Auditory Brainstem Response Results Research Articles

Micellization of cisplatin (NC-6004) reduces its ototoxicity in guinea pigs

Nanocarriers potentially reduce or prevent chemotherapy-induced side effects, facilitating the translation of nanocarrier formulation into the clinic. To date, organ-specific toxicity by nanocarriers remains to be clarified. Here, we studied the potential of polymeric micelle nanocarriers to prevent the ototoxicity, which is a common side effect of high-dose cisplatin (CDDP) therapy. In this study, we evaluated the ototoxicity of CDDP-incorporating polymeric micelles (NC-6004) in guinea pigs in comparison with that of cisplatin. Their auditory brainstem responses (ABRs) to 2, 6, 12, 20, and 30 kHz sound stimulation were measured before and 5 days after the drug administration. Groups treated with NC-6004 showed no apparent ABR threshold shifts, whereas groups treated with CDDP showed dose-dependent threshold shifts particularly at the higher frequencies. Consistent with the ABR results, groups treated with NC-6004 showed excellent hair-cell preservation, whereas groups treated with CDDP exhibited significant hair-cell loss ( P < 0.05). Synchrotron radiation-induced X-ray fluorescence spectrometry imaging demonstrated that the platinum distribution and concentration in the organ of Corti were significantly reduced ( P < 0.01) in guinea pigs treated with NC-6004 compared with guinea pigs treated with CDDP. These findings indicate that micellization of CDDP reduces its ototoxicity by circumventing the vulnerable cells in the inner ear.

Evaluation of otoacoustic emissions in clinically normal alert puppies

To evaluate distortion product otoacoustic emission (DPOAE) measurements in puppies with normal hearing. 23 clinically normal 7.5-to 10.5-week-old puppies. A cross-sectional study was performed. The DPOAE measurements were obtained with a commercially available distortion product otoacoustic measurement system and were performed in a quiet, non-sound-attenuated room. All measurements were obtained from alert puppies and were repeated 1 or 2 times to ensure that the measurements were replicable. Results that were a minimum of 8 dB higher than the noise floor were accepted. Values from the first trial in which emissions were obtained at all test frequencies were used for analysis. Otoacoustic emission measurements were easily obtained, robust, reliable, and consistent with auditory brainstem response and behavioral results. Hearing screening in alert puppies can be accomplished reliably and rapidly with otoacoustic emissions testing. Results supported the possibility of the use of DPOAE measurement in hearing screening of dogs.

Risk Factors for Hearing Loss in Very Low Birth Weight Infants: Results of Hearing Test in Infants

Purpose: An association between very low birth weight infants(VLBWI) and hearing loss has long been recognized. Early identification and intervention for hearing loss benefits language and speech/cognitive development. We investigated the risk factors and clinical outcomes of hearing loss among VLBWI. Methods: We analyzed the results of auditory brainstem response (ABR) testing of VLBWI. These infants were admitted to the neonatal intensive care unit (NICU) of Pusan National University Yangsan Hospital between December 2008 and February 2011. A follow-up was conducted subsequently. Results: ABR evaluations were performed on 65 infants, and 31 showed abnormal results (47.7%). Among the 31 infants, 10 were classified with moderate/severe/profound hearing loss (15.4%). The infants with abnormal ABR had a higher incidence of low birth weight, prolonged ventilator care, cumulative dose of furosemide, and the lowest PaO2 (P<0.05). Those with moderate/severe/profound hearing loss had a higher incidence of low Apgar scores at 5 minutes (odds ratio[OR],0.34; 95% confidence interval[CI],0.13-0.89), prolonged ventilator care (OR,1.06; 95% CI,1.01-1.12), and mild hearing loss compared to those without profound hearing loss. Follow-up evaluations on eight infants with ABR reveled improvements 5.6±3.9 months later. One infant, who had profound hearing loss in both ears, used a hearing aid. Conclusion: Factors influencing hearing loss at the first VLBWI hearing screening test included lower Apgar scores at 5 min and prolonged use of a ventilator. Most VLBWI with hearing losses were expected to recover after several months of follow-up.

