissner's, and tectorial membranes were removed, leaving the
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fable 1. Mean changes in the thresholds 5 days after DPOAE/ABR
DPOAE ABR
cis-platinum administration
2kHz
4 kHz
6 kHz
8 kHz
I0 kHz
12kHz
3.33 (3.3) 3.33 (1,7)
12.5 (3.1) 5.83 (3.0)
8.33 (4.0) 4.17 (3.5)
7.50 (4.4) 3.33 (1.7)
5.83 (6.8) 5.00 (3.4)
9.17 (5.1) 9.17 (4.4)
SEM shown in parentheses.
Table 2. Mean changes in the thresholds 14 days after DPOAE/ABR
DPOAE ABR
cis-platinum administration
2kHz
4 kHz
6 kHz
8 kHz
10 kHz
12kHz
15.00 (5.2) 5.71 (3.0)
16.43 (6,8) 5,71 (2.9)
7.14 (3.6) 5.71 (2.3)
9.29 (4.7) 5.00 (4.1)
12.86 (3.6) 8.57 (2.1)
10.00 (3.8) 5.00 (4.4)
SEM shown in parentheses.
basilar membrane. After critical point drying and sputter coating with gold palladium, the specimens were examined with a JEOL 840A scanning electron microscope.
DPOAE I/O functions was generated from the pretreatment I/O functions at each frequency. The mean I/O functions of treated animals were compared with the 95% confidence interval of normal DPOAE I/O functions.
Data analysis
In each animal, DPOAE thresholds, DPOAE I/O functions, and ABR thresholds were measured before and after treatment with cis-platinum or subcutaneous saline. The experimental animals were compared to their own pretreatment tests, and to the corresponding saline-treated control group. The changes in thresholds (i.e., thresholdpast - thresholdpr e) between the cis-platinure and saline-treated animals were compared using an analysis of variance (ANOVA) with a split plot-type design. Animals were randomly assigned to control and experimental groups; observations from them were considered independent. However, multiple observations (i.e., different frequencies) were assumed to be equally correlated within an animal. A four-factor ANOVA was performed to meet the main effects of condition (saline vs. cis-plafinum), survival (2, 5, or 14 days), measurement (DPOAE vs. ABR), and frequency (2, 4, 5, 8, 10, or 12 kHz) on change in threshold (i.e., thresholdpost - thresholdpre). SAS (SAS Institute, Cary, N.C.) was used to perform the analysis. By comparing the differences in auditory threshold within subjects, the threshold levels themselves, as measured by ABR and by DPOAE, were not important. The change in DPOAE threshold was plotted as a function of change in ABR threshold for each animal. The data were grouped across frequencies because there was no significant effect of frequency based on the initial analysis. The Pearson product-moment correlation coefficient was calculated to determine whether there was a significant correlation between the changes in DPOAE and ABR thresholds. The mean DPOAE I/O functions of the treated group were compared with those of the control group at each survival time. The 95% confidence interval of normal
RESULTS
Animals treated with cis-platinum had significantly higher DPOAE and ABR thresholds than animals treated with saline (p = 0.034, F = 5.04, df = 1). Changes in DPOAE and ABR thresholds 5 days after cis-platinum exposure are shown in Table 1, and changes 14 days after are shown in Table 2. There was no significant effect of frequency (p = 0.65, F --- 0.67, df = 5) on threshold change at any survival time. Both control and experimental animals had threshold elevations at the lowest frequencies measured, 2 and 4 kHz, and at the higher frequencies, 10 and 12 kHz. There was a trend for greater threshold change with increased survival time in the cis-platinum-treated group (Fig. 1). The changes in threshold tended to be greater 5 days after than they were 2 days after cis-platinum administration, although this trend was not statistically significant (p = 0.14, F = 2.13, df = 2). There did not seem to be any significant additional threshold shift by 14 days after exposure. In animals exposed to cis-platinum, changes in DPOAE threshold tended to be greater than changes in ABR threshold. This was nearly statistically significant (p = 0.051) as measured by the within-animal interaction of measurement and condition. Fig. 2 shows changes in DPOAE threshold as a function of change in ABR threshold for each animal. There was a significant correlation of changes in the DPOAE and ABR thresholds at 5 and 14 days (r = 0.55, df = 34, p < 0.05 and r = 0.48, df = 34, p < 0.05, respectively). At both 5 and 14 days the changes in DPOAE threshold were of greater magnitude.than the changes in ABR threshold. The DPOAE I/O functions were also evaluated before and after injection with saline or cis-platinum for
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Stimulus level (dB SPL) Fig. 3. Mean inout-output functions are plotted at 2, 5, and 14 days after treatment for two firequencies, f2 = 4 and 12 kHz. In each graph, the control group (triangles, saline-treated) is c o m p a r e d with the corresponding experimental group (diamonds, c/s-platinum treated). The area between the dashed lines represents the 95% confidence interval for normal I / 0 functions for e a c h frequency, calculated from baseline (pretreatment) measurements. The noise floor is also plofted. Error bars represent one standard error of the mean.
