Absence Of Auditory Brainstem Response Research Articles

Duration of Cochlear Microphonics in Click and Toneburst-Evoked Auditory Brainstem Response in Individuals With Auditory Neuropathy Spectrum Disorder and Normal Hearing.

The presence of ringing cochlear microphonics (CM) with an absence of auditory brainstem response (ABR) is an indicator of auditory neuropathy spectrum disorder (ANSD). The duration of CM may vary based on the stimuli used to elicit the response. Generally, ABR is recorded using clicks with very limited use of tonebursts. Thus, this study aims to understand the duration of CM in individuals with ANSD and normal hearing in response to clicks, 500 Hz toneburst, and 4000 Hz toneburst using ABR. Results show that individuals with ANSD have a longer duration of CM than those with normal hearing. The presence of CM was more evident in response to toneburst stimuli than clicks, with 500 Hz being commonly eliciting more CM in both groups. The difference in duration of CM was statistically significant in individuals with ANSD with longer duration obtained for 500 Hz followed by clicks and 4000 Hz toneburst. The duration of the stimuli used plays an important role in revealing the CM while recording ABR. This indicates that the use of toneburst, particularly low frequency such as 500 Hz, will be clinically useful in identifying ANSD especially when otoacoustic emissions are compromised.

Audiovestibular neuropathy in an immunocompetent man with cryptococcal meningitis

IntroductionCryptococcus spp. is a fungus responsible for 600,000 deaths per year worldwide, mainly in immunosuppressed subjects. However, 20% of cases occur in immunocompetent subjects. Neuropathic disorders involving the auditory nerve have been reported, but vestibular disorders have never been described in detail. We report the case of an immunocompetent man, who presented audiovestibular disorders leading to a diagnosis of cryptococcal meningitis. Case reportA 39-year-old man was referred for balance disorders and right sensorineural hearing loss. He presented right vestibulo-saccular impairment and bilateral absence of auditory brainstem responses. Brain MRI was suggestive of cryptococcal meningitis. A cystic lesion in the right flocculus compressed the vestibulocochlear nerve. During monthly follow-up, pure tone audiometry gradually improved and speech audiometry in silence returned to normal. Partial resynchronization of the auditory afferent pathways was observed only on the contralateral side to vestibulocochlear nerve compression, while complete recovery of saccular function was observed. DiscussionCryptococcal meningitis in immunocompetent subjects may be accompanied by lesions of the auditory and vestibular afferent pathways. Recovery of hearing and balance was observed in response to medical treatment and early vestibular rehabilitation.

Acquired auditory neuropathy spectrum disorder after malaria treated with quinine.

Auditory neuropathy spectrum disorder (ANSD) can cause significant hearing impairment; it occurs when there is intact outer hair cell function in the inner ear, with a dyssynchronous neural response, thought to be due to dysfunction of the inner hair cells (IHCs), the synapse of the IHCs and the auditory nerve, or of the auditory nerve itself. This case report describes the onset of ANSD in a Malawian child after severe malaria treated with quinine. Diagnosis of ANSD was made by confirming the presence of otoacoustic emissions, together with the absence of auditory brainstem response and absent acoustic reflexes.

Deterioration in Distortion Product Otoacoustic Emissions in Auditory Neuropathy Patients With Distinct Clinical and Genetic Backgrounds.

