The genetic landscape of age-related hearing loss

Age-related hearing loss (ARHL) is a prevalent concern in the elderly population. Recent genome-wide and phenome-wide association studies (GWASs and PheWASs) have delved into the identification of causative variants and the understanding of pleiotropy, highlighting the polygenic intricacies of this complex condition. While recent large-scale GWASs have pinpointed significant SNPs and risk variants associated with ARHL, the detailed mechanisms, encompassing both genetic and epigenetic modifications, remain to be fully elucidated. This review presents the latest advances in association studies, integrating findings from both human studies and model organisms. By juxtaposing historical perspectives with contemporary genomics, we aim to catalyze innovative research and foster the development of novel therapeutic strategies for ARHL.

Altered Fhod3 expression involved in progressive high-frequency hearing loss via dysregulation of actin polymerization stoichiometry in the cuticular plate

Age-related hearing loss (ARHL) is a common sensory impairment with complex underlying mechanisms. In our previous study, we performed a meta-analysis of genome-wide association studies (GWAS) in mice and identified a novel locus on chromosome 18 associated with ARHL specifically linked to a 32 kHz tone burst stimulus. Consequently, we investigated the role of Formin Homology 2 Domain Containing 3 (Fhod3), a newly discovered candidate gene for ARHL based on the GWAS results. We observed Fhod3 expression in auditory hair cells (HCs) primarily localized at the cuticular plate (CP). To understand the functional implications of Fhod3 in the cochlea, we generated Fhod3 overexpression mice (Pax2-Cre+/-; Fhod3Tg/+) (TG) and HC-specific conditional knockout mice (Atoh1-Cre+/-; Fhod3fl/fl) (KO). Audiological assessments in TG mice demonstrated progressive high-frequency hearing loss, characterized by predominant loss of outer hair cells, and a decreased phalloidin intensities of CP. Ultrastructural analysis revealed loss of the shortest row of stereocilia in the basal turn of the cochlea, and alterations in the cuticular plate surrounding stereocilia rootlets. Importantly, the hearing and HC phenotype in TG mice phenocopied that of the KO mice. These findings suggest that balanced expression of Fhod3 is critical for proper CP and stereocilia structure and function. Further investigation of Fhod3 related hearing impairment mechanisms may lend new insight towards the myriad mechanisms underlying ARHL, which in turn could facilitate the development of therapeutic strategies for ARHL.

Comparison of Postoperative Outcomes in Cystic Versus Solid Vestibular Schwannoma in a Multi-institutional Cohort

OBJECTIVE

Cystic vestibular schwannomas (cVSs) have more variable and less favorable clinical outcomes after microsurgical resection compared with solid VS (sVS). This study compares the preoperative presentation and postoperative outcomes between cVS and sVS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Two tertiary skull base referral centers.

METHODS

Consecutive adult patients who underwent VS resection from 2016 to 2021 were included. Univariate and multivariate analyses compared differences in baseline symptoms and postoperative outcomes between cVS and sVS.

RESULTS

There were a total of 315 patients (64% female; mean age, 54 yrs) and 46 (15%) were cystic. cVS were significantly larger than sVS (maximum diameter, 28 vs. 18 mm, p < 0.001) and had higher rates of dysphagia and dysphonia preoperatively (p < 0.02). cVSs were more likely to undergo translabyrinthine resection (76 vs. 50%, p = 0.001) and have a higher rate of subtotal resection (STR) compared with sVS (30 vs. 13%, p = 0.003). At latest follow-up, fewer cVS achieved good facial nerve (FN) outcome (House-Brackmann [HB] I/II) (80 vs. 90%, p = 0.048). Subanalysis of cVS and sVS matched in tumor size, and surgical approach did not show differences in the rate of STR or FN outcomes (HB I/II, 82 vs. 78%, p = 0.79).

CONCLUSION

In this large multi-institutional series, cVSs represent a distinct entity and are characterized by larger tumor size and higher incidence of atypical symptoms. Although cVSs were more likely to undergo STR and portend worse FN outcomes than sVSs, this may be due to their larger tumor size rather than the presence of the cystic component.

Socioeconomic Disparities in the Pursuit of Care at a High-Volume Institution for Surgical Resection of Vestibular Schwannomas

OBJECTIVE

Increased institutional surgical resection case volume for vestibular schwannomas (VSs) has been associated with improved patient outcomes, including reduced risk of prolonged hospital stay and readmission. Socioeconomic disparities in the pursuit of care at these high-volume institutions remain unknown.

STUDY DESIGN

Retrospective cohort epidemiological study.

SETTING

National Cancer Database, a hospital-based registry of over 1,500 facilities in the United States.

PATIENTS

Adult VS patients (age, >18 years) treated surgically.

INTERVENTIONS

High- versus low-volume facilities, defined using a facility case volume threshold of 25 cases per year. A risk-adjusted restricted cubic spline model was previously used to identify this risk threshold beyond which the incremental benefit of increasing case volume began to plateau.

MAIN OUTCOME MEASURES

Sociodemographic factors, including race, ethnicity, income, insurance status, and rurality. Multivariable analyses were adjusted for patient and tumor characteristics, including age, sex, Charlson-Deyo score, and tumor size.

RESULTS

A totoal of 10,048 patients were identified (median [interquartile range] age = 51 [41-60] years, 54% female, 87% Caucasian). Patients with Spanish/Hispanic ethnicity (OR = 0.71, 95% confidence interval [CI] = 0.52-0.96), income below median (OR = 0.63, 95% CI = 0.55-0.73]), and Medicare, Medicaid, or other government insurance versus private insurance (OR = 0.63, 95% CI = 0.53-0.74) had reduced odds of treatment at a high-volume facility. Further sensitivity analyses in which facility volume was operationalized continuously reinforced direction and significance of these associations.

CONCLUSIONS

Socioeconomic disparities exist in the propensity for VS patients to be treated at a high-volume facility. Further work is needed to understand the nature of these associations and whether interventions can be designed to mitigate them.

Altered Fhod3 Expression Involved in Progressive High-Frequency Hearing Loss via Dysregulation of Actin Polymerization Stoichiometry in The Cuticular Plate

Age-related hearing loss (ARHL) is a common sensory impairment with comlex underlying mechanisms. In our previous study, we performed a meta-analysis of genome-wide association studies (GWAS) in mice and identified a novel locus on chromosome 18 associated with ARHL specifically linked to a 32 kHz tone burst stimulus. Consequently, we investigated the role of Formin Homology 2 Domain Containing 3 (Fhod3), a newly discovered candidate gene for ARHL based on the GWAS results. We observed Fhod3 expression in auditory hair cells (HCs) and primarily localized at the cuticular plate (CP). To understand the functional implications of Fhod3 in the cochlea, we generated Fhod3 overexpression mice (Pax2-Cre+/-; Fhod3Tg/+) (TG) and HC-specific conditional knockout mice (Atoh1-Cre+/-; Fhod3fl/fl) (KO). Audiological assessments in TG mice demonstrated progressive high-frequency hearing loss, characterized by predominant loss of outer HCs and decrease phalloidin intensities of CP. Ultrastructural analysis revealed shortened stereocilia in the basal turn cochlea. Importantly, the hearing and HC phenotype in TG mice were replicated in KO mice. These findings indicate that Fhod3 plays a critical role in regulating actin dynamics in CP and stereocilia. Further investigation of Fhod3-related hearing impairment mechanisms may facilitate the development of therapeutic strategies for ARHL in humans.

The Effect of Immediate Microsurgical Resection of Vestibular Schwannoma on Hearing Preservation

OBJECTIVE

Evaluate for differences in postoperative hearing in patients who undergo immediate versus delayed hearing preservation microsurgical resection of vestibular schwannomas (VS).

STUDY DESIGN

Retrospective single-institution cohort study spanning November 2017 to November 2021.

SETTING

Single-institution tertiary care hospital.

PATIENTS

Sporadic VS in patients with American Academy of Otolaryngology-Head and Neck Surgery hearing classification A or B, with tumor size less than or equal to 2 cm and undergoing hearing preservation microsurgical resection.

INTERVENTIONS

Delayed surgical intervention defined by time from first diagnostic MRI to date of surgery being greater than 3 months.

MAIN OUTCOME MEASURES

Preoperative and postoperative audiometric performance.

