Facial Nerve Schwannoma Treatment with Stereotactic Radiosurgery (SRS) versus Resection followed by SRS: Outcomes and a Management Protocol

Background  Stereotactic radiosurgery (SRS) and resection are treatment options for patients with facial nerve schwannomas without mass effect. Objective  This article evaluates outcomes of patients treated with SRS versus resection + SRS. Method  We retrospectively compared 43 patients treated with SRS to 12 patients treated with resection + SRS. The primary study outcome was unfavorable combined endpoint, defined as worsening or new clinical symptoms, and/or tumor radiological progression. SRS (38.81 ± 5.3) and resection + SRS (67.14 ± 11.8) groups had similar clinical follow-ups. Results  At the time of SRS, the tumor volumes of SRS (mean ± standard error; 1.83 ± 0.35 mL) and resection + SRS (2.51 ± 0.75 mL) groups were similar. SRS (12.15 ± 0.08 Gy) and resection + SRS (12.16 ± 0.14 Gy) groups received similar radiation doses. SRS group (42/43, 98%) had better local tumor control than the resection + SRS group (10/12, 83%, p  = 0.04). Most of SRS (32/43, 74%) and resection + SRS (10/12, 83%) group patients reached a favorable combined endpoint following SRS ( p  = 0.52). Considering surgical associated side effects, only 2/10 patients of the resection + SRS group reached a favorable endpoint ( p  < 0.001). Patients of SRS group, who are > 34 years old ( p  = 0.02), have larger tumors (> 4 mL, 0.04), internal auditory canal (IAC) segment tumor involvement ( p  = 0.01) were more likely to reach an unfavorable endpoint. Resection + SRS group patients did not show such a difference. Conclusion  While resection is still needed for larger tumors, SRS offers better clinical and radiological outcomes compared to resection followed by SRS for facial schwannomas. Younger age, smaller tumors, and non-IAC situated tumors are factors that portend a favorable outcome.

Non-Hodgkin Lymphoma Mimicking Vestibular Schwannoma

Progressive unilateral hearing loss and an MRI are usually enough to diagnose vestibular schwannoma (VS). We were consulted by a 45-year-old man with otalgia and left-sided hearing loss as well as ipsilateral facial paralysis that had begun two weeks prior. Due to a possible atypical presentation of VS, an MRI was ordered, which revealed an intracanalicular lesion occupying the left cerebellopontine angle cistern. With no signs of systemic disease and considering the total left ear deafness, the patient underwent retrolabyrinthine mastoidectomy. During the procedure, a mass incompatible with VS was found and a biopsy was performed, which led to a diagnosis of non-Hodgkin's lymphoma (NHL). The patient was referred to an oncologist for treatment and, in time, achieved complete remission of the lesion. This case shows us that symptoms of VS may vary in tumor size and location and that atypical presentations warrant investigation. Non-Hodgkin's lymphoma (NHL), although not among the most common differential diagnoses, should be remembered due to its varied clinical presentation broadly dependent on its subtype and dissemination.

Transcanal Transpromontorial Approaches to the Internal Auditory Canal: A Systematic Review

OBJECTIVE

Exclusive endoscopic (EETTA) and expanded (ExpTTA) transcanal transpromontorial approaches have shown promising results for treating internal auditory canal (IAC) lesions. We reviewed the literature to answer the question: "Do EETTA and ExpTTA achieve high rates of complete resection and low rates of complications in treating patients with IAC pathologies?"

DATA SOURCES

PubMed, EMBASE, Scopus, Web of Science, and Cochrane were searched.

REVIEW METHODS

Studies reporting EETTA/ExpTTA for IAC pathologies were included. Indications and techniques were discussed and meta-analyzed rates of outcomes and complications were obtained with random-effect model meta-analyses.

RESULTS

We included 16 studies comprising 173 patients, all with non-serviceable hearing. Baseline FN function was mostly House-Brackmann-I (96.5%; 95% CI: 94.9-98.1%). Most lesions were vestibular/cochlear schwannomas (98.3%; 95% CI: 96.7-99.8%) of Koos-I (45.9%; 95% CI: 41.3-50.3%) or II (47.1%; 95% CI: 43-51.1%). EETTA was performed in 101 patients (58.4%; 95% CI: 52.4-64.3%) and ExpTTA in 72 (41.6%; 95% CI: 35.6-47.6%), achieving gross-total resection in all cases. Transient complications occurred in 30 patients (17.3%; 95% CI: 13.9-20.5%), with meta-analyzed rates of 9% (95% CI: 4-15%), comprising FN palsy with spontaneous resolution (10.4%; 95% CI: 7.7-13.1%). Persistent complications occurred in 34 patients (19.6%; 95% CI: 17.1-22.2%), with meta-analyzed rates of 12% (95% CI: 7-19%), comprising persistent FN palsy in 22 patients (12.7%; 95% CI: 10.2-15.2%). Mean follow-up was 16 months (range, 1-69; 95% CI: 14.7-17.4). Post-surgery FN function was stable in 131 patients (75.8%; 95% CI: 72.1-79.5%), worsened in 38 (21.9%; 95% CI: 18.8-25%), and improved in 4 (2.3%; 95% CI: 0.7-3.9%), with meta-analyzed rates of improved/stable response of 84% (95% CI: 76-90%).

CONCLUSION

Transpromontorial approaches offer newer routes for IAC surgery, but their restricted indications and unfavorable FN outcomes currently limit their use. Laryngoscope, 133:2856-2867, 2023.

Vascular Loop of the Anterior Inferior Cerebellar Artery (AICA) as a Cause of Sensorineural Hearing Loss (SNHL): A Case Report

Sensorineural hearing loss (SNHL) is one of the most common causes of hearing loss worldwide. Although highly prevalent, many patients often present with SNHL of unknown cause. Related to SNHL is tinnitus, which often presents with SNHL and can have debilitating effects on patients. The idiopathic nature of SNHL and tinnitus often makes treatment difficult, however, a relatively new etiology has been suggested as a cause of SNHL and tinnitus -- vascular loops within the internal auditory canal (IAC). This report presents the case of a 36-year-old male with bilateral SNHL and tinnitus treated with oral steroids. The patient reported subjective improvement of hearing loss and tinnitus, and the audiogram demonstrated hearing improvement, except in higher frequencies. After initial treatment, MRI revealed a vascular loop of the anterior inferior cerebral artery (AICA) in the right IAC, in contact with the vestibulocochlear nerve. Thus, this case report seeks to present a conservative strategy for SNHL and tinnitus in the presence of a vascular loop of the AICA. As a controversial cause of SNHL and tinnitus, there is no standard of treatment for AICA loops of the IAC which are often treated surgically. This case highlights the importance of an initial conservative prior to surgical intervention. Thus, we seek to contribute to the growing body of literature by further elucidating the relationship between SNHL, tinnitus, and vascular loops and discussing potential pathophysiological mechanisms to guide optimal management strategies.

Pediatric internal auditory canal cavernous hemangioma with rapid progression of sensorineural hearing loss: illustrative case

BACKGROUND

Cavernous hemangioma of the internal auditory canal is extremely rare and is characterized by symptoms such as vertigo, sensorineural hearing loss, and facial nerve dysfunction.

OBSERVATIONS

A health examination on an 11-year-old female in the fifth grade revealed hearing loss in the left ear. She also had dizziness that had persisted for approximately 1 year. Pure-tone audiometry revealed sensorineural hearing loss in her left ear. Rightward horizontal and rotatory nystagmus was detected. Facial paralysis was not present. Magnetic resonance imaging showed a lesion that was suspected to be hemangioma. The authors selected a left suboccipital retrosigmoid approach. The tumor showed a berry-tufted appearance throughout the cerebellopontine angle. The seventh cranial nerve penetrated the tumor and partly circulated outside the tumor with marked adhesion. The authors partially resected the tumor to avoid damaging the facial nerve. A histological examination identified cavernous hemangioma.