each frequency. There were no remarkable differences in the I/O functions of the control groups except in the low frequencies, 2 and 4 kHz, at both 5 and 14 days. At the higher frequencies, 10 and 12 kHz, there was no observable difference in t h e I/O functions of control animals but there was a shift in the I/O functions of the
animals, as seen in Fig. 3. There were no differences in the noise floors between groups. Qualitative changes of the basilar membrane were noted using scanned electron microscopy. Fig. 4 shows areas of OHC disorganization and loss in animals treated with c i s - p l a t i n u m compared with saline-treated anicis-platinum-treated
590 SIE and NORTON
Fig. 4. Scanning electron micrographs from the Organ of Corti of 6-week-old gerbils. Both photographs are taken from the midportion of the basal turn. The upper panel is from a saline-treated animal. The a p p e a r a n c e of both outer and inner hair cells is normal. The lower panel is from an animal sacrificed 5 days after c/s-platinum administration. The OHC a p p e a r disorganized with some evidence of OHC loss. The inner hair cells are unaffected. The scale bar in the lower panel represents 10 microns.
mals. These changes were most notable in the basal turn. No ultrastructural changes in the inner hair cells were seen. DISCUSSION
Clinical studies of cis-platinum ototoxicity are complicated by multiple factors including variations in dosing schedules, patient age, and past medical history (e.g., noise exposure, previous cranial irradiation). Animal studies have been undertaken to study the mechanism of ototoxicity and ultrastructural changes in the cochlea induced by cis-platinum exposure. ]9-25 Konishi et al. 2] administered cis-platinum in small daily doses to guinea pigs until the electrocochleograms showed suppression of the compound action potential at 73 dBSPL. The changes in electrocochleogram
OtolaryngologyHead and NeckSurgery June 1997
responses generally occur after prolonged treatment and are more pronounced in the basal turn. Changes in the cochlear microphonics are marked, whereas changes in the endocochlear potential are not as great. These findings are consistent with OHC involvement, though the underlying mechanism remains unclear. There is no significant difference between electrolyte compositions of endolymph and perilymph in experimental and saline-treated control animals. Ultrastructural examination of the Organ of Corti of these animals show loss of outer hair cells, mostly at the basal and middle turns, with sporadic loss of inner hair cells. Interestingly, there are minimal histologic changes in the kidneys of these same animals. 21 Laurell and Engstrom 26 also report that the endocochlear potential is not affected with small daily doses but it may be significantly reduced with large single doses of cis-platinum in guinea pigs. ABRs were also measured in this study and showed a high-frequency loss within 4 days of cis-platinum exposure. McAlpine and Johnstone 23 show changes in cochlear microphonics, distortion product emissions, neural sensitivity, and endocochlear potential after cisplatinum exposure. A single large dose of cis-platinum administered subcutaneously caused elevated N1 thresholds and depression of the DPOAE at 2fl-f2 1 to 3 days after injection. The degree of neural threshold change was highly correlated with the 2fl-f2 amplitude change up to 40 dB SPL. Interestingly, when cis-platinum is iontophoresed into low-frequency regions of scala media, the hearing loss progresses from low to high frequency, suggesting that the high-frequency hearing loss usually associated with cis-plafinum results from increased exposure of the basal end of the cochlea to the toxic agent. Their findings support the hypothesis that cis-platinum primarily affects the OHC, disrupting the mechanoelectrical transduction process. In the present study, a single large dose of cis-platinum reliably caused changes in DPOAE and ABR thresholds in adult gerbils. The effect seemed to be delayed with threshold shifts noted 5 days after administration of a single large dose of cis-platinum. Although this trend was not statistically significant, it is consistent with observations in patients who develop progressive sensorineural hearing loss within days of cis-platinum administration. The changes in DPOAE thresholds parallel the changes in ABR thresholds after cis-platinum administration. The magnitude of the changes in DPOAE thresholds were larger than the corresponding changes in ABR thresholds. This difference was also demonstrated in the scatter graphs, and may reflect the greater sensitivity of DPOAE to OHC function.
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The changes in I/O functions at 2 kHz and 4 kHz of the control animals at 5 and 14 days were unexpected. It is possible that the increased thresholds at low frequencies, seen in the control and experimental groups, were related to surgical removal of the pinna and cartilaginous canal necessary for placement of the ear probe. Because the detection of D P O A E relies on the mechanics of the entire system and the pinna is removed before baseline testing, edema of the canal may account for some of the low-frequency effects. It is also possible that eustachian tube dysfunction may contribute to these findings. The ears of all animals were examined with a binocular microscope before testing to rule out middle ear disease. The changes in the corresponding experimental groups tended to be larger than the changes in the control groups, though the differences were not statistically significant. It is also possible that this small low-frequency effect may represent the sporadic nature of OHC injury seen in the more apical regions of the cochlea noted in other studies of cisplatinum ototoxicity. 