The endaural subtemporal keyhole: a novel minimally invasive approach to the middle cranial fossa.

OBJECTIVE: The goal of this study was to evaluate the feasibility of a minimally invasive approach to the middle cranial fossa using a novel endaural keyhole. METHODS: The charts of all patients who underwent this novel minimally invasive approach to the middle cranial fossa were retrospectively reviewed. In addition, cadaveric dissection was performed to demonstrate the feasibility of the endaural keyhole to the middle cranial fossa. RESULTS: Six patients (5 female and 1 male; age range 47-77 years) who underwent craniotomy for CSF leak (n = 3), intracerebral hematoma evacuation (n = 2), and tumor resection (n = 1) via the endaural subtemporal approach were identified. There were no approach-related complications noted. Representative imaging from cadaveric dissection is provided with a stepwise discussion of the procedure. CONCLUSIONS: The endaural subtemporal keyhole craniotomy provides a novel approach to middle fossa skull base pathology, as well as a minimally invasive approach to intra-axial pathology of the temporal lobe and basal ganglia. Further research is needed to establish the limitations and potential complications of this novel approach.

Injury and protection of spiral ganglion neurons.

ABSTRACT: Cochlear spiral ganglion neurons (SGNs) are bipolar ganglion cells and are the first neurons in the auditory transduction pathway. They transmit complex acoustic information from hair cells to second-order sensory neurons in the cochlear nucleus for sound processing. Injury to SGNs causes largely irreversible hearing impairment because these neurons are highly differentiated cells and cannot regenerate, making treatment of sensorineural hearing loss (SNHL) arising from SGN injury difficult. When exposed to ototoxic drugs or damaging levels of noise or when there is loss of neurotrophic factors (NTFs), aging, and presence of other factors, SGNs can be irreversibly damaged, resulting in SNHL. It has been found that NTFs and stem cells can induce regeneration among dead spiral ganglion cells. In this paper, we summarized the present knowledge regarding injury, protection, and regeneration of SGNs.

Tandem cranial and spinal cerebrospinal fluid leaks presenting with otogenic tension pneumocephalus: illustrative case.

BACKGROUND: Cranial and spinal cerebrospinal fluid (CSF) leaks are associated with opposite CSF fluid dynamics. The differing pathophysiology between spontaneous cranial and spinal CSF leaks are, therefore, mutually exclusive in theory. OBSERVATIONS: A 66-year-old female presented with tension pneumocephalus. The patient underwent computed tomography (CT) scanning, which demonstrated left-sided tension pneumocephalus, with an expanding volume of air directly above a bony defect of the tegmen tympani and mastoideum. The patient underwent a left middle fossa craniotomy for repair of the tegmen CSF leak. In the week after discharge, she developed a recurrence of positional headaches and underwent head CT. Further magnetic resonance imaging of the brain and thoracic spine showed bilateral subdural hematomas and multiple meningeal diverticula. LESSONS: Cranial CSF leaks are caused by intracranial hypertension and are not associated with subdural hematomas. Clinicians should maintain a high index of suspicion for intracranial hypotension due to spinal CSF leak whenever "otogenic" pneumocephalus is found. Close postoperative follow-up and clinical monitoring for symptoms of intracranial hypotension in any patients who undergo repair of a tegmen defect for otogenic pneumocephalus is recommended.

Complex Case of Skull Base Osteomyelitis Secondary to Chronic Otitis Media.

We present a case of a 58-year-old male with type II diabetes managed with metformin and insulin, who presented to the clinic with left chronic otitis media, persistent drainage, a stenotic meatus, and a prior history of 3 canal wall-down mastoidectomies and antibiotic therapy. A revision tympanoplasty with mastoidectomy was performed, and during the postoperative period, the patient had persistent pain and otorrhea, which were managed with opioids and several courses of antibiotic therapy. After symptoms persisted, imaging and culture ultimately led to the diagnosis of fungal skull base osteomyelitis, which was eventually treated successfully. While these complications are rare, their likelihood is increased with treatment delay and in the immunocompromised patient. Close management of immunocompromised patients, including diabetic patients, is vital in identifying complications early to aid in timely diagnosis and treatment to lead to the best possible outcome.

Heterozygous MYH9 Mutations in 2 Children With Cochlear Nerve Canal Stenosis.

MYH9 is a gene that encodes for a subunit of the myosin heavy chain IIA protein. Mutations in MYH9 are associated with hematologic abnormalities, renal dysfunction, and hearing loss. Bony cochlear nerve canal stenosis (CNCS), which is diagnosed on computed tomography (CT) imaging, has been associated with congenital deafness, cochlear nerve aplasia/hypoplasia, and inner ear malformations. We report two cases of CNCS presenting with profound congenital hearing loss whom we diagnosed with mutations in MYH9 and discuss the genotype-phenotype association and implications for management.

