Vestibular nerve deficiency and vestibular function in children with unilateral hearing loss caused by cochlear nerve deficiency.

BACKGROUND: High-resolution MR imaging enables the visualization of individual nerves in the internal auditory canal (IAC). Cochlear nerve deficiency (CND) is recognized as one of the major causes of sensory neural hearing loss (SNHL), especially in cases of unilateral hearing loss in childhood. Some patients with CND are thought to have accompanying vestibular nerve deficiency (VND). However, there have been few reports focusing on VND and vestibular function in these children. AIMS: The aim of this study was to evaluate the frequency of VND and vestibular dysfunction in children with unilateral SNHL caused by CND. MATERIAL AND METHODS: Thirty-eight children with unilateral SNHL, who were diagnosed with CND by 3 T-MRI, were evaluated for VND and underwent caloric testing and cervical vestibular evoked potential (cVEMP). RESULTS: Fourteen of 38 patients (37%) had VND, and eleven (29%) of the patients [ten of the patients (71%) with VND] had at least one vestibular dysfunction. The patients with VND had significantly worse hearing and an IAC of smaller diameter than did patients without VND. CONCLUSIONS AND SIGNIFICANCE: We should pay attention to VND as well as vestibular dysfunction in hearing loss patients with CND.

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.

Clinical Profile and Results Obtained in Patients Treated by Auditory Brainstem Implants. / Perfil clínico y resultados obtenidos en los pacientes tratados mediante implante auditivo del tronco del encéfalo.

INTRODUCTION: Cochlear implants have been able to treat some types of hearing loss, but those related to cochlear nerve impairment made it necessary to find new ways to manage these deficits; leading to auditory brainstem implants (ABI). AIM: Our objective is to present the clinical profile of patients treated through an ABI and the results obtained from 1997 to 2017. MATERIAL AND METHODS: On the one hand, patients with statoacoustic nerve tumours (VIIIcranial nerve) were selected, and on the other hand, patients withoutVIII tumours with congenital malformations of the inner ear. Before and after the placement of the ABI, hearing was assessed through tonal audiometry, from which the PTA (Pure Tone Average) and the CAP (Categories of Auditory Performance) scale were obtained. RESULTS: A total of 20 patients undergoing ABI surgery were included. Eight were of tumour cause (40%) and 12 non-tumour (60%). In 15 subjects (75%) a suboccipital approach was performed and in 5 (25%) translabyrinthine. The mean of active electrodes before the implantation of Cochlear® (Nucleus ABI24) was 13/21 (61.90%) versus 8.5/12 (70.83%) of the Med-el® (ABI Med-el). An improvement in the mean PTA of 118.49dB was found against 46.55dB at 2years. On the CAP scale, values of1 were obtained in the preimplantation and of 2.57 (1-5) in the 2-year revision. CONCLUSION: The ABI is a safe option, and with good hearing results when the indication is made correctly.

Meningitis and Ramsay-Hunt syndrome in a 17-year old girl.

INTRODUCTION: Ramsay Hunt syndrome (RHS) is a rare manifestation of varicella-zoster virus (VZV) reactivation in geniculate ganglion. It usually manifests with a characteristic triad of symptoms including ipsilateral ear pain, vesicles in the external auditory canal, and facial nerve palsy. CASE: We present a case report showing RHS additionally manifested by meningitis and involvement of VIII cranial nerve. Clinical course was complicated by acute kidney injury induced by acyclovir therapy. RESULTS: Despite the involvement of the geniculate ganglion and vestibulocochlear nerve in the course of herpes zoster, and the occurrence of acute kidney injury, the patient fully recovered. CONCLUSIONS: A complete recovery of cranial nerves VII and VIII in the course of RHS can be achieved.

Hemifacial Spasm Caused by Small Epidermoid Tumor, Misinterpreted as Delayed Secondary Hemifacial Spasm Caused by Vestibular Schwannoma Treated with Gamma Knife Surgery.

