Hearing dysfunction heralds an increase in non-motor burden and a worse quality of life in Parkinson's disease: new insights from non-motor spectrum.

BACKGROUND: Sensorial non-motor symptoms (NMSs) in Parkinson's disease (PD) still lack appropriate investigation in clinical practice. This study aimed to assess if and to what extent auditory dysfunction is associated with other NMSs in PD and its impact on patient's quality of life (QoL). METHODS: We selected patients with idiopathic PD, without other concomitant neurological diseases, dementia, or diagnosis of any audiological/vestibular disease. Demographic and clinical data were collected. Patients underwent otoscopic examination, audiological testing with pure tone audiometry (PTA) and distortion product otoacoustic emissions (DPOAEs) and completed Non-Motor Symptoms Scale (NMSS) and Parkinson's Disease Questionnaires-39 (PDQ-39). ANCOVA and partial correlation analysis have been used for statistical analysis. RESULTS: 60 patients were enrolled and completed PTA and DPOAEs. 32 patients with hearing impairment (HI), assessed by PTA, (hearing threshold ≥ 25 dB) showed similar disease duration, motor impairment, and staging, compared to patients without HI, but higher scores both in NMSS and in PDQ-39, except for cardiovascular (CV), gastrointestinal (GI), urogenital (U) and sexual function (SF) of NMSS. In addition, DPOAEs showed a significant correlation with higher scores both in NMSS and PDQ-39, except for CV, SF, GI, U and perceptual problem subdomains of NMSS. CONCLUSION: This study demonstrated that PD patients with HI have a greater burden of NMS and lower related QoL and functioning. Our results highlight the importance to reconsider HI as a NMS, in parallel with the others. HI evaluation, even in asymptomatic patients, may reveal a wider pathology with a worse QoL.

Maternal exposure to zinc oxide nanoparticles causes cochlear dysfunction in the offspring.

Introduction: Zinc oxide nanoparticles (ZnO NPs) have been engineered and are largely used in material science and industry. This large and increasing use justifies a careful study about the toxicity of this material for human subjects. The concerns regard also the reproductive toxicity and the fetotoxicity. Materials and methods: The effect of the exposure to ZnO NPs on the cochlear function was studied in a group of pregnant CD1 mice and in their offspring. This study is part of a larger toxicological study about the toxicity of ZnO NPs during pregnancy. Four groups were analyzed and compared, exposed and non-exposed dams and their offspring. The cochlear function was quantitatively assessed by means of Distortion Product Otoacoustic Emissions (DPOAEs). Results and discussion: A large statistically significant difference was found between the non-exposed dams offspring and the exposed dams offspring (p = 1.6 · 10-3), whose DPOAE levels were significantly lower than those of non-exposed dams offspring and comparable to those of the adults. The DPOAE levels of the exposed and non-exposed dams were very low and not significantly different. This occurrence is related to the fact that these mice encounter a rapid aging process. Conclusion: Our findings show that maternal exposure to ZnO NPs does not reflect in overt toxicity on fetal development nor impair offspring birth, however it may damage the nervous tissue of the inner ear in the offspring. Other studies should confirm this result and identify the mechanisms through which ZnO NPs may affect ear development.

Enhanced suppression of otoacoustic emissions by contralateral stimulation in Parkinson's disease.

Dopamine depletion affects several aspects of hearing function. Previous work [Wu, Yi, Manca, Javaid, Lauer, and Glowatzki, eLife 9, e52419 (2020)] demonstrated the role of dopamine in reducing the firing rates of inner ear cells, which is thought to decrease synaptic excitotoxicity. Thus, a lack of dopamine could indirectly increase acoustic stimulation of medial olivocochlear efferents. To investigate that, here we studied contralateral suppression of distortion product otoacoustic emissions in a population of Parkinsonian patients, compared to an age-matched control group, both audiometrically tested. To rule out activation of the acoustic reflex, middle ear impedance was monitored during testing. The results show significantly stronger contralateral suppression in the patient group.