RESULTS

In total, 193 patients met inclusion criteria. Within the cohort, 70 (36%) proceeded with surgery within 3 months of diagnostic MRI with a mean observation time of 62 days, whereas 123 (63%) underwent surgery after 3 months with a mean observation time of 301 days. There was no difference in preoperative hearing between the two groups with word recognition score 99% in early intervention group and 100% in delayed intervention group ( p = 0.6). However, 64% of those who proceeded with immediate surgery had successful hearing preservation, compared to a 42% of those who had delayed intervention ( p < 0.01). In a multivariable logistic regression accounting for preoperative word recognition score, tumor size, and age at diagnosis, the odds of hearing preservation were lower in those who delayed surgery compared to immediate surgery (odds ratio, 0.31; 95% confidence interval, 0.15-0.61).

CONCLUSIONS

Patients who underwent microsurgical resection within 3 months of diagnosis demonstrated a hearing preservation advantage compared to those who did not. Findings of this study highlight the counseling challenges associated with the timing of surgical treatment of VS in patients presenting with good preoperative hearing and small tumors.

Attenuation of Age-Related Hearing Impairment in Senescence-Accelerated Mouse Prone 8 (SAMP8) Mice Treated with Fatty Acid Synthase Inhibitor CMS121

In the senescence-accelerated mouse prone 8 (SAMP8) mouse model, oxidative stress leads to premature senescence and age-related hearing impairment (ARHI). CMS121 inhibits oxytosis/ferroptosis by targeting fatty acid synthase. The aim of our study was to determine whether CMS121 is protective against ARHI in SAMP8 mice. Auditory brainstem responses (ABRs) were used to assess baseline hearing in sixteen 4-week-old female SAMP8 mice, which were divided into two cohorts. The control group was fed a vehicle diet, while the experimental group was fed a diet containing CMS121. ABRs were measured until 13 weeks of age. Cochlear immunohistochemistry was performed to analyze the number of paired ribbon-receptor synapses per inner hair cell (IHC). Descriptive statistics are provided with mean ± SEM. Two-sample t-tests were performed to compare hearing thresholds and paired synapse count across the two groups, with alpha = 0.05. Baseline hearing thresholds in the control group were statistically similar to those of the CMS121 group. At 13 weeks of age, the control group had significantly worse hearing thresholds at 12 kHz (56.5 vs. 39.8, p = 0.044) and 16 kHz (64.8 vs. 43.8, p = 0.040) compared to the CMS121 group. Immunohistochemistry showed a significantly lower synapse count per IHC in the control group (15.7) compared to the CMS121 group (18.4), p = 0.014. Our study shows a significant reduction in ABR threshold shifts and increased preservation of IHC ribbon synapses in the mid-range frequencies among mice treated with CMS121 compared to untreated mice.

Going the distance in acoustic neuroma resection: microsurgical outcomes at high-volume centers of excellence

PURPOSE

High-volume hospitals are associated with improved surgical outcomes for acoustic neuromas (ANs). Due to the benign and slow-growing nature of ANs, many patients travel to geographically distant cities, states, or countries for their treatment. However, the impact of travel burden to high-volume centers, as well as its relative benefit are poorly understood. We compared post-operative outcomes between AN patients that underwent treatment at local, low-volume hospitals with those that traveled long distances to high-volume hospitals.

METHODS

The National Cancer Database was used to analyze AN patients that underwent surgery (2004-2015). Patients in the lowest quartile of travel distance and volume (Short-travel/Low-Volume: STLV) were compared to patients in the highest quartile of travel distance and volume (Long-travel/High-Volume: LTHV). Only STLV and LTHV cases were included for analysis.

RESULTS

Of 13,370 cases, 2,408 met inclusion criteria. STLV patients (n = 1,305) traveled a median of 6 miles (Interquartile range [IQR] 3-9) to low-volume centers (median 2, IQR 1-3 annual cases) and LTHV patients (n = 1,103) traveled a median of 143 miles [IQR 103-230, maximum 4,797] to high-volume centers (median 34, IQR 28-42 annual cases). LTHV patients had lower Charlson/Deyo scores (p = 0.001), mostly received care at academic centers (81.7% vs. 39.4%, p < 0.001), and were less likely to be minorities (7.0% vs. 24.2%, p < 0.001) or underinsured (4.2% vs. 13.8%, p < 0.001). There was no difference in average tumor size. On multivariable analysis, LTHV predicted increased likelihood of gross total resection (odds ratio [OR] 5.6, 95% confidence interval [CI] 3.8-8.4, p < 0.001), longer duration between diagnosis and surgery (OR 1.3, 95% CI 1.0-1.6, p = 0.040), decreased length of hospital stay (OR 0.5, 95% CI 0.4-0.7, p < 0.001), and greater overall survival (Hazard Ratio [HR] 0.6, 95% CI 0.4-0.95, p = 0.029). There was no significant difference in 30-day readmission on adjusted analysis.

CONCLUSION

Although traveling farther to high-volume centers was associated with greater time between diagnosis and treatment for AN patients, they experienced superior postoperative outcomes compared to patients who received treatment locally at low-volume centers. Enabling access and travel to high-volume centers may improve AN patient outcomes.

Association Between Facility Surgical Volume and Excess Time in the Hospital After Surgical Resection of Vestibular Schwannomas

Importance

High surgical vestibular schwannoma case volume in a medical institution may decrease the risk of adverse outcomes among patients undergoing vestibular schwannoma surgery.

Objective

To study the association between surgical vestibular schwannoma case volume and excess time in the hospital after vestibular schwannoma surgery.

Design, Setting, and Participants

This cohort study evaluated data from the National Cancer Database from January 1, 2004, through December 31, 2019, on Commission on Cancer-accredited facilities in the US. The hospital-based sample comprised adult patients aged 18 years or older with a vestibular schwannoma treated with surgery.

Exposures

Facility case volume, defined as the mean number of surgical vestibular schwannoma cases per year in the 2 years preceding the index case.

Main Outcomes and Measures

The primary outcome was a composite of prolonged hospital stay (>90th percentile) or 30-day readmission. Risk-adjusted restricted cubic splines were used to model the probability of the outcome according to facility volume. The inflection point (in cases per year) when the declining risk of excess time in the hospital began to plateau was selected as the threshold to define high- and low-volume facilities. Outcomes were compared among patients treated at high- and low-volume facilities, with mixed-effects logistic regression models adjusting for patient sociodemographic characteristics, comorbidities, tumor size, and clustering within facilities. Collected data were analyzed between June 24 and August 31, 2022.

Results

Among 11 524 eligible patients (mean [SD] age, 50.2 [12.8] years; 53.5% female; 46.5% male) who underwent surgical resection of vestibular schwannoma at 66 reporting facilities, the median length of stay was 4 (IQR, 3-5) days, and 655 patients (5.7%) were readmitted within 30 days. The median case volume was 16 (IQR, 9-26) cases per year. An adjusted restricted cubic spline model identified a downtrending probability of excess time in the hospital with increasing volume. The declining risk of excess time in the hospital began to plateau at a facility volume of 25 cases per year. Surgery at a facility with an annual case volume at or above this threshold was independently associated with a 42% reduction in the odds of excess time in the hospital compared with surgery at a low-volume center (odds ratio, 0.58; 95% CI, 0.44-0.77).

Conclusions and Relevance

This cohort study found that among adults undergoing vestibular schwannoma surgery, a higher facility case volume was associated with a reduced risk of prolonged hospital stay or 30-day readmission. A facility case volume of 25 cases per year may represent a risk-defining threshold.

Surgical Outcomes Following Vestibular Schwannoma Resection in Patients over the Age of Sixty-five

Objective  Vestibular schwannoma (VS) are benign, often slow growing neoplasms. Some institutions opt for radiosurgery in symptomatic patients of advanced age versus surgical resection. The aim of the study is to analyze surgical outcomes of VS in patients over the age of 65 who were either not candidates for or refused radiosurgery. Methods  This includes retrospective analysis of VS patients between 1988 and 2020. Demographics, tumor characteristics, surgical records, and clinical outcomes were recorded. Patient preference for surgery over radiosurgery was recorded in the event that patients were offered both. Facial nerve outcomes were quantified using House-Brackmann (HB) scores. Tumor growth was defined by increase in size of >2 mm. Results  In total, 64 patients were included of average age 72.4 years (65-84 years). Average maximum tumor diameter was 29 mm (13-55 mm). Forty-five patients were offered surgery or GKRS, and chose surgery commonly due to radiation aversion (48.4%). Gross total resection was achieved in 39.1% ( n  = 25), near total 32.8% ( n  = 21), and subtotal 28.1% ( n  = 18). Average hospitalization was 5 days [2-17] with 75% ( n  = 48) discharged home. Postoperative HB scores were good (HB1-2) in 43.8%, moderate (HB3-4) in 32.8%, and poor (HB5-6) in 23.4%. HB scores improved to good in 51.6%, moderate in 31.3%, and remained poor in 17.1%, marking a rate of facial nerve improvement of 10.9%. Tumor control was achieved in 95.3% of cases at an average follow-up time of 37.8 months. Conclusion  VS resection can be safely performed in patients over the age of 65. Advanced age should not preclude a symptomatic VS patient from being considered for surgical resection.

