A Retrospective Study of the Effects of Traumatic Brain Injury on Auditory Function: From a Clinical Perspective

Purpose: The main purpose of this retrospective study was to identify auditory dysfunctions related to traumatic brain injury (TBI) in individuals evaluated in an Audiology clinic. Method: Peripheral and central auditory evaluations were performed from March 2014 to June 2018 in 26 patients (14 males) with TBI. The age of the participants ranged from 9 to 59 years old (34.24 ± 15.21). Six participants had blast-related TBI and 20 had blunt force TBI. Sixteen experienced a single TBI event whereas ten experienced several. Correlation analyses were performed to verify the relationship, if any, between the number of auditory tests failed and the number, type, and severity of TBIs. Result: All participants failed at least one auditory test. Nearly 60% had abnormal results on degraded speech tests (compressed and echoed, filtered or in background noise) and 25% had a high frequency hearing loss. There was no statistically significant correlation between the number of auditory tests failed and the number, type, and severity of TBIs. Conclusion: Results indicated negative and heterogenous effects of TBI on peripheral and central auditory function and highlighted the need for a more extensive auditory assessment in individuals with TBI.

Peripheral Auditory Function in Young HIV-Positive Adults With Clinically Normal Hearing

Objective Little is known about peripheral auditory function in young adults with HIV, who might be expected to show early evidence of hearing loss if HIV infection or treatment does affect peripheral function. The goal of this study was to compare peripheral auditory function in 2 age- and gender-matched groups of young adults with clinically normal hearing with and without HIV. Study Design Matched cohort study with repeated measures. Setting Infectious disease center in Dar es Salaam, Tanzania. Methods Participants included HIV-positive (n = 38) and HIV-negative (n = 38) adults aged 20 to 30 years who had clinically normal hearing, defined as type A tympanograms, air conduction thresholds ≤25 dB HL bilaterally from 0.5 to 8 kHz, and distortion product otoacoustic emissions (DPOAEs) >6 dB above the noise floor bilaterally from 1.5 to 8 kHz. Participants were tested multiple times over 6-month intervals (average, 2.7 sessions/participant) for a total of 208 observations. Primary outcome measures included tympanograms, air conduction audiograms, DPOAEs, and click-evoked auditory brainstem responses. Results HIV groups did not significantly differ in age, static immittance, or air conduction thresholds. HIV-positive status was independently associated with approximately 3.7-dB lower DPOAE amplitudes from 2 to 8 kHz (95% CI, 1.01-6.82) in both ears and 0.04-µV lower (95% CI, 0.003-0.076) auditory brainstem response wave I amplitudes in the right ear. Conclusion Young adults living with HIV have slightly but reliably smaller DPOAEs and auditory brainstem response wave I amplitudes than matched HIV-negative controls. The magnitude of these differences is small, but these results support measuring peripheral auditory function in HIV-positive individuals as they age.

Intimate Listening

Space and proximity are entangled in the idea of listening. First, I set up the relationship between intimacy and listening through Jean-Luc Nancy. Second, I consider highlights of nineteenth-century discoveries in the history of physiology and functional anatomy of the cochlea and the labyrinth of the inner ear, those spaces and chambers whose non-auditory function was determined only through painstaking experimentation. This leads to Michel Serres’ consideration of the interior and exterior noise of the body, including a proprioceptive hearing of intimate personal sounds through skin, bone, feet, and muscle, a bodily interior that resonates like boxes (boîtes). Third, I apply this shared intimacy of listening to a few examples of sound art that explore resonances across sensory modalities and bodily spaces, including the work of Jacob Kirkegaard, who employs the phenomenon of otoacoustic emission (OAE), and Adam Basanta.

Dual expression of Atoh1 and Ikzf2 promotes transformation of adult cochlear supporting cells into outer hair cells

Mammalian cochlear outer hair cells (OHCs) are essential for hearing. Severe hearing impairment follows OHC degeneration. Previous attempts at regenerating new OHCs from cochlear supporting cells (SCs) have been unsuccessful, notably lacking expression of the key OHC motor protein, Prestin. Thus, regeneration of Prestin+ OHCs represents a barrier to restore auditory function in vivo. Here, we reported the successful in vivo conversion of adult mouse cochlear SCs into Prestin+ OHC-like cells through the concurrent induction of two key transcriptional factors known to be necessary for OHC development: Atoh1 and Ikzf2. Single-cell RNA sequencing revealed the upregulation of 729 OHC genes and downregulation of 331 SC genes in OHC-like cells. The resulting differentiation status of these OHC-like cells was much more advanced than previously achieved. This study thus established an efficient approach to induce the regeneration of Prestin+ OHCs, paving the way for in vivo cochlear repair via SC transdifferentiation.

Sympathetic Nervous System Regulation of Auditory Function

<b><i>Background:</i></b> The auditory system processes how we hear and understand sounds within the environment. It comprises both peripheral and central structures. Sympathetic nervous system projections are present throughout the auditory system. The function of sympathetic fibers in the cochlea has not been studied extensively due to the limited number of direct projections in the auditory system. Nevertheless, research on adrenergic and noradrenergic regulation of the cochlea and central auditory system is growing. With the rapid development of neuroscience, auditory central regulation is an extant topic of focus in research on hearing. <b><i>Summary:</i></b> As such, understanding sympathetic nervous system regulation of auditory function is a growing topic of interest. Herein, we review the distribution and putative physiological and pathological roles of sympathetic nervous system projections in hearing. <b><i>Key Messages:</i></b> In the peripheral auditory system, the sympathetic nervous system regulates cochlear blood flow, modulates cochlear efferent fibers, affects hair cells, and influences the habenula region. In central auditory pathways, norepinephrine is essential for plasticity in the auditory cortex and affects auditory cortex activity. In pathological states, the sympathetic nervous system is associated with many hearing disorders. The mechanisms and pathways of sympathetic nervous system modulation of auditory function is still valuable for us to research and discuss.

