Transient peripheral vestibular hypofunction measured with vestibular short-latency evoked potentials following noise exposure in rats.

Exposure to 120 dB sound pressure level (SPL) band-limited noise results in delayed onset latency and reduced vestibular short-latency evoked potential (VsEP) responses. These changes are still present 4 wk after noise overstimulation. Noise-induced hearing loss (NIHL) has been shown to vary in extent and duration based on the noise intensity. This study investigated whether noise-induced peripheral vestibular hypofunction (NPVH) would also decrease in extent and/or duration with less intense noise exposure. In the present study, rats were exposed to a less intense noise (110 dB SPL) but for the same duration (6 h) and frequency range (500-4,000 Hz) as used in previous studies. The VsEP was assessed 1, 3, 7, 14, 21, and 28 days after noise exposure. In contrast to 120 dB SPL noise exposure, the 110 dB SPL noise exposures produced smaller deficits in VsEP responses that fully recovered in 62% (13/21) of animals within 1 wk. These findings suggest that NPVH, a loss or attenuation of VsEP responses with a requirement for elevated stimulus intensity to elicit measurable responses, is similar to NIHL, that is, lower sound levels produce a smaller or transient deficit. These results show that it will be important to determine the extent and duration of vestibular hypofunction for different noise exposure conditions and their impact on balance.NEW & NOTEWORTHY This is the first study to show a temporary noise-induced peripheral vestibular hypofunction that recovers following exposure to continuous noise.

Clinical characteristics of patients with unilateral auditory neuropathy.

OBJECTIVE: To analyze the clinical characteristics of patients with unilateral auditory neuropathy (UAN), and to provide guidance for future clinical diagnosis and research. METHODS: Patients who were clinically diagnosed with UAN from 2004 to 2019 were included. Clinical characteristics, audiological features, imaging findings, genetic test results and management effect were summarized and followed. RESULTS: A total of 44 patients [mean age, 4.35 ± 4.39 years; 22 (50.00%) males and 22 (50.00%) females] were enrolled for analyses. Among the 38 patients who were tested by pure-tone or behavioral audiometry, the degree of hearing loss of the affected ear was characterized as mild in 2 ears (5.26%), moderate in 5 (13.16%), severe in 9 (23.68%) and profound in 22 (57.89%). For the 44 contralateral ears, 33 (75.00%) showed normal hearing and 11 (25.00%) presented with sensorineural hearing loss. Auditory brainstem responses were absent or abnormal in all 44 affected ears, while otoacoustic emissions and/or cochlear microphonics were present. Among the 18 patients who underwent magnetic resonance imaging (MRI), 7 (38.89%) presented cochlear nerve deficiency (CND). Nineteen candidate variants were found in 12 patients among the 15 UAN patients who were conducted targeted gene capture and next generation sequencing. Thirty patients were followed up by telephone to investigate their management effect. CONCLUSIONS: Our study demonstrates comprehensive audiological features of patients with UAN to improve the clinical understanding and diagnosis. Some patients with UAN could show ipsilateral CND and MRI is essential to evaluate if the nerve is deficient. No pathogenic variants that directly related to the pathogenesis of UAN have been found in this study currently.

Cochlear nerve canal stenosis and associated semicircular canal abnormalities in paediatric sensorineural hearing loss: a single centre study.

OBJECTIVE: This study aimed to evaluate the association between cochlear nerve canal dimensions and semicircular canal abnormalities and to determine the distribution of bony labyrinth anomalies in patients with cochlear nerve canal stenosis. METHOD: This was a retrospective study in which high-resolution computed tomography images of paediatric patients with severe-to-profound sensorineural hearing loss were reviewed. A cochlear nerve canal diameter of 1.5 mm or less in the axial plane was classified as stenotic. Semicircular canals and other bony labyrinth morphology and abnormality were evaluated. RESULTS: Cochlear nerve canal stenosis was detected in 65 out of 265 ears (24 per cent). Of the 65 ears, 17 ears had abnormal semicircular canals (26 per cent). Significant correlation was demonstrated between cochlear nerve canal stenosis and semicircular canal abnormalities (p < 0.01). Incomplete partition type II was the most common accompanying abnormality of cochlear nerve canal stenosis (15 out of 65, 23 per cent). CONCLUSION: Cochlear nerve canal stenosis is statistically associated with semicircular canal abnormalities. Whenever a cochlear nerve canal stenosis is present in a patient with sensorineural hearing loss, the semicircular canal should be scrutinised for presence of abnormalities.