Management of Neurofibromatosis Type 2-Associated Vestibular Schwannomas

Neurofibromatosis type 2 (NF2) is an autosomal dominant syndrome caused by a mutation in the NF2 suppressor gene and is characterized by the development of multiple benign tumors throughout the central nervous system. Bilateral vestibular schwannomas (VSs) are pathognomonic for NF2 and are associated with progressive hearing loss and eventual deafness in most patients. This review presents current management options for NF-2-associated VSs.

Use of a Novel Clinical Decision-Making Tool in Vestibular Schwannoma Treatment

OBJECTIVE

To determine the usefulness of a personalized tool and its effect on the decision-making process for those with vestibular schwannoma (VS).

STUDY DESIGN

Prospective study.

SETTING

Single institution, academic tertiary care lateral skull base surgery program.

PATIENTS

Patients diagnosed with VS.

INTERVENTIONS

A comprehensive clinical decision support (CDS) tool was constructed from a previously published retrospective patient-reported data obtained from members of the Acoustic Neuroma Association from January to March 2017. Demographic, tumor, and treatment modality data, including associated side effects, were collected for 775 patients and integrated in an interactive and personalized web-based tool.

MAIN OUTCOME MEASURES

Pre- and posttool questionnaires assessing the process of deciding treatment for VS using a decisional conflict scale (DCS) and satisfaction with decision (SWD) scale were compared.

RESULTS

A pilot study of 33 patients evaluated at a single institution tertiary care center with mean ± SD age of 63.9 ± 13.5 years and with average tumor size of 7.11 ± 4.75 mm were surveyed. CDS implementation resulted in a mean ± SD total DCS score decrease from 43.6 ± 15.5 to 37.6 ± 16.4 ( p < 0.01) and total SWD score increase from 82.8 ± 16.1 to 86.2 ± 14.4 ( p = 0.04), indicating a significant decrease in decisional conflict and increase in satisfaction.

CONCLUSIONS

Implementing a decision-making tool after diagnosis of VS reduced decisional conflict and improved satisfaction with decision. Patients considered the tool to be an aid to their medical knowledge, further improving their comfort and understanding of their treatment options. These findings provide a basis for developing predictive tools that will assist patients in making informed medical decisions in the future.

Volumetric analysis of the aging auditory pathway using high resolution magnetic resonance histology

Numerous shown consequences of age-related hearing loss have been unveiled; however, the relationship of the cortical and subcortical structures of the auditory pathway with aging is not well known. Investigations into neural structure analysis remain sparse due to difficulties of doing so in animal models; however, recent technological advances have been able to achieve a resolution adequate to perform such studies even in the small mouse. We utilize 12 members of the BXD family of recombinant inbred mice and aged separate cohorts. Utilizing novel magnetic resonance histology imaging techniques, we imaged these mice and generated high spatial resolution three dimensional images which were then comprehensively labeled. We completed volumetric analysis of 12 separate regions of interest specific to the auditory pathway brainstem nuclei and cortical areas with focus on the effect of aging upon said structures. Our results showed significant interstrain variation in the age-related effect on structure volume supporting a genetic influence in this interaction. Through multivariable modeling, we observed heterogenous effects of aging between different structures. Six of the 12 regions of interests demonstrated a significant age-related effect. The auditory cortex and ventral cochlear nucleus were found to decrease in volume with age, while the medial division of the medial geniculate nucleus, lateral lemniscus and its nucleus, and the inferior colliculus increased in size with age. Additionally, no sex-based differences were noted, and we observed a negative relationship between auditory cortex volume and mouse weight. This study is one of the first to perform comprehensive magnetic resonance imaging and quantitative analysis in the mouse brain auditory pathway cytoarchitecture, offering both novel insights into the neuroanatomical basis of age-related changes in hearing as well as evidence toward a genetic influence in this interaction. High resonance magnetic resonance imaging provides a promising efficacious avenue in future mouse model hearing loss investigations.

Large-scale phenotyping and characterization of age-related hearing loss in outbred CFW mice

Age-related hearing loss (ARHL), or presbycusis, is one of the most prevalent conditions affecting the global population. A substantial fraction of patients with ARHL have no identifiable mutation despite over a hundred having been discovered, suggesting unidentified monogenic or polygenic causes. In this study, we investigated the hearing function of the aging outbred CFW mice through auditory brainstem response (ABR) thresholds. Through the characterization of 1,132 ABRs, we observed significant variation in both absolute thresholds and the effect of aging. We identify eight distinct patterns of hearing loss and were able to categorize nearly all data within these eight categories. Proportions within each category varied immensely between aging timepoints. We observe a small but consistent hearing deficit in female CFW mice. The resulting phenotypic data are a necessity for ARHL association mapping at a higher resolution than has previously been achieved and provides a new resource for studying ARHL.

Auditory Brain Stem Response Predictors of Hearing Outcomes after Middle Fossa Resection of Vestibular Schwannomas

Objectives To analyze the relationship between preoperative and intraoperative auditory brain stem response (ABR) characteristics and hearing outcomes in patients with vestibular schwannomas (VS) undergoing hearing preservation (HP) surgery via a middle cranial fossa (MCF) approach.

Design Prospective study.

Setting Academic tertiary skull base referral center.

Methods Pre- and postoperative pure-tone average (PTA) and word recognition score (WRS) were examined. Intraoperative ABR wave III latency, wave V latency, and amplitude were recorded. HP was defined as postoperative WRS ≥50%.

Participants Adult patients with VS and WRS ≥50% who underwent MCF tumor resection between November 2017 and September 2019.

Main Outcome Measures Postoperative hearing outcomes.

Results Sixty patients were included. Mean tumor size was 9.2 mm (range, 3–17). HP rates were 56.7% for the cohort and 69.7% for tumors <10 mm. A complete loss of wave V was associated with an 82.9% increase in postoperative PTA (p < 0.001) and 97.2% decrease in WRS (p < 0.001), whereas a diminished wave V was correlated with 62.7% increase in PTA (p < 0.001) and 55.7% decrease in WRS (p = 0.006). A diminished or absent wave V, but not increased wave III/V latency or decreased wave V amplitude, was correlated with a decline in postoperative hearing class (r = 0.735, p < 0.001). Receiver-operating characteristic analysis demonstrated that a stable wave V has the highest accuracy in predicting HP (sensitivity of 82.6%, specificity of 84.8%).

Conclusion Of the examined preoperative and intraoperative ABR characteristics, a stable wave V intraoperatively was the strongest predictor of HP after MCF resection of VS.

Level of Evidence Level III.

Cochlear ribbon synapse maturation requires Nlgn1 and Nlgn3

Hearing depends on precise synaptic transmission between cochlear inner hair cells and spiral ganglion neurons through afferent ribbon synapses. Neuroligins (Nlgns) facilitate synapse maturation in the brain, but they have gone unstudied in the cochlea. We report Nlgn3 and Nlgn1 knockout (KO) cochleae have fewer ribbon synapses and have impaired hearing. Nlgn3 KO is more vulnerable to noise trauma with limited activity at high frequencies one day after noise. Furthermore, Nlgn3 KO cochleae have a 5-fold reduction in synapse number compared to wild type after two weeks of recovery. Double KO cochlear phenotypes are more prominent than the KOs, for example, 5-fold smaller synapses, 25% reduction in synapse density, and 30% less synaptic output. These observations indicate Nlgn3 and Nlgn1 are essential to cochlear ribbon synapse maturation and function.

Local Tumor Behavior Associated With Survival Among Patients With Paraganglioma of the Head and Neck

Objective

The purpose of this study was to evaluate the utility of ICD-O-3–classified local tumor behavior as a prognosticator of head and neck paraganglioma (HNP) outcomes.

Study Design

Retrospective cohort study.

Setting

National Cancer Database between 2004 and 2016.

Methods

This study included patients aged ≥18 years who were diagnosed with HNP. Clinical outcomes and clinicopathologic features were compared with regard to local tumor behavior.