BACKGROUND: Hemifacial spasm (HFS), one of the most common hyperactive cranial rhizopathies, is a disorder characterized by spontaneous, intermittent, and repetitive contraction of unilateral facial muscle. The most common cause of HFS is a mechanical compression of the facial nerve at the root exit zone (REZ) by blood vessels located in the brainstem. The incidence of cerebellopontine angle (CPA) tumor-induced HFS ranges from 0.3%-2.5% of all patients with HFS, and the incidence of epidermoid cyst among such tumors is extremely rare (0.2% to 0.25%). We present a patient manifesting HFS induced by a small epidermoid cyst who underwent Gamma Knife surgery (GKS) for ipsilateral vestibular schwannoma (VS) more than 10 years ago. CLINICAL DESCRIPTION: A 59-year-old female was admitted to our hospital with HFS. Ten years before admission, the patient underwent GKS for ipsilateral VS. Enhanced brain magnetic resonance imaging demonstrated that the volume of VS was not increased. Also, no definitive mechanical compression of the facial nerve REZ by blood vessels was detected. We concluded that HFS was secondary to the VS treatment by GKS and decided to operate to remove the tumor and identify REZ. A standardized lateral suboccipital retrosigmoid approach was performed. The cochlear nerve was encased by a tumor mass, and the posterior inferior cerebellar artery (PICA) was displaced by the mass. During tumor excision, we ensured that the VS and displaced PICA did not directly compress the REZ. Interestingly, an unexpected lesion was found with a yellowish viscous mass located between the sixth nerve and ventral side of the seventh nerve REZ. After the tumor removal, a small piece of Teflon was inserted between the PICA and REZ of the facial nerve. Postoperatively, the patient experienced no HFS or facial nerve dysfunction. Histopathologic examination of the lesion revealed an epidermoid cyst. CONCLUSIONS: We should consider various possibilities for the cause of HFS and review brain imaging meticulously if patients were treated for CPA tumor with GKS a long time ago and the delayed HFS occurred without changes in tumor volume. HFS induced by epidermoid cyst is rare. Therefore it is critical for the neurosurgeon to ensure the absence of any abnormal contact with the REZ of the facial nerve during surgery for HFS induced by CPA tumors.

Acute vertigo and sensorineural hearing loss from infarction of the vestibulocochlear nerve: A case report.

RATIONALE: Acute unilateral audiovestibulopathy is a common neurotological syndrome. Differential diagnoses of acute unilateral audiovestibulopathy include viral infection, vascular insults, and tumors. Regarding vascular causes, ischemic stroke in the anterior inferior cerebellar artery (AICA) territory is known to be the leading cause of acute audiovestibular loss. Previous reports of AICA infarction with audiovestibulopathy failed to demonstrate magnetic resonance imaging (MRI)-positive vestibulocochlear infarctions. Only 1 report demonstrated acute infarction involving the vestibulocochlear nerve on diffusion weighted imaging (DWI)-MRI. PATIENT CONCERNS: A 67 year old man complained of sudden left hearing loss and vertigo. The patient showed left horizontal gaze-evoked nystagmus (GEN) and the head impulse test (HIT) was positive on the left side. Videonystagmography revealed spontaneous rebound nystagmus toward the right side; head-shaking nystagmus toward the right side. The patient presented with left caloric paresis (20.1%). Pure tone audiometry (PTA) revealed severe sensorineural hearing loss on the left side. DIAGNOSIS: MRI of temporal bone showed multifocal acute infarctions in the left inferior cerebellum. Moreover, images revealed tiny infarctions along the left vestibulocochlear nerve and the cochlea, implying acute vestibulocochlear nerve and labyrinthine infarction. There was no evidence of steno-occlusion of major cerebral vessels on MR angiography. INTERVENTIONS: Immediate stroke management was done. OUTCOMES: Neurological symptoms gradually improved after 3 to 5 days. LESSONS: We present a case illustrating a rare but significant finding of vestibulocochlear nerve infarction revealed by DWI-MRI. Prompt imaging protocol enabled the detection of significant findings in this patient with acute unilateral audiovestibulopathy. Clinicians should be aware of the vestibulocochlear nerve and labyrinth on MRI in patients with cerebellar stroke.

Outcomes after cochlear implant provision in children with cochlear nerve hypoplasia or aplasia.