LESSONS

The fundamental treatment for cavernous hemangioma of the internal auditory canal is complete surgical removal; however, any surgical intervention may result in hearing loss and facial paralysis. The extent of surgery needs to be decided intraoperatively based on the balance between preoperative symptoms and postoperative complications.

Internal Auditory Canal Glioneural Hamartoma: A Rare Mass Masquerading as a Vestibular Schwannoma

Glioneural hamartomas are exceedingly rare lesions. When localized to the internal auditory canal (IAC), they can cause symptoms referrable to seventh and eighth cranial nerve compression. Here, the authors present a rare case of an IAC glioneural hamartoma. A 57-year-old male presented for evaluation of presumed intracanalicular vestibular schwannomas found on work-up of dizziness and progressive right-sided hearing loss. Surgical intervention pursued progressive symptoms and new onset headaches. The patient underwent uncomplicated retrosigmoid craniectomy for gross total resection. Histopathological evaluation revealed a glioneural hamartoma. A MEDLINE database search used the terms' cerebellopontine angle' OR 'internal auditory canal' AND 'hamartoma' OR 'heterotopia'. Clinicopathological characteristics and outcomes of the present case were compared to those in the literature. The literature review yielded nine articles describing 11 cases (eight females, three males; median age 40 years, range 11-71) of intracanalicular glioneural hamartomas. Patients most commonly presented with hearing loss and were presumed to have a diagnosis of vestibular schwannoma before histologic diagnosis. Glioneural hamartomas are rare lesions that may be found in the IAC. Although benign, they may be safely resected for cranial nerve function preservation goals with a low risk of recurrence.

A Rare Case of Pleomorphic Adenoma in the Internal Auditory Canal

Pleomorphic adenoma is a common tumor of the salivary gland tumor, but it is rare in the ear. To the authors' knowledge, this patient is the first reported case of pleomorphic adenoma arising in the internal auditory canal. There have been few documents reporting the manifestations and the therapy strategy of this disease. This study clearly demonstrated the experience in treating pleomorphic adenoma, including the characteristics of the clinical manifestation, the key procedures of surgery, and key points of the diagnosis. The translabyrinthine approach under the microscope performed to remove this tumor is a good option for resecting this type of tumor.

Analysis of the effect of neuroendoscopy-assisted microscopy in the treatment of Large (Koos grade IV) vestibular schwannoma

Introduction

This article aimed to investigate the effects of the endoscopic-assisted microsurgery technique on the resection of large (Koos grade IV) vestibular schwannoma (VS) and provide a prognosis analysis of the patients.

Methods

A retrospective analysis of the use of the endoscopic-assisted microsurgery technique in 16 cases of large vestibular schwannoma surgery was carried out. Intraoperative nerve electrophysiological monitoring was conducted to explore the effect of neuroendoscopy on the resection of internal auditory canal tumors, protection of the facial nerve, and minimizing postoperative complications.

Results

Tumors were completely removed in all 16 cases, and the facial nerve was anatomically preserved in 14 cases (87.5%). There was no postoperative cerebrospinal fluid leakage and no intracranial infection complications occurred.Following the House-Brackmann (H-B) grading system, post-operative facial nerve function was grade I in 5 cases, grade II in 6 cases, grade III in 3 cases, and grade V in 2 cases. As a result, the preservation rate of facial nerve function (H-B grade I-II) was 68.8%. All 16 patients were followed up for 3 to 24 months, and no tumor recurrence was found on enhanced MRI.

Discussion

Using the endoscopic-assisted microsurgery technique in the retrosigmoid approach has many advantages over the microscopic-only approach. When compared to the microscopy-only approach, the endoscope can provide a wide-angle surgical field superior to that of a microscope in areas such as the internal auditory canal in the resection of large VS, minimize iatrogenic injuries, ensure complete removal of internal auditory canal tumors, and well as reducing postoperative complications such as cerebrospinal fluid leakage and the loss of facial and auditory nerve functions.

Large Middle Cranial Fossa Schwannoma: A Rare Presentation of Vestibular Schwannoma

Schwannomas are benign tumors composed of neoplastic Schwann cells and rarely occur in the central nervous system. Schwannomas account for approximately 8% of intracranial tumors and most commonly originate from cranial nerve VIII at the cerebellopontine angle in the posterior fossa. Herein, we report two cases of vestibular schwannomas extending in the middle fossa. The first case shows a 51-year-old male who presented with a history of mild headaches for one year associated with acute nausea, vomiting, and word-finding difficulties. Imaging revealed a large multicystic contrast-enhancing lesion in the left middle cranial fossa. The middle fossa lesion was resected with pathology indicating a schwannoma. The second case shows a 63-year-old woman who presented with seizures, right-sided hearing loss, and right-sided facial weakness. On MRI, she is found to have a large right middle fossa lesion originating from the right internal auditory canal and consistent with vestibular schwannoma with a 9 mm leftward midline shift. The histopathologic examination of the excised tumor indicated a schwannoma. Schwannomas most commonly occur in the posterior fossa when they present intracranially. However, in rare occurrences, they may present as middle fossa masses with significant intracranial compression.

An observational STROBE-MR study

OBJECTIVES

The objective of this study is to identify and define landmarks to adequately describe the internal auditory canal for inclusion in three-dimensional computational models of the cochlea and its surrounding structures.

PARTICIPANTS

Computer tomography scans of live human cochleae were collected in the retrospective period. Descriptive and comparative statistics were used to describe the data obtained from the scans.

RESULTS

The mean anterior-posterior (AP) diameter at the base of the basal turn, the diameter of the AP at the midpoint of the IAC, and the anterior and posterior length of the internal acoustic canal were measured. 57.14% of the internal acoustic canals observed presented with a cylindrical, 40.48% was funnel-shaped and 2.38 % were bud-shaped. A statistically significant differences were found between the diameters of male and female internal acoustic meatus.

CONCLUSIONS

This paper serves as a reference that provides a set of references for the description of the internal acoustic canal for inclusion in three-dimensional computational reconstruction of the cochlea and surrounding structures.

Risk Factors for Progression in Vestibular Schwannomas After Incomplete Resection: A Single Center Retrospective Study

Background and Purpose: The risk factors for progression in vestibular schwannomas (VSs) after incomplete resection (IR) remain to be elucidated. The purpose of this study was to investigate the risk factors for progression in remnant VSs after surgery.

Methods: From January 2009 to January 2018, 140 consecutive patients who underwent IR of VSs via suboccipital retrosigmoid approach in our institution were retrospectively analyzed. During follow-up, if progression was detected, the patient was classified into Progressive Group (PG); if the residual tumor was stable or shrank, the patient was classified into Stable Group (SG). Univariate analysis and multivariate analysis were used to evaluate the risk factors for progression after IR of VSs.

Results: After a mean follow-up of 80.4 months (range, 24–134 months), 35 (25.0%) patients (PG) had a progression, and no progression was detected in 105 (75.0%) patients (SG). The average tumor size was 36.5 ± 8.9 mm in PG and 31.0 ± 9.8 mm in SG, respectively. The residual tumor volume was 304.6 ± 443.3 mm³ in PG and 75.9 ± 60.0 mm³ in SG, respectively. Univariate analysis showed that preoperative tumor size, residual tumor volume, and irregular internal auditory canal (IAC) expansion were significantly different between the two groups, whereas gender, age, cystic component, or Ki-67 labeling index (LI) did not differ significantly between the two groups. Multivariate analysis showed residual tumor volume was the independent risk factor for progression.

