Vestibular functions in patients with idiopathic sudden sensorineural hearing loss and its relation to prognosis.

OBJECTIVE: Because of the anatomically close relationship between the cochlea and the vestibular organs, cochlear function disorders may be accompanied by vestibular disorders. This study aimed to evaluate vestibular functions in patients with idiopathic sudden sensorineural hearing loss using VEMP, caloric test, and VNG test battery and its relation to prognosis. MATERIALS AND METHODS: For this study, 42 patients aged 18-55 years with idiopathic sudden sensorineural hearing loss and 30 volunteers who had no hearing and balance problems were included. Audiometry, cVEMP, oVEMP, caloric tests, and VNG tests were performed. Moreover, the effects of age, sex, time of admission, degree and configuration of hearing loss, accompanying vertigo, tinnitus, and ear fullness on improvement in hearing were evaluated. RESULTS: Of the 42 patients in the study group, 26 (56.52%) were male, 20 (43.48%) were female, and the mean age was 41.54 ± 12.23 years. Of the 30 individuals in the control group, 19 (63.3%) were male, 11 (36.7%) were female, and the mean age was 39.53 ± 13.03 years. There was no significant difference in the incidence of sudden sensorineural hearing loss in terms of sex and age, and the prognosis was better for female patients. Early admission to treatment was a factor of good prognosis; profound hearing loss, bilateral hearing loss and vertigo were factors of poor prognosis. Prognosis was better in patients with rising type audiogram configuration, while the prognosis was worse in patients with flat, descending and total hearing loss. Tinnitus and ear fullness had no effect on the prognosis. No anomalies were observed in VNG findings. Moreover, abnormal caloric response was higher in patients with profound hearing loss and total hearing configuration. Shortening was observed in cVEMP / oVEMP P1 and N1 latency after treatment. Furthermore, there was an improvement in abnormal responses after treatment. CONCLUSION: In this study, vestibular function was affected in patients with idiopathic sudden sensorineural hearing loss. The present study can help the development of a clinical strategy in the evaluation of the vestibular system in idiopathic SSNHL, patient follow-up, patient information, and the implementation of vestibular rehabilitation. Note that additional studies involving larger patients series are required.

Auditory-nerve responses in mice with noise-induced cochlear synaptopathy.

Cochlear synaptopathy is the noise-induced or age-related loss of ribbon synapses between inner hair cells (IHCs) and auditory-nerve fibers (ANFs), first reported in CBA/CaJ mice. Recordings from single ANFs in anesthetized, noise-exposed guinea pigs suggested that neurons with low spontaneous rates (SRs) and high thresholds are more vulnerable than low-threshold, high-SR fibers. However, there is extensive postexposure regeneration of ANFs in guinea pigs but not in mice. Here, we exposed CBA/CaJ mice to octave-band noise and recorded sound-evoked and spontaneous activity from single ANFs at least 2 wk later. Confocal analysis of cochleae immunostained for pre- and postsynaptic markers confirmed the expected loss of 40%-50% of ANF synapses in the basal half of the cochlea; however, our data were not consistent with a selective loss of low-SR fibers. Rather they suggested a loss of both SR groups in synaptopathic regions. Single-fiber thresholds and frequency tuning recovered to pre-exposure levels; however, response to tone bursts showed increased peak and steady-state firing rates, as well as decreased jitter in first-spike latencies. This apparent gain-of-function increased the robustness of tone-burst responses in the presence of continuous masking noise. This study suggests that the nature of noise-induced synaptic damage varies between different species and that, in mouse, the noise-induced hyperexcitability seen in central auditory circuits is also observed at the level of the auditory nerve.NEW & NOTEWORTHY Noise-induced damage to synapses between inner hair cells and auditory-nerve fibers (ANFs) can occur without permanent hair cell damage, resulting in pathophysiology that "hides" behind normal thresholds. Prior single-fiber neurophysiology in guinea pig suggested that noise selectively targets high-threshold ANFs. Here, we show that the lingering pathophysiology differs in mouse, with both ANF groups affected and a paradoxical gain-of-function in surviving low-threshold fibers, including increased onset rate, decreased onset jitter, and reduced maskability.

