Prevalence of Anterior Inferior Cerebellar Artery Vascular Loop in Cerebellopontine Angle With Three-Dimensional Constructive Interference in Steady State (CISS) Sequence MRI.

Background The cerebellopontine angle (CPA) cistern houses vital neurovascular structures such as cranial nerves V, VII, and VIII and the anterior inferior cerebellar artery (AICA), often leading to neurovascular compression syndromes due to its complex anatomy. Although vascular compression is a recognized cause of certain neuralgias, its association with otologic symptoms such as tinnitus, hearing loss, and dizziness remains uncertain. Hence, this study aims to determine the prevalence of the AICA vascular loop in the CPA cistern on MRI in patients with asymptomatic audiovestibular symptoms. Methodology Adult patients who underwent MRI, including the posterior fossa's high-resolution volumetric T2 sequence (three-dimensional constructive interference in steady state (3D-CISS)), were assessed. Patients with a history of audiovestibular symptoms (tinnitus/dizziness/vertigo/sensorineural hearing loss), intracranial tumor, vascular lesions, intracranial surgery, brain radiation therapy, traumatic brain injury, poor image quality, and MRI scans without 3D-CISS sequences were excluded. Two radiologists independently reviewed 114 (228 sides) MRI studies for the vascular loop of AICA in the CPA cistern and the extension of the AICA loop into the ipsilateral internal acoustic meatus which was graded by Chavda's classification. Results The prevalence of vascular loop of AICA in the CPA cistern was as high as 47.6% in asymptomatic patients. Grade I Chavda vascular loop was the most common type followed by type II, with type III being the least common type. Conclusions Knowledge regarding the high prevalence of the AICA loop in the asymptomatic population and the lack of significant correlation between the presence of the AICA loop and otovestibular symptoms should be considered in preoperative planning for decompression procedures.

Magnetic resonance imaging of the cerebellopontine angle: comparison between constructive interference steady-state and small field-of-view technique turbo spin echo sequences.

BACKGROUND: The aim of this work was to optimize a three-dimensional (3D) turbo-spin-echo (TSE) sequence using a small field-of-view (FOV) technique for the study of the cerebellopontine angle and to compare it with a constructive interference steady-state (CISS) sequence. METHODS: A total of 30 consecutive patients underwent magnetic resonance imaging with a 3Tesla (T) scanner, including 3D CISS and the optimized 3D small FOV technique turbo spin echo (3D SFT-TSE) T2-weighted sequences for the study of the cerebellopontine angle. The 3D SFT-TSE sequence was optimized after three different steps, and a quantitative evaluation of the signal-to-noise ratio (SNR) was obtained according to the National Electrical Manufacturers Association (NEMA) method. Three neuroradiologists made a blind comparative qualitative evaluation of the images between the 3D CISS and the 3D SFT-TSE obtained after the third optimization step, based on spatial resolution, contrast resolution, and presence of artifacts and noise. RESULTS: The calculation of SNR using the NEMA method confirmed the superiority of the third optimization step over the others. For both spatial and contrast resolution, the optimized SFT-TSE was considered better (p < 0.001) than the CISS, while image artifacts and noise were considered worse in the CISS sequence (p < 0.001). Intraobserver analysis showed that all neuroradiologists preferred the 3D SFT-TSE sequence in terms of both spatial resolution and contrast resolution and found more noise and artifact disruption in the CISS sequence. CONCLUSIONS: The use of the 2D radiofrequency pulse technique with a 3D SFT-TSE T2 sequence was significantly more efficient than the 3D CISS sequence for the study of the cerebellopontine angle and inner ear structures.

The endoscopic transcanal approach to the internal auditory canal: an anatomic study.

PURPOSE: The internal auditory canal (IAC) plays a key role in lateral skull base surgery. Although several approaches to the IAC have been proposed, endoscope-assisted transcanal corridors to the IAC have rarely been studied. We sought to provide a step-by-step description of the transcanal transpromontorial approach to the IAC and analyze anatomic relationships that might enhance predictability and safety of this approach. METHODS: Ten cadaveric specimens were dissected and the extended transcanal transpromontorial approach to the IAC was established. Various morphometric measurements and anatomic landmarks were reviewed and analyzed. RESULTS: The proposed technique proved feasible and safe in all specimens. There was no inadvertent injury to the jugular bulb or internal carotid artery. The chorda tympani, a key landmark for the mastoid segment of the facial nerve, was identified in all dissections. The spherical recess of the vestibule and middle turn of cochlea are important landmarks for identification of the labyrinthine segment of the facial nerve. Identification of all boundaries of the working area is also essential for safe access. Among various morphometric measurements, the modiolus-IAC angle (≈ 150°) proved particularly consistent; given its ease of use and low variability, we believe it could serve as a landmark for identification and subsequent dissection of the IAC. CONCLUSIONS: The extended transcanal transpromontorial approach to the IAC is feasible and safe. Relying on anatomic landmarks to ensure preservation of the involved neurovascular structures is essential for a successful approach. The modiolus-IAC angle is a consistent, reproducible landmark for IAC identification and dissection.