Conclusions: VSs that underwent IR with larger preoperative size, greater residual tumor volume, or irregular IAC expansion may have a higher progression rate. Strict follow-up with shorter interval in these patients to detect early progression is necessary.

Unilateral sudden sensorineural hearing loss with vertigo as a first symptom of bilateral internal auditory canal metastases: a case report

There have been relatively few reports of bilateral internal auditory canal metastases of asymptomatic primary pulmonary adenocarcinoma presenting as unilateral sudden sensorineural hearing loss and vertigo. We report a case of a 60-year-old male patient who complained of sudden hearing loss in the right ear and vertigo. Upon a physical examination, no definite neurological signs or nystagmus were observed. Pure-tone audiometry showed deafness in the right ear at all frequencies and high-frequency sensorineural hearing loss in the left ear. The video head impulse test suggested bilateral vestibulopathy. Magnetic resonance imaging of the brain (with gadolinium contrast) revealed bilateral internal auditory canal enhancement and a variable-sized nodular and peripheral-enhancing lesion in the cerebrum and the right cerebellum. A computed tomographic and bronchoscopic biopsy identified asymptomatic primary pulmonary adenocarcinoma in the left upper lobe of the lungs. This is a rare report of bilateral internal auditory canal metastases in an asymptomatic patient with primary pulmonary adenocarcinoma who initially presented with symptoms of unilateral sudden sensorineural hearing loss with vertigo.

Endoscopic-assisted resection of vestibular schwannomas in high-riding jugular bulb

The present surgical video demonstrates safe opening of the internal auditory canal (IAC) during vestibular schwannoma surgery via a retrosigmoid approach in the sitting position. Resection of the intrameatal portion of a tumor is important for progression-free survival. Preoperative thin-sliced CT revealed a high-riding jugular bulb obscuring the trajectory. After dural opening, the IAC was approached anteriorly and superiorly. The posterior margin of IAC drilling was above the Tubingen line. Drilling was performed under continuous jugular compression. The vein was pushed down to augment visibility. An angled endoscope was helpful. IAC can be drilled safely in a high-riding jugular bulb with the technique mentioned in the video. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID2198.

Transmeatal microsurgery for intralabyrinthine and intrameatal schwannomas: a reappraisal

Objective

The interest in surgical routes to the internal auditory canal (IAC) through the external auditory canal for vestibular schwannoma removal has been recently raised by the endoscopic approaches to the lateral skull base. The aim of the study was to reappraise the transmeatal microsurgical approach (TMMa) to the labyrinth and IAC, first described 50 years ago.

Methods

A retrospective series of 8 consecutive patients treated for intralabyrinthine and intrameatal schwannomas through TMMa is presented. Main outcome measures consisted of surgical indications, postoperative complications, facial nerve status, bed mobilisation time, hospitalisation time and tumour recurrence rate.

Results

Surgical indications for TMMa were tumour growth (62.5%) and disabling vertigo (37.5%) in the present series. Complete tumour removal with no complications and postoperative normal facial nerve function was obtained in all cases. Bed mobilisation occurred after a median of 3 postoperative days (IQR 2.2-3.0) and discharge after a median of 5.6 days (IQR 4.7-7.0). After a median follow-up of 13 months (IQR 7.5-27.5), no tumour recurrence was observed.

Conclusions

TMMa indications are limited to schwannomas of the labyrinth and IAC, which dropped out from observation protocols due to unmanageable symptoms or growth. Despite the narrow mini-invasive surgical corridor, the TMMa was a safe an effective microsurgical technique in terms of tumour removal and postoperative course.

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.

Surgical management of intraoperatively diagnosed facial nerve schwannoma located at internal auditory canal and cerebellopontine angle - our experiences of 14 cases

BACKGROUND

Facial nerve schwannomas located at internal auditory canal and cerebellopontine angle (IAC/CPA FNS) were diagnosed intraoperatively, it poses a therapeutic dilemma to the surgeon.

OBJECTIVE

To report our experience in managing IAC/CPA FNS and to propose a treatment strategy.

METHODS

A total of 14 patients with IAC/CPA FNS who were diagnosed intraoperatively and treated by operation between 2015 and 2019 were retrospectively studied.

RESULTS

Unilateral hearing loss was the most common symptom and all these patients had normal facial nerve function preoperatively. Surgical approaches used in these patients including translabyrinthine (2 cases), retrosigmoid (RS) (11 cases), and middle cranial fossa (MCF) approach (1 case). Eight patients underwent partial resection, three patients underwent subtotal resection and three patients had complete tumor removal with facial nerve reconstruction. All partial resection patients and two patients underwent subtotal resection achieved a long-term HB grade I facial nerve function. The long-term facial nerve function of patients underwent complete resection and nerve grafting was no better than HB grade III.1 of the eight patients underwent partial resection experienced tumor regrowth during the follow-up.

CONCLUSIONS

Partial or subtotal resection for IAC/CPA FNS may provide an opportunity of retaining excellent facial nerve function. Regular postoperative imaging is helpful to monitor the recurrence.

Cerebellopontine Angle and Internal Auditory Canal Lipomas: Case Series and Systematic Review

OBJECTIVES/HYPOTHESIS

Cerebellopontine angle (CPA) and internal auditory canal (IAC) lipomas are rare, benign tumors comprising 0.08% of all intracranial tumors and can be mistaken for other, more common lesions of the CPA/IAC such as vestibular schwannoma. The purpose of this study was to review the literature and assess the evolution of CPA/IAC lipoma diagnosis and management. In addition, we present 17 new lipomas, matching the largest known case series of this rare tumor.

STUDY DESIGN

Retrospective case series and systematic review.

METHODS

Systematic review of the literature was performed using PubMed and Google Scholar. References from identified articles were also reviewed to identify potential additional manuscripts. Manuscripts and abstracts were reviewed to identify unique cases. For the case series, the charts of all CPA/IAC lipoma patients seen at a single institution from 2006-2019 were manually reviewed. Logistic regression and chi-squared analysis were performed where appropriate.

RESULTS

A total of 219 unique lipomas have been reported in the literature, including 17 presented in this study. Surgical management has been performed in 46% of cases and has been conducted less often in recent decades, likely due to improved radiographic diagnostic capabilities and understanding of surgical outcomes. Surgical management is associated with worse neurologic outcomes (P = .002) and has become less common in recent decades. Although growth is unlikely, it has been demonstrated in patients into their 30s.

CONCLUSIONS

Accurate radiographic diagnosis is imperative for appropriate patient management, as CPA/IAC lipomas should typically be managed through observation and serial imaging whereas vestibular schwannomas and other CPA/IAC lesions may require microsurgical or radiosurgical intervention depending on growth and symptomatology. Laryngoscope, 131:2081-2087, 2021.

Decompression of the internal auditory canal via the retrosigmoid approach in a patient with Camurati-Engelmann disease: illustrative case

BACKGROUND

Camurati-Engelmann disease (CED) is a rare condition characterized by hyperostosis of the long bones and skull base. Symptoms include contractures and pain in affected extremities but can also include manifestations of cranial hyperostosis such as intracranial hypertension, Chiari malformation, exophthalmia, frontal bossing, and several cranial neuropathies due to cranial foraminal stenosis.