Clinical characteristics in unilateral cochlear nerve canal stenosis.

OBJECTIVE: To characterize the clinical features of patients with congenital hearing loss and unilateral cochlear nerve canal stenosis (CNCS). METHODS: A retrospective review of 12 patients with unilateral CNCS diagnosed between January 2018 and December 2019 at a tertiary referral hospital was performed. RESULTS: Of the 12 patients identified, there were 6 males and 6 females. All patients presented with hearing loss, with no other chief complaints. Two patients had accessory auricles. Eleven patients had a severe to profound sensorineural hearing loss on the affected side, while 1 patient had an isolated high-frequency hearing loss. Nine patients demonstrated atresia of the cochlear nerve canal (CNC), while three patients had a stenotic, but patent, CNC. CONCLUSION: Prompt radiologic diagnosis of patients with unilateral CNCS is important for patient counseling and appropriate rehabilitation.

Efficient Delivery of Adeno-Associated Virus into Inner Ear In Vivo Through Trans-Stapes Route in Adult Guinea Pig.

Adeno-associated virus (AAV) are potent vectors to achieve treatment against hearing loss resulting from genetic defects. However, the effects of delivery routes and the corresponding transduction efficiencies for clinical applications remain elusive. In this study, we screened AAV vectors of three serotypes (AAV 8 and 9 and Anc80L65) into the inner ears of adult normal guinea pigs through trans-stapes (oval window) and trans-round window delivery routes in vivo. Trans-stapes route is akin to stape surgeries in humans. Then, auditory brainstem response (ABR) measurements were conducted to evaluate postoperative hearing, and inner ear tissues were harvested for transduction efficiency analysis. Results showed that AAV8 targeted partial inner hair cells (IHCs) in cochlear basal turn; AAV9 targeted IHCs in cochlear basal and second turn, also a part of vestibular hair cells (VHCs). In contrast, Anc80L65 contributed to green fluorescent proteins (GFP) signals of 80 - 95% IHCs and 67 - 91% outer hair cells (OHCs), as well as 69% VHCs through the trans-round window route, with 15-20 decibel (dB) ABR threshold shifts. And, through the trans-stapes (oval window) route, there were 71 - 90% IHCs and 42 - 81% OHCs, along with 64% VHCs demonstrating GFP positive, and the ABR threshold shifts were within 10 dB. This study revealed AAV could be efficiently delivered into mammalian inner ear cells in vivo through the trans-stapes (oval window) route with postoperative hearing preservation, and both delivery routes showed promise of virus-based clinical translation of hearing impairment treatment.

Intraoperative Fluorescence With Second Window Indocyanine Green Enhances Visualization During Vestibular Schwannoma Surgery.

OBJECTIVE: To investigate the utility of the so-called "second window" of indocyanine green (ICG) as a near-infrared fluorescent dye for intraoperative visualization. PATIENTS: Three patients who underwent surgical resection of vestibular schwannoma (two retrosigmoid and one middle fossa approach). INTERVENTIONS: Patients underwent intravenous infusion of ICG at a mean dose of 4.8 mg/kg at a mean of 15.3 hours before surgical incision. Once tumor dissection began, near-infrared fluorescence was used alongside conventional operative microscopy to visualize tumor tissue. MAIN OUTCOME MEASURES: Ability to distinguish tumor tissue from adjacent nerves. RESULTS: Intraoperative fluorescence allowed for enhanced visualization of the tumor-nerve plane in all patients. However, the effect varied among patients, and the effect faded with increasing surgical time. CONCLUSIONS: ICG, a well-tolerated cyanine dye, demonstrates late fluorescence hours after administration secondary to diffusion into tumor as well as normal tissues (the so-called "second window" of fluorescence). Its fluorescence in the near-infrared spectrum is a promising adjunct for enhancing visualization of tumor planes during vestibular schwannoma surgery.

Auditory and speech performance after unilateral cochlear implantation for cochlear nerve canal stenosis.