Auditory function in humans at high altitude. A scoping review.

PURPOSE: High-altitude (HA) affects sensory organ response, but its effects on the inner ear are not fully understood. The present scoping review aimed to collect the available evidence about HA effects on the inner ear with focus on auditory function. METHODS: The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews. PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, which quantified in healthy subjects the effects of HA on auditory function. RESULTS: The systematic search identified 17 studies on a total population of 888 subjects (88.7% male, age: 27.8 ± 4.1 years; median sample size of 15 subjects). Nine studies were conducted in a simulated environment and eight during real expeditions at HA. To quantify auditory function, six studies performed pure tone audiometry, four studies measured otoacoustic emissions (OAE) and eight studies measured auditory evoked responses (AER). Study protocols presented heterogeneity in the spatio-temporal patterns of HA exposure, with highly varying maximal altitudes and exposure durations. CONCLUSION: Most studies reported a reduction of auditory function with HA in terms of either elevation of auditory thresholds, lengthening of AER latencies, reduction of distortion-product and transient-evoked OAEs. Future studies in larger populations, using standardized protocols and multi-technique auditory function evaluation, are needed to further characterize the spatio-temporal pattern of HA effects along the auditory pathways and clarify the pathophysiological implications and reversibility of the observed changes.

Association between hearing sensitivity and dopamine transporter availability in Parkinson's disease.

In a previous study, we observed: (i) significant hearing function impairment, assessed with pure tone audiometry and distortion product otoacoustic emissions, in patients with Parkinson's disease, compared with a matched control group, and (ii) lateralization of the hearing dysfunction, worse on the side affected by more pronounced Parkinson's disease motor symptoms. This study investigates the association between the basal ganglia dopamine transporter availability and the hearing function in Parkinson's disease patients, focusing also on the lateralization of both dysfunctions, with respect to that of the motor symptoms, and introducing a further distinction between patients with left-sided and right-sided predominant motor symptoms. Patients with right-handed Parkinson's disease with a recent estimation of 123I-FP-CIT striatal uptake were audiologically tested with pure tone audiometry and distortion product otoacoustic emissions. Thirty-nine patients were included in the study. A statistically significant association was found, in the left-side predominant group only, between the distortion product otoacoustic emission levels and the contralateral dopamine transporter availability, and between the hearing threshold and the dopamine transporter availability difference between the ipsi- and the contralateral sides. The hearing impairment lateralization correlated to the motor symptom asymmetry was found significant only in the left-side predominant patients. The association between hearing function and basal ganglia dopamine transporter availability supports the hypothesis that the peripheral hearing function decline associated with dopamine depletion is involved in Parkinson's disease development, with a significant difference between patients with left- and right-sided predominant motor symptoms. These findings also suggest that peripheral hearing function evaluation and its lateralization could be key elements for subtyping the disease.

Effects of vestibular rehabilitation on body composition and daily-living physical activity in chronic unilateral vestibular hypofunction.

BACKGROUND: Unilateral vestibular hypofunction (UVH) may lead to modifications on metabolism and body composition. Vestibular rehabilitation (VR) demonstrated its effectiveness in ameliorating balance function and several other daily-living aspects. OBJECTIVES: The aim of this study was to evaluate metabolic composition, by means of bioelectrical impedance analysis (BIA) and daily activity, with the use of a wrist-worn movement tracker, in UVH participants before and after VR, and to compare data with a healthy control group (CG) of adults. METHODS: 46 UVH and 60 CG participants underwent otoneurological testing, self-report and performance questionnaires, BIA, and wore a device tracking daily movement and energy expenditure for one full day; this was performed before and after VR. RESULTS: UVH participants demonstrated a significant (p = 0.008) increase in muscle mass after VR, and, when compared to CG, no differences were present with respect to visceral fat and muscle mass. UVH adults reported a significant increase in energy expenditure spent in movement (p = 0.008) and during the day (p = 0.009), daily number of strides (p = 0.009) and calories spent in sweeping (p = 0.009) and stairing (p = 0.008). CONCLUSIONS: Results from this study show that VR provided an improvement of metabolic function and body composition of people with UVH, possibly by contrasting structural modifications in neural pathways stemming from the vestibular nuclei and connected to autonomous function.