OBSERVATIONS

This report describes a 27-year-old patient with suspected CED who developed progressive intermittent facial nerve paresis, hemifacial spasms, and a decrease in hearing. There were no symptoms of increased intracranial pressure or vertigo. Radiological evaluation showed a significant thickening of the skull base with serious bilateral internal auditory canal stenosis. Because of the progressive nature of the aforementioned cranial neuropathies in combination with the correlating severe radiological compression, a surgical decompression of the facial nerve and vestibulocochlear nerve was performed via a retrosigmoid approach with intraoperative monitoring. Postoperative facial nerve function was intact. Hearing and vestibular function were unchanged. There were no more episodes of facial nerve palsy or spasm.

LESSONS

To the authors' knowledge, this is the first report to describe decompression of the internal auditory canal via a retrosigmoid approach for symptomatic facial and cochlear nerve compression in a patient with CED.

Internal Auditory Canal Diverticula in Children: A Congenital Variant

OBJECTIVES/HYPOTHESIS

Internal auditory diverticula in adults have been found to exist independent of otosclerosis, and in the presence of otosclerosis. We sought to determine the prevalence of internal auditory canal (IAC) diverticula in a pediatric cohort, to assess whether IAC diverticula are a risk factor for hearing loss, and the co-occurrence of otic capsule hypoattenuation.

STUDY DESIGN

Retrospective review.

METHODS

A single-site retrospective review of high-resolution temporal bones computed tomography (CT) scans including the presence and size of diverticula and hypoattenuation of the otic capsule. Demographic, imaging, and audiometric data were collected and descriptively analyzed. Bivariate analysis of collected variables was conducted. Comparisons between sides in unilateral cases were also performed.

RESULTS

16/600 (2.7%; 95% CI [2.0%, 3.4%]) were found to have IAC diverticula. Six were bilateral. Thirty-one patients (5.2%) were found to have hypoattenuation of the otic capsule. There were no coincident cases of IAC diverticulum and hypoattenuation of the otic capsule. There was no association between the presence of IAC diverticula and age (P = .13). In six patients with unilateral diverticula, pure tone average (P = .42), and word recognition (P = .27) scores were not significantly different when compared to the normal, contralateral side.

CONCLUSIONS

The prevalence of IAC diverticula in children is lower than the prevalence in adults. IAC diverticula in children likely represent congenital variants of temporal bone anatomy. Similar to adult populations, there is evidence that IAC diverticula in children are likely not an independent risk factor for hearing loss.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1683-E1687, 2021.

[Computer tomography demonstrations of single-sided deafness]

Objective:To investigate the distribution of common inner ear and internal auditory canal malformations in children with single-sided deafness（SSD） ,and to explore the imaging etiology of SSD by comparing the quantitative parameters of key bone structures between deaf and normal ears in children with congenital SSD. Method:Forty children with SSD diagnosed in the Second Hospital of Lanzhou University from September 2016 to March 2019 were collected. All of them underwent HRCT examinations of temporal bone . The area of bone island, the width of vestibular, the width of internal auditory canal, the height of cochlear and the width of cochlear basal axis were measured. Paired t test was used to compare the difference between the hearing abnormality and normal hearing in children with SSD. Result:The rate of inner ear deformity was 62.5% in SSD group,the most common deformity was cochlear nerve canal deformity, 20 cases （50.0%） of cochlear canal stenosis and 3 cases （7.5%） of cochlear canal atresia.The second most common deformity was internal auditory canal deformity, including 5 cases （12.5%） of internal auditory canal stenosis and 1 case （2.5%） of internal auditory canal atresia. Other malformations included 1 case（2.5%） of RO, 2 cases （5.0%） of incomplete partition （IP） type II and 1 case （2.5%） of enlargement of vestibular aqueduct （EVA）. There are no significant difference in the measured results of the key structures of the inner ear between two groups except the width of cochlear nerve canal, internal auditory canal and the area of bone island. Conclusion:The main inner ear deformities in children with SSD are cochlear nerve canal stenosis and inner auditory canal stenosis. HRCT of temporal bone has high diagnostic value for inner ear deformities in children with SSD.

Solitary fibrous tumor/hemangiopericytoma in the cerebellopontine angle mimicking vestibular schwannoma: A case report and literature review

RATIONALE

Intracranial solitary fibrous tumors (SFTs) and hemangiopericytomas (HPCs) are rare spindle cell tumors of mesenchymal origin that include benign and malignant neoplasms.

PATIENT CONCERNS

We present a 66-year-old male with a 5-year history of headache and dizziness, with left progressive sensorineural hearing loss over 1 month.

DIAGNOSES

WHO grade II SFT/HPC originating from the internal auditory canal in the left cerebellopontine angle.

INTERVENTIONS

surgical resection.

OUTCOMES

No local recurrence or metastases were observed in the follow-up 3 months after the surgery.

LESSONS

Intracranial SFTs/HPCs are rare mesenchymal neoplasms that are challenging to manage. If the imaging characteristics of tumor are not typical, clinicians should depend on tissue biopsy and immunohistochemistry to make a definitive diagnosis.

Using the Arcuate Eminence-Trigeminal Notch Line to Localize the Anterior Wall of the Internal Auditory Canal in a Subtemporal Approach: An Anatomical Study

Background  This article aims to describe the regional anatomy of the anterior end of the arcuate eminence, the lateral end of the trigeminal notch, and the line connecting the two (i.e., the arcuate eminence-trigeminal notch line [ATL]) and to determine whether the ATL could be used as a landmark for localizing the internal auditory canal (IAC). Methods  Twenty sides of the middle cranial fossae were examined. The anterior end of the arcuate eminence, the lateral end of the trigeminal notch, the ATL, and other crucial structures were exposed. The relevant distance and angle of related structures in the anterior wall of the petrosal bone were measured. Results  The anterior end of the arcuate eminence and the lateral end of the trigeminal notch could be identified in all specimens. The anterior end of the arcuate eminence lay over the geniculate ganglia and the vestibule area, and could be visualized directly or determined from the intersection of the long axes of the greater superficial petrosal nerve and arcuate eminence. On the petrous ridge, the lateral end of the trigeminal notch was also the transitional point of the suprameatal tubercle and trigeminal notch. The ATL corresponded to the projection of the anterior wall of the IAC on the anterior surface of the petrous bone. Conclusion  The ATL corresponded to the projection of the anterior wall of the IAC on the anterior petrous surface and could be used as an alternative landmark for localizing the anterior wall of the IAC.

Endoscopic transmastoid posterior petrosal approach for locally aggressive tumors in the petrous part of the temporal bone involving the internal auditory canal, jugular foramen, and hypoglossal canal

OBJECTIVE

The posterior petrosal approach is an established surgical method offering wide access to skull base lesions through mastoid air cells. The authors describe their experience with the endoscopic transmastoid "posterior petrosal" approach (EPPAP) for skull base tumors involving the internal auditory canal (IAC), jugular foramen, and hypoglossal canal.

METHODS

The EPPAP was performed for 7 tumors (3 chordomas, 2 chondrosarcomas, 1 schwannoma, and 1 solitary fibrous tumor). All surgical procedures were performed under endoscopic visualization with mastoidectomy. The compact bone of the mastoid air cells and posterior surface of the petrous bone are carefully removed behind the semicircular canals. When removal of cancellous bone is extended superomedially through the infralabyrinthine space, the surgeon can expose the IAC and petrous portion of the internal carotid artery to reach the petrous apex (infralabyrinthine route). When removal of cancellous bone is extended inferomedially along the sigmoid sinus, the surgeon can safely reach the jugular foramen (transjugular route). Drilling of the inferior surface of petrous bone is extended further inferoposteriorly behind the jugular bulb to approach the hypoglossal canal and parapharyngeal space through the lateral aspect of the occipital condyle (infrajugular route).