Auditory neuropathy (AN) is a clinical disorder characterized by the absence of auditory brainstem response and presence of otoacoustic emissions. A gradual loss of otoacoustic emissions has been reported for some cases of AN. Such cases could be diagnosed as cochlear hearing loss and lead to misunderstanding of the pathology when patients first visit clinics after the loss of otoacoustic emissions. The purpose of this study was to investigate the time course of changes in distortion product otoacoustic emissions (DPOAEs) in association with patients' genetic and clinical backgrounds, including the use of hearing aids. DPOAE measurements from 31 patients with AN were assessed. Genetic analyses for GJB2, OTOF, and mitochondrial m.1555A> G and m.3243A> G mutations were conducted for all cases, and the analyses for CDH23 and OPA1 were conducted for the selected cases. Patients who were younger than 10 years of age at the time of AN diagnosis were designated as the pediatric AN group (22 cases), and those who were 18 years of age or older were designated as the adult AN group (9 cases). DPOAE was measured at least twice in all patients. The response rate for DPOAEs was defined and analyzed. The pediatric AN group comprised 10 patients with OTOF mutations, 1 with GJB2 mutations, 1 with OPA1 mutation, and 10 with indefinite causes. Twelve ears (27%) showed no change in DPOAE, 20 ears (46%) showed a decrease in DPOAE, and 12 ears (27%) lost DPOAE. Loss of DPOAE occurred in one ear (2%) at 0 years of age and four ears (9%) at 1 year of age. The time courses of DPOAEs in patients with OTOF mutations were divided into those with early loss and those with no change, indicating that the mechanism for deterioration of DPOAEs includes not only the OTOF mutations but also other common modifier factors. Most, but not all, AN patients who used hearing aids showed deterioration of DPOAEs after the start of using hearing aids. A few AN patients also showed deterioration of DPOAEs before using hearing aids. The adult AN group comprised 2 patients with OPA1 mutations, 2 with OTOF mutations, and 5 with indefinite causes. Four ears (22%) showed no change in DPOAE, 13 ears (72%) showed a decrease, and one ear (6%) showed a loss of DPOAE. Although the ratio of DPOAE decrease was higher in the adult AN group than in the pediatric AN group, the ratio of DPOAE loss was lower in the adult AN group. DPOAE was not lost in all four ears with OPA1 mutations and in all four ears with OTOF mutations in the adult group. DPOAE was decreased or lost in approximately 70% of pediatric and about 80% of adult AN patients. Eleven percent of pediatric AN patients lost DPOAEs by 1 year of age. Genetic factors were thought to have influenced the time course of DPOAEs in the pediatric AN group. In most adult AN patients, DPOAE was rarely lost regardless of the genetic cause.

Diverse etiologies manifesting auditory neuropathy characteristics from infants with profound hearing loss and clinical implications

ObjectiveAuditory neuropathy spectrum disorder (ANSD) is a hearing disorder with impaired signal transmission from the inner ear to the brain. The electrophysiological characteristics of auditory neuropathy (AN characteristics) are marked with presence of otoacoustic emissions (OAE) or cochlear microphonics (CM) in the absence of auditory brainstem response (ABR). This study aimed to review etiologies related to AN characteristics from infants with profound hearing loss (HL), either unilaterally or bilaterally. Study designProspective cohort study for thirty infants with prelingual profound HL. MethodsABR, OAE, and/or CM were analyzed to identify electrophysiological characteristics. Temporal bone computed tomography and/or internal acoustic canal magnetic resonance imaging were reviewed to identify anatomical abnormalities. The electrophysiological characteristics and cochlear nerve status were analyzed according to the laterality of deafness (unilateral vs bilateral). ResultsAmong the total 41 ears (from 30 infants) with profound HL, 13 ears (7 (36.8%) of 19 ears with unilateral HL and 6 (27.3%) of 22 ears associated with bilateral HL) showed AN characteristics (37.1%), and 21 ears showed cochlear nerve deficiency (CND) (51.2%). AN characteristics was detected about two times more frequently in cases with CND (38.1%) than with anatomically normal cochlear nerve (20.0%), the difference not reaching a statistical significance probably due to a small sample size. Detection of AN characteristics did not differ between unilateral and bilateral profound HL, even though presence of CND was more frequently detected in cases with unilateral profound HL than with bilateral cases. There were at least five types of etiologies related to AN characteristics in 13 ears (from 10 infants) in our series depending on the laterality of deafness and presence of CND. ConclusionsThis study demonstrates that there were diverse etiologies related to AN characteristics from infants with unilateral or bilateral profound HL. Association between CND and AN characteristics is suggestive but not solid at this moment and AN characteristics is not a fully penetrant feature of CND.

