Otoacoustic Emission Recordings Research Articles

Evaluation of efferent influences on neural coding using pre-clinical models of sensorineural hearing loss

The medial olivocochlear (MOC) efferent system is less explored than the ascending auditory pathway but likely contributes in important ways to neural coding and perception. These effects are thought to vary across stimulus configurations, anesthetic states, and subtypes of sensorineural hearing loss (SNHL). To explore effective assays of MOC effects on neural coding, we have recorded Interleaved otoacoustic emissions (OAEs) and envelope following responses (EFRs) from several pre-clinical SNHL chinchilla models. Our preliminary observations include increases in OAEs with inner-hair-cell loss and anesthesia, which may be due to reduced efferent strength. Additionally, we observed enhanced EFRs with an added noise masker, which also could be related to efferent effects. We are using sedated and awake OAE comparisons to develop a standard efferent assay for use in neural-coding studies. Interleaved recording of OAEs and EFRs track cochlear-gain and neural-coding changes during acoustic stimuli. A recently developed modeling framework (Farhadi et al., 2023 JASA) that includes different MOC projection pathways, including midbrain modulation-sensitive inputs, is used to guide most-effective stimulus selection. Ultimately, this model-guided experimental framework will provide unique guidance for testing MOC hypotheses related to neural coding.

Role of Otoacoustic Emissions in Hearing Assessment of Children with Autism

Evaluation of hearing is essential in the diagnostic process of children suspected having autism spectrum disorder (ASD). The aim of this study was to examine the efficiency and feasibility of utilizing otoacoustic emissions as an objective test to assess hearing in children diagnosed with ASD. A pilot study was conducted over a period of 3 years (from September 2019 to November 2022) in the Audiology Department at the Center for Specialty Surgeries, Benghazi, Libya. A total of 61 children with autism aged between 2-15 years referred for hearing evaluation were enrolled in the study. The clinical procedure consisted of otoscopic ear examination, and Otoacoustic Emission (OAE) recording. OAE testing was attempted on the study sample (n 51) who met the inclusion criteria. And successfully completed for 44 participants (86%): 40 cases (91%) from the first attempt while 4 cases (9%) needed a second or more visit. Four autistic children (9%) had absent otoacoustic emissions in one ear. Testing couldn't be completed for 7 children (14%) due to behavioral difficulties. Results of this study showed the feasibility of using Distortion Product Otoacoustic Emissions (DPOAEs) in assessment of hearing for children with autism for whom obtaining reliable behavioral responses can be challenging.

ABO blood group and cochlear function: evidence from a large sample size study

Objective The present study investigated the effect of blood group on cochlear function in a large participant sample across different age groups. The study hypothesis was that participants with blood group O would show relatively reduced cochlear function as reflected in otoacoustic emission (OAE) measures. Design Data were collected from transient evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), DPOAE input/output (I/O) function, and spontaneous otoacoustic emission (SOAE) recordings. Study sample Four hundred and sixty-three normal hearing adults aged 20–59 years among the four ABO blood groups participated in the study. Results TEOAE and DPOAE amplitudes did not reveal significant differences for participants with blood group O compared with participants with non-O blood groups. No significant differences in I/O function categories were found among participants with different blood groups. SOAE prevalence was also not significantly different across blood groups. However, previously reported age and gender differences for OAE variables were confirmed. Conclusions Participants with blood group O were not found to have significantly reduced cochlear function, based on OAE measures. Results from the current study do not support the hypothesis that normal hearing individuals with different ABO blood groups differ in level of cochlear function.

Optimizing distortion product otoacoustic emission recordings in normal-hearing ears by adopting cochlear place-specific stimuli.

Distortion product otoacoustic emissions (DPOAEs) provide a window into active cochlear processes and have become a popular clinical and research tool. DPOAEs are commonly recorded using stimulus with fixed presentation levels and frequency ratio irrespective of the test frequency. However, this is inconsistent with the changing mechanical properties of the cochlear partition from the base to the apex that lend specific frequency-dependent spatial properties to the cochlear traveling wave. Therefore, the frequency and level characteristics between the stimulus tones should also need to be adjusted as a function of frequency to maintain optimal interaction between them. The goal of this investigation was to establish a frequency-specific measurement protocol guided by local cochlear mechanics. A broad stimulus parameter space extending up to 20 kHz was explored in a group of normal-hearing individuals. The stimulus frequency ratio yielding the largest 2f1-f2 DPOAE level changed as a function of frequency and stimulus level. Specifically, for a constant stimulus level, the frequency ratio producing the largest DPOAE level decreased with increasing frequency. Similarly, at a given f2 frequency, the stimulus frequency ratio producing the largest DPOAE level became wider as stimulus level increased. These results confirm and strengthen our current understanding of DPOAE generation in the normally functioning cochlea and expand our understanding to previously unexamined higher frequencies. These data support the use of frequency- and level-specific stimulus frequency ratios to maximize DPOAE generation.