RESULTS

Of the 7 tumors, gross-total resection was achieved in 4 (57.1%), subtotal resection (> 95% removal) in 2 (28.6%), and partial resection (90% removal) in 1 (14.2%). Postoperatively, 2 of 3 patients with exudative otitis media showed improvement of hearing deterioration, as did 2 patients with tinnitus. Hypoglossal nerve palsy and swallowing difficulty were improved after surgery in 2 patients and 1 patient, respectively. In 1 patient with severe cranial nerve deficits before surgery, symptoms did not show any improvement.

CONCLUSIONS

The authors present their preliminary experience with EPPAP for skull base tumors in the petrous part of the temporal bone and the lateral part of the occipital condyle involving the cranial nerves and internal carotid arteries. The microscope showed a higher-quality image and illumination in the low-power field. However, the endoscope could offer wider visualization of the surgical field and contribute to minimizing the size of the surgical pathways, necessity of brain retraction, and eventually the invasiveness of surgery. Thus, the EPPAP may be safe and effective for skull base tumors in the petrous region, achieving balance between the radicality and invasiveness of the skull base surgery.

The relationship between the dimensions of the internal auditory canal and the anomalies of the vestibulocochlear nerve

BACKGROUND

Internal auditory canal (IAC) stenosis and vestibulocochlear nerve (VCN) abnormalities have been reported to be associated with sensorineural hearing loss. Previous studies classified the normal dimensions of the IAC and its anomalies with no consideration of the VCN. Other studies categorised the VCN development in only stenotic canals. In the present study, an anatomical classification of the normal dimensions of the IAC and its anomalies and their association with malformations of the VCN and its subdivisions were described.

MATERIALS AND METHODS

Retrospective review was undertaken for children ranged from 1 to 10 years. A total of 764 canals were investigated for pre-operative assessment of cochlear implantation. Other 100 canals of normal hearing ears were included as the control group. The maximum anteroposterior diameter, considered the width of the canal, was measured in axial plane and the length of the canal was identified in coronal plane. The canals were categorised normal: if they are from 3 to 8 mm, patulous: if they are more than 8 mm, stenotic: if they are less than 3 mm and atretic if absent, using multislice computed tomography. The VCN trunks and their subdivisions were investigated using magnetic resonance imaging.

RESULTS

Internal auditory canals were found normal in 66% with a mean width: 5.27 ± ± 0.68, patulous in 17% with a mean width 113% more than that of the control group (p = 0.000), stenotic in 13% with a mean width 73% less as compared to that of the control group (p = 0.000) and atretic in 4% of the experimental canals. The VCN trunks were found normal with well-developed subdivisions in 77.8% of the normal canals, 98.4% of the patulous canals, and 19.2% of the stenotic canals. The VCN trunks were normal with hypoplastic subdivisions in 11.3% of the normal canals, 1.6% in the patulous canals, and 61.6% in the stenotic canals with a mean width 52% less than that of the normal trunk with developed subdivisions. Hypoplastic VCN trunks with absent subdivisions were reported in 7.3% of the normal canals, 11.1% of the stenotic canals and in 3.2% of the atretic canals. The VCN trunks were not found in 3.6% of the normal canals, in 8.1% of the stenotic canals and in 96.8% of the atretic canals.

CONCLUSIONS

Internal auditory canal formation was dependent on the process of development and growth of the eighth cranial nerve and its subdivisions that greatly affected the completion of IAC canalisation. This paper could serve as a reference providing a quantitative classification of the relationship between the dimensions of the IAC and the development of the VCN trunk and its subdivisions.

The Size of Internal Auditory Canal Diverticula Is Unrelated to Degree of Hearing Loss

OBJECTIVES

To explore the relationship between hearing loss and the internal auditory canal (IAC) diverticula. To determine whether diverticula exist within or medial to the otic capsule and the prevalence in a control population.

METHODS

Retrospective review of adult patients with radiologic evidence of an IAC diverticulum, no evidence of otosclerosis, and audiometric testing. Analyzed degree of hearing loss and width, length, height, and volume of diverticulum. Hounsfield unit (HU) measurements lateral and medial to the diverticulum.

RESULTS

Pure tone average (PTA), air-bone gap, and WRS (word recognition score) did not correlate with length, width, height, and volume of the diverticula. In patients with a unilateral diverticulum, there was no difference in mean PTA or WRS when comparing the diverticulum and nondiverticulum sides. Mean HU lateral to the diverticulum (2104 HU) was found to be significantly higher than medial to the diverticulum (1818 HU). There is a 5.6% prevalence of IAC diverticula in patients who underwent high-resolution computed tomography (CT) scans for chronic sinusitis (control group).

CONCLUSION

These data support the notion that hearing loss in this population is a product of sampling bias. The size of IAC diverticula does not correlate with the degree of hearing loss, and there is no statistically significant association between sensorineural hearing loss (SNHL) and the presence of an IAC diverticulum. IAC diverticula may exist medial to, rather than within, the otic capsule given the significant difference in mean HUs medial and lateral to the diverticula.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1011-1015, 2020.

3 T - MRI improves intrameatal cranial nerve detection in CI-candidates

BACKGROUND

Cochlear implantation meanwhile is a well established standard therapy in different forms of hearing loss in most ages. Clear depiction of the cochleovestibular anatomy and the cochlear nerve are very important for indication and effectiveness of cochlear implantation. Aim/objectives: Therefore the question raises whether Highfield MRI improves precision of preoperative diagnostic imaging especially along the the intrameatal portion of the vestibulocochlear nerve.

METHODS

We analyzed the MRI scans of 216 temporal bones from 2007 until 2017. In all patients, CI was planned. We compared examinations using 1.5 and 3.0 T MR systems under the aspect of intracanalicular detection of the facial nerve, cochlear nerve, and the vestibular branches.

RESULTS

3 T-MRI was able to detect the cochlear nerve in all cases, a very important criterion for CI-indication. 3 T-MRI was also superior in the detection of facial nerve and especially the vestibular branches.

CONCLUSION AND SIGNIFICANCE

The most effective preoperative examination of CI-candidates is the combination of 3 T MRI and multislice HR-CT of the temporal bone.

Glioblastoma of the cerebellopontine angle and internal auditory canal mimicking a peripheral nerve sheath tumor: case report

Glioblastoma (GBM) of the internal auditory canal (IAC) is exceedingly rare, with only 3 prior cases reported in the literature. The authors present the fourth case of cerebellopontine angle (CPA) and IAC GBM, and the first in which the lesion mimicked a vestibular schwannoma (VS) early in its natural history. A 55-year-old man presented with tinnitus, hearing loss, and imbalance. MRI identified a left IAC/CPA lesion measuring 8 mm, most consistent with a benign VS. Over the subsequent 4 months he developed facial weakness. The tumor grew remarkably to 24 mm and surgery was recommended; the main preoperative diagnosis was malignant peripheral nerve sheath tumor (MPNST). Resection proceeded via a translabyrinthine approach with resection of cranial nerves VII and VIII, followed by facial-hypoglossal nerve anastomosis. Intraoperative frozen section suggested malignant spindle cell neoplasm, but final histopathological and molecular testing confirmed the lesion to be a GBM. The authors report the first case in which absence of any brainstem interface effectively excluded a primary parenchymal tumor, in particular GBM, from the differential diagnosis. Given the dramatic differences in treatment and prognoses between malignant glioma and MPNST, this case emphasizes the importance of surgical intervention on an aggressively growing lesion, which provides both the best probability of local control and the critical tissue diagnosis.