Results

Our study included 525 patients, of which the majority had HNP classified as locally invasive (45.9%) or borderline (37.9%). The most common anatomic sites involved were the carotid body (33.7%), intracranial regions (29.0%), or cranial nerves (25.5%). Carotid body tumors were exclusively locally invasive, whereas intracranial and cranial nerve HNP were overwhelmingly benign or borderline (94% and 91%, respectively). One-fourth of patients underwent pathologic analysis of regional lymph nodes, of which the majority were positive for metastasis (80.6%). Metastasis to distant organs was twice as common in patients with locally invasive tumors vs benign (15% vs 7.1). For benign disease, surgery with radiotherapy (adjusted hazard ratio [aHR], 40.45; P = .006) and active surveillance (aHR, 24.23; P = .008) were associated with worse survival when compared with surgery alone. For locally invasive tumors, greater age (aHR, 1.07; P < .0001) and positive surgical margins (aHR, 4.13; P = .010) were predictors of worse survival, while combined surgery and radiotherapy were predictors of improved survival vs surgery alone (aHR, 0.31; P = .027).

Conclusion

While criteria for tumor behavior could not be defined, our results suggest that such a classification system could be used to enhance HNP risk stratification and guide clinical management decisions.

Opioid Prescribing Patterns After Skull Base Surgery for Vestibular Schwannoma

OBJECTIVE

Excessive opioid prescription is a source of prescription diversion and could contribute to chronic opioid abuse. This study describes the opioid prescribing patterns and risk factors for additional opioid prescription after surgical resection of vestibular schwannoma (VS).

STUDY DESIGN

Retrospective chart review.

SETTING

Single tertiary referral center.

PATIENTS

Adult VS patients undergoing surgical resection between May 2019 and March 2020.

INTERVENTIONS

Opioid use postoperatively and up to 60 days following surgery were characterized from medical records and by querying the state-wide Controlled Substance Utilization Review and Evaluation System.

MAIN OUTCOME MEASURES

The presence of additional opioid prescriptions within 60 days of surgery.

RESULTS

A total of 109 patients (mean age 50 yrs, 65.5% female) were prescribed an average of 138.2 ± 117.8 mg of morphine equivalents (MME). Twenty-two (20.9%) required additional prescriptions of 163.2 ± 103.2 MME. Age, gender, tumor size, or surgical approach (translabyrinthine, retrosigmoid, versus middle fossa) were not associated with additional prescriptions. Patients with additional prescriptions had higher body mass index (BMI 28.8 vs. 25.8 kg/m2, p = 0.015) and required more opioid medications during hospitalization (51.8 vs. 29.1 MME, p = 0.002). On multivariate logistic regression, higher BMI (odds ratio [OR] 1.32; p = 0.001), history of headaches (OR 11.9, p = 0.011), and history of opioid use (OR 29.3, p = 0.008) were associated with additional prescription.

CONCLUSIONS

Additional opioid prescriptions may be necessary in a portion of VS patients undergoing surgery. The choice of surgical approach is not associated with excess opioid requirements. Patients with higher BMI, history of headaches, or preoperative opioid use may require additional prescriptions.

Dispersed Bone Spicules as a Cause of Postoperative Headache after Retrosigmoid Vestibular Schwannoma Surgery: A Myth?

Objectives  Dispersion of bone dust in the posterior fossa during retrosigmoid craniectomy for vestibular schwannoma (VS) resection could be a source of meningeal irritation and lead to development of persistent postoperative headaches (POH). We aim to determine risk factors, including whether the presence of bone spicules that influence POH after retrosigmoid VS resection. Design  Present study is a retrospective case series. Setting  The study was conducted at a tertiary skull-base referral center. Participants  Adult patients undergoing VS resection via a retrosigmoid approach between November 2017 and February 2020 were included for this study. Main Outcome Measures  Development of POH lasting ≥ 3 months is the primary outcome of this study. Results  Of 64 patients undergoing surgery, 49 had complete data (mean age, 49 years; 53% female). Mean follow-up time was 2.4 years. At latest follow up, 16 (33%) had no headaches, 14 (29%) experienced headaches lasting <3 months, 19 (39%) reported POH lasting ≥3 months. Twenty-seven (55%) patients had posterior fossa bone spicules detectable on postoperative computed tomography (CT). Age, gender, body mass index, length of stay, tumor diameter, size of craniectomy, the presence of bone spicules, or the amount of posterior petrous temporal bone removed from drilling did not differ significantly between patients with POH and those without. On multivariate logistic regression, patients with POH were less likely to have preoperative brainstem compression by the tumor (odds ratio [OR] = 0.21, p  = 0.028) and more likely to have higher opioid requirements during hospitalization (OR = 1.023, p  = 0.045). Conclusion  The presence of bone spicules in the posterior fossa on postoperative CT did not contribute to headaches following retrosigmoid craniectomy approach for VS resection.

Cochlear T2 Signal May Predict Hearing Outcomes After Resection of Acoustic Neuroma

OBJECTIVE

Examine the impact of preoperative cochlear Fast Imaging Employing Steady-state Acquisition (FIESTA) and Constructive Interference in Steady State (CISS) signal intensity on hearing outcomes after middle cranial fossa (MCF) resection of acoustic neuroma (AN).

METHODS

Adult patients (≥18 years) who underwent MCF AN resection for hearing preservation (HP) between November 2017 and September 2019 were retrospectively reviewed. All patients had preoperative word recognition score (WRS) ≥50%. HP was defined as postoperative WRS ≥50%. A neuroradiologist blinded to patients' clinical and audiometric outcomes reviewed patients' preoperative magnetic resonance images. Ipsilateral-to-contralateral cochlear FIESTA/CISS signal intensity ratios were determined using hand-drawn regions of interest focused on the cochlear fluid. Preoperative and postoperative pure tone average (PTA) and WRS were reviewed.

RESULTS

Fifty-one patients were reviewed (60.8% female). Mean age was 47 years and mean tumor size 9.2 mm (±3.8). Hearing was preserved in 56.9% (n = 29). FIESTA/CISS signal ratios did not significantly differ between patients with and without HP. Lower FIESTA/CISS signal ratios correlated with greater declines in hearing (r = 0.322, p = 0.011 for PTA; and r = 0.384, p = 0.004 for WRS). On multivariate analysis accounting for tumor size and preoperative PTA/WRS, decreases in FIESTA/CISS signal ratios independently predicted greater declines in hearing by PTA (b = -100.9, p = 0.012) and WRS (b = 76.208), although the latter result was not statistically significant (p = 0.078).

CONCLUSIONS

Cochlear FIESTA/CISS signal intensity may be a predictor of postoperative hearing loss after MCF AN resection. In this cohort, degraded preoperative cochlear FIESTA/CISS signal strongly predicted postoperative hearing loss.Level of Evidence: IV.

Combined translabyrinthine, anterior petrosal approach for resection of collision vestibular schwannoma and petrous apex meningioma in neurofibromatosis type 2, with auditory brainstem implant placement

The natural history of neurofibromatosis type 2 (NF2) is profound bilateral hearing loss. The decision to pursue microsurgery may be more complicated in NF2 than with sporadic tumors. Schwannomas in NF2 often occur with other skull base tumors. Treatment should be tailored to preserve auditory perception for as long as possible. The authors present the case of a man with NF2 and a vestibular schwannoma who has poor hearing on the same side as a large petrous apex meningioma, both opposite to a well-hearing ear. This case highlights surgical decision-making and technical nuances during resection of collision tumors in NF2.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21130

Maturation of the anterior petrous apex: surgical relevance for performance of the middle fossa transpetrosal approach in pediatric patients

OBJECTIVE

The middle fossa transpetrosal approach to the petroclival and posterior cavernous sinus regions includes removal of the anterior petrous apex (APA), an area well studied in adults but not in children. To this end, the authors performed a morphometric analysis of the APA region during pediatric maturation.

METHODS

Measurements of the distance from the clivus to the internal auditory canal (IAC; C-IAC), the distance of the petrous segment of the internal carotid artery (petrous carotid; PC) to the mesial petrous bone (MPB; PC-MPB), the distance of the PC to the mesial petrous apex (MPA; PC-MPA), and the IAC depth from the middle fossa floor (IAC-D) were made on thin-cut CT scans from 60 patients (distributed across ages 0-3, 4-7, 8-11, 12-15, 16-18, and > 18 years). The APA volume was calculated as a cylinder using C-IAC (length) and PC-MPB (diameter). APA pneumatization was noted. Data were analyzed by laterality, sex, and age.