Improving Hearing in Stapedectomy With Intraoperative Auditory Brainstem Response

To determine the efficacy of using intraoperative auditory brainstem response (ABR) in improving immediate hearing results of patients undergoing primary laser stapedotomy. Case series with chart review. Community hospital. The study included 32 consecutive patients, with 34 ears undergoing primary stapedotomy by a single surgeon at a single institution using a single prosthesis design. Intraoperative ABR was performed at the beginning of each surgery and after the stapes prosthesis was inserted. Surgical adjustments were made if initial ABR results did not demonstrate hearing improvement. ABR then was repeated at the conclusion of the procedure. Audiometry was performed postoperatively in all patients. There were 22 left ears and 12 right ears studied. Two patients underwent bilateral staged surgery. Eight patients, or 23% of the group, had intraoperative adjustments made to improve hearing results. Hearing was improved in 33 of 34 ears, or 97%. The surgical revision rate was 3%. The average preoperative air-bone gap (ABG, calculated as an average from 250, 500, and 1000 Hz) was 29.0 dB HL in the left ear group and 26.6 dB HL in the right ear group. The average postoperative ABG was 9.9 dB HL in the left ear group and 9.4 dB HL in the right ear group. All patients had postoperative audiometric results consistent with final intraoperative ABR results. Intraoperative ABR may significantly improve immediate hearing results in patients and greatly reduce the need for revision surgery.

Manifestações audiológicas em crianças e adultos com AIDS

according to the literature, the incidence of hearing impairment in patients with HIV / AIDS might be caused by alterations in external, middle and / or internal ear. to characterize and to compare the results of audiological assessment and Auditory Brainstem Response in children and adults with AIDS. audiological and electrophysiological (Auditory Brainstem Response) assessment of hearing was carried out in 51 children and 22 adults with HIV/AIDS (research groups I and II, respectively) and in 50 healthy children and 25 healthy adults (control groups I and II, respectively). Participants ranged in age between 3 and 10 years (children) and between 18 and 50 years (adults). the most frequent observed alteration for children with AIDS was related to the middle ear whereas for adults with AIDS it was related to the internal ear. Higher occurrence of abnormal results was observed for adults with AIDS as compared to children with AIDS. children and adults with AIDS present alterations in audiological assessment and Auditory Brainstem Response. This suggests the involvement of peripheral and central auditory pathways. Findings of the present study emphasize the effectiveness of using electrophysiological hearing measures in order to better identify the brain injury level in patients with AIDS, besides allowing the monitoring of the development rate of the disease.

Fitting model of ABR age dependency in a clinical population of normal hearing children

The purpose of this study was to present a simple and powerful fitting model that describes age-dependent changes of auditory brainstem responses (ABR) in a clinical population of normal hearing children. A total of 175 children (younger than 200 weeks postconceptional age) were referred for audiologic assessment with normal ABR results. ABR parameters of normal hearing children between 2003 and 2008 were included. The results of the right ears recorded at 90 dB nHL were analyzed. A simple and accurate fitting model was formulated based on these data. A very similar age-dependent effect was found for peaks III and V, and I–III and I–V intervals; latencies decrease as postconceptional age increases. It shows that the total age-dependent effect will be completed after 1.5–2 years. The age-dependent effect can be modeled by a relatively simple and accurate exponential function. This fitting model can be easily implemented to analyze ABR results of infants in daily clinical practice. We speculate about the underlying physiological processes.

Comparative Study of the Auditory Steady-State Response (ASSR) and Click Auditory Brainstem Evoked Response (ABR) Thresholds among Filipino Infants and Young Children