27 DPOAE amplitude decreased at all levels of stimulation in treated animals. This shift differs from the changes seen after aminoglyc0side administration. Brown, et al.28 have shown that aminoglycoside administration causes a shift in the threshold but no change in the responses at higher levels of stimulation, above 65 or 70 dBSPL. Several factors may account for these observed differences. The mechanism of cis-platinum ototoxicity may be different from the mechanism of aminoglycoside ototoxicity. 29,3° There is some evidence that single large doses of cis-platinum may cause significant changes in the endocochlear potential, as well as OHC damage in animals. 26 Although cis-platinum characteristically causes a high-frequency sensorineural loss, no significant frequency was observed. However, the highest frequencies used in this study, 10 and 12 kHz, do not stimulate the most basal aspect of the gerbil cochlea. 3~ The range of the stimulus frequencies used in this study was limited by the sensitivity of the sound transducers. Had we been able to reliably test responses to higher frequencies, we might have demonstrated a significant effect. Clinically, cis-platinum is usually given as a single dose every 3 to 4 weeks. In experimental studies of cisplatinum ototoxicity, animals are usually given daily doses over an extended period of time to elicit a profound sensorineural hearing loss. This experiment was designed to determine whether a single dose of cis-platinure would cause a detectable threshold shift. There was no mortality or significant morbidity associated with this dose of cis-platinum in gerbils. O f course, it is difficult to compare doses of cis-platinum in gerbils to
humans. However, this particular dosage was associated with minimal morbidity and caused changes in auditory function. Furthermore, the changes in DPOAE and A B R thresholds were "moderate," similar to the clinical situation. Therefore, this model may be useful in studying various aspects of cis-platinum ototoxicity. It is interesting to speculate on the mechanism of cis-platinum ototoxicity based On these findings. The large changes in DPOAE thresholds relative to changes in A B R thresholds in the same animals support findings by multiple investigators that one of the main sites of cis-platinum ototoxicity is the OHC. 22,23 It seems reasonable that DPOAE, or evoked otoacoustic emissions in general, may be a useful clinical tool for monitoring ototoxic effects of drugs that primarily affect OHC function. SUMMARY
Gerbils developed signs of ototoxicity after treatment with a single large dose of cis-platinum administered subcutaneously at 6 weeks of age. The changes were manifest as threshold shifts in both the DPOAE I/O functions and the ABR. The changes were most notable at the low (2 to 4 kHz) and the high (10 to 12 kHz) frequencies tested. This effect was not statistically significant. Also, these changes were first detected 5 days after cis-platinum was given. We gratefully acknowledge the technical assistance of Branson Warren, the editorial advice of Dr. Edwin W Rubel, and statistical consultation from. Dean Billheimer and Dr. Lynne Werner. REFERENCES 1. Piel IJ, Meyer D, Pertia CE WolfeVI. Effects of eis-diamminedichloroplatinurn (NSC-119875) on hearing function in man. Cancer Chemother Rep 1974;58:871-5. 2. Strauss M, TowfighiJ, Lord S, Lipton A, HarveyHA, Brown B. Cis-platinumototoxicity:clinical experience and temporal bone histopathology. Laryngoscope 1983;93:1554-9. 3. Pasic TR, Dobie RA. Cis-platinum ototoxicity in children. Laryngoscope 1991;101:985-91. 4. WeatherlyRA, Owens J2r, Catlin FI, MahoneyDH. Cis-platinum ototoxicity in children. Laryngoscope1991;101:917-24. 5. Blakley BW, Myers SE Patterns of hearing loss resulting from eis-platinum therapy. Otolaryngol Head Neck Surg 1993; 109:385-91. 6. Hayes DM, Cvitkovie E, Golbey RB. High dose cis-platinum diammine dichloride: amelioration of renal toxicity by mannitol diuresis. Cancer 1977;39:1372-81. 7. Fausti SA, Schechter MA, Rappaport BZ, Frey RH, Mass RE. Early detection of cisplatin ototoxicity. Cancer 1984;53:22431. 8. Laurell G, Borg E. Ototoxicity if cisplatin in gynaecological cancer patients. Scand Audiol 1988;17:241-7. 9. LaurelI G, Jungelius U. High-dose cisplatin treatment: hearing loss and plasma concentrations. Laryngoscope 1990;100: 724-34. 10. Reddell RR, Kefford RF, Grant JM, Coates AS, Fox RaM, Tattersall MHN. Ototoxicity in patients receiving cisplatin:
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11. 12.
13. 14. 15. 16. 17. 18. 19.
20.
importance of dose and method of drug administration. Cancer Treat Res 1982;66:19-23. Schaefer SD, Post JD, Close LG, Wright CG. Ototoxicity of low- and moderate-dose cisplatin. Cancer 1985;56:1934-9. Kopelman J, Budnick AS, Kramer MB, Sessions liB, Wong GY. Ototoxicity of high-dose cisplafin by bohis administration in patients with advanced cancers and normal hearing. Laryngoscope 1988;98:858-64. Melarned LB, Selim MA, Schuchman D. Cisplatin ototoxicity in gynecologic cancer patients. Cancer 1985;55:41-3. Schell MJ, McHaney VA, Green AA, et al. Hearing loss in children and young adults receiving cisplatin with or without prior cranial radiation. J Clin Oncol 1989;7:754-60. Wright CG, Schaefer SD. Inner ear histopathology in patients treated with cis-platinum. Laryngoscope 1982;92:1408-13. Gaskill SA, Brown AM. The behavior of the acoustic distortion product, 2fl-f2, from the human ear and its relation to auditory sensitivity. J Acoust Soc Am 1990;88:821-39. Lonsbury-Marfin BL, Martin GK. The clinical utility of distortion-product otoacoustic emissions. Ear Hear 1990;11:144-54. Schweitzer VG. Ototoxicity of chemotherapeutic agents. Otolaryngol Clin North Am 1993;26:759-89. Stadnicki SW, Heischman RW, Schaeppi U, Meriam R Cisdichlorodiammineplatinum (II) (NSC-119875): Hearing loss and other toxic effects in Rhesus monkeys. Cancer Chemother Rep 1975;59:467-80. Estrem SA, Babin RW, Ryn JH, Moore KC. Cisdiamminedichloroplatinum(II) ototoxicity in the guinea pig. Otolaryngol Head Neck Surg 1981;89:638-45.