RESULTS

APA parameters did not differ by laterality or sex. APA pneumatization was seen on 20 of 60 scans (33.3%) in patients ≥ 4 years. The majority of the APA region growth occurred by ages 8-11 years, with PC-MPA and PC-MPB increasing 15.9% (from 9.4 to 10.9 mm, p = 0.08) and 23.5% (from 8.9 to 11.0 mm, p < 0.01) between ages 0-3 and 8-11 years, and C-IAC increasing 20.7% (from 13.0 to 15.7 mm, p < 0.01) between ages 0-3 and 4-7 years. APA volume increased 79.6% from ages 0-3 to 8-11 years (from 834.3 to 1499.2 mm3, p < 0.01). None of these parameters displayed further significant growth. Finally, IAC-D increased 51.1% (from 4.3 to 6.5 mm, p < 0.01) between ages 0-3 and adult, without significant differences between successive age groups.

CONCLUSIONS

APA development is largely complete by the ages of 8-11 years. Knowledge of APA growth patterns may aid approach selection and APA removal in pediatric patients.

The Relationship Between the Functional Gait Assessment and Quality-of-Life Data in Patients Undergoing Vestibular Schwannoma Resection

OBJECTIVE

To examine the relationship between the Functional Gait Assessment (FGA) and quality of life (QOL) measurements relating to balance before and after vestibular schwannoma (VS) resection and to assess the role of preoperative FGA in predicting postoperative QOL.

STUDY DESIGN

A prospective clinical study of adult patients undergoing VS resection between September 2018 and December 2019. FGA was administered 1 week before and after surgery. Dizziness Handicap Inventory (DHI) and Penn Acoustic Neuroma Quality of Life (PANQOL) were administered preoperatively and at 3 months postoperatively.

SETTING

Single tertiary center.

PATIENTS

Patients (age ≥ 18 years old) with VS undergoing microsurgical resection. Excluded were patient with previous surgery or radiation.

INTERVENTION

VS resection.

MAIN OUTCOMES AND MEASURES

Primary outcome: correlation between FGA and QOL surveys. Secondary outcome: correlation between preoperative measurements of balance and postoperative PANQOL.

RESULTS

One hundred thirty-eight patients were analyzed (mean age: 48 years old, 65.9% female). The translabyrinthine approach was most commonly performed. Under multivariate analysis, preoperative FGA significantly correlated with preoperative PANQOL balance score (p < 0.0001), preoperative PANQOL total score (p = 0.0002), and preoperative DHI (p < 0.0001). However, postoperative FGA did not significantly correlate with postoperative PANQOL balance or total scores (p = 0.446 and p = 0.4, respectively), or postoperative DHI (p = 0.3). Univariate analysis demonstrated that preoperative DHI and preoperative FGA were predictive of changes in postoperative PANQOL balance and total scores. However under multivariate analysis, preoperative FGA did not predict changes in postoperative PANQOL balance or total score (p = 0.24; p = 0.28, respectively). Preoperative DHI remained predictive of changes in postoperative PANQOL balance (p = 0.03) score but not of postoperative PANQOL total score (p = 0.37).

CONCLUSIONS

Although FGA and QOL data significantly correlated in the preoperative setting, our results did not suggest that preoperative FGA can be used to determine postoperative QOL. Additionally, the lack of correlation between FGA and QOL measurements in the acute postoperative setting suggests that further research is needed to determine contributors to postoperative QOL.

Noise Exposure and Distortion Product Otoacoustic Emission Suprathreshold Amplitudes: A Genome-Wide Association Study

BACKGROUND

Although several candidate-gene association studies have been conducted to investigate noise-induced hearing loss (NIHL) in humans, most are underpowered, unreplicated, and account for only a fraction of the genetic risk. Mouse genome-wide association studies (GWASs) have revolutionized the field of genetics and have led to the discovery of hundreds of genes involved in complex traits. The hybrid mouse diversity panel (HMDP) is a collection of classic inbred and recombinant inbred strains whose genomes have been either genotyped at high resolution or sequenced. To further investigate the genetics of NIHL, we report the first GWAS based on distortion product otoacoustic emission (DPOAE) measurements and the HMDP.

METHODS

A total of 102 strains (n = 635) from the HMDP were evaluated based on DPOAE suprathreshold amplitudes before and after noise exposure. DPOAE amplitude variation was set at 60 and 70 dB SPL of the primary tones for each frequency separately (8, 11.3, 16, 22.6, and 32 kHz). These values provided an indirect assessment of outer hair cell integrity. Six-week-old mice were exposed for 2 h to 10 kHz octave-band noise at 108 dB SPL. To perform local expression quantitative trait locus (eQTL) analysis, gene expression microarray profiles were generated using cochlear RNA from 64 hybrid mouse strains (n = 3 arrays per strain).

RESULTS

Several new loci were identified and positional candidate-genes associated with NIHL were prioritized, especially after noise exposure (1 locus at baseline and 5 loci after exposure). A total of 35 candidate genes in these 6 loci were identified with at least 1 probe whose expression was regulated by a significant cis-eQTL in the cochlea. After careful analysis of the candidate genes based on cochlear gene expression, 2 candidate genes were prioritized: Eya1 (baseline) and Efr3a (post-exposure).

DISCUSSION AND CONCLUSION

For the first time, an association analysis with correction for population structure was used to map several loci for hearing traits in inbred strains of mice based on DPOAE suprathreshold amplitudes before and after noise exposure. Our results identified a number of novel loci and candidate genes for susceptibility to NIHL, especially the Eya1 and Efr3a genes. Our findings validate the power of the HMDP for detecting NIHL susceptibility genes.

Factors Associated With Unilateral Hearing Loss and Impact on Communication in US Adults

OBJECTIVE

To investigate the factors associated with unilateral hearing loss (UHL) and its impact on communication in US adults.

STUDY DESIGN

Cross-sectional study.

SETTING

Nationally representative sample of US adults.

METHODS

We analyzed data from the 2011-2012 and 2015-2016 National Health and Nutritional Examination Survey, in which participants aged 20 to 69 years completed an audiometric evaluation (n = 8138). UHL was defined as a speech frequency pure-tone average ≥25 dB in the worse hearing ear and <25 dB in the better hearing ear. Logistic regression was used to examine the association between UHL and relevant factors.

RESULTS

The prevalence of UHL was 8.1% (95% CI, 7.3%-9.0%) in US adults. Factors associated with UHL included older age, male sex, white race, lower level of education, diabetes, cardiovascular disease, and off-work noise exposure. Among adults with UHL, 40% (95% CI, 32%-48%) reported subjective trouble with hearing, a rate higher than the 12% (95% CI, 11%-14%) among normal-hearing adults. After adjusting for relevant factors, adults with UHL were more likely to report difficulties with following conversations with noise (odds ratio [OR], 1.7; 95% CI, 1.2-2.5) and frustration when talking to family and friends (OR, 3.0; 95% CI, 1.9-4.6). Higher levels of communication difficulties were observed with worsening level of UHL.

CONCLUSIONS

Adults with UHL report significant communication difficulties in comparison to normal-hearing adults. Further research is needed to understand the psychosocial impact of UHL on adults and ways to improve communication support for adults with UHL.

Cell Type-Specific Decomposition of Gingival Tissue Transcriptomes

Genome-wide transcriptomic analyses in whole tissues reflect the aggregate gene expression in heterogeneous cell populations comprising resident and migratory cells, and they are unable to identify cell type-specific information. We used a computational method (population-specific expression analysis [PSEA]) to decompose gene expression in gingival tissues into cell type-specific signatures for 8 cell types (epithelial cells, fibroblasts, endothelial cells, neutrophils, monocytes/macrophages, plasma cells, T cells, and B cells). We used a gene expression data set generated using microarrays from 120 persons (310 tissue samples; 241 periodontitis affected and 69 healthy). Decomposition of the whole-tissue transcriptomes identified differentially expressed genes in each of the cell types, which mapped to biologically relevant pathways, including dysregulation of Th17 cell differentiation, AGE-RAGE signaling, and epithelial-mesenchymal transition in epithelial cells. We validated selected PSEA-predicted, differentially expressed genes in purified gingival epithelial cells and B cells from an unrelated cohort (n = 15 persons), each of whom contributed with 1 periodontitis-affected and 1 healthy gingival tissue sample. Differential expression of these genes by quantitative reverse transcription polymerase chain reaction corroborated the PSEA predictions and pointed to dysregulation of biologically important pathways in periodontitis. Collectively, our results demonstrate the robustness of the PSEA in the decomposition of gingival tissue transcriptomes and its ability to identify differentially regulated transcripts in particular cellular constituents. These genes may serve as candidates for further investigation with respect to their roles in the pathogenesis of periodontitis.