To explore the correlation between the width of the bony cochlear nerve canal (CNC) and long-term auditory rehabilitation after unilateral cochlear implantation (CI) in pediatric patients with congenital deafness and bilateral cochlear nerve canal stenosis (CNCS). A retrospective review was performed on 10 patients with bilateral CNCS and bilateral congenital profound hearing loss who each underwent unilateral cochlear implantation. The width of the CNC was determined on computed tomography (CT) imaging and following CI, auditory and speech performance following CI were graded using categories of auditory performance (CAP), speech intelligibility rating (SIR), and the meaningful auditory integration scale (MAIS) at 24 months following implantation. No correlation was noted between CAP score and CNCS at 24 months post CI (P > .05). A positive correlation was noted between SIR score and CNC width (ρ = .81, P < .05). Similarly, a positive correlation was noted between MAIS and CNC width (ρ = .71, P < .05). The width of the CNC in patients with CNCS is positively correlated with some long-term auditory and speech outcomes after CI.

Anatomic Assessment of the Limits of an Endoscopically Assisted Retrolabyrinthine Approach to the Internal Auditory Canal.

Objective Data regarding the surgical advantages and anatomic constraints of a hearing-preserving endoscopic-assisted retrolabyrinthine approach to the IAC are scarce. This study aimed to define the minimum amount of retrosigmoid dural exposure necessary for endoscopic exposure of the IAC and the surgical freedom of motion afforded by this approach. Methods Presigmoid retrolabyrinthine approaches were performed on fresh cadaveric heads. The IAC was exposed under endoscopic guidance. The retrosigmoid posterior fossa dura was decompressed until the fundus of the IAC was exposed. Surgical freedom of motion at the fundus was calculated after both retrolabyrinthine and translabyrinthine approaches. Results The IAC was entirely exposed in nine specimens with a median length of 12 mm (range: 10-13 mm). Complete IAC exposure could be achieved with 1 cm of retrosigmoid dural exposure in eight of nine mastoids. For the retrolabyrinthine approach, the median anterior-posterior surgical freedom was 13 degrees (range: 6-23 degrees) compared with 46 degrees (range: 36-53 degrees) for the translabyrinthine approach ( p = 0.014). For the retrolabyrinthine approach, the median superior-inferior surgical freedom was 40 degrees (range 33-46 degrees) compared with 47 degrees (range: 42-51 degrees) for the translabyrinthine approach ( p = 0.022). Conclusion Using endoscopic assistance, the retrolabyrinthine approach can expose the entire IAC. We recommend at least 1.5 cm of retrosigmoid posterior fossa dura exposure for this approach. Although this strategy provides significantly less instrument freedom of motion in both the horizontal and vertical axes than the translabyrinthine approach, it may be appropriate for carefully selected patients with intact hearing and small-to-medium sized tumors involving the IAC.

Cochlear Nerve Canal Stenosis: Association With MYH14 and MYH9 Genes.

The bony cochlear nerve canal transmits the cochlear nerve as it passes from the fundus of the internal auditory canal to the cochlea. Stenosis of the cochlear nerve canal, defined as a diameter less than 1.0 mm in transverse diameter, is associated with inner ear anomalies and severe to profound congenital hearing loss. We describe an 11-month-old infant with nonsyndromic congenital sensorineural hearing loss with cochlear nerve canal stenosis. Next-generation sequencing revealed heterozygous mutations in MYH9 and MYH14, encoding for the inner ear proteins myosin heavy chain IIA and IIC. The patient's hearing was rehabilitated with bilateral cochlear implantation.

Predicting outcome of velopharyngeal surgery in drug-induced sleep endoscopy by traction velum.

BACKGROUND: Outcomes of surgical management of obstructive sleep apnea-hypopnea syndrome (OSAHS) can be difficult to predict preoperatively. AIMS/OBJECTIVES: To study the effect of applying traction to the velum during drug-induced sleep endoscopy (DISE) in OSAHS patients, and to describe the use of traction velum in predicting surgical success. MATERIALS AND METHODS: 41 adult surgical patients with OSA (Friedman tongue position II and III) were evaluated by DISE. All patients subsequently underwent velopharyngeal surgery in the form of uvulopalatopharyngoplasty with tonsillectomy plus barbed reposition pharyngoplasty. RESULTS: Surgical responders (n = 26, 63.4%) and nonresponders (n = 15, 36.6%) demonstrated no significant differences with regard to preoperative AHI, age, sex, body mass index, and mean/lowest O2 saturation. Responders had a marked decrease in desaturation events (2.96 vs 0.03, p < 0.001) and percentage change in number of desaturation events before/after traction velum (56.7 vs 4.5, p < 0.001). Regression analysis revealed that reduction in mean desaturation events, with traction velum, by a percentage > 26.8% (odds ratio [OR] 1.046; 95% confidence interval [CI] 1.018-1.075; p = 0.001) was the only independent predictor of surgery success. CONCLUSIONS AND SIGNIFICANCE: OSAHS patients' velopharyngeal surgical outcome can be predicted by measuring the percentage change in the number of oxygen desaturation events before and after traction velum in DISE.