Key anatomical landmarks for middle fossa surgery: a surgical anatomy study

OBJECTIVE

Middle fossa surgery is challenging, and reliable surgical landmarks are essential to perform accurate and safe surgery. Although many descriptions of the middle fossa components have been published, a clinically practical description of this very complex anatomical region is lacking. Small structure arrangements in this area are often not well visualized or accurately demarcated with neuronavigation systems. The objective is to describe a "roadmap" of key surgical reference points and landmarks during middle fossa surgery to help the surgeon predict where critical structures will be located.

METHODS

The authors studied 40 dry skulls (80 sides) obtained from the anatomical board at their institution. Measurements of anatomical structures in the middle fossa were made with a digital caliper and a protractor, taking as reference the middle point of the external auditory canal (MEAC). The results were statistically analyzed.

RESULTS

The petrous part of the temporal bone was found at a mean of 16 mm anterior and 24 mm posterior to the MEAC. In 87% and 99% of the sides, the foramen ovale and foramen spinosum, respectively, were encountered deep to the zygomatic root. The posterior aspect of the greater superficial petrosal nerve (GSPN) groove was a mean of 6 mm anterior and 25 mm medial to the MEAC, nearly parallel to the petrous ridge. The main axis of the IAC projected to the root of the zygoma in all cases. The internal auditory canal (IAC) porus was found 5.5 mm lateral and 4.5 mm deep to the lateral aspect of the trigeminal impression along the petrous ridge (mean measurement values). A projection from this point to the middle aspect of the root of the zygoma, being posterior to the GSPN groove, could estimate the orientation of the IAC.

CONCLUSIONS

In middle fossa approaches, the external acoustic canal is a reliable reference before skin incision, whereas the zygomatic root becomes important after the skin incision. Deep structures can be related to these 2 anatomical structures. An easy method to predict the location of the IAC in surgery is described. Careful study of the preoperative imaging is essential to adapt this knowledge to the individual anatomy of the patient.

Internal auditory canal exostosis: A technical case report

Background:

Exostoses of the internal auditory canal is a rare finding that may present with disabling symptoms of dizziness, hearing loss, and vestibular dysfunction based on the extent of cranial nerve compression. The purpose of this case report is to discuss the presentation and outcomes in a patient who presented with this disorder.

Case Description:

A 19-year-old female presented to the neurotologist with left ear discomfort, pain with left lateral gaze, and dizziness. She underwent extensive evaluation including audiometric testing, videonystagmography, and neuroimaging, which confirmed left auditory and vestibular hypofunction and compression of the contents of the internal auditory canal from the exostosis. After extensive counseling, the patient elected to undergo a suboccipital craniectomy to remove the internal auditory canal exostosis. She experienced complete resolution of symptoms.

Conclusions:

Exostoses of the internal auditory canal, although rare, can present with severe symptoms of dizziness, hearing loss, and vestibular hypofunction based on the extent of cranial nerve compression. Imaging, particularly with thin-cut computed tomography, is invaluable in making the correct diagnosis. Severe cases can be treated successfully with surgery with minimal or no complications and excellent outcome.

The 'full-blown' MRI of sudden hearing loss: 3D FLAIR in a patient with bilateral metastases in the internal auditory canals

We report a case of a 57-year-old man with bilateral masses in the internal auditory canal. The peculiar findings at magnetic resonance imaging with tridimensional fluid-attenuated inversion recovery sequence combined with clinical data provided new insights into understanding the pathophysiology of the hearing loss.

Retrosigmoid transmeatal and suprajugular approach for cerebellopontine angle meningioma: operative video

Surgical management of cerebellopontine angle meningiomas is challenging due to the intricate neurovascular structures within the limited operative field and the compression of eloquent structures including the brainstem. Surgery on tumors extending into the temporal bone is especially difficult and demands complicated approaches. However, modifications to the retrosigmoid approach utilizing intradural temporal bone drilling enable access to such tumoral extensions without any additional invasive approaches. This video demonstrates the case of a cerebellopontine angle meningioma extending into the internal acoustic meatus and jugular foramen that was surgically treated through the retrosigmoid transmeatal and suprajugular approaches under continuous vagus nerve monitoring. The video can be found here: https://youtu.be/aUD1vr6TbOc .

Resection planning for robotic acoustic neuroma surgery

Acoustic neuroma surgery is a procedure in which a benign mass is removed from the internal auditory canal (IAC). Currently, this surgical procedure requires manual drilling of the temporal bone followed by exposure and removal of the acoustic neuroma. This procedure is physically and mentally taxing to the surgeon. Our group is working on the development of an acoustic neuroma surgery robot (ANSR) to perform the initial drilling procedure. Planning the ANSR's drilling region using preoperative CT requires expertise and takes about 35 min. We propose an approach for automatically producing a resection plan for the ANSR that would avoid damage to sensitive ear structures and require minimal editing by the surgeon. We first compute an atlas-based segmentation of the mastoid section of the temporal bone, refine it based on the position of anatomical landmarks, and apply a safety margin to the result to produce the automatic resection plan. In experiments with CTs from nine subjects, our automated process resulted in a resection plan that was verified to be safe in every case. Approximately 2 min were required in each case for the surgeon to verify and edit the plan to permit functional access to the IAC. We measured a mean Dice coefficient of 0.99 and surface error of 0.08 mm between the final and automatically proposed plans. These preliminary results indicate that our approach is a viable method for resection planning for the ANSR and drastically reduces the surgeon's planning effort.

Multiple Unilateral Vestibular Schwannomas: Segmental NF2 or Sporadic Occurrence?

Objective To report a case of a patient presenting with two separate unilateral vestibular schwannomas (VSs) without other stigmata of neurofibromatosis type 2 (NF2).

Study Design This article discusses a case report and review of the literature.

Setting Tertiary academic referral center.

Participants A 41-year-old female was referred for evaluation of a left-sided 1.8-cm cerebellopontine angle tumor centered on the porus acusticus and a separate ipsilateral 3-mm intracanalicular tumor appearing to arise from the superior vestibular nerve. The patient denied a family history of NF2. Neurotologic examination was unremarkable and close review of magnetic resonance imaging did not find any other stigmata of NF2.

Results The patient underwent left-sided retrosigmoid craniotomy with gross total resection of both tumors. Final pathology confirmed benign schwannoma. The INI1/SMARCB1 staining pattern did not suggest NF2 or schwannomatosis.

Conclusions This is only the third report of a case with multiple unilateral VSs occurring in a patient without other features of NF2. Herein, the authors review the two other reports and discuss potential mechanisms for this rare phenomenon.

Bilateral internal auditory canal gangliogliomas mimicking neurofibromatosis Type II

Background:

Gangliogliomas are rare low grade, typically well-differentiated, tumors that are composed of mature ganglion cells and neoplastic glial cells. These tumors can appear at virtually any location along the neuroaxis but classically occur in the temporal lobe of young patients. In a small number of cases, gangliogliomas have presented as masses in the brainstem or involving cranial nerves. With the exception of vestibular schwannomas, bilateral tumors in the region of the internal auditory canal (IAC) or cerebellopontine angle (CPA) are exceedingly rare.

Case Description:

We report a case of a 58-year-old male who presented with hearing loss, tinnitus, and vertigo. Initial magnetic resonance imaging revealed bilateral nonenhancing IAC/CPA tumors. Based on this finding, a presumptive diagnosis of neurofibromatosis Type II was made, which was initially managed conservatively with close observation. He returned for follow-up with worsening vertigo and tinnitus, thus prompting the decision to proceed with surgical resection of the symptomatic mass. Intriguingly, pathological study demonstrated a WHO Grade I ganglioglioma.