Embryonic and Neonatal Mouse Cochleae Are Susceptible to Zika Virus Infection.

Congenital Zika Syndrome (CZS) is caused by vertical transmission of Zika virus (ZIKV) to the gestating human fetus. A subset of CZS microcephalic infants present with reduced otoacoustic emissions; this test screens for hearing loss originating in the cochlea. This observation leads to the question of whether mammalian cochlear tissues are susceptible to infection by ZIKV during development. To address this question using a mouse model, the sensory cochlea was explanted at proliferative, newly post-mitotic or maturing stages. ZIKV was added for the first 24 h and organs cultured for up to 6 days to allow for cell differentiation. Results showed that ZIKV can robustly infect proliferating sensory progenitors, as well as post-mitotic hair cells and supporting cells. Virus neutralization using ZIKV-117 antibody blocked cochlear infection. AXL is a cell surface molecule known to enhance the attachment of flavivirus to host cells. While Axl mRNA is widely expressed in embryonic cochlear tissues susceptible to ZIKV infection, it is selectively downregulated in the post-mitotic sensory organ by E15.5, even though these cells remain infectible. These findings may offer insights into which target cells could potentially contribute to hearing loss resulting from fetal exposure to ZIKV in humans.

Embryology, Malformations, and Rare Diseases of the Cochlea. / Embryologie, Fehlbildungen und seltene Erkrankungen der Cochlea.

Despite the low overall prevalence of individual rare diseases, cochlear dysfunction leading to hearing loss represents a symptom in a large proportion. The aim of this work was to provide a clear overview of rare cochlear diseases, taking into account the embryonic development of the cochlea and the systematic presentation of the different disorders. Although rapid biotechnological and bioinformatic advances may facilitate the diagnosis of a rare disease, an interdisciplinary exchange is often required to raise the suspicion of a rare disease. It is important to recognize that the phenotype of rare inner ear diseases can vary greatly not only in non-syndromic but also in syndromic hearing disorders. Finally, it becomes clear that the phenotype of the individual rare diseases cannot be determined exclusively by classical genetics even in monogenetic disorders.

Migraine and Cochlear Symptoms.

Migraine is one of the most common and highest burdens of disease. As a primary cerebral dysfunction illness, migraine might exhibit other system-related symptoms, including vestibular and cochlear symptoms. With the publication of the diagnostic criteria of vestibular migraine, the link between migraine and vestibular symptoms became clear. However, the relationship between migraine and cochlear symptoms is far from straightforward. Therefore, we focus on the correlation between migraine and deafness, sudden sensorineural hearing loss, acute tinnitus, and chronic tinnitus to better understand the relationship between migraine and cochlear symptoms.

Umbilical Cord Mesenchymal Stromal Cell-Derived Exosomes Rescue the Loss of Outer Hair Cells and Repair Cochlear Damage in Cisplatin-Injected Mice.

Umbilical cord-derived mesenchymal stromal cells (UCMSCs) have potential applications in regenerative medicine. UCMSCs have been demonstrated to repair tissue damage in many inflammatory and degenerative diseases. We have previously shown that UCMSC exosomes reduce nerve injury-induced pain in rats. In this study, we characterized UCMSC exosomes using RNA sequencing and proteomic analyses and investigated their protective effects on cisplatin-induced hearing loss in mice. Two independent experiments were designed to investigate the protective effects on cisplatin-induced hearing loss in mice: (i) chronic intraperitoneal cisplatin administration (4 mg/kg) once per day for 5 consecutive days and intraperitoneal UCMSC exosome (1.2 µg/µL) injection at the same time point; and (ii) UCMSC exosome (1.2 µg/µL) injection through a round window niche 3 days after chronic cisplatin administration. Our data suggest that UCMSC exosomes exert protective effects in vivo. The post-traumatic administration of UCMSC exosomes significantly improved hearing loss and rescued the loss of cochlear hair cells in mice receiving chronic cisplatin injection. Neuropathological gene panel analyses further revealed the UCMSC exosomes treatment led to beneficial changes in the expression levels of many genes in the cochlear tissues of cisplatin-injected mice. In conclusion, UCMSC exosomes exerted protective effects in treating ototoxicity-induced hearing loss by promoting tissue remodeling and repair.