OtolaryngologyHead and Neck Surgery June 1997
21. Konishi T, Gupta B, Prazma J. Ototoxicity of c/s-diammine platinum (II) in guinea pigs. Am J Otolaryngol 1983;4:18-26. 22. Marco-Algarra J, Basterra J, Marco J. Cis-diaminedichloro platinum ototoxicity: an experimental study. Acta Otolaryngol (Stockh) 1985;99:343-7. 23. McAlpine D, Johnstone BM. The ototoxic mechanism of cisplatin. Hear Res 1990;47:191-204. 24. Schweitzer VG, Rarey KE, Dolan DE Abrams G, Litterst CJ, Sheridan C. Ototoxicity of cisplatin vs. platinum analogs CBDCA (JM-8) and CHIP (JM-9). Otolaryngol Head Neck Surg 1986;94:458-70. 25. Schweitzer VG. Cisplatin-induced ototoxicity: effect of pigmentation and inhibitory agents. Laryngoscope 1993; 103:1-52. 26. Laurell G, Engstrom B. The ototoxic effect of cisplatin on guinea pigs in relation to dosage. Hear Res 1989;38:27-34. 27. Barton SE, Daigneault EA. Effect of cisplatin on hair cell morphology and lateral wall Na, K-ATPase activity. Hear Res 1987;26:131-7. 28. Brown AM, McDowell B, Forge A. Acoustic distortion products can be used to monitor the effects of chronic gentamicin treatment. Hear Res 1989;42:143-56. 29. Yung MW, Dorman EB. Electrocochleography during intravenous infusion of cisplatin. Arch Otolaryngol Head Neck Surg 1986; 112:823-6. 30. Anniko M, Sobin A. Cisplatin: evaluation of its ototoxic potential. Am J Otolaryngol 1986;7:276-93. 31. Woolf NK, Ryan AE The development of auditory function in the cochlea of the mongolian gerbil. Hear Res 1984;13:277-83.
Temporal Bone Histopathology This 1-day workshop, presented and sponsored by the Department of Otolaryngology, University of Minnesota, and the N1DCD National Temporal Bone, Hearing and Balance Pathology Resource Registry, will be held Sept. 26, 1997, at the University of Minnesota, Minneapolis, Minn. It will provide hands-on instruction in the techniques of study of the human temporal bone and associated brain tissue. For further information, contact Patricia Schachern, Lions Research Building, Room 226, 2001 Sixth St., SE, Minneapolis, MN 55455; phone, (612)626-9876; fax, (612)626-9871; e-mail, [email protected].
C/s-platinum
is an antineoplastic agent with known ototoxic effects. 1-5 It is used in the treatment of testicular, ovarian, and head and neck squamous cell malignancies in adults. Children receive cis-plafinum for the treatment of central nervous system tumors, neuroblastoma, and osteosarcoma. It is usually administered in a single dose over several hours or in smaller doses over 2 to 5 days. The dose is generally repeated every 3 to 4 weeks. Although nephrotoxicity has been the main
From the Children's Hospital and Medical Center, Seattle, and the Department of Otolaryngology-Head and Neck Surgery, University of Washington (Drs. Sie and Norton). Support provided by NIDCD T32 DC 00018 and K08 DC00011(SJN), NIH. Presented at the Annual Meeting of the American Academy of Otolaryngology-Headand Neck Surgery, Kansas City, Mo., Sept. 22-26, 1991. Reprint requests: Kathleen C. Y. Sie, Division of OtolaryngologyHead and Neck Surgery CH-62, Children's Hospital and Medical Center, 4800 Sand Point Way NE, Seattle, WA 98105. Copyright © 1997 by the American Academy of OtolaryngologyHead and Neck Surgery Foundation, Inc. 0194-5998/97/$5.00 + 0 2311173191
dose-limiting side effect, that has been effectively managed with concomitant use of diuretics and intravenous hydration. Unfortunately, the regimen used to ameliorate nephrotoxicity has not changed the ototoxic effects of cis-platinum. 6 The reported incidence of hearing loss associated with cis-platinum administration in adults ranges from 4% to 50%. 2,7-11 However, if ultra-high frequency audiometry is used, the incidence of threshold changes may be as great as 100%. 12 The ototoxic effect in adults is characterized as an irreversible, progressive, bilateral high-frequency sensorineural hearing loss associated with tinnitus. 2,8,1],13 Transient changes in threshold and unilateral losses have also been described. 2,13 The degree of hearing loss seems to be associated With cumulative dose, method of administration, previous cranial radiation, and age of the patient, with younger and older patients more commonly affected. 3,4,8,1°,13,14 In adults, the hearing loss is usually moderate, with thresholds in the 15 to 40 dB HL range. 2 The symptoms and audiologic findings in patients with cis-platinum ototoxicity are most consistent with a cochlear process, which is more pronounced in the basal turn. Ultrastructural examination of human temporal bones has shown that the primary site of the cis-plat-
585
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586 SIE and NORTON
inum ototoxicity is the outer hair cells (OHCs) of the basal and middle turns of the cochlea. The supporting cells and the stria vascularis are generally preserved. Changes in spiral ganglion cells have also been reported in the basal turn, where OHC damage is most extensive. 