[Facial nerve protection in surgery for rare tumors of the internal auditory canal].

Objective:To explore strategies for preserving facial nerve function during surgeries for rare tumors of the internal auditory canal. Methods:A total of 235 cases of internal auditory canal tumors treated between 2010 and 2023 were included, encompassing vestibular schwannomas, cavernous hemangiomas, meningiomas, and other rare tumors. Various data, including clinical presentations, imaging classifications, and treatment processes, were meticulously analyzed to delineate the characteristics of rare tumors and assess pre-and postoperative facial nerve function. Results:Among all internal auditory canal tumors, vestibular schwannomas accounted for 91.9%. In rare tumors, facial nerve schwannomas constituted 5.3%, cavernous hemangiomas 26.3%, meningiomas 15.8%, and arterial aneurysms 10.5%. Significantly, patients with cavernous hemangiomas displayed pronounced invasion of the facial nerve by the tumor, in contrast to other tumor types where clear boundaries with the facial nerve were maintained. During surgery, individualized approaches and strategies for facial nerve protection were implemented for different tumor types, involving intraoperative dissection, tumor excision, and facial nerve reconstruction. Conclusion:Preservation of the facial nerve is crucial in the surgical management of rare tumors of the internal auditory canal. Accurate preoperative diagnosis, appropriate timing of surgery, selective surgical approaches, and meticulous intraoperative techniques can maximize the protection of facial nerve function. Personalized treatment plans and strategies for facial nerve functional reconstruction are anticipated to enhance surgical success rates, reduce the risk of postoperative facial nerve dysfunction, and ultimately improve the quality of life for patients.

[Primary central nervous system lymphoma presenting as a unilateral internal auditory canal lesion: a case report].

A 61-year-old man with right hearing loss and staggering for seven months was diagnosed with sudden deafness although previous evaluation with MRI indicated minor abnormal findings. During follow-up, he developed hypogeusia, right facial nerve palsy, pain in right mandible, right-sided temporal pain, and cerebellar ataxia. Cerebrospinal fluid examination at admission revealed reduced glucose concentration and elevated soluble interleukin-2 receptor (sIL-2R) level, whereas serum sIL-2R level was within the normal range. Brain MRI showed a swollen contrast-enhanced lesion extending from the right internal auditory canal to the middle cerebellar peduncle. Gallium-67 (67Ga) single-photon emission-computed tomography-computed tomography (SPECT-CT) revealed abnormal accumulation at the lesion site. Pathologic analysis of the tumor after resection led to the diagnosis of primary central nervous system lymphoma. In the present case, the MRI and 67Ga SPECT-CT characteristics were distinct from those of vestibular schwannoma. In addition, elevation of sIL-2R in the cerebrospinal fluid but not in serum was useful for differential diagnosis.

Palliative Treatment of Leptomeningeal Carcinomatosis From Renal Cell Carcinoma With Local CyberKnife Radiotherapy and Systemic Pazopanib Therapy: A Case Report.

Leptomeningeal carcinomatosis (LMC) from renal cell carcinoma (RCC) is rare. There is no established treatment strategy for LMC, and the prognosis is extremely poor. We describe a case of LMC from RCC treated with local CyberKnife radiotherapy (CKR) and systemic therapy with pazopanib. The patient was a 63-year-old man with brain metastases from right RCC. Surgery and CKR were performed for the brain metastases, and the lesions were subsequently controlled. The patient developed isolated lesions in the pituitary stalk, right internal auditory canal, left ventricular choroid plexus (CP), left facial nerve, and medulla oblongata after the surgery and CKR for brain metastases. We diagnosed LMC and treated the patient with systemic therapy with pazopanib. We performed local therapy with CKR for lesions of the pituitary stalk, right internal auditory canal, left facial nerve, and medulla oblongata. The CP lesion was not treated with CKR because the lesion tended to shrink after systemic therapy with pazopanib. There were no symptoms due to LMC until the end of life and no adverse events due to CKR. Ten years and five months after the nephrectomy for RCC, one year and four months after the initial CKR for brain metastases, and nine months after the diagnosis of LMC, the patient died due to pleural effusion from lung metastases. Our case suggests that CKR combined with pazopanib may be effective as a palliative treatment for LMC from RCC.