INTRODUCTION: Cochlear nerve aplasia or hypoplasia is found in up to a half of patients with unilateral or bilateral hearing loss. There is an ongoing discussion regarding the indication of cochlear implants for hearing rehabilitation in cases with radiologically-defined aplasia or hypoplasia of the cochlear nerve in those patients, especially in children. At present there is conflicting evidence whether the audiological outcomes of those children with a CI are comparable to those of children with a CI and a radiologically-normal cochlear nerve. The primary aim of this study was to assess the audiological abilities before and after CI provision in children with cochlear nerve hypoplasia or aplasia. Additionally, we aimed to determine if audiological outcomes differed in children with aplasia from those with hypoplasia. Such data should be helpful in determining if CI provision is appropriate for such children. METHODS: This retrospective study presents 7 children who were diagnosed with cochlear nerve aplasia or hypoplasia and received a CI. The pre- and postoperative audiological performance and the hearing and speech development of the children were examined. RESULTS: 4 children were unilateral CI users and 3 were bilateral CI users. Hearing reactions could be detected in all children. Already at first fitting, prompt responses and reactions to songs were observed. The aided thresholds in free field in children with hypoplasia were between 30 and 60 dB. Even in children with aplasia, the results in free field with CI averaged between 30 and 70 dB. Therefore the aided thresholds in children with hypoplasia and in children with aplasia of the CN are similar. It could be demonstrated that hearing reactions improve with the long term use of the implant. Improvement in general development could be observed in all children despite the very heterogeneous conditions and the accompanying handicaps. CONCLUSION: The results of this study support the hypothesis that children with radiologically-defined CN hypoplasia or aplasia and detectable responses to electrical or acoustical stimuli can improve their sound detection thresholds and their awareness of sound when provided with a CI.

Extremely common radiographic finding of cochlear nerve deficiency among infants with prelingual single-sided deafness and its clinical implications.

OBJECTIVES: To clarify the common radiographic findings of audiologically documented prelingual single-sided deafness (SSD) and identify the prevalence of cochlear nerve deficiency (CND) in SSD infants referred from the newborn hearing screening program. METHODS: Between March 2012 and March 2017, the records of all infants referred to our otology clinic after undergoing newborn hearing screening program were retrospectively reviewed. Twenty-four consecutive well infants without risk factors who had a confirmed diagnosis of prelingual SSD under the age of 1 year and who underwent internal auditory canal (IAC) magnetic resonance imaging (MRI) were included. The sizes of cochlear nerve (CN), IAC, and cochlear nerve canal (CNC) were measured on MRI. The presence of CND was visually determined by comparing the CN size to the ipsilateral facial nerve (FN) in the affected side via an oblique sagittal view of IAC MRI and defined when CN was absent or smaller than FN. RESULTS: CND was seen in all 24 deaf ears (100%) on MRI. There was one with incomplete partition type I, and another with combined cochleovestibular nerve absence. Twenty-four subjects demonstrated either an absent (20/24, 83.3%) or small (4/24, 16.7%) CN. When the absent and small CN groups were compared, the former group had a higher prevalence of narrow CNC and narrow IAC. Of the 20 infants without identifiable CN on the affected side, 17 (85%) had narrow IAC and 17 (85%) had narrow CNC. In the 20 ears with absent CN, only one had both normal-sized IAC and CNC. CONCLUSION: The contribution of CND to prelingual SSD in Korean infants reached 100%, according to IAC MRI alone.

Paroxismia vestibular: reporte de un caso / Vestibular paroxysmia: case report

Presentamos el caso de un paciente joven quien presenta 4 a 5 crisis diarias de vértigo espontáneo de segundos de duración, todos o casi todos los días desde hace 9 meses. Estas crisis no tienen gatillo posicional, y hay completa ausencia de sintomatologia entre crisis. Como discutimos en el artículo, este cuadro coíncide con los recientemente publicados criterios para una paroxismia vestibular, entidad supuestamente secundaria a la compresión neurovascular del nervio vestibular. El paciente respondió de forma inmediata y completa a carbamazepina a dosis bajas, el tratamiento de elección en la paroxismia vestibular.

We present the case of a young patient, with a 9-month long history of 4 to 5 daily spells of spontaneous vertigo, each lasting only seconds. There is no positional trigger, and there is a complete lack of symptoms between attacks. As is discussed in the article, this matches the recently published criteria for Vestibular Paroxysmia, an entity allegedly secondary to neurovascular compression of the vestibular nerve. The patient responded immediately and completely to carbamazepine at low dosage, the preferred treatment for vestibular paroxysmia.

Sensitivity and specificity of vestibular bed-side examination in detecting VIII cranial nerve schwannoma with sensorineural sudden unilateral hearing loss as presenting symptom.