Sixteen-and-a-half syndrome with metastatic pons tumor: A case report.

RATIONALE: One-and-a-half syndrome (OAAH) is characterized as the combination of ipsilateral horizontal gaze palsy and internuclear ophthalmoplegia. OAAH syndrome accompanied with 7th and 8th cranial nerve palsy is called 16-and-a-half syndrome. We aimed to report the case of 16-and-a-half syndrome with metastatic pons tumor. PATIENT CONCERNS: A 57-year-old male diagnosed with nonsmall-cell lung cancer (NSCLC) with brain metastasis occurring 15 months ago was referred to our clinic with the chief complaint of horizontal diplopia and right gaze palsy. DIAGNOSIS: According to the patient symptom, ocular examination, and radiographic findings, he was diagnosed as 16-and-a-half syndrome which was caused by brain tumor metastasis from NSCLC. INTERVENTIONS: We referred him to hemato-oncology department and he was treated with radiation and supportive therapy. OUTCOMES: Unfortunately, the patient passed away 1 month later without improvement of ophthalmoplegia. LESSONS: The clinical findings of our case indicate 16-and-a-half syndrome caused by brain tumor metastasis from NSCLC, which to our knowledge has not been previously reported. The case highlights a rare cause of OAAH spectrum disease and the importance of a systemic work-up including associated neurologic symptoms and brain imaging in patients with horizontal gaze palsy.

Diffuse large B-cell lymphoma recurrence presenting as multiple, progressive cranial neuropathies.

A 58-year-old man with a history of rheumatoid arthritis and stage IV diffuse large B-cell lymphoma, in complete remission with no evidence of residual disease on positron emission tomography/CT after completing six cycles of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone chemotherapy, presented with acute onset of dysphagia to solids and liquids. On further evaluation, his dysphagia was attributed to a vagus nerve palsy, and later during his admission, he developed rapidly progressing left facial and vestibulocochlear nerve palsies. Imaging studies displayed pathological enhancement of bilateral seventh and eighth cranial nerves, concerning for leptomeningeal recurrence of lymphoma. Cerebrospinal fluid analysis and flow cytometry were confirmatory, revealing markedly atypical monotypic CD19 positive B cells.

The management of pediatric hearing loss caused by auditory neuropathy spectrum disorder.

PURPOSE OF REVIEW: Auditory neuropathy spectrum disorder (ANSD) is a condition in which auditory testing reveals normal otoacoustic emissions, but auditory brainstem testing is abnormal or absent and speech discrimination is poor. This constellation of findings ostensibly suggests that the cochlea is healthy and an abnormality of conduction or processing of sound occurs along the nerve fibers. As more is learned about this condition, it is becoming clear that ANSD describes heterogeneous, distinct clinical entities that must be taken into account when devising treatment modalities. RECENT FINDINGS: Modern auditory testing, genetic testing, and neuroimaging can allow for an accurate understanding of the location of the lesion causing ANSD in the auditory pathway. Contributing causes can include genetic mutations, absent or deficient cochlear nerve, hypoxia and jaundice among others. Hearing aids can be successful in the management of ANSD. Several studies suggest that cochlear implantation can lead to successful hearing outcomes in a subset of this patient population. SUMMARY: Auditory neuropathy spectrum disorder represents a relatively rare but important diagnosis for clinicians. Treatment for this condition includes hearing aids and FM systems in more mild cases, and cochlear implants in severe cases. Cochlear implantation for many patients can lead to a good hearing outcomes but the outcome can vary greatly depending on the underlying etiology of ANSD.

Commentary on the regulatory implications of noise-induced cochlear neuropathy.

OBJECTIVE: A discussion on whether recent research on noise-induced cochlear neuropathy in rodents justifies changes in current regulation of occupational noise exposure. DESIGN: Informal literature review and commentary, relying on literature found in the authors' files. No formal literature search was performed. STUDY SAMPLE: Published literature on temporary threshold shift (TTS) and cochlear pathology, in humans and experimental animals, as well as the regulations of the US Occupational Safety and Health Administration (OSHA). RESULTS: Humans are less susceptible to TTS, and probably to cochlear neuropathy, than rodents. After correcting for inter-species audiometric differences (but not for differences in susceptibility), exposures that caused cochlear neuropathy in rodents already exceed OSHA limits. Those exposures also caused "pathological TTS" (requiring more than 24 h to recover), which does not appear to occur with human broadband noise exposure permissible under OSHA. CONCLUSION: It would be premature to conclude that noise exposures permissible under OSHA can cause cochlear neuropathy in humans.