Early Noise-Induced Hearing Loss Accelerates Presbycusis Altering Aging Processes in the Cochlea.

Several studies identified hearing loss as a risk factor for aging-related processes, including neurodegenerative diseases, as dementia and age-related hearing loss (ARHL). Although the association between hearing impairment in midlife and ARHL has been widely documented by epidemiological and experimental studies, the molecular mechanisms underlying this association are not fully understood. In this study, we used an established animal model of ARHL (C57BL/6 mice) to evaluate if early noise-induced hearing loss (NIHL) could affect the onset or progression of age-related cochlear dysfunction. We found that hearing loss can exacerbate ARHL, damaging sensory-neural cochlear epithelium and causing synaptopathy. Moreover, we studied common pathological markers shared between hearing loss and ARHL, demonstrating that noise exposure can worsen/accelerate redox status imbalance [increase of reactive oxygen species (ROS) production, lipid peroxidation, and dysregulation of endogenous antioxidant response] and vascular dysfunction [increased expression of hypoxia-inducible factor-1alpha (HIF-1α) and vascular endothelial growth factor C (VEGFC)] in the cochlea. Unveiling the molecular mechanisms underlying the link between hearing loss and aging processes could be valuable to identify effective therapeutic strategies to limit the effect of environmental risk factors on age-related diseases.

Onset and resolution failure of recurrent benign paroxysmal positional vertigo: the role of cervical range of motion.

PURPOSE: To explore possible associations between cervical spine mobility, measured by cervical range of motion (CROM) and a possible earlier onset of recurrent benign paroxysmal positional vertigo (BPPV), as well as an increased failure rate of canalith repositioning procedures. METHODS: Medical records of 749 patients (247, 253 and 249 patients with a CROM ≤ 45°, between 45.1° and 55° and > 55.1°, respectively) with a first-time diagnosis of non-traumatic BPPV were included in this retrospective study. Age, gender, canal involvement and CROM values were treated as prospective prognostic factors for time of BPPV recurrence onset (RO) and number of manoeuvres needed to achieve resolution (resolution rate, RR). A multiple regression analysis was performed. RESULTS: A significant increase in the incidence of recurrent BPPV was found in patients with reduced CROM (139 [56.27%;], 102 [40.31%] and 87 [34.93%], respectively, belonging to ≤ 45°, 45.1°-55° and > 55.1° subgroups; X2 = 9.42, p = 0.008). A strong association between age, CROM and recurrent BPPV RO and RR was demonstrated, respectively (multiple correlation coefficients = 0.492678 and 0.593493, respectively, p value < 10-4). Canal involvement was in line with the previous experiences. CONCLUSION: The results from this retrospective analysis unveiled the previously unexplored relation between reduction in cervical spine mobility and BPPV recurrence and treatment failure. The data from this study do not indicate the mechanisms by which this comorbidity might directly cause recurrent BPPV. However, they may suggest CROM to be evaluated, in association with other known risk factors for increased susceptibility to BPPV recurrence.

Temporomandibular disorders and cervicogenic dizziness: Relations between cervical range of motion and clinical parameters.