Mutations of MAP1B encoding a microtubule-associated phosphoprotein cause sensorineural hearing loss

The pathophysiology underlying spiral ganglion cell defect–induced deafness remains elusive. Using the whole exome sequencing approach, in combination with functional assays and a mouse disease model, we identified the potentially novel deafness-causative MAP1B gene encoding a highly conserved microtubule-associated protein. Three novel heterozygous MAP1B mutations (c.4198A>G, p.1400S>G; c.2768T>C, p.923I>T; c.5512T>C, p.1838F>L) were cosegregated with autosomal dominant inheritance of nonsyndromic sensorineural hearing loss in 3 unrelated Chinese families. Here, we show that MAP1B is highly expressed in the spiral ganglion neurons in the mouse cochlea. Using otic sensory neuron–like cells, generated by pluripotent stem cells from patients carrying the MAP1B mutation and control subject, we demonstrated that the p.1400S>G mutation caused the reduced levels and deficient phosphorylation of MAP1B, which are involved in the microtubule stability and dynamics. Strikingly, otic sensory neuron–like cells exhibited disturbed dynamics of microtubules, axonal elongation, and defects in electrophysiological properties. Dysfunctions of these derived otic sensory neuron–like cells were rescued by genetically correcting MAP1B mutation using CRISPR/Cas9 technology. Involvement of MAP1B in hearing was confirmed by audiometric evaluation of Map1b heterozygous KO mice. These mutant mice displayed late-onset progressive sensorineural hearing loss that was more pronounced in the high frequencies. The spiral ganglion neurons isolated from Map1b mutant mice exhibited the deficient phosphorylation and disturbed dynamics of microtubules. Map1b deficiency yielded defects in the morphology and electrophysiology of spiral ganglion neurons, but it did not affect the morphologies of cochlea in mice. Therefore, our data demonstrate that dysfunctions of spiral ganglion neurons induced by MAP1B deficiency caused hearing loss.

Dysfunctions of spiral ganglion neurons caused by Map1b deficiency leads to sensorineural hearing loss.

Clinical Predictors of Facial Nerve Outcomes After Surgical Resection of Vestibular Schwannoma

OBJECTIVE

To identify clinical predictors of facial nerve (FN) outcomes after microsurgical resection of vestibular schwannoma (VS).

STUDY DESIGN

Prospective cohort study.

SETTING

Academic medical center.

METHODS

Consecutive patients undergoing VS resection from November 2017 to October 2019 were included. FN function was evaluated with the House-Brackmann (HB) scale and stratified into good (HB I-II) and poor (HB III-VI) function. Analyses included descriptive statistics, correlation, and logistic regression.

RESULTS

Of 256 patients who met criteria (mean age, 47.7 years; 62.5% female), 227 (88.7%) achieved good FN function postoperatively and 238 (93.0%) at latest follow-up (mean, 154.8 days). Operative approaches consisted of translabyrinthine (50.8%), retrosigmoid (25.0%), and middle fossa craniotomies (24.2%). Extent of resection was decided intraoperatively, and gross or near total resection was accomplished in 237 (92.6%) cases. Postoperative HB grade correlated with latest HB grade (0.615, P < .001). Factors associated with good postoperative FN function included small tumor size (≤15 mm; odds ratio [OR], 2.425; P = .042), gross or near total resection (OR, 3.170; P = .041), and ≥100-µV intraoperative FN electromyographic response to a 0.05-mA stimulus (OR, 22.242; P < .001). Factors associated with good FN function at latest follow-up included gross total resection (OR, 7.764; P = .003) and ≥100-µV FN electromyographic response (OR, 8.518; P < .001), accounting for surgical approach and tumor size.

CONCLUSION

Microsurgical resection of VS can be accomplished with excellent FN outcomes. Gross total resection and ≥100-µV intraoperative FN electromyographic response predicted excellent FN outcomes. Immediate postoperative FN function is a prognosticator of long-term FN function.

Middle fossa approach for a pediatric facial nerve meningioma

Pediatric cerebellopontine angle (CPA) meningiomas are extremely rare and are usually treated with a retrosigmoid surgical approach or radiation. The authors present the use of a middle fossa approach for the treatment of a symptomatic CPA meningioma in a 22-month-old female. The patient initially presented at 17 months with isolated progressive, long-standing right-sided facial weakness. MRI demonstrated a 5.0 × 5.0-mm right CPA lesion just superior to the cisternal segment of cranial nerve (CN) VII, which demonstrated growth on interval imaging. At 22 months of age she underwent a successful middle fossa craniotomy, including wide exposure of the porus acusticus, allowing for a gross-total resection with preservation of CNs VII and VIII. Pathological analysis revealed a WHO grade I meningioma. The patient remained neurologically stable on follow-up. The middle fossa approach can be used to safely access the CPA in properly selected pediatric patients.

Predicting Functional Outcomes and Length of Stay Following Acoustic Neuroma Resection

OBJECTIVES

To examine whether simple mobility assessments can predict functional limitations and length of hospitalization after acoustic neuroma (AN) resection.

STUDY DESIGN

Prospective case series.

METHODS

A prospective clinical study of adult patients undergoing AN resection by either the translabyrinthine, retrosigmoid, or middle fossa approach was conducted at a tertiary center. Preoperative mobility assessments included the functional gait assessment (FGA) and the 10-m walk (10 MW). Postoperatively, the Activity Measure for Post-Acute Care (AMPAC, at 48 hours), FGA, and 10 MW (at 1 week) were obtained. Demographic and medical data were collected.

RESULTS

One hundred and thirty-eight patients were analyzed (mean age: 48.3 years, 68.8% female). Mean length of stay (LOS) was 3.1 days. The translabyrinthine approach was most commonly performed (48.6%). On regression analyses, preoperative FGA (P = 0.03) and 48-hour postoperative AM-PAC (P < 0.001) independently predicted LOS, even after accounting for age, gender, body mass index, and tumor size. On receiver operating characteristic analysis, a preoperative FGA cut score of 25.5 predicted a protracted hospital stay (>4 days) with a sensitivity of 77% and specificity of 50% (area under curve: 68.5).

CONCLUSION

This study demonstrated that preoperative mobility assessments can predict functional limitations and LOS after AN resection. These objective tools can be used by clinicians to manage expectations and guide preoperative counseling in patients considering surgery.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:644-648, 2021.

A de novo SIX1 variant in a patient with a rare nonsyndromic cochleovestibular nerve abnormality, cochlear hypoplasia, and bilateral sensorineural hearing loss

Background

Childhood hearing impairment affects language and cognitive development. Profound congenital sensorineural hearing impairment can be due to an abnormal cochleovestibular nerve (CVN) and cochleovestibular malformations, however, the etiology of these conditions remains unclear.

Methods

We used a trio‐based exome sequencing approach to unravel the underlying molecular etiology of a child with a rare nonsyndromic CVN abnormality and cochlear hypoplasia. Clinical and imaging data were also reviewed.

Results

We identified a de novo missense variant [p(Asn174Tyr)] in the DNA‐binding Homeodomain of SIX1, a gene which previously has been associated with autosomal dominant hearing loss (ADHL) and branchio‐oto‐renal or Branchio‐otic syndrome, a condition not seen in this patient.

Conclusions

SIX1 has an important function in otic vesicle patterning during embryogenesis, and mice show several abnormalities to their inner ear including loss of inner ear innervation. Previous reports on patients with SIX1 variants lack imaging data and nonsyndromic AD cases were reported to have no inner ear malformations. In conclusion, we show that a de novo variant in SIX1 in a patient with sensorineural hearing loss leads to cochleovestibular malformations and abnormalities of the CVN, without any other abnormalities. Without proper interventions, severe to profound hearing loss is devastating to both education and social integration. Choosing the correct intervention can be challenging and a molecular diagnosis may adjust intervention and improve outcomes, especially for rare cases.

Tophaceous Gout of the Middle Ear: Case Reports and Review of the Literature

Tophaceous gout of the middle ear is a rare occurrence that presents as a granular white-colored mass. It is frequently misdiagnosed as cholesteatoma or tympanosclerosis in patients who otherwise may not manifest any clinical or biochemical signs of gout. While uncommon, it can lead to clinically significant disease such as conductive hearing loss. The present report describes 2 cases of middle ear gouty tophi initially mistaken for another entity. Both patients underwent surgery, and the diagnosis of gout was revealed after final histopathological analysis. A review of the literature is also presented.