Objective: To compare the results of auditory steady-state response (ASSR) and click auditory brainstem response (click ABR) among infants and young children tested at the Ear Unit of a Tertiary General Hospital.&#x0D; &#x0D; Methods:&#x0D; Design: Cross-sectional Study&#x0D; Setting: Tertiary General Hospital&#x0D; Population: Within-subject comparisons of click auditory brainstem response (click ABR) thresholds and auditory steady-state response (ASSR) thresholds among 55 infants and young children, 2 months to 35 months of age referred to the Ear Unit for electrophysiologic hearing assessment.&#x0D; Results: Click ABR showed strong positive correlation to all frequencies and averages of ASSR. Highest correlation was noted with the average of 1-4 kHz ASSR results with Pearson r = 0.89 (Spearman r=0.80), the average of 2-4 kHz had strong positive correlation r = 0.88 (0.79). Correlation was consistently strong through all ASSR frequencies (0.5 kHz at r=0.86 (0.74), 1 kHz at r=0.88 (0.78), 2 kHz at r=0. 87 (0.79), 4 kHz at r=0.85 (0.76)). Average differences of click ABR and ASSR thresholds were 8.2±12.9dB at 0.5 kHz, 8.6±12.6dB at 1 kHz, 5.3±11.8dB at 2 kHz and 7.8±13.4dB at 4 kHz. Among patients with no demonstrable waveforms by click ABR with maximal click stimulus, a large percentage presented with ASSR thresholds. Of these, 80.5% (33 of 41) had measurable results at 0.5 kHz with an average of 107.3±11.1dB, 85.4% (35 of 41) at 1 kHz with an average of 110.5±11.8dB, 73.2% (30 of 41) at 2 kHz with an average of 111.2±11.1dB and 63.4% (26 of 41) at 4 kHz with and average of 112.2±8.21dB. Auditory steady-state response results were comparable to auditory brainstem response results in normal to severe hearing loss, and provided additional information necessary for complete audiologic assessment especially among patients with severe to profound hearing loss wherein click ABR showed no responses. Up to 85.4% of patients that would have been noted to have no waveforms by click ABR still demonstrated measurable thresholds by ASSR&#x0D; &#x0D; Conclusion: Our study suggests that ASSR may be the best available tool for assessing children with severe to profound hearing loss, and is a comparably effective tool in overall hearing assessment for patients requiring electrophysiological testing. The advantages of ASSR over click ABR include: 1) detection of frequency-specific thresholds and; 2) the detection of hearing loss thresholds beyond the limits of click ABR.&#x0D; &#x0D; &#x0D; Key words: Auditory Steady-State Response, ASSR, Auditory Brainstem-Evoked Response, ABR, Hearing Thresholds, Electrophysiologic Testing&#x0D;

Cochlear Nerve Action Potential Monitoring with the Microdissector in Vestibular Schwannoma Surgery

We developed a cochlear nerve action potential (CNAP) monitoring technique using a microdissector and compared the results of CNAP and auditory brainstem response (ABR) monitoring. Thirty-six patients underwent vestibular schwannoma resection via the retrosigmoid approach to preserve hearing. Both CNAP with the microdissector and surface ABR were recorded during the operation. We used the microdissector as an intracranial electrode for CNAP monitoring. The CNAP waveform was classified into four types: triphasic, biphasic, positive, and flat. At the completion of the tumor resection, the triphasic waveform was observed in 11 patients and the biphasic waveform was observed in 11 patients. Hearing function was preserved in all of them, although it was preserved in only two patients with other CNAP waveform types. The prognostic value of CNAP is significantly higher than that of ABR. We found that although CNAP with a microdissector does not provide real-time monitoring, with the classification of waveforms it can be used as predictable tool for postoperative hearing more accurately than ABR.

Correlation between Audiovestibular Function Tests and Hearing Outcomes in Severe to Profound Sudden Sensorineural Hearing Loss

This study investigated whether audiovestibular function tests, namely auditory brain stem response (ABR) and vestibular-evoked myogenic potential (VEMP) tests were correlated to hearing outcomes after controlling the effects of other potential confounding factors in severe to profound sudden sensorineural hearing loss (SSHL). Eighty-eight patients with severe to profound SSHL were enrolled in this study. Pretreatment hearing levels, results of audiovestibular function tests, and final hearing outcomes were recorded from retrospective chart reviews. Other factors, including age, gender, delay of treatment, vertigo, diabetes mellitus, and hypertension, were collected as well. Comparative analysis between multiple variables and hearing outcomes was conducted using the cumulative logits model in overall subjects. Further, multivariate analysis of prognostic factors was conducted in the stratified groups of severe (70 dB HL <hearing level < or =90 dB HL) and profound (hearing level >90 dB HL) SSHL. Multivariate analysis showed that pretreatment hearing levels, presence of vertigo, and results of ABR and VEMP testing were significant outcome predictors in the overall subjects. Stratification analysis demonstrated that both the presence of ABR and VEMP waveforms were significantly correlated with better hearing outcomes in the group of severe SSHL [ABR: adjusted odds ratio (aOR) = 14.7, 95% confidence interval (CI) = 1.78 to 122, p = 0.01; VEMP: aOR = 5.91, 95% CI = 1.18 to 29.5, p = 0.03], whereas the presence of vertigo was the only significant negative prognostic factor in the group of profound SSHL (aOR = 0.24, 95% CI = 0.06 to 0.95, p = 0.04). Other variables, including age, gender, diabetes mellitus, hypertension, and delay of treatment, were not significantly related to hearing outcomes in both groups (p > 0.05). A predictive hearing recovery table with the combined ABR and VEMP results was proposed for the group of severe SSHL. ABR and VEMP tests should be included in the battery of neurootological examinations in patients with severe SSHL because the presence of both waveforms might indicate favorable hearing outcomes. The presence of vertigo might portend a worse prognosis in patients with profound SSHL. A presumed table in predicting hearing outcomes was suggested for patients with severe SSHL.