OBJECTIVE: To analyze the cervical range of motion (CROM) and clinical parameters in patients affected by myogenous temporomandibular disorders (TMD), cervicogenic dizziness (CGD), both TMD and CGD (TMD/CGD), and a group of healthy subjects (HS). METHODS: CROM degrees, Dizziness Handicap Inventory (DHI), Tampa Scale for Kinesiophobia (TSK-17), Hospital Anxiety and Depression Scale (HADS), and Jaw Functional Limitation Scale 20 (JFLS-20) scores were compared between 46 TMD patients, 49 CGD subjects, 43 TMD/CGD patients, and 98 HS. RESULTS: TMD/CGD and CGD patients demonstrated significantly lower CROM degrees and higher DHI, TSK-17, and HADS values when compared to TMD patients. TMD/CGD and TMD patients demonstrated higher JFLS-20 values when compared to CGD and HS. Significant negative correlations were found in TMD/CGD and TMD patients between JFLS-20 and CROM in flexion and extension. DISCUSSION: Present findings demonstrated a relation between spine movement impairment and TMD.

Changes in daily energy expenditure and movement behavior in unilateral vestibular hypofunction: Relationships with neuro-otological parameters.

The vestibular system has been found to affect energy homeostasis and body composition, due to its extensive connections to the brainstem and melanocortin nuclei involved in regulating the metabolism and feeding behavior. The aim of this study was to evaluate - by means of a wrist-worn physical activity tracker and bioelectrical impedance analysis (BIA) - the energy expenditure (EE) in resting (REE) and free-living conditions and movement behavior in a group of chronic unilateral vestibular hypofunction (UVH) patients when compared with a control group (CG) of healthy participants. Forty-six chronic UVH and 60 CG participants underwent otoneurological (including video-Head Impulse Test [vHIT] for studying vestibulo-ocular reflex [VOR] and static posturography testing [SPT]), and EE and movement measurements and self-report (SRM) andperformance measures (PM). As well as significant (p < 0.001) changes in SPT variables (area and path length) and SRM/PM, UVH participants also demonstrated significantly (p < 0.001) lower values in REE, movement EE, hours/day spent upright, number of strides and distance covered and total daily EE (p = 0.007) compared to the CG. UVH patients consumed significantly lower Kcal/min in sweeping (p = 0.001) and walking upstairs and downstairs (p < 0.001) compared to the CG. Multiple correlations were found between free-living and resting EE and neuro-otological parameters in UVH participants. Since the melanocortin system could be affected along the central vestibular pathways as a consequence of chronic vestibular deafferentation, data collected by reliable wearables could reflect the phenomena that constitute an increased risk of falls and sedentary lifestyle for patients affected by UVH, and could improve rehabilitation stages.

Sleep Performance and Chronotype Behavior in Unilateral Vestibular Hypofunction.

OBJECTIVE: To evaluate sleep behavior and its relation to otoneurological parameters in a group of patients with chronic unilateral vestibular hypofunction (UVH) without self-reported sleep disturbances when compared with healthy subjects serving as a control group (CG). METHODS: Fifty-one patients affected by UVH underwent a retrospective clinical and instrumental otoneurological examination, a 1-week actigraphy sleep analysis, and a series of self-report and performance measures (SRM/PM). A CG of 60 gender- and age-matched healthy subjects was also enrolled. A between-group analysis of variance was performed for each variable, while correlation analysis was performed in UVH patients between otoneurological, SRM/PM, and actigraphy measure scores. RESULTS: When compared with CG subjects, UVH patients were found to be spending less time sleeping and taking more time to go from being fully awake to asleep, based on actigraphy-based sleep analysis. Also, SRM/PM depicted UVH patients to have poor sleep quality and to be more prone to an evening-type behavior. Correlations were found between vestibular-related functionality indexes and subjective sleep quality, as well as between longer disease duration and reduced sleep time. CONCLUSION: For the first time, a multiparametric sleep analysis was performed on a large population-based sample of chronic UVH patients. While a different pattern in sleep behavior was found, the cause is still unclear. Further research is needed to expand the extent of knowledge about sleep disruption in vestibular disorders. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:2341-2347, 2021.