A New Pathogenic Variant in POU3F4 Causing Deafness Due to an Incomplete Partition of the Cochlea Paved the Way for Innovative Surgery.

Incomplete partition type III (IP-III) is a relatively rare inner ear malformation that has been associated with a POU3F4 gene mutation. The IP-III anomaly is mainly characterized by incomplete separation of the modiolus of the cochlea from the internal auditory canal. We describe a 71-year-old woman with profound sensorineural hearing loss diagnosed with an IP-III of the cochlea that underwent cochlear implantation. Via targeted sequencing with a non-syndromic gene panel, we identified a heterozygous c.934G > C p. (Ala31Pro) pathogenic variant in the POU3F4 gene that has not been reported previously. IP-III of the cochlea is challenging for cochlear implant surgery for two main reasons: liquor cerebrospinalis gusher and electrode misplacement. Surgically, it may be better to opt for a shorter array because it is less likely for misplacement with the electrode in a false route. Secondly, the surgeon has to consider the insertion angles of cochlear access very strictly to avoid misplacement along the inner ear canal. Genetic results in well describes genotype-phenotype correlations are a strong clinical tool and as in this case guided surgical planning and robotic execution.

A new phenomenon of cochlear otosclerosis: an acquired or congenital disease? - A clinical report of cochlear otosclerosis.

BACKGROUND: No cochlear otosclerosis in infants with congenital bilateral SNHL has been reported. AIMS/OBJECTIVES: We report an infant male with bilateral cochlear otosclerosis, suggesting that cochlear otosclerosis may be a congenital disease and to further analyze the etiology of and genetic expression in congenital bilateral cochlear otosclerosis. We also describe the clinical characteristics and experience of patients with bilateral cochlear otosclerosis treated with cochlear implants (CIs). MATERIALS AND METHODS: Seven patients, including an infant, who were diagnosed with cochlear otosclerosis underwent CI surgery. Their medical records, audiological and radiological results, surgical procedures, and CI outcomes were collected and reviewed. RESULTS: The median age at hearing loss was 38 years, ranging from 0 to 47 years. The child had bilateral hearing loss at birth and received a CI at 1 year of age. He also had growth retardation and was diagnosed with 3q+/3p- syndrome. All patients (8 ears) had better postoperative auditory performance than that preoperatively. CONCLUSIONS AND SIGNIFICANCE: Although cochlear otosclerosis often starts at middle age and progresses slowly, it may be a congenital disease that is related to chromosome abnormality. This disease presents with SNHL or MHL, and treatment with a CI is beneficial.

Sudden Otovestibular Dysfunction in 3 Metastatic Melanoma Patients Treated With Immune Checkpoint Inhibitors.

Immune-related adverse events have been described in 86%-96% of high-risk melanoma patients treated with immune checkpoint inhibitors (ICI), while in 17%-59% of cases these are classified as severe or even life-threatening. The most common immune-related adverse events include diarrhea, fatigue, hypothyroidism, and hepatitis. Bilateral uveitis and unspecific vertigo have been described in 1% of cases, respectively, in the pivotal studies of ICIs, but the affection of the vestibule-cochlear system has not been reported before. In this case series, we present 3-stage IV melanoma patients with sudden onset of otovestibular dysfunction (hearing loss and vestibulopathy), partly combined with uveitis because of ICIs. We describe detailed diagnostic work-up and therapeutic interventions and discuss possible pathogenic mechanisms of this rare and disabling event.