Comparison of Auditory Brainstem Response Results in Normal-Hearing Patients With and Without Tinnitus

Comparison of Auditory Brainstem Response Results in Normal-Hearing Patients With and Without Tinnitus

Ototoxic Effect of Topical Ciclopirox as an Antimycotic Preparation

To evaluate the ototoxicity of ciclopirox-containing solution as an otologic preparation for the treatment of otomycosis. Ciclopirox is a synthetic antimycotic agent available in a variety of formulations to treat superficial fungal infections. Ciclopirox has demonstrated both fungicidal and fungistatic activity in vitro against a broad spectrum of pathogenic fungi. It also possesses a broad-spectrum antibacterial properties, anti-inflammatory, and antiedema effect. The ototoxic effect of ciclopirox-containing solutions has not been known, so the current study was designed to observe the ototoxic effect of this solution experimentally. Experiments were performed in 22 young male albino guinea pigs (weight, 450-550 g). The 10 animals in the experimental group received ciclopirox solution, and the control group was divided into two groups of six animals each. The first group received saline solution (negative control) and the second received gentamicin (40 mg/mL; ototoxic control). Under general anesthesia, pretreatment auditory brainstem responses (ABRs) from the right ears were obtained from the animals in all groups. The right tympanic membranes were totally perforated, and a small piece of Gelfoam was applied to the middle ear directly to the round window membrane. Ear solutions were applied through transcanal approach to the middle ear twice a day in 2 weeks. Twenty-two animals of perforated tympanic membrane were observed during a 2-week period. Posttreatment ABRs were obtained in all groups in a week after the last administration. Baseline ABR results were normal in right ears of all animals tested. Animals undergoing placement of Gelfoam with either ciclopirox solution or saline in the middle ear showed no changes in the ABR threshold. The gentamicin group showed a significant change in the ABR threshold. In the guinea pig, when applied topically to the middle ear, ciclopirox does not cause a reduction in the ABR threshold. Because its safety has not yet been confirmed in patients, caution should be observed when prescribing this agent.

Comparison of Auditory Brainstem Response Results in Normal-Hearing Patients With and Without Tinnitus

To evaluate electrophysiologically the auditory nerve and the auditory brainstem function of patients with tinnitus and normal-hearing thresholds using the auditory brainstem response (ABR). Case-control study. Ambulatory section of the Department of Otolaryngology, Hospital de Base de Brasília. Thirty-seven individuals with tinnitus and 38 without tinnitus, with ages ranging from 20 to 45 years and pure-tone thresholds of 25 dB or better at frequencies between 500 and 8000 Hz. We compared the latencies of waves I, III, and V; the interpeak intervals I-III, III-V, and I-V; the interaural latency difference (wave V); and the V/I amplitude ratio between the 2 groups. Among the 37 patients in the study group, abnormal results were found in 16 (43%) in at least 1 of the 8 parameters evaluated. When we analyzed the latencies, although the values were on average in the normal range used in the present study, the tinnitus group presented a significant prolongation of the latencies of waves I, III, and V when compared with the control group. Furthermore, we found the interpeak I-III, III-V, and I-V values to be within the normal limits, but the interpeak III-V value was significantly (P = .003) enlarged in the study group compared with the control group. The V/I amplitude ratio found in the tinnitus group was within normal limits; however, a significant (P = .004) difference was found when the 2 groups were compared. The averages of the interaural latency difference (wave V) did not show significant differences in relation to the control group. We conclude that, although the averages obtained in several analyzed parameters were within normal limits, the ABR results from the patients with and without tinnitus and normal hearing are different, suggesting that ABR might contribute to the workup of these patients. Our data show that there are changes in the central pathways in the study group. The meaning of these changes must be further investigated.