Usefulness of postural sway spectral analysis in the diagnostic route and clinical integration of cervicogenic and vestibular sources of dizziness: A cross-sectional preliminary study.

BACKGROUND: Posturography power spectra (PS) implementation has been proven to discriminate between sensory inputs detriment of vestibular and proprioceptive origin. OBJECTIVE: To deepen the role of posturography testing in the diagnostic route of dizzy conditions, by comparing two groups of patients -93 affected by cervicogenic dizziness (CGD) and 72 by unilateral vestibular hypofunction (UVH) -with a group of 98 age- and gender-matched healthy subjects, serving as control group (CON). METHODS: All participants underwent otoneurological testing including video head impulse test (vHIT) and posturography testing with PS analysis. They also filled in Dizziness Handicap Inventory (DHI), Tampa Scale for Kinesiophobia and Hospital Anxiety and Depression Scale questionnaires. RESULTS: UVH and CGD patients were found to have significant increase in vestibular- and proprioceptive-related PS values when compared with CON. Receiver operating characteristic curves found PS values to reliably discriminate both groups from CON. Positive and negative correlations were respectively found between vestibular-/proprioceptive-related PS domain and DHI in both groups and between PS and vHIT scores in UVH patients. CONCLUSIONS: PS analysis demonstrated to be useful in differentiating CGD and UVH patients each other and when compared to CON, to objectively represent perceived symptoms filled along the DHI scale and to corroborate the rate of vestibular deficit in UVH patients.

Postural and clinical outcomes of sustained natural apophyseal glides treatment in cervicogenic dizziness patients: A randomised controlled trial.

OBJECTIVE: To evaluate how self-report and posturographic measures could be affected in patients with cervicogenic dizziness undergoing sustained natural apophyseal glides. DESIGN: Randomised controlled single-blind study. SETTING: Tertiary rehabilitation centre. SUBJECTS: Patients affected by cervicogenic dizziness, diagnosed by applying accepted criteria. Forty-one patients (19 male, 22 female: mean age 44.3 ± 14.8 years) receiving treatment, and 39 patients (18 male, 21 female: mean age 43.8 ± 13.9 years) receiving placebo were included in the study. INTERVENTIONS: The treatment group underwent sustained natural apophyseal glides, while the placebo was constituted by a detuned laser. Both groups received their interventions six times over 4 weeks. MAIN MEASURES: Outcomes were tested by means of self-report measures such as perceived dizziness, neck disability, anxiety and depression. Also, cervical range of motion and posturography testing with power spectra frequency were analysed. RESULTS: When compared to placebo, treated patients demonstrated a significant decrease in perceived dizziness (post-treatment total Dizziness Handicap Inventory score 20.5 ± 5.3 as compared to 26.2 ± 6 baseline), neck disability and pain (Neck Disability Index and Neck Pain Index post-treatment scores 12.5 ± 4.3 and 45.6 ± 15.1, respectively, as compared to baseline scores of 15.1 ± 4.8 and 62.5 ± 14.3), as well as significant improvement in cervical range of motion and some posturographic parameters. CONCLUSION: Sustained natural apophyseal glides may represent a useful intervention in reaching short-term beneficial effects in patients with cervicogenic dizziness, with respect to self-perceived symptoms, proprioceptive integration and cervical range of motion improvement.

Changes in body composition in unilateral vestibular hypofunction: relationships between bioelectrical impedance analysis and neuro-otological parameters.