Thalamocortical Connection Changes with Recovery of Impaired Consciousness in a Stroke Patient with Parietal Lobe Injury

A 52-year-old female patient underwent craniectomy and hematoma removal for a spontaneous intracerebral hemorrhage in the left parietal lobe, as well as intraventricular and subarachnoid hemorrhages (Fig. 1-A). Brain magnetic resonance images obtained three months after onset showed leukomalactic lesions in the left parieto-occipital lobes (Fig. 1-A). Initially, the patient was in a vegetative state with a Coma Recovery Scale-revised score of 11 (auditory function: 2, visual function: 4, motor function: 2, verbal function: 1, communication: 0, and arousal: 2) (1). Subsequently, she underwent comprehensive rehabilitation, which included neurotropic drug treatments (armodafinil, pramipexole, amantadine, levodopa, and baclofen) and physical and occupational therapies (including tilt table standing). In addition, transcranial direct current stimulation was administered by using a neuroConn DC-stimulator. The anode was placed on the left parietal lobe (centered on the supraparietal lobule) and the cathode was placed on the opposite supraorbital region. The transcranial direct current stimulation intensity was 2 mA and the duration was 20 minutes/session with one session/day and seven sessions/week. Repetitive transcranial magnetic stimulation using a MagPro stimulator was applied to mid-portion of the right intraparietal sulcus at a frequency of 10 Hz with an 80% motor threshold intensity and 160 pulses for 8 minutes/session with one session/day and seven sessions/week. After one month of rehabilitation, the patient had recovered to a nearly normal conscious state with a Coma Recovery Scale-revised score of 21 (auditory function: 4, visual function: 5, motor function: 5, verbal function: 2, communication: 2, arousal: 3) [1]. The patient’s sister provided signed, informed consent, and the study protocol was approved by our institutional review board.

Solvent-Induced Hearing Loss from Occupational Exposure In Asia – A systematic review

Exposure to certain solvents in the workplace can cause hearing loss. This study aims to bring attention to the existing literature on the adverse effects of solvents on workers' auditory function in a diverse Asia occupational setting. The literature search used in this study is PubMed and Web of Science. 87% of the selected studies reported that the highest prevalence of hearing loss was from solvents plus noise-exposed group. Evidence shows that interaction between the solvent and the noise could be both additive and synergistic. More epidemiology studies on solvent-induced hearing loss using diverse approaches are warranted in Asia region. Keywords: hearing loss, organic solvent, pure tone audiometry, chemical-induced hearing loss eISSN: 2398-4287© 2021. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians/Africans/Arabians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. DOI:

Congenital Hypothyroidism and the Deleterious Effects on Auditory Function and Language Skills: A Narrative Review

Congenital hypothyroidism (CH) is an endocrine disease commonly found in newborns and is related to the absence or reduction of thyroid hormones (THs), which are essential for development since intrauterine life. Children with CH can develop hearing problems as THs are crucial for the auditory pathway’s development and maturation. Sensory deprivations, especially in hearing disorders at early ages of development, can impair language skills, literacy, and behavioral, cognitive, social, and psychosocial development. In this review we describe clinical and molecular aspects linking CH and hearing loss.

Auditory Threshold Variability in the SAMP8 Mouse Model of Age-Related Hearing Loss: Functional Loss and Phenotypic Change Precede Outer Hair Cell Loss

Age-related hearing loss (ARHL) is the most common sensory deficit in aging society, which is accompanied by increased speech discrimination difficulties in noisy environments, social isolation, and cognitive decline. The audiometric degree of ARHL is largely correlated with sensory hair cell loss in addition to age-related factors not captured by histopathological analysis of the human cochlea. Previous studies have identified the senescence-accelerated mouse prone strain 8 (SAMP8) as a model for studying ARHL and age-related modifications of the cochlear redox environment. However, the SAMP8 population exhibits a large variability in auditory function decline over age, whose underlying cause remains unknown. In this study, we analyzed auditory function of SAMP8 mice by measuring auditory brainstem response (ABR) thresholds at the age of 6 weeks (juvenile), 12 weeks (young adult), and 24 weeks (adult). Consistent with previous studies, SAMP8 mice exhibit an early progressive, age-related decline of hearing acuity. However, a spatiotemporal cytohistological analysis showed that the significant increase in threshold variability was not concurrently reflected in outer hair cell (OHC) loss observed in the lower and upper quartiles of the ABR threshold distributions over age. This functional loss was found to precede OHC loss suggesting that age-related phenotypic changes may be contributing factors not represented in cytohistological analysis. The expression of potassium channels KCNQ4 (KV7.4), which mediates the current IK,n crucial for the maintenance of OHC membrane potential, and KCNQ1 (KV7.1), which is an essential component in potassium circulation and secretion into the endolymph generating the endocochlear potential, showed differences between these quartiles and age groups. This suggests that phenotypic changes in OHCs or the stria vascularis due to variable oxidative deficiencies in individual mice may be predictors of the observed threshold variability in SAMP8 mice and their progressive ARHL. In future studies, further phenotypic predictors affected by accumulated metabolic challenges over age need to be investigated as potentially underlying causes of ARHL preceding irreversible OHC loss in the SAMP8 mouse model.