Identification of Perinatal Risk Factors for Auditory Neuropathy Spectrum Disorder.

OBJECTIVES/HYPOTHESIS: To identify medical risk factors associated with auditory neuropathy spectrum disorder (ANSD). STUDY DESIGN: Retrospective case-control study. METHODS: During a 2-year period (2013-2014) patients with newly diagnosed ANSD were identified at a tertiary care facility. Twenty-two patients (n = 22) were identified aged 0.5 to 8.1 years. There were 15 males and seven females. Sixteen had bilateral, four had left-sided, and two had right-sided ANSD. Two age-matched, side-matched, and gender-matched control groups were then collected. The first group was 22 normal-hearing children (n = 22). The second was 22 children with sensorineural hearing loss (SNHL) (n = 22) who did not meet the criteria for ANSD. The chart of each subject was reviewed for the following five-predictor variables: prematurity, low birth weight, jaundice, use of mechanical ventilation, and administration of ototoxic medications. Analysis of variance was performed to analyze the prevalence of perinatal risk factors among the three groups. Multivariate linear regression was then applied. RESULTS: When comparing the ANSD group to both the normal-hearing and SNHL groups, the subjects with ANSD had statistically significant higher rates of prematurity, low birth weight, jaundice, and mechanical ventilation. Multiple regression analysis was performed to identify predictors of ANSD compared to each control group individually. Jaundice in the first month of life approached significance when comparing the ANSD group to the normal-hearing group, and was the only medical risk factor found to be statistically significant when comparing the ANSD group to the SNHL group. CONCLUSIONS: A history of neonatal hyperbilirubinemia was significantly more common in children with ANSD compared to children with severe SNHL. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:671-674, 2021.

Clinical Characteristics of Patients With Papilloma in the External Auditory Canal.

OBJECTIVES: To determine the clinical characteristics of papilloma involving the external auditory canal (PEAC) in a region of China. STUDY DESIGN: A retrospective study. METHODS: Demographics, manifestations, imaging results, histopathology, and treatment of 67 patients diagnosed with PEAC in a period of 6 years were analyzed at Shanghai Eye, Ear, Nose and Throat Hospital in China. RESULTS: PEAC were encountered in patients between the ages of 12 and 82 years (mean 53.8 years). It was more prevalent in men (82%) than in women (18%) (P < .05). The clinical presentation was usually a mass in EAC, aural fullness, and hearing loss. Otoscopic and radiological examination were used together for initial diagnosis and pretreatment planning. Unilateral involvement was more common than bilateral involvement (P < .05). The average time between onset of first symptom and surgical resection and/or biopsy was 6.5 months (range, 0.25-60 months). All patients underwent gross total resection. In 5 patients, (7.5%) carcinoma was detected in the specimen. Fifteen patients (22%) had recurrence; recurrent tumors were detected after an average period of 10 months after surgery (range, 4-24 months). CONCLUSION: PEAC is largely a benign lesion with a low risk of malignancy. Optimal management is via gross total resection. However, the risk of recurrence is high, which motivates a need for long-term monitoring. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:1132-1137, 2021.

An Update on Epidemiology and Management Trends of Vestibular Schwannomas.

OBJECTIVE: To determine the current epidemiology and management trends for patients with vestibular schwannomas (VS). STUDY DESIGN: Retrospective cohort study. SETTING: The Surveillance, Epidemiology, and End Results (SEER) tumor registry. PATIENTS: The SEER database was queried to identify patients diagnosed with VS from 1973 to 2015. Demographics, patient and tumor characteristics, and treatment methods were analyzed. RESULTS: A total of 14,507 patients with VS were identified. The mean age at diagnosis was 55 ±â€Š14.9 years. Age-adjusted incidence from 2006 to 2015 was 1.4 per 100,000 per year and remained relatively stable. Incidence across age varied with sex, as younger women and older men had increased incidences comparatively. A higher percentage of patients underwent surgery alone (43%), followed by observation (32%), radiation alone (23%), and combined radiation and surgery (2%). Age 65 and older was associated with observation (odds ratio [OR] 1.417; p = 0.029) whereas age 20 to 39 and 40 to 49 were associated with surgery (OR 2.013 and 1.935; p < 0.001). Older age was associated with radiation. Larger tumor size was associated with surgery and combined treatment. African American patients and American Indian or Alaskan Native patients were more likely to undergo observation than surgery. CONCLUSIONS: The overall incidence of VS is 1.4 per 100,000 per year and has remained relatively stable. There is a trend toward more conservative management with observation, which may be secondary to earlier diagnosis given widespread use of magnetic resonance imaging. Further studies are necessary to investigate differences in disease patterns and disparities in management.

