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Patients with petrous bone cholesteatoma most commonly present with hearing loss and facial paralysis. Other clinical presentations can include otorrhea, tinnitus, aural fullness, otalgia, and dizziness. Here, we report a patient with petrous bone cholesteatoma who presented with cerebrospinal fluid rhinorrhea. This patient was initially misdiagnosed with rhinogenic cerebrospinal fluid leakage, and was finally diagnosed with the supralabyrinthine type of petrous bone cholesteatoma. During the surgical repair through the transmastoid trans-superior semicircular canal approach, the fistula was found in the superior wall of the internal auditory canal. He had satisfactory outcomes after the surgery, with no recurrent cerebrospinal fluid rhinorrhea., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: Rhabdomyosarcoma is a common soft tissue tumor, but isolated involvement of anterior portion of petrous bone is exceedingly rare. Here, we present a case of embryonal rhabdomyosarcoma involving the anterior petrous without involvement of the mastoid and middle ear., Patient: A 6-year-old boy presented with a progressive right side lower motor neuron facial paresis for 1-month duration along with headache and recurrent vomiting episodes. Radiology showed a contrast-enhancing lesion involving the right petrous apex. He underwent craniotomy and excision of the lesion. Based on the frozen section, a diagnosis of rhabdomyosarcoma was rendered, and gross total resection could be achieved. Postoperative course was uneventful., Conclusion: Isolated petrous bone involvement of embryonal rhabdomyosarcoma is a rare presentation. Intra-operative frozen section plays a key role in decision making regarding the extent of excision. Hence, a prompt and accurate diagnosis is essential in managing these cases.

Background and Objectives: Triangular corridors have been used as reliable surgical entry points for open transcranial approaches to the petrous apex (PA) and petroclival region (PCR). The endoscopic endonasal approaches have grown rapidly in the last decade, and the indications have advanced. The knowledge of accurate and reliable anatomic landmarks through endoscopic endonasal route is essential and remain to be established. The purpose of this study was to describe the feasibility and surgical exposure of the anteromedial petrous (Gardner's) triangle as a novel corridor to the PA and PCR., Methods: Five anatomic specimens were dissected. The PA and PCR were accessed through endoscopic endonasal approaches and contralateral transmaxillary approach. The limits of the anteromedial petrous (Gardner's) triangle were identified and dissected and associated measurements performed., Results: The dissection was divided into 6 steps. The limits of the anteromedial petrous (Gardner's) triangle were identified and defined by the paraclival internal carotid artery anterolaterally, the abducens nerve posteromedially, and the petroclival synchondrosis inferiorly. Three lines were established following the limits of the triangle. The mean distance of the anterolateral limit was 10.03 mm (SD = 0.94), of the posteromedial limit was 20.06 mm (SD = 2.90), and of the inferior limit was 17.99 mm (SD = 2.99). The mean area was 87.56 mm 2 (SD = 20.06). The 3 anatomic landmarks with a critical role to safely define the triangle were the pterygosphenoidal fissure, the petrosal process of the sphenoid bone, and the petroclival synchondrosis., Conclusion: The anteromedial (Gardner's) triangle is a well-defined bone corridor which provides access to the entire petrous bone and petroclival junction through endoscopic endonasal route. Regardless of the anatomic variations or tumor location, the landmarks of the abducens nerve, paraclival internal carotid artery, and petroclival synchondrosis are key for understanding lateral access to tumors extending from the clivus., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Significance Statement: Petrous cholesteatoma is rare but frequently leads to complications. A thorough radiological evaluation helps in identifying the pathology and the extent of disease. Sound anatomical knowledge is vital for the planning of surgical approach to get adequate access without damaging important structures. Presentations in congenital lesions are varied due to the uneven growth model of the temporal bone. To the best of our knowledge, the pattern of involvement in this case has never been reported earlier., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background and Objective: The combined petrosectomy is one of the workhorse skull base approaches to the petroclival region. Traditionally, this approach starts with a temporosuboccipital craniotomy, followed by the mastoidectomy/anterior petrosectomy, and completed with the dural opening/tumor resection. This sequence of events (neurosurgery-neuro-otology-neurosurgery) involves at least 2 handoffs and change of surgical teams and instrumentation. This report describes a resequencing of events and a modification of the technique used to craft the temporosuboccipital craniotomy, with aims to reducing handoffs between surgical teams and improving operating room workflow., Methods: Adhering to PROCESS guidelines, a case series is provided in addition to the surgical technique and surgical images., Results: The technique for performing a combined petrosectomy is described with illustrations. This description shows that the temporal bone drilling may be performed before the craniotomy to allow for direct visualization of the dura and sinuses before completing the craniotomy. In doing so, only 1 transition between the otolaryngologist and neurosurgeon is necessary, thereby improving operating room workflow and time management. A series of 10 patients is presented, showing the feasibility of this procedure and providing operative details that were previously absent in the peer-reviewed literature., Conclusions: Combined petrosectomy, although often performed in a 3-step manner with the neurosurgeon starting the craniotomy, can be performed as described here in a 2-step manner, with similar outcomes and reasonable operating time., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Aneurysmal bone cysts are expansile benign lesions associated with compressive destruction and obscure pathogenesis. The most common sites of temporal bone involvement are the petrous apex, squamous portions and mastoid., Case Report: This paper reports a right temporal aneurysmal bone cyst in a 51-year-old man who presented clinically with facial palsy, and hearing loss and impaired vestibular function. Magnetic resonance imaging and computed tomography findings were consistent with a diagnosis of aneurysmal bone cyst. Inter-operative findings showed that the lesion had caused compressive damage to the internal auditory canal. Following surgical excision, the patient experienced vertigo, indicating recovery of vestibular function. Follow-up imaging revealed complete resection without clinical recurrence., Conclusion: To our knowledge, this is the first report of aneurysmal bone cyst invasion of the inner auditory canal. Our clinical experience indicates that vestibular nerve damage recovery is relatively uncommon. This case report will hopefully inform future studies.