Bilateral Hearing Loss and Unilateral Cochlear Ossification in a Patient With Chronic Myelogenous Leukemia.

Bilateral sensorineural deafness and unilateral cochlear ossification have rarely been described in patients with chronic myeloid leukemia (CML). A 21-year-old man presented to a hospital with right-sided sudden hearing loss and tinnitus. He was diagnosed with CML. Five days later, sudden hearing loss appeared in the other ear. Abnormality of the right-sided inner ear structure was revealed by preoperative magnetic resonance imaging; honeycomb-like cochlear ossification was observed during cochlear implant surgery in the right ear. The patient's auditory performance exhibited significant improvement after bilateral cochlear implantation in our hospital. Hematological disorders must be considered in patients with sensorineural hearing loss. Cochlear implantation is feasible in patients with CML who exhibit sensorineural deafness, but cochlear ossification should be carefully evaluated by means of preoperative imaging examinations.

[Cochleo-vestibular lesions and prognosis in patients with profound sudden sensorineural hearing loss: a comparative analysis].

Objective: To investigate the characteristics of cochleo-vestibular dysfunction in patients with profound sudden deafness, and the prognosis of inner ear hemorrhage. Methods: From January 2017 to December 2018, 92 inpatients with profound sudden sensorineural hearing loss were enrolled in the Department of Otorhinolaryngology, First Affiliated Hospital of Sun Yat-sen University. Our studied patients included 47 males and 45 females, aged 20-78 (39.3±6.1) years. According to the results of inner ear magnetic resonance imaging (MRI), the patients were divided into two groups: inner ear hemorrhage group and non-inner ear hemorrhage group. The clinical features, vestibular tests and audiological examination results during follow up were compared between the two groups. SPSS 22.0 software was used for statistical analysis. Results: The inner ear hemorrhage group consisted of 32 cases (34.8%, 32/92), all of whom complained of vertigo (100%, 32/32). Simultaneous vertigo attack and hearing loss occurred in 78.1% of this group (24/32). Neither semicircular canals function, nor cervical vestibular evoked myogenic potential (c-VEMP), nor ocular vestibular evoked myogenic potential (o-VEMP) in the affected side was normal (100%, 32/32). The rates of benign paroxysmal positional vertigo (BPPV) and disequilibrium were 37.5% (12/32) and 25.0% (8/32) respectively. Hearing improved in 28.1% (9/32) two weeks after treatment, and became stable at one month's follow up. In 60 cases without inner ear hemorrhage, 58.3% of them (35/60) experienced vertigo, which occurred simultaneously with hearing loss in 21 patients (60%, 21/35). The abnormal rates of semicircular canals function, c-VEMP and o-VEMP were 71.6% (43/60), 78.3% (47/60) and 66.7% (40/60), respectively. The incidence of BPPV was 16.7% (10/60) and 8.3% (5/60) in cases with disequilibrium. Hearing improved in 58.3% (35/60) two week after treatment, and became stable at three months' follow up. Significant difference was found in either vertigo rate, or simultaneous vertigo/hearing loss rate, or abnormal c-VEMP/o-VEMP rates, or accompanying BPPV, or disequilibrium rates between the two groups (P<0.05 each). Moreover, we observed better hearing recovery in non-inner ear hemorrhage group in the two weeks, one month, three months and six months' follow up, when compared with those in inner ear hemorrhage groups (P<0.05 each). Conclusions: Inner ear hemorrhage is associated with more severe cochlea-vestibular lesion and poorer prognosis, in comparison to the non-inner ear hemorrhage,in patients with profound sudden sensorineural hearing loss.

Auditory and Olfactory Deficits in Essential Tremor - Review of the Current Evidence.