The effect of increase in blood glucose level on hearing loss

ObjectivePrevious studies have shown that hearing function is also vulnerable to the effects of diabetes mellitus which can be shown by brainstem auditory evoked potential and distortion product otoacoustic emission recordings. This study aimed to investigate the changes of brainstem auditory evoked potential and distortion product otoacoustic emission in hyperglycemia and whether there is a relationship between reactive oxygen substances production and hearing deterioration in the rat model. Methods25 streptozotocin induced diabetic rats were divided into three groups: control, high blood glucose, and diabetes mellitus. Brainstem auditory evoked potential and distortion product otoacoustic emission were recorded, and thiobarbituric acid reactive substances levels were measured in the brainstem tissue. ResultsAt 8 kHz, the latencies of I, II, III, IV, and V brainstem auditory evoked potential waves in high blood glucose and diabetes mellitus groups were elongated, at 16 kHz, only these wave latencies of the diabetes mellitus group were prolonged compared with the control group. A significant decrease was also found in distortion product otoacoustic emission amplitudes at 4, 6, 8, and 10 kHz in the high blood glucose and diabetes mellitus groups compared to the control group. There was a significant increase in thiobarbituric acid reactive substances values due to the increase in blood glucose levels in the high blood glucose and diabetes mellitus groups compared to the control group. ConclusionThese results suggested that high blood glucose levels may cause hearing impairment not only in the diabetic state but also in the period of hyperglycemia before the onset of manifest diabetes mellitus and reactive oxygen substances may play an important role in the pathophysiology of diabetes mellitus. We suggest that regulating high glucose levels even before the onset of manifest diabetes mellitus may prevent hazardous effects on hearing function. Level of evidenceLevel 3.

Vestibular and radiological characteristics of children affected by unilateral auditory neuropathy spectrum disorder

ObjectiveAuditory neuropathy spectrum disorders (ANSD) are defined by the association of a preserved outer hair cell function and an impaired auditory nerve neural response, and present mostly bilaterally. Unilateral ANSD are consequently only seldom described, and most frequently as isolated cases. This study aims to describe the audiological, vestibular and radiological characteristics of a population of children with unilateral ANSD. Material and methodsWe isolated 22 patients with unilateral ANSD, 12 boys and 10 girls from 0 to 95 months, in a database of auditory evoked potentials. We reviewed the audiological, radiological and vestibular assessments. The audiological assessment included tympanometry, otoacoustic emission recording and auditory evoked potential. Otolithic function was assessed by performing cervical vestibular evoked myogenic potential. The canal function was determined by video head impulse test and/or caloric test. The radiological evaluation consisted of an MRI of the internal auditory canal. ResultsMany patients with a type A tympanometry had no response to otoacoustic emission (53,8%), in the presence of a cochlear microphonic potential.Vestibular assessment was performed in 9 of the 22 patients. 4 children had impaired otolithic and/or canal function.MRI evaluation of the inner ear was performed in 18 patients. Aplasia or hypoplasia of the cochlear nerve was found in 17 of them. MRI showed additional vestibular or brainstem abnormalities in 7 of the 18 children.All children with impaired vestibular function had vestibular or brainstem radiological alterations in addition to cochlear branch aplasia or hypoplasia. ConclusionsRadiological and vestibular abnormalities are common in children with unilateral ANSD and suggest that a radiological and vestibular assessment is required.

Pitfalls in the Detection of Hearing Loss via Otoacoustic Emissions

Otoacoustic emissions (OAEs) are currently used as a valuable audiological test or as a hearing screening tool. There are many commercially available OAE recording systems that are used both for clinical practice and for research. However, there is little information in the literature comparing their performance in detecting hearing loss. The purpose of this prospective, nonrandomized, and controlled study was to evaluate the screening performance obtained from recent and older versions of the Otometrics Accuscreen OAE screening device in comparison with the Otodynamics ILO-292 OAE system, which has been used as the gold standard. Testing included otoscopic assessment, pure tone audiometry, tympanometry, and transiently evoked OAE (TEOAE) recordings. There was about a 77% agreement between the two versions of the Accuscreen device. Agreement between the two Accuscreen devices and the ILO was approximately 70% for the old and 80% for the new. The newer version of Accuscreen seems to perform better than the old, being more consistent with the reference ILO system and with the audiometry profiles of the tested subjects. In order to set robust standards for OAE evaluation and analysis, additional studies comparing different OAE hearing screening systems are needed.