[Intraoperative monitoring of cochlear nerve function during cerebello-pontine angle surgery]. / Intraoperatives Monitoring des N. cochlearis bei Eingriffen im Kleinhirnbrückenwinkel.

BACKGROUND: Surgical procedures in the cerebello-pontine angle (CPA), e. g. for vestibular schwannoma, have an increased risk for damage to the cochlear nerve. Consequently, hearing deterioration up to complete deafness may result with severe impact on quality of life. Methods for intraoperative monitoring of function may minimize such risks. OBJECTIVE: Review of current methods for intraoperative monitoring of the cochelar nerve and summary of new developments. MATERIALS AND METHODS: Analysis and summary of literature, discussion of new methods. RESULTS: Early auditory evoked potentials using click stimuli remain the standard method for intraoperative monitoring of cochlear nerve function. Amplitude and latency changes indicate a risk of postoperative hearing deterioration; however demonstrate only limited further differentiation of hearing quality. As novel methods, near-field recordings may allow faster feedback and auditory steady state responses potentially enable frequency specific testing. CONCLUSIONS: Intraoperative monitoring of the cochlear nerve is an integral component of CPA surgery. It enables detection of potential nerve damage and thus contributes to avoiding postoperative functional deficits. Development and implementation of novel and additional approaches may further improve its clinical value.

Missed Anterior Inferior Cerebellar Artery Aneurysm Mimicking Vestibular Neuritis-Clues to Prevent Misdiagnosis.

We discuss a case with combined vestibulocochlear and facial neuropathy mimicking a less urgent peripheral vestibular pattern of acute vestibular syndrome (AVS). With initial magnetic resonance imaging read as normal, the patient was treated for vestibular neuropathy until headaches worsened and a diagnosis of subarachnoid hemorrhage was made. On conventional angiography, a ruptured distal right-sided aneurysm of the anterior inferior cerebellar artery was diagnosed and coiled. Whereas acute vestibular loss usually points to a benign peripheral cause of AVS, combined neuropathy of the vestibulocochlear and the facial nerve requires immediate neuroimaging focusing on the cerebellopontine angle. Imaging should be assessed jointly by neuroradiologists and the clinicians in charge to take the clinical context into account.

Malignant peripheral nerve sheath tumors of the eighth cranial nerve arising without prior irradiation.

OBJECTIVE Malignant peripheral nerve sheath tumors (MPNSTs) of the eighth cranial nerve (CN) are exceedingly rare. To date the literature has focused on MPNSTs occurring after radiation therapy for presumed benign vestibular schwannomas (VSs), while MPNSTs arising without prior irradiation have received little attention. The objectives of the current study are to characterize the epidemiology, clinical presentation, disease course, and outcome using a large national cancer registry database and a systematic review of the English literature. Additionally, a previously unreported case is presented. METHODS The authors conducted an analysis of the Surveillance, Epidemiology, and End Results (SEER) database, a systematic review of the literature, and present a case report. Data from all patients identified in the SEER database with a diagnosis of MPNST involving the eighth CN, without a history of prior radiation, were analyzed. Additionally, all cases reported in the English literature between January 1980 and March 2015 were reviewed. Finally, 1 previously unreported case is presented. RESULTS The SEER registries identified 30 cases between 1992 and 2012. The average incidence was 0.017 per 1 million persons per year (range 0.000-0.0687 per year). The median age at diagnosis was 55 years, and 16 (53%) were women. Thirteen cases were diagnosed upon autopsy. Of the 17 cases diagnosed while alive, the median follow-up was 118 days, with 3 deaths (18%) observed. When compared with the incidence of benign VS, 1041 VSs present for every 1 MPNST arising from the eighth CN. Including a previously unreported case from the authors' center, a systematic review of the English literature yielded 24 reports. The median age at diagnosis was 44 years, 50% were women, and the median tumor size at diagnosis was 3 cm. Eleven patients (46%) reported isolated audiovestibular complaints typical for VS while 13 (54%) exhibited facial paresis or other signs of a more aggressive process. Treatment included microsurgery alone, microsurgery with adjuvant radiation, or microsurgery with chemoradiation. Sixty-one percent of patients receiving treatment experienced recurrence, 22% of which were diagnosed with drop metastases to the spine. Ultimately, 13 patients (54%) died of progressive disease at a median of 3 months following diagnosis. The ability to achieve gross-total resection was the only feature that was associated with improved disease-specific survival. CONCLUSIONS MPNSTs of the eighth CN are extremely rare and portend a poor prognosis. Nearly half of patients initially present with findings consistent with a benign VS, often making an early diagnosis challenging. In light of these data, early radiological and clinical follow-up should be considered in those who elect nonoperative treatment, particularly in patients with a short duration of symptoms or atypical presentation. These data also provide a baseline rate of malignancy that should be considered when estimating the risk of malignant transformation following stereotactic radiosurgery for VS.