Background: Essential tremor (ET) is the most common adult movement disorder, characterized by several motor and increasingly well recognized non-motor symptoms. Sensory deficits, such as hearing impairment and olfactory dysfunction, are amongst them. This review analyzes the available evidence of these sensory deficits and their possible mechanistic basis in patients with ET. Method: A PubMed literature search on the topic was performed in the May 2019 database. Results: Nineteen articles on hearing impairment and olfactory dysfunction in ET patients were identified. The prevalence of hearing impairment is higher in ET patients than healthy controls or Parkinson disease. Cochlear pathologies are suggested as the underlying cause, but there is still a lack of information about retrocochlear pathologies and central auditory processing. Reports on olfactory dysfunction have conflicting results. The presence of mild olfactory dysfunction in ET was suggested. Conflicting results may be due to the lack of consideration of the disease's heterogeneity, but according to recent data, most studies do not find prominent evidence of olfactory loss in ET. Conclusion: Although there is increasing interest in studies on non-motor symptoms in ET, there are few studies on sensory deficits, which are of particularly high prevalence. More studies are needed on to investigate the basis of non-motor symptoms, including sensory deficits.

New Classification of Cochlear Hypoplasia Type Malformation: Relevance in Cochlear Implantation.

OBJECTIVES: This paper attempts to create a new classification type of cochlear hypoplasia (CH)-type malformation taking into consideration of vestibular section and internal auditory canal (IAC). MATERIALS AND METHODS: Preoperative computed-tomography (CT) scans of cochlear implant (CI) candidates (N=31) from various clinics across the world with CH type malformation were taken for analysis. CT dataset were loaded into 3D-slicer freeware for three-dimensional (3D) segmentation of the inner-ear by capturing complete inner-ear structures from the entire dataset. Cochlear size in terms of diameter of available cochlear basal turn and length of cochlear lumen was measured from the dataset. In addition, structural connection between IAC and cochlear portions was scrutinized, which is highly relevant to the proposed CH classification in this study. RESULTS: CH group-I has the normal presence of IAC leading to cochlear and vestibular portions, whereas CH group-II is like CH group-I but with some degree of disruption in vestibular portion. In CH group-III, a disconnection between IAC and the cochlear portion irrespective of other features. Within all these three CH groups, the basal turn diameter varied between 3.1 mm and 9.6 mm, and the corresponding cochlear lumen length varied between 3 mm and 21 mm for the CI electrode array placement. CONCLUSION: A new classification of CH mainly based on the IAC connecting the cochlear and vestibular portions is presented in this study. CI electrode array length could be selected based on the length of the cochlear lumen, which can be observed from the 3D image.

Long-range cis-regulatory elements controlling GDF6 expression are essential for ear development.

Molecular mechanisms governing the development of the mammalian cochlea, the hearing organ, remain largely unknown. Through genome sequencing in 3 subjects from 2 families with nonsyndromic cochlear aplasia, we identified homozygous 221-kb and 338-kb deletions in a noncoding region on chromosome 8 with an approximately 200-kb overlapping section. Genomic location of the overlapping deleted region started from approximately 350 kb downstream of GDF6, which codes for growth and differentiation factor 6. Otic lineage cells differentiated from induced pluripotent stem cells derived from an affected individual showed reduced expression of GDF6 compared with control cells. Knockout of Gdf6 in a mouse model resulted in cochlear aplasia, closely resembling the human phenotype. We conclude that GDF6 plays a necessary role in early cochlear development controlled by cis-regulatory elements located within an approximately 500-kb region of the genome in humans and that its disruption leads to deafness due to cochlear aplasia.

Cochlear Patency after Translabyrinthine and Retrosigmoid Vestibular Schwannoma Surgery.