Association between ABO blood group status and cochlear/neural function: auditory brainstem response findings

Background ABO blood group status may be a risk factor for some diseases, including hearing loss. Individuals with blood group O show a higher prevalence of hearing loss after industrial noise exposure. Group O individuals with normal hearing show reduced amplitudes in otoacoustic emission recordings. Whether blood group status affects auditory brainstem responses (ABR), which reflect cochlear hair cell and auditory nerve bioelectric activity, is unclear. Aims/objectives To compare cochlear and peripheral neural function across ABO blood groups by recording cochlear microphonic (CM) and wave I ABR responses. Material and methods Sixty normal-hearing young adults, with 15 participants from each blood group, completed 70 dB nHL click stimulus ABR measures. CM amplitude, wave I amplitude and wave I latency data were obtained for both ears. One-way ANOVA tests compared results across the ABO groups. Results A statistically significant difference for wave I peak-to-peak amplitudes across the four groups was found. Post-hoc comparisons revealed group O had significantly reduced wave I amplitudes compared to group A participants. A consistent trend of reduced CM amplitudes and prolonged wave I latencies was shown in group O participants. Conclusions and significance Emerging evidence exists that ABO blood group status may influence auditory function.

Односторонняя внезапная сенсоневральная тугоухость при COVID-19. Клинические наблюдения и обзор литературы

At the end of 2019, an outbreak of a new coronavirus infection began in China, Wuhan, which is the first pandemic of the 21st century. The International Committee on Taxonomy of Viruses has classified the causative agent of the new disease as SARS-CoV-2, and on February 11, 2020, the World Health Organization (WHO) announced the official name of the infection – COVID-19. According to statistics for August 2021, the number of people infected with SARS-CoV-2 in the world is 216 million, and the number of deaths is 4.5 million. COVID-19 can be asymptomatic or manifest with various clinical manifestations, including neurological and otorhinolaryngological. The article describes 3 clinical cases of unilateral sudden hearing impairment in patients with confirmed COVID-19. The diagnosis of unilateral sensorineural hearing loss was established using acumetry, tone threshold audiometry, acoustic impedance measurement, and recording of otoacoustic emissions. In most cases, COVID-19 is characterized by a certain clinical picture, however, with an asymptomatic and mild course, an atypical manifestation of the disease with the development of sudden sensorineural hearing loss is possible.

Effects of familial Mediterranean fever on the middle ear

ObjectiveTo evaluate middle and inner ear function and hearing status of children with familial Mediterranean fever (FMF). MethodsWe assigned 56 patients with FMF to the study group and 52 healthy volunteers to the control group. The mean age of patients in the study and control groups were 10.10 ± 3.70 and 9.77 ± 3.74 years, respectively. Physical examination and hearing evaluation were performed in both groups. The audiological test battery included 226-Hz tympanometry, pure tone audiometric evaluation, acoustic stapedial reflex measurements, distortion product otoacoustic emission recording, and wide-band tympanometry assessment. ResultsThe groups were similar in age and sex ratio (p > 0.05 for both comparisons). Pure tone audiogram and distortion product otoacoustic emission results were also similar for both groups (p > 0.05). The ipsilateral acoustic stapedial reflex were present in both of the groups and all participants had Type A tympanogram. The contralateral acoustic stapedial reflex thresholds were significantly higher in the familial Mediterranean fever group (p < 0.05 for all comparisons). The ambient and peak pressure absorbance values of wide-band tympanometry were significantly lower at 2000 Hz and significantly higher at 4000 Hz in the familial Mediterranean fever group (p < 0.05 for both comparisons). The severity and duration of disease adversely affected the absorbance values of wide-band tympanometry at 2000 and 4000 Hz (p < 0.05). ConclusionTo our knowledge, this is the first study to demonstrate the adverse subclinical effects of familial Mediterranean fever on the middle ear. We recommend that children diagnosed with FMF should be closely monitored for future clinical middle ear pathologies.