The objectives of this study were to identify signs of vestibular nerve suffering through a bedside vestibular examination protocol in case of sudden sensorineural unilateral hearing loss without spontaneous signs of vestibular impairment and to propose a bed-side vestibular examination based protocol for the focused execution of gadolinium-enhanced magnetic resonance imaging (MRI) only if a vestibular schwannoma is suspected. 96 patients, 52 men, 44 women, mean age 57.73 +/- 12.85 years, suffering from sudden sensorineural unilateral hearing loss, which presented neither vertigo nor spontaneous nystagmus, were enrolled. Pure tone audiometry, tympanometry, measurement of acoustic reflexes and Anderson test to detect adaptation, bedside vestibular examination through head shaking test, vibration test, head impulse test, hyperventilation test and detection of nystagmus in supine and lateral decubitus to search for signs of vestibular impairment were performed. Patients with signs of vestibular impairment and pure tone audiometry threshold at high frequencies better than 70 dB nHL were subjected to auditory brainstem responses. Gadolinium enhanced MRI centred on internal acoustic canals was carried out in all patients with sudden sensorineural unilateral hearing loss. Main outcome measures were signs of vestibular impairment at vestibular bedside examination and presence of vestibular schwannoma on MRI. Signs of vestibular impairment were detected in 22/96 cases (22.9%); a vestibular schwannoma was detected by MRI in 5/96 cases (5.2%), always when vestibular impairment was present. In case of sudden sensorineural unilateral hearing loss, vestibular bedside examination seems to be useful to restrict the suspicion of a vestibular schwannoma to cases with signs of vestibular impairment, reducing the number of MRI exams, with considerable economic savings.

The Role of MRI in Diagnosing Neurovascular Compression of the Cochlear Nerve Resulting in Typewriter Tinnitus.

BACKGROUND AND PURPOSE: Typewriter tinnitus, a symptom characterized by paroxysmal attacks of staccato sounds, has been thought to be caused by neurovascular compression of the cochlear nerve, but the correlation between radiologic evidence of neurovascular compression of the cochlear nerve and symptom presentation has not been thoroughly investigated. The purpose of this study was to examine whether radiologic evidence of neurovascular compression of the cochlear nerve is pathognomonic in typewriter tinnitus. MATERIALS AND METHODS: Fifteen carbamazepine-responding patients with typewriter tinnitus and 8 control subjects were evaluated with a 3D T2-weighted volume isotropic turbo spin-echo acquisition sequence. Groups 1 (16 symptomatic sides), 2 (14 asymptomatic sides), and 3 (16 control sides) were compared with regard to the anatomic relation between the vascular loop and the internal auditory canal and the presence of neurovascular compression of the cochlear nerve with/without angulation/indentation. RESULTS: The anatomic location of the vascular loop was not significantly different among the 3 groups (all, P > .05). Meanwhile, neurovascular compression of the cochlear nerve on MR imaging was significantly higher in group 1 than in group 3 (P = .032). However, considerable false-positive (no symptoms with neurovascular compression of the cochlear nerve on MR imaging) and false-negative (typewriter tinnitus without demonstrable neurovascular compression of the cochlear nerve) findings were also observed. CONCLUSIONS: Neurovascular compression of the cochlear nerve was more frequently detected on the symptomatic side of patients with typewriter tinnitus compared with the asymptomatic side of these patients or on both sides of control subjects on MR imaging. However, considering false-positive and false-negative findings, meticulous history-taking and the response to the initial carbamazepine trial should be regarded as more reliable diagnostic clues than radiologic evidence of neurovascular compression of the cochlear nerve.

[Tinnitus in patients with hemifacial spasm: a treatable combination?] / Tinnitus bij patiënten met hemifaciale spasmen.

BACKGROUND: About 5-15% of people in the Western world will suffer from an extended period of tinnitus during their lifetime. This is often a non-treatable, disabling disorder. Tinnitus can be classified as pulsatile or non-pulsatile. Pulsatile tinnitus can be caused by a treatable neurovascular compression. CASE DESCRIPTION: Here we describe two patients, a 68-year old woman and 40-year old man suffering from pulsatile tinnitus and hemifacial spams due to neurovascular compression of the facial and acoustic nerve in the anterior cranial fossa. After microvascular decompression using the Jannetta procedure, in which a sponge was placed between the blood vessel and the nerve, the tinnitus and hemifacial spasm disappeared. CONCLUSION: Recognition of hemifacial spasm in patients with tinnitus is important because the symptoms are treatable when it is due to neurovascular compression. Because hemifacial spasm can manifest in subtle forms - for instance unilateral blinking - this important symptom can easily be overlooked.

