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

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.

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.

Peripheral hearing in Parkinson's disease: a systematic review

OBJECTIVE

To investigate the implications of Parkinson's disease (PD) in the peripheral auditory system, a systematic survey of the scientific literature was conducted.

DESIGN

Systematic review.

STUDY SAMPLE

An electronic search of the non-gray literature in the last decade was conducted using the digital databases MEDLINE® (PubMed interface), LILACS® (Virtual Health Library), Web of Science® (CAPES publications portal), and SciELO®. Studies addressing peripheral auditory function as part of the range of nonmotor PD symptoms were selected for analysis.

RESULTS

Pure tone audiometry data suggested that sensorineural hearing loss was more severe in the PD population than in the control groups. The effects of PD on cochlear function were evidenced by a decrease in the levels of otoacoustic emissions.

CONCLUSIONS

Sensorineural hearing loss and cochlear impairment are more severe in the PD population than in the control groups. Additional studies are recommended to further understand the characteristics of the peripheral auditory system in PD patients, which constitutes an emerging subject in the scientific literature.

Neuroinflammatory disorders of the brain and inner ear: a systematic review of auditory function in patients with migraine, multiple sclerosis, and neurodegeneration to support the idea of an innovative 'window of discovery'

Background

Hearing can be impaired in many neurological conditions and can even represent a forme fruste of specific disorders. Auditory function can be measured by either subjective or objective tests. Objective tests are more useful in identifying which auditory pathway (superior or inferior) is most affected by disease. The inner ear's perilymphatic fluid communicates with the cerebrospinal fluid (CSF) via the cochlear aqueduct representing a window from which pathological changes in the contents of the CSF due to brain inflammation could, therefore, spread to and cause inflammation in the inner ear, damaging inner hair cells and leading to hearing impairment identifiable on tests of auditory function.

Methods

A systematic review of the literature was performed, searching for papers with case-control studies that analyzed the hearing and migraine function in patients with neuro-inflammatory, neurodegenerative disorders. With data extracted from these papers, the risk of patients with neurological distortion product otoacoustic emission (DPOAE) was then calculated.

Results

Patients with neurological disorders (headache, Parkinson's disease, and multiple sclerosis) had a higher risk of having peripheral auditory deficits when compared to healthy individuals.

Conclusion

Existing data lend credence to the hypothesis that inflammatory mediators transmitted via fluid exchange across this communication window, thereby represents a key pathobiological mechanism capable of culminating in hearing disturbances associated with neuroimmunological and neuroinflammatory disorders of the nervous system.

Listening with an Ageing Brain - a Cognitive Challenge

Hearing impairment has been recently identified as a major modifiable risk factor for cognitive decline in later life and has been becoming of increasing scientific interest. Sensory and cognitive decline are connected by complex bottom-up and top-down processes, a sharp distinction between sensation, perception, and cognition is impossible. This review provides a comprehensive overview on the effects of healthy and pathological aging on auditory as well as cognitive functioning on speech perception and comprehension, as well as specific auditory deficits in the 2 most common neurodegenerative diseases in old age: Alzheimer disease and Parkinson syndrome. Hypotheses linking hearing loss to cognitive decline are discussed, and current knowledge on the effect of hearing rehabilitation on cognitive functioning is presented. This article provides an overview of the complex relationship between hearing and cognition in old age.

Hearing Loss in Neurological Disorders

Sensorineural hearing loss (SNHL) affects approximately 466 million people worldwide, which is projected to reach 900 million by 2050. Its histological characteristics are lesions in cochlear hair cells, supporting cells, and auditory nerve endings. Neurological disorders cover a wide range of diseases affecting the nervous system, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), autism spectrum disorder (ASD), etc. Many studies have revealed that neurological disorders manifest with hearing loss, in addition to typical nervous symptoms. The prevalence, manifestations, and neuropathological mechanisms underlying vary among different diseases. In this review, we discuss the relevant literature, from clinical trials to research mice models, to provide an overview of auditory dysfunctions in the most common neurological disorders, particularly those associated with hearing loss, and to explain their underlying pathological and molecular mechanisms.