Radiation-Induced Malignant Peripheral Nerve Sheath Tumor of the Vagus Nerve Following Radiation Treatment of Cervical Paraganglioma.

Radiation-induced sarcoma is a known but rare complication of radiation treatment for skull base paraganglioma. We present the cases of a female patient with multiple paraganglioma syndrome treated with external beam radiation treatment who presented 4 years later with a malignant peripheral nerve sheath tumor of the vagus nerve.

Fluctuating Sensorineural Hearing Loss.

BACKGROUND: Several otologic conditions can present with fluctuating sensorineural hearing loss, including Ménière's disease, autoimmune inner ear disease, and enlarged vestibular aqueduct. Although these 3 etiologies vary greatly, distinguishing between these conditions at initial presentation can be challenging. Furthermore, initial treatment of these conditions is often similar. In this review, we discuss historical and current perspectives on diagnosis and treatment of these conditions. SUMMARY: A literature search was performed regarding fluctuating hearing loss, and current treatment of these etiologies of fluctuating hearing loss was summarized. Immediate measures at the onset of acute hearing loss include corticosteroid therapy, while preventative and chronic therapies, which can limit disease severity and frequency, vary based on the specific condition treated. Key Messages: Fluctuating hearing loss can represent a range of pathologies, but the precise etiology may not be clear at initial presentation. Timely treatment and long-term follow-up, along with appropriate diagnostics, are necessary to optimize long-term hearing.

Linked-read Sequencing Analysis Reveals Tumor-specific Genome Variation Landscapes in Neurofibromatosis Type 2 (NF2) Patients.

HYPOTHESIS: We hypothesize that genomic variants including deletions, insertions, inversions, and tandem duplications beyond the changes in tumor suppressor NF2 gene affect gene expression of tumor-specific pathways in vestibular schwannomas (VS) patients with Neurofibromatosis type 2 (NF2), thus contributing to their clinical behavior. BACKGROUND: Genomic variation could reconfigure transcription in NF2 transformation process. Therefore, genome-wide high-resolution characterization of structural variants (SV) landscapes in NF2 tumors can expand our understanding of the genes regulating the clinical phenotypes in NF2-associated VS. METHODS: We performed whole-genome haplotype-specific structural variation analysis using synthetic linked reads generated through microfluidics-based barcoding of high molecular weight DNA followed by high-coverage Illumina paired-end whole-genome sequencing from 10 patients' tumors of different growth rates and their matching blood samples. RESULTS: NF2 tumor-specific deletions and large SVs were detected and can be classified based on their association with tumor growth rates. Through detailed annotation of these mutations, we uncover common alleles affected by these deletions and large SVs that can be associated with signaling pathways implicated in cell proliferation and tumorigenesis. CONCLUSION: The genomic variation landscape of NF2-related VS was investigated through whole-genome linked-read sequencing. Large SVs, in addition to deletions, were identified and may serve as modulators of clinical behavior.

Revision Surgery for Vestibular Schwannomas.

Objectives To describe clinical outcomes of patients undergoing revision surgery for vestibular schwannomas. Design Retrospective case series. Setting Tertiary private neurotologic practice. Participants Patients who underwent revision surgeries for recurrent/residual vestibular schwannomas between 1985 and 2015. Main Outcome Measures Degree of resection, facial nerve function, cerebrospinal fluid (CSF) leak. Results A total of 234 patients underwent 250 revision surgeries for recurrent/residual vestibular schwannomas. Of these, 86 carried a diagnosis of neurofibromatosis type 2 (NF2). The mean number of prior surgeries was 1.26, and 197 (85%) prior surgeries had been performed elsewhere. The average age at surgery was 43. The most common approach employed at the time of revision surgery was translabyrinthine (87%), followed by transcochlear (6%), middle fossa (5%), and retrosigmoid (2%). Gross total resection was achieved in 212 revision surgeries (85%). Preoperative House-Brackmann facial nerve function was similar in non-NF2 and NF2 groups (mean: 2.7). Mean postoperative facial nerve function at last follow-up was 3.8 in the non-NF2 group and 3.9 in the NF2 group. History of radiation and the extent of resection were not associated with differences in facial nerve function preoperatively or postoperatively. CSF leaks occurred after 21 surgeries (8%), and six (2%) patients required reoperation. Conclusions This is the largest series of revision surgery for vestibular schwannomas to date. Our preferred approach is the translabyrinthine craniotomy, which can be readily modified to include the transcochlear approach for improved access. CSF leak rate slightly exceeds that of primary surgery, and gross total resection is achievable in the vast majority of patients.