Efficacy and safety of N-acetylcysteine in prevention of noise induced hearing loss: a randomized clinical trial.

Despite a robust hearing conservation program, military personnel continue to be at high risk for noise induced hearing loss (NIHL). For more than a decade, a number of laboratories have investigated the use of antioxidants as a safe and effective adjunct to hearing conservation programs. Of the antioxidants that have been investigated, N-acetylcysteine (NAC) has consistently reduced permanent NIHL in the laboratory, but its clinical efficacy is still controversial.

Does interferon beta-1a impact pure-tone hearing sensitivity among individuals with multiple sclerosis?

Background: Previous studies reported that particular types of interferon medications might contribute to hearing loss in some patients. The package insert included in the original Food and Drug Administration application for intramuscular interferon beta-1a (Avonex) stated that some patients in the treatment group reported decreased hearing sensitivity.

Objective: The purpose of the present investigation was to assess if individuals with multiple sclerosis (MS) taking intramuscular interferon beta-1a have significantly poorer hearing thresholds than those not currently using any disease-modifying therapies.

Neurotrophins differentially stimulate the growth of cochlear neurites on collagen surfaces and in gels.

The electrodes of a cochlear implant are located far from the surviving neurons of the spiral ganglion, which results in decreased precision of neural activation compared to the normal ear. If the neurons could be induced to extend neurites toward the implant, it might be possible to stimulate more discrete subpopulations of neurons, and to increase the resolution of the device. However, a major barrier to neurite growth toward a cochlear implant is the fluid filling the scala tympani, which separates the neurons from the electrodes.

Implications of blast exposure for central auditory function: a review.

Auditory system functions, from peripheral sensitivity to central processing capacities, are all at risk from a blast event. Accurate encoding of auditory patterns in time, frequency, and space are required for a clear understanding of speech and accurate localization of sound sources in environments with background noise, multiple sound sources, and/or reverberation. Further work is needed to refine the battery of clinical tests sensitive to the sorts of central auditory dysfunction observed in individuals with blast exposure.

Performance on tests of central auditory processing by individuals exposed to high-intensity blasts.

Thirty-six blast-exposed patients and twenty-nine non-blast-exposed control subjects were tested on a battery of behavioral and electrophysiological tests that have been shown to be sensitive to central auditory processing deficits. Abnormal performance among the blast-exposed patients was assessed with reference to normative values established as the mean performance on each test by the control subjects plus or minus two standard deviations. Blast-exposed patients performed abnormally at rates significantly above that which would occur by chance on three of the behavioral tests of central auditory processing: the Gaps-In-Noise, Masking Level Difference, and Staggered Spondaic Words tests.

Development and validation of a cisplatin dose-ototoxicity model.

Background: Cisplatin is effective in the treatment of several cancers but is a known ototoxin resulting in shifts to hearing sensitivity in up to 50-60% of patients. Cisplatin-induced hearing shifts tend to occur first within an octave of a patient's high frequency hearing limit, termed the sensitive range for ototoxicity (SRO), and progress to lower frequencies. While it is currently not possible to know which patients will experience ototoxicity without testing their hearing directly, monitoring the SRO provides an early indication of damage.

Development and evaluation of a portable audiometer for high-frequency screening of hearing loss from ototoxicity in homes/clinics.

Cancer treatment often requires patients to be exposed to drugs that can damage hearing. Drugs such as cisplatin can cause permanent damage to hearing if not detected early. Damage typically occurs first in the more basal regions of the cochlea which are specific for high-frequency (HF) hearing and progresses to more apical regions that are relevant to speech understanding.

Influence of acute hyperglycemia on otoacoustic emissions and the medial olivocochlear reflex.

Stimulus-frequency (SF) otoacoustic emission (OAE) amplitude and the amplitude of medial olivocochlear (MOC) inhibition of SF OAEs for ipsilateral, contralateral and bilateral MOC reflex elicitors were recorded in six subjects with type 2 diabetes during a glucose tolerance test (GTT). Five of the six subjects were tested twice for a total of 11 trials and three subjects were tested in a control experiment. During the GTT experiment, the subjects' blood glucose was elevated from a euglycemic level below 150 mg/dL to a hyperglycemic level above 160 mg/dL following the consumption of a bolus of 80 g of sugar.