OBJECTIVES: To assess the incidence and onset of cochlear obliteration after translabyrinthine and retrosigmoid vestibular schwannoma surgery. MATERIALS AND METHODS: We retrospectively identified a consecutive series of eighty ears in eighty vestibular schwannoma patients who were treated via a translabyrinthine or retrosigmoid approach by a single neuro-otological surgical team in a tertiary referral center from May 2011 to January 2018. Postoperative, high- resolution T2-weighted turbo spin echo three-dimensional magnetic resonance (MR) images of the posterior fossa were evaluated at the level of the membranous labyrinth and internal auditory canal. Perilymphatic patency of the vestibule, basal, and apical cochlear turns were scored and classified as patent, hypointense, partially obliterated, or completely obliterated. RESULTS: Twenty-five vestibular schwannomas were treated with surgery via a translabyrinthine approach, and fifty-five were treated using a retrosigmoid approach; of these, 8% and 65%, respectively, showed no signs of perilymphatic alterations in the basal or apical turns, while 84% and 20%, respectively, showed partial or complete obliteration in the basal or apical turns with a mean postoperative interval of 127 and 140 days, respectively. All the patients who underwent multiple MR scans and had a completely patent perilymphatic system on the first postoperative scan remained patent during subsequent scans; 16% of the patients showed worsened perilymphatic appearance. The onset of cochlear obliteration occurred within 2-7 months in most translabyrinthine patients. CONCLUSION: These findings may support the need for simultaneous cochlear electrode or dummy implantation in translabyrinthine surgery. Second-stage implantation could be feasible in cases where a retrosigmoid approach is used; however, the implantation should be considered within the initial months to avoid cochlear obliteration. Findings on the first postoperative MR could indicate the need for intensified MR follow-up and may even predict the occurrence of cochlear obliteration.

Clinical Characteristics of Patients with Cochlear Fistulas Caused by Chronic Otitis Media with Cholesteatoma.

OBJECTIVES: To analyze the clinical characteristics of cochlear fistulas (CFs) and propose a new fistula classification system with regard to the cochlea. MATERIALS AND METHODS: A retrospective chart review was conducted between January 2008 and December 2015 to identify patients who had undergone surgery for cholesteatoma with an associated CF. The following data were collected: preoperative symptoms, findings of temporal bone computed tomography (TBCT), fistula stage, cholesteatoma classification, surgical technique, and pre- and postoperative pure-tone audiometry. RESULTS: We analyzed a total of 159 patients, out of which 9 (5.7%) were diagnosed with a CF. The average duration of the chronic otitis media was 19.8 years. Cholesteatomas that induced CF rarely existed in the nonaggressive state; recurrent otorrhea was observed in all but one of our subjects. All the patients with CF had a distinct origin of cholesteatoma that developed from the retraction of posterior pars tensa; further, 88.9% cholesteatomas extended to and filled the sinus tympani. Preoperative audiometry revealed total hearing loss in 4 (44.4%) patients. Further, five patients with residual hearing before surgery had stage I fistulas, and the bone conduction thresholds remained stable after surgery. CONCLUSION: Cochlear fistulas were often detected in patients with (1) a history of chronic otitis media (exceeding 10 years), (2) frequently recurring otorrhea, and (3) pars tensa cholesteatomas that extended to the posterior mesotympanum and filled the sinus tympani. Such patients can suffer from potentially severe and irreparable sensorineural hearing loss.

CDK5RAP2 primary microcephaly is associated with hypothalamic, retinal and cochlear developmental defects.