Competing Interests: The authors disclose no conflicts of interest.

Purpose: Report our experience in the management of posterior petrous surface meningiomas (PPSMs), and identify features that affect hearing, facial nerve (FN) function, and control of the disease., Methods: Retrospective case series of 131 patients surgically managed for PPSMs. FN status, hearing and tumour radicality were assessed and compared between patients with tumours of different locations (Desgeorges classification) and internal auditory canal involvement (IAC)., Results: At the time of surgery 74.8% of patients had a hearing loss. Hearing was mostly unserviceable in tumors attached to the meatus. Pure tone audiometry did not correlate to IAC extension, while speech discrimination scores were statistically worse when the tumor occupied the IAC (unpaired t test, p = 0.0152). Similarly, extrameatal tumors undergoing removal by otic preserving techniques maintained postoperative hearing, whereas hearing worsened significantly in tumors involving the IAC (paired t test, p = 0.048). The FN was affected preoperatively in 11.4% of cases. Postoperative FN palsy was significantly correlated to the IAC involvement (Fisher's exact test, p = 0.0013), while it was not correlated to tumor size. According to the Desgeorges classification, a postoperative FN palsy complicated the majority of anteriorly extending tumors and, two-fifths of meatus centred tumors. 75% of posterior located tumors had a postoperative FN grade I HB., Conclusions: Since the involvement of the IAC by the tumor affects both hearing and FN function, the IAC is of primary importance in PPSMs and should be studied and addressed as much as the tumor location in the CPA., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The petrous apex (PA) is involved in a myriad of pathological conditions, some of which are exclusive in children. Diagnosis may be difficult due to vague clinical presentation, and local examination is challenging owing to its inaccessible location. This is further complicated by multiple unfused sutures and ongoing PA pneumatization in children. Cross-sectional imaging is vital for the evaluation of the PA lesions, due to their precarious location and proximity to the major neurovascular structures. Several classification systems have been proposed for these lesions based on their site of origin, solid or cystic appearance, surgical or non-surgical (no touch lesions) management, and benign or malignant nature. In this article, we emphasize the distinctive role of different cross-sectional imaging modalities in the diagnosis of pediatric PA lesions, with special attention to normal variants that should not be mistaken for pathology. We also propose a radiological classification and algorithmic approach to aid in the precise diagnosis and facilitate appropriate management of the various PA lesions in children.

Background: The choice of surgical approach for a petrous apex lesion depends on its relationship with the internal carotid artery, degree of medial expansion and pathology. The correct identification of patients who will benefit from this approach is necessary., Case Reports: Two adult patients presented with a lesion in the left petrous apex. Computed tomography showed a homogeneous mass extending anteromedially, and abutting the internal carotid artery and the sphenoid sinus in both patients. Using magnetic resonance imaging, a third recurrence of cholesterol granuloma in case one and cholesteatoma in case two were diagnosed. Both patients underwent trans-sphenoid excision, as the sphenoid sinus was well pneumatised and the lesion was medial to the internal carotid artery., Conclusion: Nasal endoscopic access to the petrous apex via the trans-sphenoid corridor should be preferred for benign lesions extending anteromedially in cases where lateral access is impeded by the internal carotid artery, the labyrinth and the facial nerve, and anterior trans-sphenoidal access offers a low-morbidity alternative.