Hypertrophic pachymeningitis of the internal auditory canal and cerebellopontine angle from a large recurrent attic cholesteatoma.

OBJECTIVES: To describe a rare complication of cholesteatoma. METHODS: Case report with literature review. RESULTS: We report a case of a 37-year-old male who presented for evaluation of otorrhea, headache, and progressive left sensorineural hearing loss. Clinical and radiologic evaluation demonstrated a large recurrent attic cholesteatoma with erosion into the lateral and superior semicircular canals, and diffuse enhancement of the internal auditory canal and cerebellopontine angle suggestive of hypertrophic pachymeningitis secondary to cholesteatoma. After treatment with a course of antibiotics and canal wall down mastoidectomy surgery for cholesteatoma exteriorization, he experienced improvement of his symptoms and resolution of hypertrophic pachymeningitis. CONCLUSION: Hypertrophic pachymeningitis is a rarely described complication of cholesteatoma. In the context of cholesteatoma, treatment with antibiotics and surgical removal or exteriorization of cholesteatoma are effective treatments for HP.

Detailed analysis of inner ear malformations in CHARGE syndrome patients - correlation with audiological results and proposal for computed tomography scans evaluation methodology.

OBJECTIVES: The aim was to describe the spectrum of inner ear malformations in CHARGE syndrome and propose a Computed Tomography (CT) detailed scan evaluation methodology. The secondary aim was to correlate the CT findings with hearing thresholds. METHODS: Twenty ears of ten patients diagnosed with CHARGE syndrome were subjected to CT analysis focusing on the inner ear and internal acoustic canal. The protocol used is presented in detail. ASSR results were analyzed and correlated with inner ear malformations. RESULTS: Cochlear hypoplasia type III was the most common malformation found in 12 ears (60%). Cochlear hypoplasia type II, aplasia with a dilated vestibule, and rudimentary otocyst were also identified. In 20%, no cochlear anomaly was found. The lateral Semicircular Canal (SCC) absence affected 100% of ears, the absence of the posterior SCC 95%, and the superior SCC 65%. Better development of cochlea structures and IAC correlated significantly with the lower hearing thresholds. CONCLUSION: This study demonstrated that rudimentary SCC or a complete absence of these SCCs was universally observed in all patients diagnosed with CHARGE syndrome. This finding supports the idea that inner ear anomalies are a hallmark feature of the CHARGE, contributing to its distinct clinical profile. The presence of inner ear malformations has substantial clinical implications. Audiological assessments are crucial for CHARGE syndrome, as hearing loss is common. Early detection of these malformations can guide appropriate interventions, such as hearing aids or cochlear implants, which may significantly improve developmental outcomes and communication for affected individuals. Recognizing inner ear malformations as a diagnostic criterion presents implications beyond clinical diagnosis. A better understanding of these malformations can advance the knowledge of CHARGE pathophysiology. It may also help guide future research into targeted therapies to mitigate the impact of inner ear anomalies on hearing and balance function.

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.

Detailed analysis of inner ear malformations in CHARGE syndrome patients - correlation with audiological results and proposal for computed tomography scans evaluation methodology