2 Wright and Schaefer 15 also examined temporal bones from patients treated with cis-platinum and found changes in the myelinated fibers of the basal turn. It is unclear whether these changes were acute ototoxic effects or degenerative changes because the temporal bones studied were from older patients. Distortion product otoacoustic emissions (DPOAEs) are cochlear responses to two simultaneous stimuli of a known frequency relationship. The stimuli are referred to as f! and f2; fl is lower than f2. There are many "distortion products" that occur at mathematically predictable frequencies due to the nonlinearities of the cochlea. The greatest response in humans and rodents is seen at 2fl-f2, the cubic distortion tone. Considerable data indicate that DPOAEs can provide information regarding the functional status of OHCs. 16,17 With evidence that cis-platinum preferentially affects OHC function, it is hypothesized that DPOAEs would change with cis-platinum treatment. If DPOAEs are affected by cis-platinum, they may be a useful clinical tool for monitoring cis-platinum ototoxicity. The main purpose of this experiment was to establish cis-platinum ototoxicity in gerbils, so that they can be used to study developmental differences in ototoxicity. Gerbils are common laboratory rodents that undergo postnatal auditory development. Most investigators have used guinea pigs (reviewed by Schweitzer18), whose auditory systems are mature at birth. In the present study, DPOAEs and auditory brain stem evoked response (ABR) thresholds were measured in adult gerbils before and after each received a single large dose of cis-platinum, and in age-matched controls before and after normal saline. DPOAEs and ABRs were measured 2, 5, and 14 days after drug administration. Changes in DPOAE thresholds were compared with changes in ABR thresholds in response to stimulus frequencies between 2 and 12 kHz. METHODS Animals
A breeding colony of Mongolian gerbils, Meriones unguiculates, was maintained in the University of Washington vivarium. The protocol for this study was approved by the Institutional Animal Care and Use Committee in compliance with the "Guide for the Care and Use of Laboratory Animals" (NIH publication 8023, revised 1978). All animals had free access to food and water. The cages were checked daily for new litters. The pups were
considered one day of age on the day they were first noted. Thirty-one animals, from 6 to 8 weeks of age, were included. At this age, gerbils are young adults and their auditory responses are mature. Treatment
Each animal received cis-platinum (10 mg&g subcutaneously) or an equivalent volume of normal saline subcutaneously. Cis-platinum (cis-dichlorodiammine platinum II) was dissolved in sterile water (1 mg/1 cc) within 15 minutes before injection. The animals were randomly divided into six groups, in which DPOAEs and ABRs were measured 2, 5, or 14 days after drug or saline administration. Animals were observed for gross signs of wasting; those that became cachetic were euthanized. Distortion product otoacoustic emissions and auditory brain stem responses (details provided below) were measured on anesthetized animals before and after drug administration. Removal of the pinna and lateral external auditory canal was necessary to allow adequate ear probe placement. Anesthesia
Animals were premedicated with atropine sulfate (about 400 mcg/kg intramuscularly). Anesthesia was induced with ketamine hydrochloride (75 mg&g) and xylazine (5 mg/kg) intramuscularly before surgical procedures and measurement of DPOAEs and ABRs. The animals were able to breathe spontaneously under this technique. The foot-withdrawal reflex of each was checked every 20 minutes to assess the level of anesthesia. Additional doses of ketamine and xylazine, in increments of one third the original dose, were given to suppress the foot-withdrawal reflex. Each animal's core body temperature was maintained at 37 ° to 38 ° C using a thermocoupled warming blanket and rectal probe. DPOAE
After each animal had been anesthetized and the outer ear removed, the tympanic membrane was examined with an operating microscope; none of the animals had evidence of middle ear disease at the time of testing. All testing performed in a double-walled soundproof booth. Each animal was placed on a custom platform equipped with a head holder to maintain a fixed head position. After the animal was positioned and its temperature equilibrated, an ear probe was positioned in the bony meatus. The ear probe consisted of an Etymotic Research 10B microphone and two sound delivery tubes connected to ER-2 earphones. The two stimuli were produced by different channels of a Hewlett-Packard 8904A Multifunction Synthesizer,
OtolaryngologyHead and Neck Surgery Volume 116 Number 6 Part 1
with f2:fl = 1.3; L1 = L2; and f2 = 2, 4, 5, 8, 10, and 12 kHz. Before each measurement, both channels were calibrated from 0.5 to 20 kHz with the microphone probe. The microphone output was displayed on a HewlettPackard 3561A Dynamic Signal Analyzer (DSA), and the tracing was used to check both the seal of the ear probe and the output of the sound delivery tubes. After calibration, DPOAE input-output (I/O) functions were generated with stimuli from 10 to 80 dB sound pressure level (SPL) on 5 dB increments for each f2 frequency. The cubic distortion tone (2fl-f2) was measured by the HP 3561A DSA with a fast-Fourier transform using a frequency span of 400 Hz centered at the 2fl-f2 frequency with a resolution of 6 Hz. The 2flf2 frequency was monitored, and the threshold was determined by the stimulus level at which the 2fl-f2 level was above the noise floor by at least 2 dB. The noise floor was measured by determining the root mean square seven points above and seven points below the cubic distortion tone; the measurement was taken in volts and converted to decibels SPL.
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Histology
Scanning electron micrographs of the basilar membrane were examined qualitatively. Four cochleas from two animals injected with a single dose of cis-platinum were examined after 5 days. Two control animals were also studied.