Unbound Bilirubin Concentration is Associated With Abnormal Automated Auditory Brainstem Response for Jaundiced Newborns

This study was conducted to determine whether incidental jaundice affects automated auditory brainstem response results. We reviewed the medical charts of jaundiced newborns of > or = 34 weeks of gestation who underwent automated auditory brainstem response testing within 4 hours of plasma total bilirubin concentration and unbound bilirubin concentration measurements. We tested the hypothesis that the likelihood of abnormal automated auditory brainstem response results would increase as total bilirubin and unbound bilirubin concentrations increased. Forty-four infants with proximate total bilirubin concentration, unbound bilirubin concentration, and automated auditory brainstem response measurements were identified, and 4 (9%) had bilateral refer automated auditory brainstem response results. The mean total bilirubin concentration of 21.4 mg/dL (SD: 4.0 mg/dL; range: 14.4-29.5 mg/dL) for the 40 infants with bilateral pass automated auditory brainstem response results was not significantly different from that of 23.0 mg/dL (range: 14.9-33.1 mg/dL) for the 4 infants with bilateral refer automated auditory brainstem response results. However, the mean unbound bilirubin concentration of 1.32 microg/dL (range: 0.22-2.99 microg/dL) for the 40 infants with bilateral pass results was significantly lower than the mean of 2.62 microg/dL (range: 0.88-4.41 microg/dL) for the 4 infants with bilateral refer results. Logistic regression showed that increasing unbound bilirubin concentrations but not increasing total bilirubin concentrations were associated with of bilateral refer automated auditory brainstem response results. The probability of bilateral refer automated auditory brainstem response results increases significantly with increasing unbound bilirubin concentrations but not with increasing total bilirubin concentrations. Because unbound bilirubin concentrations are also more closely correlated with bilirubin neurotoxicity than are total bilirubin concentrations, bilateral refer automated auditory brainstem response results for jaundiced newborns may indicate increased risk of bilirubin neurotoxicity, in addition to the possibility of congenital deafness.

Infant hearing screening: effects of timeline

Universal infant hearing screening using otoacoustic emission and auditory brain-stem response audiometry is widely administered to attain the goals of early identification of, and intervention for hearing impairment. Concerns regarding screening specificity have, however, been raised. False positives may result from vernix occlusion in the ear canal or transient middle ear effusion, and can result in substantial costs to health care systems. The current study investigates the effects of age and time interval between tests on hearing assessment results. Three hundred and seventeen positive screens from a 2-stage distortion product otoacoustic emission (DPOAE) screening programme in Hong Kong, who subsequently received diagnostic auditory brainstem response (ABR) assessment and monitoring, were investigated. Differences in diagnostic ABR results were compared among infants of different ages at tests, and with different time lapses after DPOAE screening. The proportion of those having persistent hearing impairment, conductive loss and impairment of moderate degree or above, were also compared. A significantly higher rate of normal ABR thresholds (60%versus 24%) was noted in infants assessed after age 50 days, and in infants diagnostically assessed with a time lapse of over 20 days post-DPOAE screening (65%versus 42%). Delaying diagnostic ABR assessment may reveal a higher percentage of normal thresholds, and hence probably higher specificity. Time delay may allow for spontaneous resolution of transient outer and middle ear conditions. However, the goals of early identification and intervention, as well as possible parental anxiety with delayed assessment, should also be considered when reviewing infant hearing screening schedules.