BACKGROUND: Primary hereditary microcephaly (MCPH) comprises a large group of autosomal recessive disorders mainly affecting cortical development and resulting in a congenital impairment of brain growth. Despite the identification of >25 causal genes so far, it remains a challenge to distinguish between different MCPH forms at the clinical level. METHODS: 7 patients with newly identified mutations in CDK5RAP2 (MCPH3) were investigated by performing prospective, extensive and systematic clinical, MRI, psychomotor, neurosensory and cognitive examinations under similar conditions. RESULTS: All patients displayed neurosensory defects in addition to microcephaly. Small cochlea with incomplete partition type II was found in all cases and was associated with progressive deafness in 4 of them. Furthermore, the CDK5RAP2 protein was specifically identified in the developing cochlea from human fetal tissues. Microphthalmia was also present in all patients along with retinal pigmentation changes and lipofuscin deposits. Finally, hypothalamic anomalies consisting of interhypothalamic adhesions, a congenital midline defect usually associated with holoprosencephaly, was detected in 5 cases. CONCLUSION: This is the first report indicating that CDK5RAP2 not only governs brain size but also plays a role in ocular and cochlear development and is necessary for hypothalamic nuclear separation at the midline. Our data indicate that CDK5RAP2 should be considered as a potential gene associated with deafness and forme fruste of holoprosencephaly. These children should be given neurosensory follow-up to prevent additional comorbidities and allow them reaching their full educational potential. TRIAL REGISTRATION NUMBER: NCT01565005.

Association between speech perception in noise and electrophysiological measures: an exploratory study of possible techniques to evaluate cochlear synaptopathy in humans.

Objective: The primary aim of this study was to investigate whether scores for a speech-in-noise test were associated with the results of two electrophysiological techniques mainly targeting low spontaneous rate, high-threshold auditory fibres.Design: Cross-sectional study. Participants were evaluated with the hearing-in-noise test (HINT), along with the Auditory Brainstem Response (ABR) with and without ipsilateral noise. The wave V/I amplitude ratio for the ABR without ipsilateral noise and ABR wave V latency shift in the presence of ipsilateral noise were obtained.Study sample: Twenty adults aged between 20 and 34 years (10 females) who did not report occupational exposure to noise were selected. All participants presented with normal hearing thresholds (0.250-8 kHz) and the presence of distortion product otoacoustic emissions, bilaterally.Results: A significant association between the wave V/I amplitude ratio for the left ear and the HINT scores for the left ear was found.Conclusions: Based on the results of this study, in normal-hearing listeners, the wave V/I ratio is associated with speech-in-noise performance, specifically in the left ear. This non-invasive procedure has the potential to be used in clinical populations who present with speech-in-noise difficulties despite having normal audiograms.

Pattern of cochlear obliteration after vestibular Schwannoma resection according to surgical approach.

OBJECTIVES/HYPOTHESIS: To investigate the prevalence and course of cochlear obliteration according to microsurgical approach to inform clinical decision making regarding optimal timing of cochlear implantation. STUDY DESIGN: Retrospective radiologic review and chart review. METHODS: Patients who underwent microsurgical resection of vestibular schwannoma (VS) with a minimum of two available postoperative magnetic resonance imaging (MRI) scans were analyzed. The prevalence and timing of cochlear and labyrinthine obliteration was classified using relevant MRI sequences. RESULTS: MRI studies in 60 patients were analyzed: 20 translabyrinthine (TL), 20 retrosigmoid, and 20 middle fossa (MF) cases. The first and last postoperative MRI was obtained a median of 3.4 months (interquartile range (IQR), 3.0-3.7 months) and 35 months (IQR, 27-83 months) after surgery, respectively. At the time of the first postoperative MRI, 21 (35%) patients had partial basal turn obliteration, and none of the patients had complete basal turn obliteration. At the time of the last postoperative MRI, six (10%) patients had partial basal turn obliteration and 17 (28%) patients had complete basal turn obliteration. The pattern of partial or complete basal turn obliteration differed significantly among all three surgical approaches (P < .001). Specifically, the risk of partial or complete obliteration of the basal turn was highest in the TL cohort and lowest in the MF cohort. CONCLUSIONS: The prevalence and timing of cochlear obliteration after VS microsurgery varies significantly according to surgical approach. The risk of early and complete obliteration is highest in the TL group and lowest in the MF cohort. These data may inform clinical decision making regarding optimal timing of cochlear implantation in patients with advanced hearing loss after microsurgical resection. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:474-481, 2020.