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After the DPOAEs were measured, ABRs were obtained with subdermal Grass pin electrodes that were placed over each external auditory meatus, with the ground in the left leg. The stimuli were tone pips at 2, 4, 6, 8, 10, and 12 kHz presented at 22.2 per second. Each tone pip had a 2-msec duration with a 1-msec linear rise and fall time. The ABRs were measured by averaging differential response signals from the electrodes. The signals were led to a Grass P15 preamplifier (x100), band-pass filtered between 30 Hz and 3 kHz, viewed on an oscilloscope, and further amplified for input to a 12-bit A to D converter. The responses within the first 10 msec after the stimulus offset were averaged over 512 stimulus repetitions by a Macintosh computer. Responses to tone pips at 80 dB SPL were measured; then the stimulus intensity was decreased in 5 dB intervals until Wave V could no longer be visually identified. The level at which Wave V was first identifiable and replicable was defined as the ABR threshold. ABRs were measured 5 dB below, at, and 5 dB above threshold. All responses were repeated to demonstrate replicability.
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After the appropriate treatment and time interval, each animal was deeply anesthetized with ketamine (100 mg/kg) and xylazine (6.25 mg/kg). The animal was decapitated and the cochlea was immediately isolated from the temporal bone. The cochlea was perfused with glutaraldehyde 3% and sucrose 3% in 0.1 mol/L phosphate buffer and immersed in the fresh fixative overnight. The following day, the specimen was osmicated and the bony capsule, stria vascularis, Reissner's, and tectorial membranes were removed, leaving the
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588 SIE and NORTON
fable 1. Mean changes in the thresholds 5 days after DPOAE/ABR
DPOAE ABR
cis-platinum administration
2kHz
4 kHz
6 kHz
8 kHz
I0 kHz
12kHz
3.33 (3.3) 3.33 (1,7)
12.5 (3.1) 5.83 (3.0)
8.33 (4.0) 4.17 (3.5)
7.50 (4.4) 3.33 (1.7)
5.83 (6.8) 5.00 (3.4)
9.17 (5.1) 9.17 (4.4)
SEM shown in parentheses.
Table 2. Mean changes in the thresholds 14 days after DPOAE/ABR
DPOAE ABR
cis-platinum administration
2kHz
4 kHz
6 kHz
8 kHz
10 kHz
12kHz
15.00 (5.2) 5.71 (3.0)
16.43 (6,8) 5,71 (2.9)
7.14 (3.6) 5.71 (2.3)
9.29 (4.7) 5.00 (4.1)
12.86 (3.6) 8.57 (2.1)
10.00 (3.8) 5.00 (4.4)
SEM shown in parentheses.
basilar membrane. After critical point drying and sputter coating with gold palladium, the specimens were examined with a JEOL 840A scanning electron microscope.
DPOAE I/O functions was generated from the pretreatment I/O functions at each frequency. The mean I/O functions of treated animals were compared with the 95% confidence interval of normal DPOAE I/O functions.
Data analysis
In each animal, DPOAE thresholds, DPOAE I/O functions, and ABR thresholds were measured before and after treatment with cis-platinum or subcutaneous saline. The experimental animals were compared to their own pretreatment tests, and to the corresponding saline-treated control group. The changes in thresholds (i.e., thresholdpast - thresholdpr e) between the cis-platinure and saline-treated animals were compared using an analysis of variance (ANOVA) with a split plot-type design. Animals were randomly assigned to control and experimental groups; observations from them were considered independent. However, multiple observations (i.e., different frequencies) were assumed to be equally correlated within an animal. A four-factor ANOVA was performed to meet the main effects of condition (saline vs. cis-plafinum), survival (2, 5, or 14 days), measurement (DPOAE vs. ABR), and frequency (2, 4, 5, 8, 10, or 12 kHz) on change in threshold (i.e., thresholdpost - thresholdpre). SAS (SAS Institute, Cary, N.C.) was used to perform the analysis. By comparing the differences in auditory threshold within subjects, the threshold levels themselves, as measured by ABR and by DPOAE, were not important. The change in DPOAE threshold was plotted as a function of change in ABR threshold for each animal. The data were grouped across frequencies because there was no significant effect of frequency based on the initial analysis. The Pearson product-moment correlation coefficient was calculated to determine whether there was a significant correlation between the changes in DPOAE and ABR thresholds. The mean DPOAE I/O functions of the treated group were compared with those of the control group at each survival time. The 95% confidence interval of normal
RESULTS
Animals treated with cis-platinum had significantly higher DPOAE and ABR thresholds than animals treated with saline (p = 0.034, F = 5.04, df = 1). Changes in DPOAE and ABR thresholds 5 days after cis-platinum exposure are shown in Table 1, and changes 14 days after are shown in Table 2. There was no significant effect of frequency (p = 0.65, F --- 0.67, df = 5) on threshold change at any survival time. Both control and experimental animals had threshold elevations at the lowest frequencies measured, 2 and 4 kHz, and at the higher frequencies, 10 and 12 kHz. There was a trend for greater threshold change with increased survival time in the cis-platinum-treated group (Fig. 1). The changes in threshold tended to be greater 5 days after than they were 2 days after cis-platinum administration, although this trend was not statistically significant (p = 0.14, F = 2.13, df = 2). There did not seem to be any significant additional threshold shift by 14 days after exposure. In animals exposed to cis-platinum, changes in DPOAE threshold tended to be greater than changes in ABR threshold. This was nearly statistically significant (p = 0.051) as measured by the within-animal interaction of measurement and condition. Fig. 2 shows changes in DPOAE threshold as a function of change in ABR threshold for each animal. There was a significant correlation of changes in the DPOAE and ABR thresholds at 5 and 14 days (r = 0.55, df = 34, p < 0.05 and r = 0.48, df = 34, p < 0.05, respectively). At both 5 and 14 days the changes in DPOAE threshold were of greater magnitude.than the changes in ABR threshold. The DPOAE I/O functions were also evaluated before and after injection with saline or cis-platinum for