Advances in understanding of presbycusis

The pathophysiology of age-related hearing loss (ARHL), or presbycusis, involves a complex interplay between environmental and genetic factors. The fundamental biomolecular mechanisms of ARHL have been well described, including the roles of membrane transport, reactive oxygen species, cochlear synaptopathy, vascular insults, hormones, and microRNA, to name a few. The genetic basis underlying these mechanisms remains under-investigated and poorly understood. The emergence of genome-wide association studies has allowed for the identification of specific groups of genes involved in ARHL. This review highlights recent advances in understanding of the pathogenesis of ARHL, the genetic basis underlying these processes and suggests future directions for research and potential therapeutic avenues.

Intentional Subtotal Resection of Vestibular Schwannoma: A Reexamination

Background  Treatment of vestibular schwannomas (VS) remains controversial. Historical surgical series prioritized gross total resections (GTR); however, near total resections (NTR) and intentional subtotal resections (STR) aiming at improving cranial nerve outcomes are becoming more popular. Objective  The main purpose of this article is to assess the tumor control and facial nerve outcomes in VS patients treated with STR or NTR. Methods  VS patients undergoing STR or NTR at our institution between 1984 and 2016 were retrospectively reviewed. Patient demographics, extent of tumor resection, facial nerve injury, tumor recurrence, and need for Gamma Knife radiosurgery were analyzed. Facial nerve outcomes were quantified using House-Brackmann (HB) scores. Tumor regrowth was defined by the San Francisco criteria. Results  Four-hundred fifty-seven VS resections were performed in a 32-year period. Sixty cases met inclusion criteria. The mean (range) follow-up duration was 30.9 (12-103) months. The STR cohort ( n  = 33) demonstrated regrowth in 12 patients (36.3%) at an average of 23.6 months. The NTR cohort ( n  = 27) did not experience tumor recurrence. Risk of tumor recurrence was positively correlated with preoperative tumor size ( p  = 0.002), size of residual tumor ( p  < 0.001), and STR ( p  < 0.001). Facial nerve outcomes of HB1-2 were observed in the majority of patients in both cohorts (74.1% NTR, 56% STR), though NTR was associated with a higher likelihood of facial nerve recovery ( p  = 0.003). Conclusion  GTR remains the gold standard as long as facial nerve outcomes remain acceptable. NTR achieved superior tumor control and higher likelihood of facial nerve recovery compared with STR.

Hearing Preservation in Vestibular Schwannoma Surgery

Modern imaging techniques allow early detection of small vestibular schwannomas (VSs) with minimal or no hearing impairment. While controversy surrounds the management of these tumors, given their benign nature and unpredictable natural history, microsurgical excision is the only modality that offers the opportunity to cure the tumor and preserve hearing. Hearing preservation in VS surgery may be accomplished via the middle fossa or retrosigmoid approaches. Appropriate patient selection and surgical approach is critical in achieving the best hearing outcomes. This article highlights the preoperative assessment, patient selection and prognostic factors, intraoperative monitoring of hearing, and surgical approaches to optimize hearing preservation during VS removal.

De novo variants in GREB1L are associated with non-syndromic inner ear malformations and deafness

Congenital inner ear malformations affecting both the osseous and membranous labyrinth can have a devastating impact on hearing and language development. With the exception of an enlarged vestibular aqueduct, non-syndromic inner ear malformations are rare, and their underlying molecular biology has thus far remained understudied. To identify molecular factors that might be important in the developing inner ear, we adopted a family-based trio exome sequencing approach in young unrelated subjects with severe inner ear malformations. We identified two previously unreported de novo loss-of-function variants in GREB1L [c.4368G>T;p.(Glu1410fs) and c.982C>T;p.(Arg328*)] in two affected subjects with absent cochleae and eighth cranial nerve malformations. The cochlear aplasia in these affected subjects suggests that a developmental arrest or problem at a very early stage of inner ear development exists, e.g., during the otic pit formation. Craniofacial Greb1l RNA expression peaks in mice during this time frame (E8.5). It also peaks in the developing inner ear during E13-E16, after which it decreases in adulthood. The crucial function of Greb1l in craniofacial development is also evidenced in knockout mice, which develop severe craniofacial abnormalities. In addition, we show that Greb1l-/- zebrafish exhibit a loss of abnormal sensory epithelia innervation. An important role for Greb1l in sensory epithelia innervation development is supported by the eighth cranial nerve deficiencies seen in both affected subjects. In conclusion, we demonstrate that GREB1L is a key player in early inner ear and eighth cranial nerve development. Abnormalities in cochleovestibular anatomy can provide challenges for cochlear implantation. Combining a molecular diagnosis with imaging techniques might aid the development of individually tailored therapeutic interventions in the future.

Age-related hearing loss: Unraveling the pieces

Age-related hearing loss (ARHL) is the most common cause of hearing loss in the world. The development of ARHL in each individual is multifactorial, involving both intrinsic and extrinsic factors. This review highlights several of the key findings in the ARHL literature and discusses future directions.

LEVEL OF EVIDENCE

NA.

Role of Neuropilin-1/Semaphorin-3A signaling in the functional and morphological integrity of the cochlea

Neuropilin-1 (Nrp1) encodes the transmembrane cellular receptor neuropilin-1, which is associated with cardiovascular and neuronal development and was within the peak SNP interval on chromosome 8 in our prior GWAS study on age-related hearing loss (ARHL) in mice. In this study, we generated and characterized an inner ear-specific Nrp1 conditional knockout (CKO) mouse line because Nrp1 constitutive knockouts are embryonic lethal. In situ hybridization demonstrated weak Nrp1 mRNA expression late in embryonic cochlear development, but increased expression in early postnatal stages when cochlear hair cell innervation patterns have been shown to mature. At postnatal day 5, Nrp1 CKO mice showed disorganized outer spiral bundles and enlarged microvessels of the stria vascularis (SV) but normal spiral ganglion cell (SGN) density and presynaptic ribbon body counts; however, we observed enlarged SV microvessels, reduced SGN density, and a reduction of presynaptic ribbons in the outer hair cell region of 4-month-old Nrp1 CKO mice. In addition, we demonstrated elevated hearing thresholds of the 2-month-old and 4-month-old Nrp1 CKO mice at frequencies ranging from 4 to 32kHz when compared to 2-month-old mice. These data suggest that conditional loss of Nrp1 in the inner ear leads to progressive hearing loss in mice. We also demonstrated that mice with a truncated variant of Nrp1 show cochlear axon guidance defects and that exogenous semaphorin-3A, a known neuropilin-1 receptor agonist, repels SGN axons in vitro. These data suggest that Neuropilin-1/Semaphorin-3A signaling may also serve a role in neuronal pathfinding in the developing cochlea. In summary, our results here support a model whereby Neuropilin-1/Semaphorin-3A signaling is critical for the functional and morphological integrity of the cochlea and that Nrp1 may play a role in ARHL.

Neuropilin-1 is a member of the neuropilin family acting as an essential cell surface receptor involved in semaphorin-dependent axon guidance and VEGF-dependent angiogenesis and lies within our previously identified ARHL GWAS interval. In this study, we investigated the role of Neuropilin-1/Semaphorin-3A signaling in the functional and morphological integrity of the cochlea, specifically the innervation and vascularization patterns. Detailed analyses of the cochleae of 4-month-old Nrp1 CKO mice showed abnormalities in ribbon synapses, innervation of the hair cells, and microvessels of the stria vascularis. We show also that Neuropilin-1/Semaphorin-3A signaling plays an important role in cochlear innervation.

Intratympanic Steroid Injection for Treatment of Idiopathic Sudden Hearing Loss

Objective.

To conduct a clinical trial of intratympanic steroid injection for idiopathic sudden sensorineural hearing loss in subjects who failed oral steroid therapy.

Study Design and Setting.

Open-label methylprednisolone injection clinical trial in a tertiary neurotologic referral center. Twenty subjects (14 males; 6 females) received 4 injections within a 2-week period (4 days apart). Hearing, dizziness/p, and tinnitus were evaluated before and after treatment.

Results.

There were no serious unexpected adverse events and 2 types of expected adverse events (tympanic membrane perforation, nausea after injection). No increases in dizziness or tinnitus lasting longer than 24 hours were observed after injections. One of 20 (5%) improved to near-normal hearing. In addition, there was statistically significant improvement in 4-frequency pure-tone average and speech discrimination score at 1 month after treatment.

Conclusion.

Four intratympanic injections of methylprednisolone improved pure-tone average or speech discrimination scores for a subset of sudden hearing loss subjects that failed to benefit from oral steroids.

Significance.

A clinical trial of intratympanic injections for idiopathic sudden hearing loss was successfully completed and promising results were found.