Age-related changes in the auditory brainstem response.

Purpose: This cross-sectional study had two goals: (1) Identify and quantify the effects of aging on the auditory brainstem response (ABR); (2) Describe how click rate and hearing impairment modify effects of aging. RESEARCH DESIGN AND ANALYSIS: ABR measures were obtained from 131 predominately male Veteran participants aged 26 to 71 yr. Metrics analyzed include amplitude and latency for waves I, III, and V, and the I-V interpeak latency interval (IPI) at three repetition rates (11, 51, and 71 clicks/sec) using both polarities.

Audiometric hearing status of individuals with and without multiple sclerosis.

The purpose of the present investigation was to determine whether differences exist in audiometric hearing status between individuals with and without multiple sclerosis (MS) and between individuals with relapsing-remitting MS (RRMS) and individuals with secondary progressive MS (SPMS). Forty-seven subjects with MS (26 with RRMS and 21 with SPMS) and forty-nine control subjects without MS completed both a comprehensive case-history questionnaire and a conventional hearing evaluation. Statistical analyses, accounting for the potential confounding factors of age, sex, noise exposure, and use of ototoxic medications, revealed significant differences in hearing thresholds between subjects with and without MS at select audiometric test frequencies (p < 0.

Ototoxicity risk assessment combining distortion product otoacoustic emissions with a cisplatin dose model.

An objective method for identifying ototoxic hearing loss among patients receiving cisplatin is necessary since the ability of patients to take a behavioral test may change over the course of treatment. Data from 56 monitoring visits by 19 Veterans taking cisplatin were used to identify combinations of distortion-product otoacoustic emission (DPOAE) metrics and ototoxicity risk factors that best identified ototoxic hearing loss. Models were tested that incorporated DPOAE metrics generated statistically using partial least-squares analysis.

Tinnitus onset rates from chemotherapeutic agents and ototoxic antibiotics: results of a large prospective study.

Background And Purpose: To report on the incidence and relative risk of tinnitus onset from a variety of drug therapies known to be ototoxic. Two main questions were asked: (1) What is the prevalence and incidence of tinnitus among patients treated with cisplatin, carboplatin, or ototoxic antibiotic therapies? (2) Do commonly reported treatment or subject factors confound or modify the incidence of tinnitus onset?

Data Collection And Analysis: A prospective observational study design was used to evaluate occurrence of significant otologic changes in 488 veterans (962 ears) receiving chemotherapeutic agents (cisplatin, carboplatin), ototoxic antibiotics (primarily aminoglycoside), or nonototoxic drugs (control medications). A subset of 260 veterans lacking tinnitus prior to drug exposure was used to compare rates of tinnitus onset.

Distortion-product otoacoustic emission test performance for ototoxicity monitoring.

Introduction: A nonbehavioral method for monitoring ototoxicity in patients treated with cisplatin is needed because patients enduring chemotherapy may not be well or cooperative enough to undergo repeated hearing tests. Distortion-product otoacoustic emissions (DPOAEs) provide a nonbehavioral measure of auditory function that is sensitive to cisplatin exposure. However, interpreting DPOAE findings in the context of ototoxicity monitoring requires that their accuracy be determined in relation to a clinically accepted gold standard test.

Evaluation of audiometric threshold shift criteria for ototoxicity monitoring.

Background: There is disagreement about ototoxicity monitoring methods. Controversy exists about what audiometric threshold shift criteria should be used, which frequencies should be tested, and with what step size. An evaluation of the test performance achieved using various criteria and methods for ototoxicity monitoring may help resolve these issues.

Auditory and vestibular dysfunction associated with blast-related traumatic brain injury.

The dramatic escalation of blast exposure in military deployments has created an unprecedented amount of traumatic brain injury (TBI) and associated auditory impairment. Auditory dysfunction has become the most prevalent individual service-connected disability, with compensation totaling more than 1 billion dollars annually. Impairment due to blast can include peripheral hearing loss, central auditory processing deficits, vestibular impairment, and tinnitus.

Diabetes-related changes in auditory brainstem responses.

Objectives/hypothesis: Determine effects on auditory brainstem response (ABR) of diabetes mellitus (DM) severity.