Description:

We report a case of a 58-year-old male who presented with hearing loss, tinnitus, and vertigo. Initial magnetic resonance imaging revealed bilateral nonenhancing IAC/CPA tumors. Based on this finding, a presumptive diagnosis of neurofibromatosis Type II was made, which was initially managed conservatively with close observation. He returned for follow-up with worsening vertigo and tinnitus, thus prompting the decision to proceed with surgical resection of the symptomatic mass. Intriguingly, pathological study demonstrated a WHO Grade I ganglioglioma.

Conclusion:

This is the first reported case of bilateral IAC/CPA gangliogliomas. When evaluating bilateral IAC/CPA lesions with unusual imaging characteristics, ganglioglioma should be included in the differential diagnosis.

Endoscopic Transcanal Retrocochlear Approach to the Internal Auditory Canal with Cochlear Preservation: Pilot Cadaveric Study

Contemporary operative approaches to the internal auditory canal (IAC) require the creation of large surgical portals for visualization with associated morbidity, including hearing loss, vestibular dysfunction, facial nerve injury, and skull base defects that increase the risk of cerebrospinal fluid leak. Transcanal approaches to the IAC have been possible only via a transcochlear technique. To preserve cochlear function, we describe a novel endoscopic transcanal infracochlear approach to the IAC in cadaveric temporal bones. Navigation fiducials were secured on fresh cadaveric heads, and real-time computed tomography imaging was used for surgical guidance. With a combination of curved instruments and rigid angled endoscopy, a transcanal hypotympanotomy and subcochlear tunnel were created with superior extension to access the IAC. Postprocedure imaging and temporal bone dissection confirmed access to the IAC without injury to the cochlea or neighboring neurovascular structures.

Diagnosis and treatment of cavernous hemangioma of the internal auditory canal

OBJECTIVE

Cavernous hemangioma of the internal auditory canal (IAC) is an extremely rare type of tumor, and only 50 cases have been reported in the literature prior to this study. The aim in this study was to describe the symptomatology, radiological features, and surgical outcomes for patients with cavernous hemangioma of the IAC and to discuss the diagnostic criteria and treatment strategy for the disease.

METHODS

The study included 6 patients with cavernous hemangioma of the IAC. All patients presented with sensorineural hearing loss and tinnitus, and 2 also suffered from vertigo. Five patients reported a history of facial symptoms with hemispasm or palsy: 3 had progressive facial weakness, 1 had a hemispasm, and 1 had a history of recovery from sudden facial paresis. All patients underwent CT and MRI to rule out intracanalicular vestibular schwannomas and facial nerve neuromas. Five patients had their tumors surgically removed, while 1 patient, who did not have facial problems, was followed up with a wait-and-scan approach.

RESULTS

All patients had a presurgical diagnosis of cavernous hemangioma of the IAC, which was confirmed pathologically in the 5 patients who underwent surgical removal of the tumor. The translabyrinthine approach was used to remove the tumor in 4 patients, while the middle cranial fossa approach was used in the 1 patient who still had functional hearing. Tumors adhered to cranial nerves VII and/or VIII and were difficult to dissect from nerve sheaths during surgeries. Complete hearing loss occurred in all 5 patients. In 3 patients, the facial nerve could not be separated from the tumor, and primary end-to-end anastomosis was performed. Intact facial nerve preservation was achieved in 2 patients. Patients were followed up for at least 1 year after treatment, and MRI showed no evidence of tumor regrowth. All patients experienced some level of recovery in facial nerve function.

CONCLUSIONS

Cavernous hemangioma of the IAC can be diagnosed preoperatively through analysis of clinical features and neuroimaging. Early surgical intervention may preserve the functional integrity of the facial nerve and provide a better outcome after nerve reconstruction. However, preservation of functional hearing may not be achieved, even with the retrosigmoid or middle cranial fossa approaches. The translabyrinthine approach seems to be the most appropriate approach overall, as the facial nerve can be easily located and reconstructed.

Lipochoristoma of the Internal Auditory Canal

Objective Lipochoristomas comprise 0.1% of all cerebellopontine angle tumors and may be misdiagnosed as vestibular schwannomas. We describe a lipochoristoma of the internal auditory canal (IAC) and present the salient features of the evaluation, diagnosis, and management.

Study Design and Methods Retrospective case review.

Results (Case Report) A 51-year-old woman presented with left-sided severe hearing loss, tinnitus, mild episodic vertigo, and facial paresthesias progressive over 1 year. Magnetic resonance imaging (MRI) demonstrated a small (5 × 4 mm) T1 hyperintense lobulated lesion in the distal internal auditory canal. With fat-suppressed images, there was no enhancement of the lesion. A diagnosis of IAC lipochoristoma was made. Conservative management was recommended, and on 17-month follow-up there was no interval growth. The patient remains symptomatically stable with improved equilibrium but persistent left-sided hearing loss.

Conclusions Differential diagnosis of an enhancing lesion in the IAC includes acoustic neuroma, meningioma, epidermoid and arachnoid cysts, lipochoristoma, and metastatic tumors. Fat-suppressed MRI sequences aid in a definitive diagnosis of lipochoristomas. Because lipochoristomas may have a tendency for more indolent growth and intimate involvement of the auditory nerve, conservative management with interval imaging is recommended. Surgical treatment is reserved for growing lesions or those with disabling vestibular symptoms.

Rare Presentation of Giant Cell Tumor in the Internal Auditory Canal: Case Report and Review of the Literature

Giant cell tumor (GCT) is a benign but locally aggressive bone tumor that usually involves the end of long bones. It is a relatively common neoplasm in patients, constituting 5 to 10% of all benign bone tumors. Approximately 2% of GCTs occur in the craniofacial skeleton with a predilection for the ethmoid, sphenoid, and temporal bones. The skull base location is unique and not commonly described. Hearing loss, headache, tinnitus, and subcutaneous masses are the most commonly reported symptoms in GCTs of the skull base. In this case report we present the first description of a GCT within the internal auditory canal causing cranial neuropathy and review the recent pertinent literature.

Endoscopic transcanal corridors to the lateral skull base: Initial experiences

OBJECTIVES/HYPOTHESIS

Surgical approaches to the lateral skull base, internal auditory canal (IAC), and petrous bone are widely known and have been extensively recorded. Despite the benign nature and limited dimensions of lesions located in this anatomical region, extirpative surgical approaches are often required to reach and remove the disease. The aim of present report was to describe our initial experiences with minimally invasive endoscopic approaches to the lateral skull base.

STUDY DESIGN

Retrospective review of patients' charts and video recordings from surgery.

METHODS

Twelve patients were included in the study. Three main corridors to the lateral skull base were identified: the transcanal suprageniculate corridor, the transcanal transpromontorial corridor, and the transcanal infracochlear corridor. Landmarks, tips, and pitfalls of the approaches have been reviewed and highlighted.

RESULTS

These corridors provide a direct approach to pathology involving the fundus, IAC, cochlea, petrous apex and geniculate ganglion region, without any external incision. The pathology was successfully removed in most cases with no important postoperative complications and reasonable facial nerve outcomes.

CONCLUSIONS

The transcanal endoscopic approaches to the lateral skull base proved to be successful for pathology removal involving the fundus, IAC, cochlea, petrous apex, and geniculate ganglion region. Future widespread application of this kind of approach in lateral skull base surgery will depend on the development of technology, and surgical and anatomical refinements.

LEVEL OF EVIDENCE

4.