Large-scale phenotyping of noise-induced hearing loss in 100 strains of mice

A cornerstone technique in the study of hearing is the Auditory Brainstem Response (ABR), an electrophysiologic technique that can be used as a quantitative measure of hearing function. Previous studies have published databases of baseline ABR thresholds for mouse strains, providing a valuable resource for the study of baseline hearing function and genetic mapping of hearing traits in mice. In this study, we further expand upon the existing literature by characterizing the baseline ABR characteristics of 100 inbred mouse strains, 47 of which are newly characterized for hearing function. We identify several distinct patterns of baseline hearing deficits and provide potential avenues for further investigation. Additionally, we characterize the sensitivity of the same 100 strains to noise exposure using permanent thresholds shifts, identifying several distinct patterns of noise-sensitivity. The resulting data provides a new resource for studying hearing loss and noise-sensitivity in mice.

Prognostic implications of and audiometric evidence for hearing fluctuation in Meniere's disease

OBJECTIVES/HYPOTHESIS

1) To establish criteria for significant hearing fluctuation by assessing the range and occurrence of hearing fluctuations over the course of Meniere's disease; 2) to determine if audiometric evidence exists to support the notion that Meniere's disease is a pathophysiologic process involving the whole cochlea; and 3) to suggest prognostic implications for initial hearing fluctuation in patients with Meniere's disease.

STUDY DESIGN

Retrospective case series review.

METHODS

A total of 488 patients diagnosed by 1995 American Academy of Otolaryngology-Head and Neck Surgery Meniere's disease criteria for whom audiometric data were prospectively collected (2 cohorts: 341 and 146 patients initially seen between April 2002 to July 2003 and between January to December 2010, respectively). Based on several definitions for significant hearing fluctuation, change in hearing was categorized as "same," "worse," or "better" between any two consecutive evaluations. The relationship of initial hearing fluctuation to future hearing fluctuation and future hearing loss was evaluated.

RESULTS

Hearing fluctuation was evident in Meniere's disease patients with heterogeneous audiometric follow-up; and the characteristics of these hearing fluctuations, including the mean incidence, is described. Audiometric data suggests that there is a high congruence in Meniere's disease between changes in low- and high-frequency thresholds. Initial hearing fluctuation is associated with the occurrence of future and more frequent hearing fluctuations.

CONCLUSION

Understanding the range of hearing fluctuations establishes a basis for determining audiometric thresholds used in evaluating future therapeutic trials aimed at the prevention of hearing loss in Meniere's disease. This knowledge will also inform the counseling directed toward patients diagnosed with Meniere's disease.

A comprehensive catalogue of the coding and non-coding transcripts of the human inner ear

The mammalian inner ear consists of the cochlea and the vestibular labyrinth (utricle, saccule, and semicircular canals), which participate in both hearing and balance. Proper development and life-long function of these structures involves a highly complex coordinated system of spatial and temporal gene expression. The characterization of the inner ear transcriptome is likely important for the functional study of auditory and vestibular components, yet, primarily due to tissue unavailability, detailed expression catalogues of the human inner ear remain largely incomplete. We report here, for the first time, comprehensive transcriptome characterization of the adult human cochlea, ampulla, saccule and utricle of the vestibule obtained from patients without hearing abnormalities. Using RNA-Seq, we measured the expression of >50,000 predicted genes corresponding to approximately 200,000 transcripts, in the adult inner ear and compared it to 32 other human tissues. First, we identified genes preferentially expressed in the inner ear, and unique either to the vestibule or cochlea. Next, we examined expression levels of specific groups of potentially interesting RNAs, such as genes implicated in hearing loss, long non-coding RNAs, pseudogenes and transcripts subject to nonsense mediated decay (NMD). We uncover the spatial specificity of expression of these RNAs in the hearing/balance system, and reveal evidence of tissue specific NMD. Lastly, we investigated the non-syndromic deafness loci to which no gene has been mapped, and narrow the list of potential candidates for each locus. These data represent the first high-resolution transcriptome catalogue of the adult human inner ear. A comprehensive identification of coding and non-coding RNAs in the inner ear will enable pathways of auditory and vestibular function to be further defined in the study of hearing and balance. Expression data are freely accessible at https://www.tgen.org/home/research/research-divisions/neurogenomics/supplementary-data/inner-ear-transcriptome.aspx.

FoxO1-dependent induction of acute myeloid leukemia by osteoblasts in mice

Osteoblasts, the bone forming cells, affect self-renewal and expansion of hematopoietic stem cells (HSCs), as well as homing of healthy hematopoietic cells and tumor cells into the bone marrow. Constitutive activation of β-catenin in osteoblasts is sufficient to alter the differentiation potential of myeloid and lymphoid progenitors and to initiate the development of acute myeloid leukemia (AML) in mice. We show here that Notch1 is the receptor mediating the leukemogenic properties of osteoblast-activated β-catenin in HSCs. Moreover, using cell-specific gene inactivation mouse models, we show that FoxO1 expression in osteoblasts is required for and mediates the leukemogenic properties of β-catenin. At the molecular level, FoxO1 interacts with β-catenin in osteoblasts to induce expression of the Notch ligand, Jagged-1. Subsequent activation of Notch signaling in long-term repopulating HSC progenitors induces the leukemogenic transformation of HSCs and ultimately leads to the development of AML. These findings identify FoxO1 expressed in osteoblasts as a factor affecting hematopoiesis and provide a molecular mechanism whereby the FoxO1/activated β-catenin interaction results in AML. These observations support the notion that the bone marrow niche is an instigator of leukemia and raise the prospect that FoxO1 oncogenic properties may occur in other tissues.

Genome-wide association study identifies nox3 as a critical gene for susceptibility to noise-induced hearing loss

In the United States, roughly 10% of the population is exposed daily to hazardous levels of noise in the workplace. Twin studies estimate heritability for noise-induced hearing loss (NIHL) of approximately 36%, and strain specific variation in sensitivity has been demonstrated in mice. Based upon the difficulties inherent to the study of NIHL in humans, we have turned to the study of this complex trait in mice. We exposed 5 week-old mice from the Hybrid Mouse Diversity Panel (HMDP) to a 10 kHz octave band noise at 108 dB for 2 hours and assessed the permanent threshold shift 2 weeks post exposure using frequency specific stimuli. These data were then used in a genome-wide association study (GWAS) using the Efficient Mixed Model Analysis (EMMA) to control for population structure. In this manuscript we describe our GWAS, with an emphasis on a significant peak for susceptibility to NIHL on chromosome 17 within a haplotype block containing NADPH oxidase-3 (Nox3). Our peak was detected after an 8 kHz tone burst stimulus. Nox3 mutants and heterozygotes were then tested to validate our GWAS. The mutants and heterozygotes demonstrated a greater susceptibility to NIHL specifically at 8 kHz both on measures of distortion product otoacoustic emissions (DPOAE) and on auditory brainstem response (ABR). We demonstrate that this sensitivity resides within the synaptic ribbons of the cochlea in the mutant animals specifically at 8 kHz. Our work is the first GWAS for NIHL in mice and elucidates the power of our approach to identify tonotopic genetic susceptibility to NIHL.

Noise-induced hearing loss (NIHL) is the most common work-related disease in the world and the second cause of hearing loss. Although several candidate gene association studies for NIHL in humans have been conducted, each are underpowered, un-replicated, and account for only a fraction of the genetic risk. Buoyed by the prospects and successes of human association studies, several groups have proposed mouse genome-wide association studies. The environment can be carefully controlled, facilitating the study of complex traits like NIHL. In this manuscript, we describe, for the first time, an association analysis with correction for population structure for the mapping of several loci for susceptibility to NIHL in inbred strains of mice. We identify Nox3 as the associated gene for susceptibility to NIHL that the genetic susceptibility is frequency specific and that it occurs at the level of the cochlear synaptic ribbon.

RNA-Seq Analysis of Allele-Specific Expression in the Mouse Cochlea

Objectives:

Age-related hearing impairment or presbycusis is one of the most common sensory abnormalities in the world. Mouse models have been widely used in studies of hearing loss to separate genetic and environmental influences. We will describe novel cis- and trans-regulation and dominance patterns in gene expression levels from cochlea of mice.

Methods:

Next-generation sequencing (RNA-Seq) data has been acquired from cochlea of three F1 mouse hybrid strains (n = 4) from parental strains C57BL/6J, DBA/2J, C3H/HeJ.

Results:

An analysis of allele-specific expression will be reported and novel transcripts, isoforms, cis and trans-regulation, long non-coding RNAs, and dominance patterns will be discussed in relation to known genes.

Conclusions:

This will help to elucidate mechanisms and better understand the genetic backdrop of age related hearing impairment.