Diagnostic methods for determining auditory function in infants

Objectives - ал overview of the subjective and objective methods of hearing testing in infants that can be used in clinical practice. Results. Both subjective and objective methods of hearing function testing can be used in infants. The most well-known and common in practice tests are: behavioral audiometry, visual reinforcement audiometry, impedancemetry, recording of otoacoustic emissions (OAE) and various classes of auditory evoked potentials. Conclusion. It is necessary to conduct a comprehensive hearing examination, using both subjective and objective research methods, for the accurate detection of the hearing thresholds in infants.

Reciprocal Matched Filtering in the Inner Ear of the African Clawed Frog (Xenopus laevis).

Anurans (frogs and toads) are the most vocal amphibians. In most species, only males produce advertisement calls for defending territories and attracting mates. Female vocalizations are the exceptions among frogs, however in the African clawed frog (Xenopus laevis) both males and females produce distinct vocalizations. The matched filter hypothesis predicts a correspondence between peripheral auditory tuning of receivers and properties of species-specific acoustic signals, but few studies have assessed this relationship between the sexes. Measuring hearing sensitivity with a binaural recording of distortion product otoacoustic emissions, we have found that the ears of the males of this species are tuned to the dominant frequency of the female's calls, whereas the ears of the females are tuned close to the dominant frequency of the male's calls. Our findings provide support for the matched filter hypothesis extended to include male-female calling. This unique example of reciprocal matched filtering ensures that males and females communicate effectively in high levels of background noise, each sex being most sensitive to the frequencies of the other sex's calls.

Hearing of neonates without risk indicators for hearing loss and use of antimalarial drugs during pregnancy: a historical cohort study in the Northern Region of Brazil

IntroductionStudies have demonstrated the ototoxic effects of antimalarial drugs in individuals who receive these drugs, but little is known regarding the toxicity of these drugs in the newborn auditory system when administered to the mother receive the drug during pregnancy. ObjectiveTo verify the incidence of hearing loss in neonates who have no other associated risk indicators, born to mothers treated for malaria during pregnancy. MethodsA retrospective, quantitative cohort study was developed at Hospital de Base Dr. Ary Pinheiro and Clínica Limiar, both located in the municipality of Porto Velho (Rondônia). The sample consisted of 527 newborns divided into two groups: exposed to antimalarials drugs during pregnancy group (n = 32) and non-exposed group (n = 495). Data collection took place from September 2014 to December 2015, through an interview with the mothers and/or guardians of the newborn, through the newborns’ and the mothers’ records, and the neonatal hearing screening database of the above-mentioned institutions. ResultsAll the neonates in the exposed group, assessed through the recording of transient otoacoustic emissions associated with the automated brainstem auditory evoked potential test, underwent neonatal hearing screening in the first examination. Among the newborns in the non-exposed group, 30 showed failure and were retested. Of these, one continued to fail and was referred for diagnosis, in whom the results showed to be within the normal range. Among the neonates of the exposed group, infection with Plasmodium vivax was the most frequent, and was similarly distributed among the gestational trimesters, and chloroquine was the most commonly used antimalarial drug treatment more often given during the third trimester; these findings did not show any influence on the audiological findings of the studied neonates. ConclusionThe present study did not identify any cases of hearing loss in neonates born to mothers who used antimalarial drugs during gestation.

Cervical Vestibular Evoked Myogenic Potential in Children with Auditory Neuropathy Spectrum Disorder of prelingual onset

children with ANSD of pre-lingual onset, and to compare c-VEMP findings to those in children with non- ANSD sensorineural (non -ANSD SNHL) of pre-lingual onset.Methods: The study included 35 children with bilateral ANSD, and 32 children with bilateral non-ANSD SNHL of severe, severe to profound, or profound degree. Both groups of children had the onset SNHL pre-lingually. The study also included 15 control children. Mean age and SD were 6.9 years ± 2.9 for the control children, 7.8 years ± 3.1 for the ANSD children, and 8.8 years ± 3.4 for the non-ANSD children. All participant children were subjected to full history taking, otological examination, hearing assessment, recording for auditory brainstem response and cochlear microphonics, Distortion product otoacoustic emission recording, and c-VEMP recording.Results: Results showed that the vast majority of ANSD children (88% of ears) had intact c-VEMP response. Moreover, there was no statistically significant difference between the ANSD children and control children as regards the VEMP parameters (P1-N1 amplitude, asymmetric ratio, P1 latency, N1 latency, and inter-aural latency differences of P1 and N1). There was no statistically significant difference between ANSD with risk factors and those without risk factors as regards VEMP parameters. Results indicate that the vast majority of ANSD children with pre-lingual onset, even those with risk factors, have normal saccular function along with intact and normally functioning inferior vestibular nerve, and the other central connections responsible for the VEMP response. On the other hand, 53.1% of ears children with non-ANSD SNHL had an absent c-VEMP response, and 46.9% of ears had intact and normal c-VEMP response. The overall results indicate that while the pathology of non-ANSD SNHL involves the saccule in more than half of children, the underlying pathology ANSD spares the saccule and its central connection.Conclusions: Results suggest that the site of lesion in ANSD children of pre-lingual onset is restricted to the auditory system with sparing the vestibular system in the majority of children. These findings support the choice of cochlear implantation as the best line of management in children with ANSD, even in the presence of risk factors. So cochlear implantation in children with ANSD is safer than children with SNHL as there will be no fear of bilateral saccular dysfunction in the case saccular damage occurred in the surgery side as a result of the surgical procedure.