A Case Report

We describe the case of a 39-year-old man in whom diagnostic work-up for combined right-sided hearing loss revealed a lipoma of the internal auditory canal (IAC). This very rare diagnosis has significant implications for therapeutic management because lipomas, unlike other lesions in the IAC, should not be surgically removed in most cases. We emphasize the importance of the combined use of magnetic resonance imaging and computed tomography to reliably establish the diagnosis of a lipoma, differentiate it from other potential lesions of the internal auditory canal, and exclude additional pathologies in the petrosal bone.

Disabling vertigo and tinnitus caused by intrameatal compression of the anterior inferior cerebellar artery on the vestibulocochlear nerve: a case report, surgical considerations, and review of the literature

Microvascular compression of the vestibulocochlear nerve is known as a cause of tinnitus and vertigo in the literature, but our review of the literature shows that the compression is usually located in the cerebellopontine angle and not intrameatal.

We present a case of intrameatal compression of the anterior inferior cerebellar artery (AICA) on the vestibulocochlear nerve of a 40-year-old woman with symptoms of disabling vertigo and intermittent high-frequency tinnitus on the left side without any hearing loss for ∼ 4 years. Magnetic resonance imaging of the brain did not show any abnormality, but magnetic resonance angiography showed a left intrameatal AICA loop as a possible cause of the disabling symptoms. After the exclusion of other possible reasons for disabling vertigo, surgery was indicated. The intraoperative findings proved the radiologic findings. The large AICA loop was found extending into the internal auditory canal and compressing the vestibulocochlear nerve. The AICA loop was mobilized and separated from the vestibulocochlear nerve.

The patient's symptoms resolved immediately after surgery, and no symptoms were noted during 2 years of follow-up in our clinic. Her hearing was not affected by the surgery.

In addition to other common reasons, such as acoustic neuroma, disabling vertigo and tinnitus can occur from an intrameatal arterial loop compression of the vestibulocochlear nerve and may be treated successfully by drilling the internal acoustic meatus and separating the arterial conflict from the vestibulocochlear nerve.

Labyrinthine artery aneurysm as an internal auditory canal mass

We present the first case report of a labyrinthine artery aneurysm masquerading as an internal auditory canal tumor. A 72-year-old woman presented with sudden onset right facial paralysis, facial pain, hearing loss, and vertigo. She demonstrated dense right-sided facial paralysis involving all branches of the facial nerve, left beating horizontal nystagmus, and anacusis of the right ear. Magnetic resonance imaging with contrast demonstrated a 6 × 7 mm peripherally enhancing lesion with lack of central uptake filling the right internal auditory canal. The patient elected to proceed with translabyrinthine approach to the internal auditory canal for definitive resection of the mass as well as to decompress the neural structures of the internal auditory canal in an attempt to recover neural function, particularly of the facial nerve. Intraoperatively, the internal auditory canal mass was resected with minimal difficulty, with intraoperative dissection notable for brisk bleeding at the medial base of the tumor just as the tumor was dissected off its medial fibrous attachments. Final pathology of the resected mass revealed a blood vessel with mucinous degeneration of the medial layer of the vessel wall, with immunohistochemical staining confirming the presence and structure of aneurysmal blood vessel.

Intraoperatively diagnosed cerebellopontine angle facial nerve schwannoma: how to deal with it

OBJECTIVE

This study aimed to report our experience in the management of patients with intraoperatively diagnosed intracranial facial nerve schwannomas (FNSs) and propose a decision-making strategy.

METHODS

Twenty-three patients with FNS of the internal auditory canal and/or cerebellopontine angle operated on between 1992 and 2012 were identified.

RESULTS

Preoperatively, all cases have been radiographically diagnosed as vestibular schwannomas. Operative procedures consisted of total tumor resection with grafting in 43.4% of patients, near-total resection leaving behind the tumor capsule overlying the facial nerve in 21.7%, total tumor resection with preservation of anatomic continuity of the facial nerve in 13%, and subtotal resection in 4.3%. Four patients (17.4%) underwent bony decompression with no tumor removal.

CONCLUSION

Management of FNS diagnosed at surgery represents a significant clinical challenge. We considered total tumor resection with grafting when patients presented with preoperative facial nerve palsy (≥ grade III). Both subtotal and near-total tumor removal can be performed in patients with preoperative good facial function and/or large tumors with brainstem compression. Patients with small tumors who were selected for hearing preservation surgery can be considered for bony decompression. Fascicle preservation surgery may be an option when a clear cleavage plane between the tumor and the facial nerve is found.

Usefulness of endoscope-assisted microsurgery for removal of vestibular schwannomas

The usefulness of endoscope-assisted microsurgical removal of vestibular schwannomas in the internal auditory canal (IAC) was evaluated. Microsurgical removal using the endoscope was done in 28 procedures and microsurgical removal without an endoscope was done in 43 procedures. A retrosigmoid approach was used. The tumor location in the IAC was classified as grade 1 (located up to the mid-portion), 2, 3, or 4 (located up to the fundus with bony destruction) according to the tumor extent, and residual tumor in the IAC was evaluated as grade A (remnant tumor was not observed), B, C, or D (remnant tumor was observed over the mid-portion) according to the extent of remnant tumor. The residual tumor in the IAC was less in the endoscope-assisted group than in the microsurgery group. There was a significant difference only in grade 2, that is, tumor located beyond the mid-portion of the IAC. There was no significant difference in the results of preservation of useful hearing, facial nerve function, and tumor recurrence between the two groups. The benefit of endoscope-assistance microsurgery was shown for those patients whose tumors extended beyond the mid-portion of the IAC but did not reach the fundus.

Intraosseous cavernous angioma of the petrous bone

OBJECTIVE

Intraosseous cavernous angioma (CA) of the petrous bone is rare and preoperative diagnosis can be challenging, especially when its epicenter is outside the internal auditory canal (IAC) or geniculate ganglion.

METHODS

A 45-year-old man presented to our clinic with right-sided hearing loss, tinnitus, and unsteadiness. Neuroimaging revealed a right posterior petrous mass. Aggressive subtotal resection with decompression of the IAC was achieved through a right suboccipital craniotomy. Histopathological findings were consistent with CA.

CONCLUSION

As was the case with this patient, we believe that CA should be included in the differential diagnosis of petrous region pathology with bony involvement. Surgery is warranted due to its expansive nature and to decompress the adjacent neural structures.

Primary central nervous system lymphoma presenting as bilateral tumors of the internal auditory canal

The increasing incidence of central nervous system (CNS) lymphoma in the general population, especially in young adults with AIDS, should alert the otolaryngologist that in future there will be an even greater incidence of this rare disease. It may be responsible for hearing loss accompanied by other neurological deficits. CNS lymphoma often has a rapidly progressive course. Early diagnosis and rapid therapy are crucial for a better prognosis. We report a case of primary CNS lymphoma involving both internal auditory canals that presented with sudden deafness and disequilibrium accompanied by facial and abducens nerve palsy.

Ganglioneuroma of the internal auditory canal presenting as a vestibular schwannoma

In most series, 90% of cerebellopontine angle tumors are vestibular schwannomas. Meningiomas and epidermoid tumors follow with decreased frequency. Ganglioneuroma is a benign tumor usually found in the retroperitoneum and posterior mediastinum. We report a case of a 21-year-old man with gradual sensorineural hearing loss and a minimally enhancing lesion of the internal auditory canal, which was excised through a middle fossa approach and found histologically to be a ganglioneuroma. Like vestibular schwannomas, these lesions are benign in nature and may be managed in a similar fashion, although the possibility of malignant transformation may support surgical resection over conservative management or radiosurgery. Ganglioneuromas should be considered in patients with atypical radiographic findings for vestibular schwannomas.