Electrically Evoked Auditory Event-Related Responses in Patients with Auditory Brainstem Implants: Morphological Characteristics, Test-Retest Reliability, Effects of Stimulation Level, and Association with Auditory Detection.

OBJECTIVE: This study aimed to (1) characterize morphological characteristics of the electrically evoked cortical auditory event-related potentials (eERPs) and explore the potential association between onset eERP morphology and auditory versus nonauditory stimulation; (2) assess test-retest reliability of onset eERPs; (3) investigate effects of stimulation level on onset eERPs; and (4) explore the feasibility of using the onset eERP to estimate the lowest stimulation level that can be detected for individual stimulating electrodes in patients with auditory brainstem implants (ABIs). DESIGN: Study participants included 5 children (S1 to S5) and 2 adults (S6 to S7) with unilateral Cochlear Nucleus 24M ABIs. Pediatric ABI recipients ranged in age from 2.6 to 10.2 years (mean: 5.2 years) at the time of testing. S6 and S7 were 21.2 and 24.6 years of age at the time of testing, respectively. S6 and S7 were diagnosed with neurofibromatosis II (NF2) and implanted with an ABI after a surgical removal of the tumors. All pediatric subjects received ABIs after being diagnosed with cochlear nerve deficiency. The lowest stimulation level that could be detected (behavioral T level) and the estimated maximum comfortable level (C level) was measured for individual electrodes using clinical procedures. For electrophysiological measures, the stimulus was a 100-msec biphasic pulse train that was delivered to individual electrodes in a monopolar-coupled stimulation mode at stimulation levels ranging from subthreshold to C levels. Electrophysiological recordings of the onset eERP were obtained in all subjects. For studies evaluating the test-retest reliability of the onset eERP, responses were measured using the same set of parameters in two test sessions. The time interval between test sessions ranged from 2 to 6 months. The lowest stimulation level that could evoke the onset eERP was defined as the objective T level. RESULTS: Onset eERPs were recorded in all subjects tested in this study. Inter- and intrasubject variations in morphological characteristics of onset eERPs were observed. Onset eERPs with complex waveforms were recorded for electrodes that evoked nonauditory sensations, based on feedback from subjects, as well as for electrodes without any indications of nonauditory stimulations. Onset eERPs in patients with ABIs demonstrated good test-retest reliability. Increasing stimulation levels resulted in increased eERP amplitudes but showed inconsistent effects on response latencies in patients with ABIs. Objective and behavioral T levels were correlated. CONCLUSIONS: eERPs could be recorded in both non-NF2 and NF2 patients with ABIs. eERPs in both ABI patient groups show inter- and intrasubject variations in morphological characteristics. However, onset eERPs measured within the same subject in this study tended to be stable across study sessions. The onset eERP can potentially be used to estimate behavioral T levels in patients with ABIs. Further studies with more adult ABI recipients are warranted to investigate whether the onset eERP can be used to identify electrodes with nonauditory stimulations.

Comparison of three diagnostic tests in detecting vestibular deficit in patients with peripheral vestibulopathy.

OBJECTIVES: This study aimed to evaluate the results of the video head impulse test and of the caloric and rotatory chair tests in patients with dizziness. Agreement between test results was assessed and the best protocol for detecting peripheral vestibulopathy was identified. METHODS: Participants comprised 116 patients, 75 with a peripheral vestibulopathy and 41 with non-peripheral vestibulopathy. The main outcome measures were classified as normal or abnormal according to our laboratory data. RESULTS: Agreement between tests was low. Vestibulopathy testing that required all three results to be abnormal had a sensitivity of 0.547, a specificity of 0.878, and positive and negative predictive values of 0.891 and 0.514, respectively. Vestibulopathy testing that required just one result to be abnormal had a sensitivity of 0.933, a specificity of 0.292, and positive and negative predictive values of 0.701 and 0.705, respectively. CONCLUSION: In peripheral vestibulopathy, there was weak concordance in the assessment of horizontal semicircular canal function among the different tests. However, the video head impulse test had sufficient statistical power to be recommended as the first-line test.