PURPOSE: Experimental works have indicated the potential of the vestibular system to affect body composition to be mediated by its extensive connections to brainstem nuclei involved in regulating metabolism and feeding behavior. The aim of this study was to evaluate-by means of bioelectrical impedance analysis (BIA)-the body composition in a group of chronic UVH normal-weighted patients when compared with an equally balanced group of healthy participants, serving as a control group (CG). METHODS: Forty-six chronic UVH and 60 CG participants underwent otoneurological (including video Head Impulse Test [vHIT] and static posturography testing [SPT]), BIA measurements and self-report (SRM) and performance measures (PM). RESULTS: Beyond significant (p < 0.001) changes in SPT variables (surface and length) and SRM/PM (including Dizziness Handicap Inventory, Dynamic Gait Index and Activity Balance Confidence scales), UVH participants demonstrated significant (p < 0.001) higher values of fat mass and visceral fat and lower values of muscle mass (p = 0.004), when compared to CG. Significant correlations were found in UVH participants between otoneurological and BIA measurements. CONCLUSION: These study findings represent the first clinical in-field attempt at depicting, with the use of BIA parameters, changes in body composition related to chronic UVH. Since such alterations in metabolic parameters could be considered both the consequences and/or the cause of vestibular-related quality of life deficit, BIA parameters could be considered as cheap, easy to use, noninvasive assessments in case of chronic UVH.

Combination of in-situ collagen injection and rehabilitative treatment in long-lasting facial nerve palsy: a pilot randomized controlled trial.

BACKGROUND: Many rehabilitative attempts have been made to prevent or reduce residual deficits in patients with established and long-term facial palsy (FP). In many clinical settings in-situ injection of collagen-based medical devices have been demonstrated to provide nutritional support for tissues. AIM: To test the effectiveness of a collagen-based treatment for patients complaining of long standing FP, who are following a proprioceptive neuromuscular facilitation protocol (Kabat method) (group A), compared to a FP group only undergoing the Kabat method (group B). DESIGN: Randomised controlled trial. SETTING: Tertiary referral outpatient center and University Hospital. POPULATION: Forty-one patients with a medical diagnosis of long-term unilateral peripheral FP. METHODS: Twenty-one Group A patients were compared, after randomization, to nineteen matched group B patients after 8 weeks of treatment. The outcomes were electromyographic findings, validated questionnaires (Facial Disability Index, FDI and General health-related quality of life assessment, QOL) and clinical grading (House-Brackmann, HB, and synkinesis grading scale). A correlation analysis was performed between pre-/post-treatment differences (Δ) in outcome and clinical-demographic measures. RESULTS: A significant within-subjects improvement, both in electrophysiological and questionnaire scores, was found in both groups. When compared with group B, group A patients exhibited a significant reduction of post-treatment polyphasic potentials of voluntary activity of orbicularis oculi (P=0.017) and oris (P=0.015) and a significant increase in post-treatment duration of voluntary activity of orbicularis oris (P=0.018). Group A subjects demonstrated a significant improvement in questionnaire subscales regarding overall disease perception. Although positive correlations between the ∆FDI and ∆percentage of polyphasic potentials of voluntary activity were found in both groups, negative correlations in group A were found between disease duration and ∆duration of voluntary activity of orbicularis oculi and oris. CONCLUSIONS: The combination of physical rehabilitative procedures with in-situ collagen injections, possibly acting in redirecting the phenomena of reinnervation/reorganization, demonstrated encouraging results in patients affected by long term FP. CLNICAL REHABILITATION IMPACT: In-situ collagen injection could be a safe option enlarging the 'window of opportunity' to improve the voluntary muscle contraction pattern and general and specific disability referred by patients affected by long standing FP.

Diagnostic route of cervicogenic dizziness: usefulness of posturography, objective and subjective testing implementation and their correlation.