Auditory neuropathy: A case report and review of literature

Auditory Neuropathy (AN), also known as Auditory Dyssynchrony(AD) is a very often missed diagnosis in clinical practice. In AN, sound enters the inner ear normally but the transmission of signals from inner ear to brain is impaired. Due to the lack of advanced audiological test facilities in Bangladesh, mostly AN remains undiagnosed. Here we described a 25 years old male, presented with difficulty in understanding speech for last 10 years. On audiologic evaluation, bilateral moderate sensorineural hearing loss was found on Pure tone audiogram (PTA). Speech discrimination scores were poor and disproportionate to his hearing threshold. Presence of Otoacoustic emission (OAE) revealed the normal function of cochlea. Conversely, absence of Auditory brainstem response (ABR) confirmed the definite dysfunction at auditory neural pathway and hence, the diagnosis of AN was confirmed. Since AN is an underdiagnosed condition in Bangladesh, otolaryngologists should be aware of this clinical entity. All the suspected cases should be referred to specialized centers, where advanced audiological facilities are available. DOI: http://dx.doi.org/10.3329/bjo.v19i2.17638 Bangladesh J Otorhinolaryngol 2013; 19(2): 135-139

Long Ringing Cochlear Microphonics - Not Unique to Auditory Neuropathy Spectrum Disorder in Children

Long Ringing Cochlear Microphonics - Not Unique to Auditory Neuropathy Spectrum Disorder in Children Background: The detection of cochlear microphonics in surface recordings has been considered a distinctive sign of outer hair cell integrity in participants with auditory neuropathy spectrum disorder. The study highlights that this notion could result in misdiagnosis of patients. Methods: The study reports three children with sloping hearing loss who were misdiagnosed as auditory neuropathy spectrum disorder based on absence of auditory brainstem response and presence of long ringing cochlear microphonics. The study also reports of three children with abnormal cochlear microphonics who have neurological abnormalities. Results: The abnormal cochlear microphonics (long ringing) with absent auditory brainstem response was noted in sloping hearing loss participants. In addition, abnormal cochlear microphonics was also observed along with auditory brainstem response in children with neurological abnormalities. Conclusion: Our results show that abnormal CM detection in surface recording is not a distinctive feature of auditory neuropathy spectrum disorder and participants who are diagnosed with auditory neuropathy spectrum disorder based on traditional diagnostic criteria should be reviewed to rule out possible misdiagnosis.

Assistive Devices for Patients with Auditory Neuropathy: Hearing Aid Use

Auditory neuropathy (AN) is a hearing disorder characterized by disruption of temporal coding of acoustic signals in the auditory nerve resulting from lesions involving auditory nerve fibers, the inner hair cells, or their synapses with auditory nerve terminals. Disruption of auditory nerve discharge underlies both the absence of auditory brainstem responses (ABRs) and impairment of speech perception. AN may be related to genetic disorders or result from a wide range of other etiologies. It can be identified either as an isolated disorder (isolated AN) or associated with multisystem involvement (non-isolated AN). Effectiveness and choice of assistive devices depend crucially upon etiology, site of lesion, and stage of the disease. Cochlear implants constitute an effective rehabilitative tool able to restore speech perception in many patients with genetic AN, especially those affected by the isolated form of the disorder. Some children with isolated AN have proved to be good hearing aid users, showing satisfactory open-set speech perception abilities in the aided condition. Over 50% of children discharged from neonatal intensive care units showing the electrophysiological profile of AN (absent ABRs, presence of otoacoustic emissions) benefit from hearing aid use, the provision of amplification resulting in remarkable improvement in speech perception. It can be concluded that differences in cochlear implant outcome or hearing aid use in patients with AN are related to the pathophysiological mechanisms underlying alteration of auditory nerve discharge associated with individual etiologies.

Different Manifestations of Auditory Neuropathy

Auditory neuropathy (AN) is characterized by a range of auditory deficits including elevated pure tone thresholds, reduced speech recognition scores, absence of auditory brainstem responses (ABR), and preservation of evoked otoacoustic emissions and the cochlear microphonic (CM) response. With increased advocacy for early implantation, patients with auditory neuropathy may be considered for implantation at or before one year of age. The decision for early implantation of very young patients with clinical test results that suggest AN should be made cautiously as a subset of patients presenting with the clinical constellation of AN may demonstrate reversible hearing loss over time.