OtolaryngologyHead and Neck Surgery
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Volume 116 N u m b e r 6 Part I
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each frequency. There were no remarkable differences in the I/O functions of the control groups except in the low frequencies, 2 and 4 kHz, at both 5 and 14 days. At the higher frequencies, 10 and 12 kHz, there was no observable difference in t h e I/O functions of control animals but there was a shift in the I/O functions of the
animals, as seen in Fig. 3. There were no differences in the noise floors between groups. Qualitative changes of the basilar membrane were noted using scanned electron microscopy. Fig. 4 shows areas of OHC disorganization and loss in animals treated with c i s - p l a t i n u m compared with saline-treated anicis-platinum-treated
590 SIE and NORTON
Fig. 4. Scanning electron micrographs from the Organ of Corti of 6-week-old gerbils. Both photographs are taken from the midportion of the basal turn. The upper panel is from a saline-treated animal. The a p p e a r a n c e of both outer and inner hair cells is normal. The lower panel is from an animal sacrificed 5 days after c/s-platinum administration. The OHC a p p e a r disorganized with some evidence of OHC loss. The inner hair cells are unaffected. The scale bar in the lower panel represents 10 microns.
mals. These changes were most notable in the basal turn. No ultrastructural changes in the inner hair cells were seen. DISCUSSION
Clinical studies of cis-platinum ototoxicity are complicated by multiple factors including variations in dosing schedules, patient age, and past medical history (e.g., noise exposure, previous cranial irradiation). Animal studies have been undertaken to study the mechanism of ototoxicity and ultrastructural changes in the cochlea induced by cis-platinum exposure. ]9-25 Konishi et al. 2] administered cis-platinum in small daily doses to guinea pigs until the electrocochleograms showed suppression of the compound action potential at 73 dBSPL. The changes in electrocochleogram
OtolaryngologyHead and NeckSurgery June 1997
responses generally occur after prolonged treatment and are more pronounced in the basal turn. Changes in the cochlear microphonics are marked, whereas changes in the endocochlear potential are not as great. These findings are consistent with OHC involvement, though the underlying mechanism remains unclear. There is no significant difference between electrolyte compositions of endolymph and perilymph in experimental and saline-treated control animals. Ultrastructural examination of the Organ of Corti of these animals show loss of outer hair cells, mostly at the basal and middle turns, with sporadic loss of inner hair cells. Interestingly, there are minimal histologic changes in the kidneys of these same animals. 21 Laurell and Engstrom 26 also report that the endocochlear potential is not affected with small daily doses but it may be significantly reduced with large single doses of cis-platinum in guinea pigs. ABRs were also measured in this study and showed a high-frequency loss within 4 days of cis-platinum exposure. McAlpine and Johnstone 23 show changes in cochlear microphonics, distortion product emissions, neural sensitivity, and endocochlear potential after cisplatinum exposure. A single large dose of cis-platinum administered subcutaneously caused elevated N1 thresholds and depression of the DPOAE at 2fl-f2 1 to 3 days after injection. The degree of neural threshold change was highly correlated with the 2fl-f2 amplitude change up to 40 dB SPL. Interestingly, when cis-platinum is iontophoresed into low-frequency regions of scala media, the hearing loss progresses from low to high frequency, suggesting that the high-frequency hearing loss usually associated with cis-plafinum results from increased exposure of the basal end of the cochlea to the toxic agent. Their findings support the hypothesis that cis-platinum primarily affects the OHC, disrupting the mechanoelectrical transduction process. In the present study, a single large dose of cis-platinum reliably caused changes in DPOAE and ABR thresholds in adult gerbils. The effect seemed to be delayed with threshold shifts noted 5 days after administration of a single large dose of cis-platinum. Although this trend was not statistically significant, it is consistent with observations in patients who develop progressive sensorineural hearing loss within days of cis-platinum administration. The changes in DPOAE thresholds parallel the changes in ABR thresholds after cis-platinum administration. The magnitude of the changes in DPOAE thresholds were larger than the corresponding changes in ABR thresholds. This difference was also demonstrated in the scatter graphs, and may reflect the greater sensitivity of DPOAE to OHC function.