Progressive cranial nerve involvement and grading of facial paralysis in gelsolin amyloidosis.

INTRODUCTION: Hereditary gelsolin amyloidosis (GA) is a rare condition caused by the gelsolin gene mutation. The diagnostic triad includes corneal lattice dystrophy (type 2), progressive bilateral facial paralysis, and cutis laxa. Detailed information on facial paralysis in GA and the extent of cranial nerve injury is lacking. METHODS: 29 GA patients undergoing facial corrective surgery were interviewed, examined, and studied electroneurophysiologically. RESULTS: All showed dysfunction of facial (VII) and trigeminal (V) nerves, two-thirds of oculomotor (III) and hypoglossal (XII) nerves, and half of vestibulocochlear (acoustic) (VIII) nerve. Clinical involvement of frontal, zygomatic, and buccal facial nerve branches was seen in 97%, 83%, and 52% of patients, respectively. Electromyography showed marked motor unit potential loss in facial musculature. CONCLUSIONS: Cranial nerve involvement in GA is more widespread than previously described, and correlates with age, severity of facial paralysis, and electromyographic findings. We describe a grading method for bilateral facial paralysis in GA, which is essential for evaluation of disease progression and the need for treatment.

The internal acoustic canal--another review area in paediatric sensorineural hearing loss.

Morphological abnormalities of the internal acoustic canal (IAC), albeit rare, are sometimes associated with hearing loss in children. We present an illustration of the spectrum of IAC abnormalities together with a brief review of the embryology and anatomy of the IAC and the techniques used when imaging the petrous temporal bone. This review focuses on morphological abnormalities of the IAC together with their clinical implications and impact on clinical management.

The middle ear muscle reflex in the diagnosis of cochlear neuropathy.

Cochlear neuropathy, i.e. the loss of auditory nerve fibers (ANFs) without loss of hair cells, may cause hearing deficits without affecting threshold sensitivity, particularly if the subset of ANFs with high thresholds and low spontaneous rates (SRs) is preferentially lost, as appears to be the case in both aging and noise-damaged cochleas. Because low-SR fibers may also be important drivers of the medial olivocochlear reflex (MOCR) and middle-ear muscle reflex (MEMR), these reflexes might be sensitive metrics of cochlear neuropathy. To test this hypothesis, we measured reflex strength and reflex threshold in mice with noise-induced neuropathy, as documented by confocal analysis of immunostained cochlear whole-mounts. To assay the MOCR, we measured contra-noise modulation of ipsilateral distortion-product otoacoustic emissions (DPOAEs) before and after the administration of curare to block the MEMR or curare + strychnine to also block the MOCR. The modulation of DPOAEs was 1) dominated by the MEMR in anesthetized mice, with a smaller contribution from the MOCR, and 2) significantly attenuated in neuropathic mice, but only when the MEMR was intact. We then measured MEMR growth functions by monitoring contra-noise induced changes in the wideband reflectance of chirps presented to the ipsilateral ear. We found 1) that the changes in wideband reflectance were mediated by the MEMR alone, and 2) that MEMR threshold was elevated and its maximum amplitude was attenuated in neuropathic mice. These data suggest that the MEMR may be valuable in the early detection of cochlear neuropathy.

[The neurovascular conflict of the vestibulocochlear nerve. Etiology, diagnostics, the methods for the surgical and conservative treatment].