Effect of early onset otitis media on brainstem and cortical auditory processing

BackgroundOtitis media (OM) leads to significant reduction in the hearing sensitivity. The reduced auditory input, if in the early years of life when the auditory neural system is still maturing, may adversely influence the structural as well as functional development of the system. Past research has reported abnormalities in both the structure and function of brainstem nuclei following auditory deprivation, but, it has not necessarily focused on children who had OM in their first year of life. It can also be said that if auditory processing is affected at the brainstem level because of early onset OM (reduced auditory input in the crucial periods of neural development), then, it may be said that auditory processing is also affected at the cortical level because it receives distorted input from the brainstem. Therefore, the purpose of this study was to document the effects of early onset OM on auditory processing, if any, at the brainstem as well as at cortical levels. A related purpose of the study was to investigate the persistence of the effects of early onset OM, if any, on auditory processing.MethodsA cross sectional approach and a standard group comparison design was used in the study. Thirty children, who had OM between 6 and 12 months of age and who were in the age range of 3.1 – 5.6 years participated in the study. Children with OM were divided into 3 groups based on their age. Click evoked auditory brainstem responses (ABRs) and late latency responses (LLRs) were recorded from these children, and the responses were compared with those from age and gender matched normal children without any history of OM. The data from the 2 groups was statistically analyzed through independent t test. Pearson's Product Moment correlation was computed to examine the relationship between results of ABR and LLR in children with early onset OM.ResultsThe mean central conduction time was significantly increased and the mean amplitude of wave I and III of ABRs was significantly reduced in children with early onset OM compared to normal children. Also, the latency of all LLR waves was significantly less in children with early onset OM than in normal children. However, significant differences in mean values of either ABR or LLR (latencies or interwave intervals as the case may be) were observed only in 3-year old children. There was a significant, but negative association between central conduction time and latency of LLRs.ConclusionOM in the first year of life leads to negative effects on brainstem signal processing even if it has occurred only for a short duration (maximum of 3 months). In such a situation, auditory cortical structures probably show compensatory changes through central gain to offset the prolonged central conduction time. Although the results of the present study showed that the negative effects of early onset OM (occurring in the first year of life) on auditory processing disappeared by the time the children were 4.1 years, there is need for longitudinal studies on this to confirm the findings.

Evaluation of brainstem function in patients with spasmodic dysphonia using vestibular evoked myogenic potentials and auditory brainstem responses

Conclusion. The vestibular area is closer than the auditory region to nucleus ambiguus. If a ‘shared’ lesion involves regions of adjacent nuclei of the brainstem in patients with spasmodic dysphonia then vestibular area involvement is more possible than that of the auditory region. Objectives. The authors hypothesize that lower brainstem lesions and involvement of descending pathways of the spinal tract may be the site of lesion in patients with spasmodic dysphonia. Patients and methods. Ten patients with spasmodic dysphonia were tested using the auditory brainstem response (ABR) and vestibular evoked myogenic potentials (VEMPs). Results. No ABR abnormalities were found in right ears. Results of ABR on the left ear showed that one patient had abnormal ABR. This patient had severe sensorineural hearing loss on the left side. VEMPs displayed normal response in two patients bilaterally. First positive (p13) and second negative (n23) waves of VEMP could not be recorded in three cases unilaterally and in five patients bilaterally.

Vestibular-evoked myogenic potentials and caloric stimulation in infants with congenital cytomegalovirus infection

The influence of congenital cytomegalovirus infection on cochlear function has been well recognised; however, its impact on the vestibular system in infants has not been examined. The purpose of the present study was to evaluate vestibular function in a group of infants, using caloric stimulation tests and vestibular-evoked myogenic potential measurements. Vestibular-evoked myogenic potentials and auditory brainstem responses were recorded and caloric stimulation was performed in 66 infants aged three months, comprising 40 healthy controls and 26 infants with congenital cytomegalovirus infection. No reaction to caloric stimulation was elicited from 16 examined ears, no vestibular-evoked myogenic potentials were recorded from 12 ears, and profound sensorineural hearing loss was diagnosed in eight ears. Pathological results were observed predominantly in infants with symptoms of intrauterine congenital cytomegalovirus infection present at birth. In infants with clinical symptoms of congenital CMV infection present at birth, abnormal vestibular test results occurred more frequently than abnormal auditory brainstem response results. Vestibular organs should be routinely examined in individuals with congenital cytomegalovirus infection.

Etiologies of hearing impairment among infants and toddlers: 1986–1987 versus 2001

This study compares etiological factors for hearing loss, relevant neuro-sensory impairments and demographics between two groups of children referred for early hearing habilitation in Israel. Group I was referred in the years 1986-1987 (n=73) and group II was referred during 2001 (n=73). Family history, pregnancy, risk factors, developmental milestones, medical history, auditory brainstem response, tympanometry, otoacoustic emissions and behavioral audiometric results were retrospectively retrieved in 2003 from medical records at the MICHA Society for Deaf Children in Israel. New referrals per year have doubled themselves over the 15 years that elapsed between 1986-1987 and 2001. No changes in gender and age at time of admission were found. The prevalence of mild-to-moderate hearing loss was higher in Group II while severe and profound hearing loss was more prevalent in Group I. Assisted reproductive technologies were involved only in Group II. There were more twin births and post-natal hypoxia in Group II. Rh incompatibility was reported only in Group I. Severe hearing loss was associated with younger age at admission. No significant associations were found between age at admission and etiology with the exception of the fact that children with genetic background were admitted at an earlier age. Since no significant association between genetic background and severity of hearing loss was found, it is conclude that the association between severity of hearing loss and age at admission did not account for changes in etiology in our sample. Classic risk factors for hearing loss among infants and toddlers have not changed much over time, and the few changes that have been noticed are probably due to expanded medical knowledge and improved technologies.