Acute Unilateral Vestibulopathy.

Normal vestibular end organs generate an equal resting-firing frequency of the axons, which is the same on both sides under static conditions. An acute unilateral vestibulopathy leads to a vestibular tone imbalance. Acute unilateral vestibulopathy is defined by the patient history and the clinical examination and, in unclear cases, laboratory examinations. Key signs and symptoms are an acute onset of spinning vertigo, postural imbalance and nausea as well as a horizontal rotatory nystagmus beating towards the non-affected side, a pathological head-impulse test and no evidence for central vestibular or ocular motor dysfunction. The so-called big five allow a differentiation between a peripheral and central lesion by the bedside examination. The differential diagnosis of peripheral labyrinthine and vestibular nerve disorders mimicking acute unilateral vestibulopathy includes central vestibular disorders, in particular "vestibular pseudoneuritis" and other peripheral vestibular disorders, such as beginning Menière's disease. The management of acute unilateral vestibulopathy involves (1) symptomatic treatment with antivertiginous drugs, (2) causal treatment with corticosteroids, and (3) physical therapy.

Cochlear implantation in children with single-sided deafness: does aetiology and duration of deafness matter?

For adult patients with single-sided deafness (SSD), treatment with a cochlear implant (CI) is well established as an acceptable and beneficial hearing rehabilitation method administered routinely in clinical practice. In contrast, for children with SSD, CI has been applied less often to date, with the rationale to decide either on a case-by-case basis or under the realm of clinical research. The aim of our clinical study was to evaluate the longitudinal benefits of CI for a group of children diagnosed with SSD and to compare their outcomes with respect to patient characteristics. Evaluating a pool of paediatric SSD patients presenting for possible CI surgery revealed that the primary aetiology of deafness was congenital cochlear nerve deficiency. A subgroup of children meeting the CI candidacy criteria for the affected ear (the majority with acquired hearing loss) were enrolled in the study. Preliminary group results suggest substantial improvements in speech comprehension in noise and in the ability to localise sound, which was demonstrated through objective and subjective assessments after CI treatment for the group, with results varying from patient to patient. Our study shows a trend towards superior outcomes for children with acquired hearing loss and a shorter duration of hearing loss compared to congenitally deafened children who had a longer duration of SSD. This indicates an interactive influence of the age at onset, aetiology and duration of deafness upon the restoration of binaural integration and the overall benefits of sound stimulation to two ears after CI treatment. Continued longitudinal investigation of these children and further studies in larger groups may provide more guidance on the optimal timing of treatment for paediatric patients with acquired and congenital SSD.

Hearing Loss After Activation of Hearing Preservation Cochlear Implants Might Be Related to Afferent Cochlear Innervation Injury.

OBJECTIVE: Characterize hearing loss (HL) after hearing preservation cochlear implantation and determine the association between high charge electrical stimulation (ES) and late loss of acoustic hearing. METHODS: A retrospective cohort analysis of all hearing preservation implantees at our center (n = 42) assayed HL as a function of maximum charge. We analyzed serial audiometry from 85 patients enrolled in the multicenter Hybrid S8 trial to detail the hearing loss greater than 1 month after implantation. Cochleotypic explant cultures were used to assess susceptibility to high levels of ES. RESULTS: Early HL after implantation tends to be mild and averages 12.2 dB. After activation of the Hybrid S8 device, 17 (20%) of 85 patients experienced acceleration of HL. Compared with the majority of patients who did not lose significant hearing after activation, these patients experienced more severe HL at 1 year. Five patients implanted at our center experienced acceleration of HL after high charge exposure. In patients implanted at our center, high charge was associated with late HL (Pearson 0.366, p = 0.016). In rat cochleotypic explants, high voltage ES damaged afferent nerve fibers, reflected by blebbing and a 50% reduction in the number of fibers innervating the organ of Corti. In contrast, hair cells displayed only minor differences in cell number and morphology. CONCLUSIONS: Based on clinical and in vitro data, we theorize that the combination of acoustic amplification and ES in the setting of intact hair cells and neural architecture may contribute, in part, to cochlear toxicity, perhaps by damaging the afferent innervation.