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The changes in I/O functions at 2 kHz and 4 kHz of the control animals at 5 and 14 days were unexpected. It is possible that the increased thresholds at low frequencies, seen in the control and experimental groups, were related to surgical removal of the pinna and cartilaginous canal necessary for placement of the ear probe. Because the detection of D P O A E relies on the mechanics of the entire system and the pinna is removed before baseline testing, edema of the canal may account for some of the low-frequency effects. It is also possible that eustachian tube dysfunction may contribute to these findings. The ears of all animals were examined with a binocular microscope before testing to rule out middle ear disease. The changes in the corresponding experimental groups tended to be larger than the changes in the control groups, though the differences were not statistically significant. It is also possible that this small low-frequency effect may represent the sporadic nature of OHC injury seen in the more apical regions of the cochlea noted in other studies of cisplatinum ototoxicity. 27 DPOAE amplitude decreased at all levels of stimulation in treated animals. This shift differs from the changes seen after aminoglyc0side administration. Brown, et al.28 have shown that aminoglycoside administration causes a shift in the threshold but no change in the responses at higher levels of stimulation, above 65 or 70 dBSPL. Several factors may account for these observed differences. The mechanism of cis-platinum ototoxicity may be different from the mechanism of aminoglycoside ototoxicity. 29,3° There is some evidence that single large doses of cis-platinum may cause significant changes in the endocochlear potential, as well as OHC damage in animals. 26 Although cis-platinum characteristically causes a high-frequency sensorineural loss, no significant frequency was observed. However, the highest frequencies used in this study, 10 and 12 kHz, do not stimulate the most basal aspect of the gerbil cochlea. 3~ The range of the stimulus frequencies used in this study was limited by the sensitivity of the sound transducers. Had we been able to reliably test responses to higher frequencies, we might have demonstrated a significant effect. Clinically, cis-platinum is usually given as a single dose every 3 to 4 weeks. In experimental studies of cisplatinum ototoxicity, animals are usually given daily doses over an extended period of time to elicit a profound sensorineural hearing loss. This experiment was designed to determine whether a single dose of cis-platinure would cause a detectable threshold shift. There was no mortality or significant morbidity associated with this dose of cis-platinum in gerbils. O f course, it is difficult to compare doses of cis-platinum in gerbils to
humans. However, this particular dosage was associated with minimal morbidity and caused changes in auditory function. Furthermore, the changes in DPOAE and A B R thresholds were "moderate," similar to the clinical situation. Therefore, this model may be useful in studying various aspects of cis-platinum ototoxicity. It is interesting to speculate on the mechanism of cis-platinum ototoxicity based On these findings. The large changes in DPOAE thresholds relative to changes in A B R thresholds in the same animals support findings by multiple investigators that one of the main sites of cis-platinum ototoxicity is the OHC. 22,23 It seems reasonable that DPOAE, or evoked otoacoustic emissions in general, may be a useful clinical tool for monitoring ototoxic effects of drugs that primarily affect OHC function. SUMMARY
Gerbils developed signs of ototoxicity after treatment with a single large dose of cis-platinum administered subcutaneously at 6 weeks of age. The changes were manifest as threshold shifts in both the DPOAE I/O functions and the ABR. The changes were most notable at the low (2 to 4 kHz) and the high (10 to 12 kHz) frequencies tested. This effect was not statistically significant. Also, these changes were first detected 5 days after cis-platinum was given. We gratefully acknowledge the technical assistance of Branson Warren, the editorial advice of Dr. Edwin W Rubel, and statistical consultation from. Dean Billheimer and Dr. Lynne Werner. REFERENCES 1. Piel IJ, Meyer D, Pertia CE WolfeVI. Effects of eis-diamminedichloroplatinurn (NSC-119875) on hearing function in man. Cancer Chemother Rep 1974;58:871-5. 2. Strauss M, TowfighiJ, Lord S, Lipton A, HarveyHA, Brown B. Cis-platinumototoxicity:clinical experience and temporal bone histopathology. Laryngoscope 1983;93:1554-9. 3. Pasic TR, Dobie RA. Cis-platinum ototoxicity in children. Laryngoscope 1991;101:985-91. 4. WeatherlyRA, Owens J2r, Catlin FI, MahoneyDH. Cis-platinum ototoxicity in children. Laryngoscope1991;101:917-24. 5. Blakley BW, Myers SE Patterns of hearing loss resulting from eis-platinum therapy. Otolaryngol Head Neck Surg 1993; 109:385-91. 6. Hayes DM, Cvitkovie E, Golbey RB. High dose cis-platinum diammine dichloride: amelioration of renal toxicity by mannitol diuresis. Cancer 1977;39:1372-81. 7. Fausti SA, Schechter MA, Rappaport BZ, Frey RH, Mass RE. Early detection of cisplatin ototoxicity. Cancer 1984;53:22431. 8. Laurell G, Borg E. Ototoxicity if cisplatin in gynaecological cancer patients. Scand Audiol 1988;17:241-7. 9. LaurelI G, Jungelius U. High-dose cisplatin treatment: hearing loss and plasma concentrations. Laryngoscope 1990;100: 724-34. 10. Reddell RR, Kefford RF, Grant JM, Coates AS, Fox RaM, Tattersall MHN. Ototoxicity in patients receiving cisplatin:
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Temporal Bone Histopathology This 1-day workshop, presented and sponsored by the Department of Otolaryngology, University of Minnesota, and the N1DCD National Temporal Bone, Hearing and Balance Pathology Resource Registry, will be held Sept. 26, 1997, at the University of Minnesota, Minneapolis, Minn. It will provide hands-on instruction in the techniques of study of the human temporal bone and associated brain tissue. For further information, contact Patricia Schachern, Lions Research Building, Room 226, 2001 Sixth St., SE, Minneapolis, MN 55455; phone, (612)626-9876; fax, (612)626-9871; e-mail, [email protected].