Ototoxic Effect of Burow Solution Applied to the Guinea Pig Middle Ear

To analyze the ototoxicity of Burow solution as an otologic preparation. Burow solution has been used for years in the treatment of acute or chronic otitis externa and chronic suppurative otitis media. This acidic solution has antibacterial and antiedematous properties. Ototoxic effect of Burow solution has not been known, so the current study was designed to observe the ototoxic effect of Burow solution experimentally. Experiments were performed in 32 young, male albino guinea pigs (weight, 450-550 g). Twenty animals in the experimental group were divided into 2 groups of 10 animals each. The first group received 13% Burow solution (13% aluminum subacetate), and the second received 4% Burow solution (4% aluminum subacetate). Twelve animals in the control group were divided into 2 groups of 6 animals each. The first group received gentamicin (40 mg/mL; ototoxic control), and the second received saline solution (negative control). Under general anesthesia, pretreatment auditory brainstem responses (ABRs) from the right ear were obtained from the animals in all groups. The right tympanic membranes were widely perforated, and a small piece of Gelfoam was applied to the middle ear. Ear solutions at concentrations of 0.1 mL were applied through transcanal approach to the middle ear twice a day in 10 days. Under general anesthesia, the Gelfoam was removed from the right middle ear, and posttreatment ABRs were obtained 14 days later after the initial time in all groups. Baseline ABR results were normal in right ears of all animals tested. Animals undergoing placement of Gelfoam with either 13% Burow solution, 4% Burow solution, or saline in the middle ear showed no changes in ABR threshold. The gentamicin group showed significant change in the ABR threshold. Burow solution was considered to be an effective and safe otologic preparation.

High- and Low-Frequency Probe Tone Tympanometry in Chinese Infants

ObjectiveTo assess the utility of low- and high-frequency tympanometry in the diagnosis of middle ear dysfunction in Chinese infants. MethodsTympanograms were obtained with 226 Hz, 678 Hz and 1000 Hz probe tones from infants aged 5-25 weeks with normal auditory brainstem responses (ABRs) (15 infants, 30 ears) and with prolonged wave I latencies (17 infants, 20 ears), suggesting middle ear dysfunction, using a GSI Tympstar middle ear analyzer Version II. ResultsThe single-peaked tympanogram was the most characteristic type in both groups and seen in 25 ears (83.3%) in the normal ABR group and in 18 ears (90%) in the delayed wave I group, respectively. The peak pressure, peak compensated static acoustic admittance and gradient of 226 Hz tympanometry were of no significant differences between the two groups. The 678 Hz tympanograms of admittance, susceptance and conductance demonstrated non-peak, single-, double- and tri-peaked patterns in both groups. The agreement between ABRs and 678 Hz tympanograms of admittance,susceptance and conductance were 70.0%, 58.0% and 64.0% (kappa=0.324, 0.234 and 0.118) respectively. For 1000 Hz probe tone, admittance, susceptance and conductance tympanograms showed single peaked patterns in 28(93.3%), 25 (83.3%) and 26(86.7%) of the 30 normal ears. Admittance, susceptance and conductance tympanograms using the 1000 Hz probe tone were flat in 15 (75%), 17 (85%) and 13 (65%) of the ears in infants with prolonged wave I latencies. For 1000 Hz admittance, susceptance and conductance Tympanograms, the agreement between tympanometry and ABR results were 90.0%, 92.0% and 86.0% with kappa at 0.783, 0.831 and 0.690, respectively. Conclusion1000 Hz probe tone tympanometry is a promising middle ear function test for infants of 1-6 months age, while 226 Hz and 678 Hz probe tones are less efficient in detecting middle ear dysfunction in infants.