PURPOSE: To evaluate posturography measurements, and their association with other clinical tests used for cervicogenic dizziness diagnosis, in a cohort of subjects suffering from cervicogenic dizziness, compared with healthy subjects. MATERIALS AND METHODS: Ninety-three cervicogenic dizziness patients and 98 age- and gender-matched healthy subjects underwent video-Head impulse test, posturography testing, evaluation of cervical spine movements by means of cervical range of motion goniometer and self-report and performance measures, including Dizziness Handicap Inventory, Neck Disability Index, Neck Pain Intensity, Tampa Scale for Kinesiophobia and Hospital Anxiety and Depression Scale. RESULTS: Cervicogenic dizziness patients demonstrated significant increases in classical posturography parameters (i.e., surface and length) and in power spectra values within middle and high-frequency interval depicting balance control alterations especially due to proprioceptive integration changes. Furthermore, decreases in degrees of cervical range of motion and increases of self-report and performance measures - highlighting significant complaints of subjective feeling of dizziness - were found in these patients when compared with healthy subjects. Multiple correlations were found between posturography testing and cervical range of motion and Dizziness Handicap Inventory as well as between different self-report and performance measures in cervicogenic dizziness patients. CONCLUSIONS: The implementation of posturography - including power spectra analysis - coupled with appropriate exclusion of other disorders, may represent a useful tool in improving cervicogenic dizziness assessment in terms of cost, time consumption and correlation with other measurements.Implications for rehabilitationUncertainties in diagnostic assessment of cervicogenic dizziness reflect doubts regarding the causes underpinning the symptoms of imbalance, unsteadiness, and disorientation.Posturography measurement is a low-cost, time-sparing technique and its implementations have proven to be useful in detecting significant alterations in body sway during perturbating situations.Implementation of power spectra analysis on posturography testing may represent a useful tool in improving cervicogenic dizziness assessment also in terms of rehabilitative treatment follow-up.

Lateralization of cochlear dysfunction as a specific biomarker of Parkinson's disease.

In the last decade, animal studies highlighted the sensitivity of hearing function to lack of specific cochlear dopamine receptors, while several studies on humans reported association between hearing loss and Parkinson's disease, partially recovered after levodopa administration in de novo patients. Taken together, these observations suggest investigating the possible use of cochlear function outcome variables, particularly, otoacoustic emissions, as sensitive biomarkers of Parkinson's disease. Any lateralization of hearing dysfunction correlated with Parkinson's disease lateralization would (i) further confirm their association and (ii) provide a disease-specific differential outcome variable. Differential indicators are particularly useful for diagnostic purposes, because their effectiveness is not limited by physiological inter-subject fluctuations of the outcome variable. Recent advances in the acquisition and analysis techniques of otoacoustic emissions suggest using them for evaluating differential cochlear damage in the two ears. In this study, we quantitatively evaluated hearing function in a population of subjects with Parkinson's disease, to investigate the occurrence of hearing loss, and, particularly, whether hearing dysfunction shows lateralization correlated with motor symptoms. Pure tone audiometry and distortion product otoacoustic emissions were used as outcome variables in 80 patients (mean age 65 ± 9 years) and 41 controls (mean age 64 ± 10 years). An advanced customized acquisition and analysis system was developed and used for otoacoustic testing, which guarantees response stability independent of probe insertion depth, and has the sensitivity necessary to accurately assess the low levels of otoacoustic response typical of elderly subjects. To our knowledge, this is the first study introducing the distinction between ipsilateral and contralateral ear, with respect to the body side more affected by Parkinson's disease motor symptoms. Significant asymmetry was found in the auditory function, as both otoacoustic responses and audiometric hearing levels were worse in the ipsilateral ear. Significantly worse hearing function was also observed in patients with Parkinson's disease compared to controls, confirming previous studies. Several pathophysiological mechanisms may be hypothesized to explain asymmetric cochlear damage in Parkinson's disease, including the impairment of dopamine release and the involvement of extra-dopaminergic circuits, with the cholinergic pathway as a likely candidate. The observed asymmetry in the audiological response of patients with Parkinson's disease suggests that lateralization of hearing dysfunction could represent a specific non-motor signature of the disease. The possible diagnostic use of cochlear dysfunction asymmetry as a specific biomarker of Parkinson's disease deserves further investigation, needing a more precise quantitative assessment, which would require a larger sample size.