Abstract Objectives The aim was to describe the spectrum of inner ear malformations in CHARGE syndrome and propose a Computed Tomography (CT) detailed scan evaluation methodology. The secondary aim was to correlate the CT findings with hearing thresholds. Methods Twenty ears of ten patients diagnosed with CHARGE syndrome were subjected to CT analysis focusing on the inner ear and internal acoustic canal. The protocol used is presented in detail. ASSR results were analyzed and correlated with inner ear malformations. Results Cochlear hypoplasia type III was the most common malformation found in 12 ears (60%). Cochlear hypoplasia type II, aplasia with a dilated vestibule, and rudimentary otocyst were also identified. In 20%, no cochlear anomaly was found. The lateral Semicircular Canal (SCC) absence affected 100% of ears, the absence of the posterior SCC 95%, and the superior SCC 65%. Better development of cochlea structures and IAC correlated significantly with the lower hearing thresholds. Conclusion This study demonstrated that rudimentary SCC or a complete absence of these SCCs was universally observed in all patients diagnosed with CHARGE syndrome. This finding supports the idea that inner ear anomalies are a hallmark feature of the CHARGE, contributing to its distinct clinical profile. The presence of inner ear malformations has substantial clinical implications. Audiological assessments are crucial for CHARGE syndrome, as hearing loss is common. Early detection of these malformations can guide appropriate interventions, such as hearing aids or cochlear implants, which may significantly improve developmental outcomes and communication for affected individuals. Recognizing inner ear malformations as a diagnostic criterion presents implications beyond clinical diagnosis. A better understanding of these malformations can advance the knowledge of CHARGE pathophysiology. It may also help guide future research into targeted therapies to mitigate the impact of inner ear anomalies on hearing and balance function. Level of evidence: 4.

The "Near"-Narrowed Internal Auditory Canal Syndrome in Adults: Clinical Aspects, Audio-Vestibular Findings, and Radiological Criteria for Diagnosis.

INTRODUCTION: Vestibular Paroxysmia (VP) refers to short attacks of vertigo, spontaneous or triggered by head movements, and implies the presence of a compressive vascular loop in contact with the cochleovestibular nerve (CVN). Classically, a narrowed internal auditory canal (IAC) corresponds to a diameter of less than 2 mm on CT, usually associated with a hypoplastic CVN on MRI. The aim of this study was to discuss a distinct clinical entity mimicking VP in relation to a "near"-narrowed IAC (NNIAC) and to propose radiological criteria for its diagnosis. METHODS: Radiological measurements of the IAC were compared between three groups: the study group (SG, subjects with a clinical presentation suggestive of VP, but whose MRI of the inner ear and pontocerebellar angle excluded a compressive vascular loop) and two control groups (adult and children) with normal vestibular evaluations and no history of vertigo. RESULTS: 59 subjects (18 M and 41 F) were included in the SG. The main symptoms of NNIAC were positional vertigo, exercise- or rapid head movements-induced vertigo, and dizziness. The statistical analysis in the study group showed that the threshold values for diagnosis were 3.3 mm (in tomodensitometry) and 2.9 mm (in MRI) in coronal sections of IAC. Although a significantly lower mean value for axial IAC diameter was found in SG compared with controls, the statistics did not reveal a threshold due to the large inter-individual variations in IAC measurements in normal subjects. There was no significant difference in IAC diameter between the adult and pediatric controls. CONCLUSIONS: In the present study, we report a new anatomopathological condition that appears to be responsible for a clinical picture very similar-but not identical-to VP in association with the presence of an NNIAC. The diagnosis requires a careful analysis of the IAC's shape and diameters in both axial and coronal planes.

Embryonal tumor with multilayered rosettes arising from the internal auditory canal of an adult: Illustrative case with molecular investigations.

Embryonal tumors with multilayered rosettes (ETMRs) are aggressive central nervous system (CNS) tumors that usually occur in young children. Here, we describe the first incidence of ETMR in an adult patient that also originated in the novel location of the internal auditory canal (IAC). The 36-year-old patient initially presented with unsteadiness, diplopia, and tinnitus. The tumor in the IAC was discovered on brain magnetic resonance imaging, and gross total resection was performed followed by pathological and molecular diagnosis. The patient received whole brain and spinal cord radiotherapy after an intracranial recurrence and adjuvant chemotherapy consisting of four cycles of ifosfamide, cisplatin, and etoposide. Progression was rapid; however, the patient survived for 22 months after diagnosis before succumbing to the disease. Molecular investigation revealed a DICER1 mutation at exon 25, and methylation classification categorized the tumor as ETMR, non-C19MC-altered. This case underscores the diverse possible presentations of ETMR, DICER1-mutated and the importance of molecular techniques to characterize and promptly treat atypical ETMR.

Simultaneous cochlear implantation during resection of a cerebellopontine angle meningioma: case report.