Auditory event-related potentials and function of the medial olivocochlear efferent system in children with auditory processing disorders

Objective: The objectives were to investigate the function of central auditory pathways and of the medial efferent olivocochlear system (MOCS).Design: Event-related potentials (ERP) were recorded following the delivery of the stimulus /da/ in quiet and in ipsilateral, contralateral, and binaural noise conditions and correlated to the results of the auditory processing disorders (APD) diagnostic test battery. MOCS function was investigated by adding ipsilateral, contralateral, and binaural noise to transient evoked otoacoustic emission recordings. Auditory brainstem responses and pure tone audiogram were also evaluated.Study Sample: Nineteen children (7 to 12 years old) with APD were compared with 24 age-matched controls.Results: Otoacoustic emissions and ABR characteristics did not differ between groups, whereas ERP latencies were significantly longer and of higher amplitudes in APD children than in controls, in both quiet and noise conditions. The MOCS suppression was higher in APD children.Conclusions: Findings indicate that children with APD present with neural deficiencies in both challenging and nonchallenging environments with an increase in the timing of several central auditory processes correlated to their behavioural performances. Meanwhile, their modulation of the auditory periphery under noisy conditions differs from control children with higher suppression.

Mouse Panx1 Is Dispensable for Hearing Acquisition and Auditory Function.

Panx1 forms plasma membrane channels in brain and several other organs, including the inner ear. Biophysical properties, activation mechanisms and modulators of Panx1 channels have been characterized in detail, however the impact of Panx1 on auditory function is unclear due to conflicts in published results. To address this issue, hearing performance and cochlear function of the Panx1−/− mouse strain, the first with a reported global ablation of Panx1, were scrutinized. Male and female homozygous (Panx1−/−), hemizygous (Panx1+/−) and their wild type (WT) siblings (Panx1+/+) were used for this study. Successful ablation of Panx1 was confirmed by RT-PCR and Western immunoblotting in the cochlea and brain of Panx1−/− mice. Furthermore, a previously validated Panx1-selective antibody revealed strong immunoreactivity in WT but not in Panx1−/− cochleae. Hearing sensitivity, outer hair cell-based “cochlear amplifier” and cochlear nerve function, analyzed by auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recordings, were normal in Panx1+/− and Panx1−/− mice. In addition, we determined that global deletion of Panx1 impacts neither on connexin expression, nor on gap-junction coupling in the developing organ of Corti. Finally, spontaneous intercellular Ca2+ signal (ICS) activity in organotypic cochlear cultures, which is key to postnatal development of the organ of Corti and essential for hearing acquisition, was not affected by Panx1 ablation. Therefore, our results provide strong evidence that, in mice, Panx1 is dispensable for hearing acquisition and auditory function.

A New Hypothesis on the Frequency Discrimination of the Cochlea.

Medial olivocochlear efferent (MOCE) neurons innervate outer hair cells (OHCs) of the cochlea, which in turn leads to basilar membrane motion. We hypothesized that MOCE-induced alterations in basilar membrane motion, independent of traveling waves, is responsible for the cochlear frequency discrimination of sound. Eleven guinea pigs underwent bilateral otoscopic and audiologic evaluations under general anesthesia. The study comprised two parts. Part I (n=11) included spontaneous otoacoustic emission (SOAE) recordings with or without contralateral pure-tone acoustic stimuli (1 and 8 kHz) at 60 dB sound pressure level (SPL). Part II involved pure-tone (1 or 8 kHz) acoustic trauma in the right ears of two randomly selected subgroups (G1: 1 kHz; n=4 and G8: 8 kHz; n=4). The remaining three animals served as controls. After frequency-specific deafness was confirmed by distortion product otoacoustic emission (DPOAE), SOAEs were recorded in the left ears in the presence of a contralateral pure-tone (1 and 8 kHz) stimulus of 60 dB SPL. Furthermore, the surface of the organ of Corti was examined by scanning electron microscopy (SEM). The contralateral pure tone led to frequency-specific activation in SOAEs in part I (without trauma) and part II (with trauma) measurements. SEM showed heterogeneous OHC damage along the cochlea in traumatized ears with pure tone. We suggest that MOCEs convey acoustic information from traumatized ears to intact ears. Traumatized ears can show frequency-specific activation in the presence of diffuse damage in OHCs that excludes the passive transmission of the pressure wave from the perilymph to the basilar membrane.