Intraoperative auditory brainstem responses in patients with cerebellopontine angle meningiomas involving the inner auditory canal: analysis of the predictive value of the responses

Meningiomas of the cerebellopontine angle (CPA) can either arise from or secondarily grow into the inner auditory canal (IAC). This location may have a great impact on hearing function following surgery to remove these lesions. The aim of this retrospective study was to investigate the reliability and predictive importance of auditory brainstem responses (ABRs) for the determination of postoperative auditory function in patients with CPA meningiomas in comparison with results obtained in patients who undergo surgery for vestibular schwannomas. In a consecutive series of 1800 meningiomas surgically treated between 1978 and 2002, 421 lesions were located in the CPA. In 38 patients with CPA meningiomas involving the IAC, the findings of intraoperative ABR monitoring and the hearing status of each patient before and after surgery were retrospectively analyzed. On analysis, ABR monitoring demonstrated stable findings in 24 patients throughout tumor resection and fluctuating signals in 10 patients. Among the 24 patients with stable ABRs, postoperative hearing function improved in three patients, remained the same in 15, and worsened in six patients, including one patient who displayed postoperative deafness. There was even one patient recovering from preoperative deafness. Among the 10 patients with unstable ABRs, intermittent decreases in amplitude and deformations of variable duration in the ABR wave were noted. The risk of deafness was considerably higher in patients with prolonged phases of intermittent ABR deterioration. The presence and absence of ABRs during surgery for CPA meningiomas reliably predicted the presence and absence of postoperative auditory function. Intermittent deterioration of ABRs may result in postoperative deafness, depending on the duration of these events during surgery. Improvements in hearing are only seen when the ABRs are stable for amplitudes and latencies throughout surgery.

Cochlear implantation in an adult patient with auditory neuropathy

We present a case report of effective cochlear implantation for an adult patient with auditory neuropathy. A 34-year-old man developed bilateral hearing loss at approximately 10 years of age. His speech discrimination score was very severe despite only moderate sensorineural hearing loss. Absence of auditory brainstem responses (ABR) and preservation of distortion product otoacoustic emissions (DPOAE) were confirmed by our audiological examinations. After cochlear implantation, good responses for electrically evoked compound action potential (EAP) and electrically evoked ABR (EABR) were observed. Postoperatively, his audiological performance was significantly improved. We conclude that cochlear implantation can be a valid option for patients with auditory neuropathy.

Preserved otoacoustic emission in a child with a profound unilateral sensorineural hearing loss

We report a case of profound unilateral sensorineural hearing loss with good response of otoacoustic emission. The patient was a 5-year-old boy, who was diagnosed to have unilateral hearing impairment on pure tone audiometry at the first visit. The affected ear showed the absence of auditory brainstem response; however, its transiently evoked otoacoutic emission and distortion product otoacoustic emission were considered to be normal. These findings indicated that the outer hair cell of cochlea was not impaired and that the impairment should be localized between inner hair cells, primary afferent fiber or its synapses, spiral ganglion of the cochlea and acoustic fiber, or at a combination of these areas. That is, evaluation of otoacoustic emission was useful in determining the region of impairment in sensorineural hearing loss. Further follow-up will be necessary to differentiate the present case from auditory neuropathy.

Acoustic neuroma surgery: absent auditory brainstem response does not contraindicate attempted hearing preservation.

Absence of auditory brainstem response (ABR) waveforms has been associated with a poor likelihood of hearing preservation following resection of acoustic neuromas. Our experience is reviewed for patients with absent preoperative ABR regarding hearing preservation, hearing improvement, and return of ABR. Retrospective review of 22 cases of acoustic neuroma resection. Nine patients with absent preoperative ABR were identified. All underwent tumor resection utilizing intraoperative cochlear nerve action potential (CNAP) monitoring. Postoperative hearing results and ABR waveforms were examined. Charts were reviewed and tabulated for age, sex, tumor side, tumor size, preoperative and postoperative audiometric and ABR results, intraoperative monitoring results by ABR and CNAP, and surgical complications. Hearing preservation was achieved in seven of nine patients (78%) with absent preoperative ABR, as well as six of seven patients (86%) with tumors less than or equal to 20 mm in greatest dimension. Although intraoperative ABR monitoring was not possible in any of these patients, CNAP monitoring was successful in all. Return of ABR waveforms was observed in four of the six patients (67%) tested from 3 to 22 months postoperatively. Four of the seven patients (57%) enjoyed improvement in hearing class as defined by the guidelines of the American Academy of Otolaryngology-Head and Neck Surgery. Absent ABR waveforms have not been a negative prognostic sign regarding hearing preservation. CNAP monitoring is possible in these patients and likely helps to minimize iatrogenic cochlear nerve trauma. Patients with no ABR waveforms have hope of hearing preservation and even improvement following acoustic neuroma resection performed utilizing CNAP monitoring and hearing preservation surgical techniques.