Cerebellopontine angle (CPA) meningiomas commonly involve the internal auditory canal (IAC). We report a case of a 68-year-old lady with idiopathic profound bilateral deafness with a meningioma which was discovered on workup for cochlear implantation. We performed simultaneous excision of her CPA and IAC meningioma with insertion of a cochlear implant (CI). She regained functional hearing with marked improvement in quality of life. Intraoperative electrophysiological testing can be used to confirm preservation of the cochlear nerve enabling simultaneous implantation which is preferable for clinical and logistical reasons. This creates an option for hearing rehabilitation at the time of IAC/CPA tumour surgery in appropriate patients.

Cavitating Lesions around the Cochlea Can Affect Audiometric Threshold and Clinical Practice.

There are several pathologies that can change the anatomy of the otic capsule and that can distort the bone density of the bony structures of the inner ear, but otosclerosis is one of the most frequent. Similar behavior has been shown in patients affected by osteogenesis imperfecta (OI), a genetic disorder due to a mutation in the genes coding for type I (pro) collagen. In particular, we note that otosclerosis and OI can lead to bone resorption creating pericochlear cavitations in contact with the internal auditory canal (IAC). In this regard, we have collected five cases presenting this characteristic; their audiological data and clinical history were analyzed. This feature can be defined as a potential cause of a third-window effect, because it causes an energy loss during the transmission of sound waves from the oval window (OW) away from the basilar membrane.

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.

Facial nerve schwannoma: Case report and brief review of the literature.

Schwannomas are rare nerve sheath tumors that can occur throughout the body, and are symptomatic based on location, size, and impingement on adjacent structures. These tumors are often benign lesions and occur sporadically or from genetic conditions such as neurofibromatosis. Schwannomas may arise from peripheral nerves, gastrointestinal nerves, spinal nerve roots and cranial nerves. Facial nerve schwannomas arise from cranial nerve VII, commonly involving the geniculate ganglion, labyrinthine segment, and internal auditory canal. While small lesions are asymptomatic, larger lesions can cause facial nerve paralysis, and facial spasms. Lesions in the internal auditory canal can cause hearing loss, tinnitus, vertigo, and otalgia. High-resolution CT imaging and MRI imaging are useful for distinguishing between other pathologies that arise from the same region. High-resolution CT scans can show bony degeneration of nearby structures such as the labyrinth or ossicles. MRI imaging shows hypo intensity on T1 imaging, and hyperintensity on T2 imaging. On T1 postcontrast, enhancement can be homogenous or heterogeneous with cystic degeneration if the lesion is large. Nodular enhancement is commonly seen on facial nerve schwannomas within the internal auditory canal. Vestibular schwannomas involving CN VIII are more common, and appear similar to facial nerve schwannomas, but can be distinguished apart due to growth in the geniculate ganglion and/or the labyrinthine segment. Management of asymptomatic or mild lesions is typically conservative with follow up imaging, and surgery for larger lesions. Here, we present a case of a facial nerve schwannoma in a 57-year-old woman.

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.

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.

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.

Nervus intermedius: Microsurgical and anatomic relationships to the cerebellopontine angle neurovascular complex.

Background: The nervus intermedius (NI) comprises fibers originating from the trigeminal, superior salivary, and solitary tract nuclei, which join the facial nerve (cranial nerve [CN] VII). Neighboring structures include the vestibulocochlear nerve (CN VIII), the anterior inferior cerebellar artery (AICA), and its branches. Microsurgical procedures at the cerebellopontine angle (CPA) benefit from understanding NI anatomy and relationships, especially for the microsurgical treatment of geniculate neuralgia, where the NI is transected. This study sought to characterize common relationships between the NI rootlets, CN VII, CN VIII, and the meatal loop of AICA at the internal auditory canal (IAC). Methods: Seventeen cadaveric heads underwent retrosigmoid craniectomy. Following complete unroofing of the IAC, the NI rootlets were individually exposed to identify their origins and insertion points. The AICA and its meatal loop were traced to assess their relationship with the NI rootlets. Results: Thirty-three NIs were identified. The median number of NI rootlets was 4 per NI (interquartile range, 3-5). The rootlets mainly originated from the proximal premeatal segment of CN VIII (81 of 141, 57%) and inserted onto CN VII at the IAC fundus (89 of 141, 63%). When crossing the acoustic-facial bundle, the AICA most frequently passed between the NI and CN VIII (14 of 33, 42%). Five composite patterns of neurovascular relationships were identified regarding NI. Conclusion: Although certain anatomical trends can be identified, the NI has a variable relationship with the adjacent neurovascular complex at the IAC. Therefore, anatomical relationships should not be used as the sole method of NI identification during CPA surgery.