The present review of the current literature concerning pathogenesis, formation of neurovascular conflict of the vestibulocochlear nerve, its epidemiology, clinical manifestations, diagnostics, and the methods for the surgical and conservative treatment is focused on the indications for decompression of the vestibulocochlear nerve and its effectiveness in the patients presenting with the neurovascular conflict of the vestibulocochlear nerve.

Towards a Diagnosis of Cochlear Neuropathy with Envelope Following Responses.

Listeners with normal audiometric thresholds can still have suprathreshold deficits, for example, in the ability to discriminate sounds in complex acoustic scenes. One likely source of these deficits is cochlear neuropathy, a loss of auditory nerve (AN) fibers without hair cell damage, which can occur due to both aging and moderate acoustic overexposure. Since neuropathy can affect up to 50 % of AN fibers, its impact on suprathreshold hearing is likely profound, but progress is hindered by lack of a robust non-invasive test of neuropathy in humans. Reduction of suprathreshold auditory brainstem responses (ABRs) can be used to quantify neuropathy in inbred mice. However, ABR amplitudes are highly variable in humans, and thus more challenging to use. Since noise-induced neuropathy is selective for AN fibers with high thresholds, and because phase locking to temporal envelopes is particularly strong in these fibers, the envelope following response (EFR) might be a more robust measure. We compared EFRs to sinusoidally amplitude-modulated tones and ABRs to tone-pips in mice following a neuropathic noise exposure. EFR amplitude, EFR phase-locking value, and ABR amplitude were all reduced in noise-exposed mice. However, the changes in EFRs were more robust: the variance was smaller, thus inter-group differences were clearer. Optimum detection of neuropathy was achieved with high modulation frequencies and moderate levels. Analysis of group delays was used to confirm that the AN population was dominating the responses at these high modulation frequencies. Application of these principles in clinical testing can improve the differential diagnosis of sensorineural hearing loss.

Saccular dysfunction in children with sensorineural hearing loss and auditory neuropathy/auditory dys-synchrony.

CONCLUSION: There is a correlation between the AN/AD disorder and the saccular dysfunction in children with severe sensorineural hearing loss, which means that saccular dysfunction can be a concomitant sign of AN/AD. In conclusion, the term of audio-vestibular dys-synchrony (AVS) is a more suitable description for this condition. OBJECTIVES: Patients with auditory neuropathy/auditory dys-synchrony (AN/AD) characteristically demonstrate poor neural responses from the vestibulocochlear nerve and brainstem while displaying evidence of intact outer hair cells function. Therefore, the objective of this study is studying of the relationship of the saccular dysfunction with AN/AD disorder in children with sensorineural hearing loss. METHODS: In this cross-sectional study, 100 children with bilateral severe-to-profound sensorineural hearing losses underwent audiologic tests and cervical vestibular-evoked myogenic potentials (cVEMPs) at the Audiology Department of Hamadan University of Medical Sciences (Hamadan, Iran). RESULTS: Eleven children with bilateral severe sensorineural hearing loss were given to unilateral AN/AD disorder (11 ears), and two children (4 ears) had bilateral AN/AD (total = 13 children). The ears with AN/AD took the form of unrepeatable or absent waves of ABR and presence of OAEs. The statistical analysis of an independent t-test between AN/AD ears as compared to non-AN/AD ears of these 13 children showed that the mean latencies of p13 and the mean latencies of n23 and the mean peak-to-peak amplitude had significant differences.

Cochlear neuropathy in the rat exposed for a long period to moderate-intensity noises.

Damaging effects on the cochlea of high-intensity acoustic overexposures have been extensively documented, but only few works have focused on the danger of moderate noise levels. Using scanning and transmission electron microscopy, we explored the noise-induced neuroepithelial changes that occur in the cochlea of rats subjected to moderate intensities, 70 and 85 dB SPL, for an extended period of time (6 hr/day over 3 months). Although the full quota of outer and inner sensory hair cells remained present, we detected discrete abnormalities, likely resulting from metabolic impairment, in both types of hair cell within the basal region of the cochlea. In contrast, important noise-dependent losses of spiral ganglion neurons had occurred. In addition, we found cytoplasmic accumulations of lipofuscin-like aggregates in most of the surviving cochlear neurons. These results strongly suggest that noise levels comparable to those of certain working environments, with sufficient exposure duration, pose a severe risk to the cochlea. Moreover, our data support the notion that long-duration exposure to moderate noise is a causative factor of presbycusis.