Spontaneous otoacoustic emission recordings during contralateral pure-tone activation of medial olivocochlear reflex.

We hypothesized that cochlear frequency discrimination occurs through medial olivocochlear efferent (MOCE)-induced alterations in outer hair cell (OHC) electromotility, which is independent from basilar membrane traveling waves. After obtaining informed consent, volunteers with normal hearing (n = 10; mean age: 20.6±1.2 years) and patients with unilateral deafness (n = 10; mean age: 30.2±17.9 years) or bilateral deafness (n = 8; mean age: 30.7±13.8 years) underwent a complete physical and audiological examination, and audiological tests including transient evoked otoacoustic emission and spontaneous otoacoustic emission (TEOAE and SOAE, respectively). SOAE recordings were performed during contralateral pure-tone stimuli at 1 and 3kHz. SOAE recordings in the presence of contralateral pure-tone stimuli showed frequency-specific activation out of the initial frequency range of SOAE responses. Basilar membrane motion during pure-tone stimulation results from OHC activation by means of MOCE neurons rather than from a traveling wave. Eventually, frequency-specific responses obtained from SOAEs suggested that OHC electromotility may be responsible for frequency discrimination of the cochlea independently from basilar membrane motion.

Auditory neuropathy in a patient with hemochromatosis

ObjectiveTo evaluate the auditory function of an individual with genetically confirmed hemochromatosis. MethodsA 57 year old male with mildly impaired sound detection thresholds underwent a range of behavioural, electroacoustic and electrophysiologic assessments. These included the recording of otoacoustic emissions and auditory brainstem responses, measurement of monaural temporal resolution and evaluation of binaural speech processing. Findings for this patient were subsequently compared with those of 80 healthy controls with similar audiometric thresholds. ResultsThe patient showed the three cardinal features of auditory neuropathy, presenting with evidence of normal cochlear outer hair cell function, disrupted neural activity in the auditory nerve/brainstem and impaired temporal processing. His functional hearing ability (speech perception) was significantly affected and suggested a reduced capacity to use localization cues to segregate signals in the presence of background noise. ConclusionWe present the first case of an individual with hemochromatosis and auditory neuropathy. The findings for this patient highlight the need for careful evaluation of auditory function in individuals with the disorder.

An investigation of hearing impairment in de-novo Parkinson's disease patients: A preliminary study.

To investigate the peripheral auditory pathway in Parkinson's disease (PD) by using objective, quantitative and non-invasive audiological techniques, transient-evoked (TEOAE) and distortion product (DPOAE) otoacoustic emissions, in order to detect subclinical alterations of cochlear functioning and possible changes after dopaminergic stimulation. We enrolled 11 untreated de-novo PD patients and 11 age and sex-matched healthy controls. Subjects underwent a routine audiological evaluation and otoacoustic emission recordings. The patients were then slowly-titrated to a stable dose of 100 mg levodopa four times in a day. A post-treatment assessment was made in order to detect significant changes in audiological responses. Finally, possible associations between clinical data and hearing results were also evaluated. At pure-tone audiometry, higher auditory threshold levels were observed in PD when compared to the controls. Moreover, DPOAE responses in PD patients were found low at almost all tested frequencies, suggesting subclinical cochlear damage. Interestingly, after dopaminergic treatment, a significant increase in DPOAE responses was detected. Notably, DPOAE dysfunction correlated with clinical severity, whereas high hearing thresholds appeared positively related with more prolonged disease duration. Our findings demonstrate that otoacoustic emission recording and pure-tone audiometry reveal levodopa-sensitive cochlear dysfunction and hearing loss in PD. A parallel improvement in subjective motor symptoms and DPOAE objective responses could help clinicians in monitoring therapeutic responses and dynamic changes during the course of the disease.