Study Design: A cross-sectional study investigating DM severity and ABR in military Veteran subjects with (166) and without (138) DM and with no more than moderate hearing loss.

Methods: Subjects were classified by three age tertiles (<50, 50-56, and 57+).

Diabetes-related changes in hearing.

Objectives/hypothesis: Determine the effects on hearing of diabetes mellitus (DM) severity.

Study Design: We conducted a cross-sectional study among Veterans to investigate the relationship of diabetes severity and hearing in randomly selected subjects with (165) and without (137) DM and who had no more than a moderate hearing loss.

Methods: Subjects were classified by three age tertiles (<50, 50-56, and 57+ years).

On the synthesis of multiple frequency tone burst stimuli for efficient high frequency auditory brainstem response.

The development and digital waveform synthesis of a multiple-frequency tone-burst (MFTB) stimulus is presented. The stimulus is designed to improve the efficiency of monitoring high-frequency auditory-brainstem-response (ABR) hearing thresholds. The pure-tone-based, fractional-octave-bandwidth MFTB supports frequency selective ABR audiometry with a bandwidth that falls between the conventional click and single-frequency tone-burst stimuli.

Factors affecting sensitivity of distortion-product otoacoustic emissions to ototoxic hearing loss.

Objectives: (1) To determine the ototoxicity detection rate (sensitivity) for distortion-product otoacoustic emissions (DPOAEs) testing in adults who received ototoxic medications and experienced pure-tone threshold changes during the course of treatment; (2) to determine the extent to which DPOAE sensitivity to ototoxicity depends on the type of drug administered (platinum or antibiotic), magnitude of ototoxic threshold shifts, pre-exposure pure-tone threshold, and DPOAE data; and (3) to build a model to predict DPOAE sensitivity.

Design: DPOAE and audiometric data were obtained as part of a prospective Veterans Affairs study investigating methods of ototoxicity monitoring. Data were analyzed from 90 ears of 53 subjects receiving ototoxic medications and showing significant hearing changes in at least one ear.

Auditory brainstem response differences in diabetic and non-diabetic veterans.

A number of studies have found statistically significant delays in auditory brainstem latencies of patients with diabetes compared with non-diabetic controls. However, the mechanisms ascribed as responsible for the latency differences between diabetic and non-diabetic patients vary among studies, and the latency differences, while significant, are small. In this 5-year prospective study, auditory brainstem response testing was conducted with 416 non-diabetic and 375 diabetic veterans from the Portland Veterans Affairs Medical Center as part of a larger study.

Instrumentation system upgrade supports mobile personalized healthcare delivery.

Clinicians and patients need mobile tools to detect ototoxic change early and prevent hearing loss. We report on the development of an upgrade of our existing desktop-based clinical-audiological instrumentation into a mobile instrument platform which efficiently supports personalized ototoxicity monitoring on the hospital wards as well as clinic by a trained clinician. Our new wireless-enabled system also serves as the instrumentation platform for the next phase of our work which is remote healthcare delivery with patient-guided at-home ototoxicity monitoring using an evidence-based individualized SRO protocol.

An efficient test protocol for identification of a limited, sensitive frequency test range for early detection of ototoxicity.

A primary focus of research at the National Center for Rehabilitative Auditory Research (NCRAR) has been to develop methodology for rapid and efficient early detection of ototoxicity. It has been shown that an individualized, limited frequency range can be identified, which is sensitive to early ototoxic changes in the auditory system. In this study, a rapid identification protocol for identifying the uppermost target frequency within this sensitive range of ototoxicity (SRO) was investigated.

Time-expanded speech and speech recognition in older adults.

Speech understanding deficits are common in older adults. In addition to hearing sensitivity, changes in certain cognitive functions may affect speech recognition. One such change that may impact the ability to follow a rapidly changing speech signal is processing speed.

Screening for Auditory Impairment-Which Hearing Assessment Test (SAI-WHAT): RCT design and baseline characteristics.

Background: Effective screening programs should not merely detect presence of disease, but also lead to long-term benefit. We describe the rationale and design of the first randomized clinical trial to study the long-term effects of routine screening for hearing loss. We also describe the baseline characteristics of the randomized cohort.