Introduction: Internal auditory canal (IAC) diverticula, also known as IAC cavitary lesions or anterior cupping of the IAC, observed in otopathologic specimens and high-resolution computed tomography (CT) scans of the temporal bone are thought to be related to otosclerosis. Herein, we examined the usefulness of CT scans in identifying diverticula and determined whether IAC diverticula are associated with otosclerosis on otopathology., Methods: One hundred five consecutive specimens were identified from the National Temporal Bone Hearing and Balance Pathology Resource Registry. Inclusion criteria included the availability of histologic slides and postmortem specimen CT scans. Exclusion criteria included cases with severe postmortem changes or lesions causing bony destruction of the IAC., Results: Ninety-seven specimens met criteria for study. Of these, 42% of the specimens were from male patients, and the average age of death was 77 years (SD = 18 yr). IAC diverticula were found in 48 specimens, of which 46% were identified in the CT scans. The mean area of the IAC diverticula was 0.34 mm 2 . The sensitivity and specificity of detecting IAC diverticula based on CT were 77% and 63%, respectively. Overall, 27% of specimens had otosclerosis. Histologic IAC diverticula were more common in specimens with otosclerosis than those without (37.5% versus 16%; p = 0.019). Cases with otosclerosis had a greater mean histologic diverticula area compared with nonotosclerosis cases (0.69 mm 2 versus 0.14 mm 2 ; p = 0.001)., Conclusion: IAC diverticula are commonly found in otopathologic specimens with varied etiologies, but larger diverticula are more likely to be associated with otosclerosis. The sensitivity and specificity of CT scans to detect IAC diverticula are limited., Competing Interests: J.C. has a patent pending at Grace Medical. E.K. is a scientific advisor at Desktop Metal and has a patent pending at Grace Medical. H.S. is in the surgical advisory board of MedEl and a shareholder at Rescue Hearing. M.J.McK. is the co-founder and CMO of Akouos Inc. A.Q. has a sponsored research agreement with Frequency Therapeutics, sponsored research agreement, patent pending at Grace Medical, and consulting for Alcon. The remaining authors disclose no conflicts of interest., (Copyright © 2022, Otology & Neurotology, Inc.)

Cholesterol granulomas are the most common primary lesions of the petrous apex. Although their benign character, impingement of critical neurovascular structures can cause significant symptomatology such as hearing impairment. We present unique results after treatment of a cholesterol granuloma located in the petrous apex causing sensorineural hearing impairment. A transmastoidal approach was performed using an intraoperative computed tomography-guided navigation system. The video, which is included for reference, illustrates clear drainage of the cyst and drain positioning. The hearing improved completely in the lower frequencies at 500 and 1000 Hz and with a 19 dB improvement in overall bone conduction in the affected ear.

Objective: Concerns about the approach-related morbidity of the extradural anterior petrosal approach (EAPA) have been raised, especially regarding temporal lobe and venous injuries, hearing impairment, facial nerve palsy, cerebrospinal fluid fistula, and seizures. There is lack in the literature of studies with detailed analysis of surgical complications. The authors have presented a large series of patients who were treated with EAPA, focusing on complications and their avoidance., Methods: The authors carried out a retrospective review of patients who underwent EAPA at their institution between 2012 and 2021. They collected preoperative clinical characteristics, operative reports, operative videos, findings on neuroimaging, histological diagnosis, postoperative course, and clinical status at last follow-up. For pathologies without petrous bone invasion, the amount of petrous apex drilling was calculated and classified as low (< 70% of the volume) or high (≥ 70%). Complications were dichotomized as approach related and resection related., Results: This study included 49 patients: 26 with meningiomas, 10 brainstem cavernomas, 4 chondrosarcomas, 4 chordomas, 2 schwannomas, 1 epidermoid cyst, 1 cholesterol granuloma, and 1 osteoblastoma. The most common approach-related complications were temporal lobe injury (6.1% of patients), seizures (6.1%), pseudomeningocele (6.1%), hearing impairment (4.1%), and dry eye (4.1%). Approach-related complications occurred most commonly in patients with a meningioma (p = 0.02) and Meckel's cave invasion (p = 0.02). Gross-total or near-total resection was correlated with a higher rate of tumor resection-related complications (p = 0.02) but not approach-related complications (p = 0.76). Inferior, lateral, and superior tumoral extension were not correlated with a higher rate of tumor resection-related complications. No correlation was found between high amount of petrous bone drilling and approach- or resection-related complications., Conclusions: EAPA is a challenging approach that deals with critical neurovascular structures and demands specific skills to be safely performed. Contrary to general belief, its approach-related morbidity seems to be acceptable at dedicated skull base centers. Morbidity can be lowered with careful examination of the preoperative neuroradiological workup, appropriate patient selection, and attention to technical details.

The Anterior transpetrosal approach is a skull base surgical procedure that can provide a wide operative view of the petroclival and the prepontine region. This approach requires one to accurately understand the anatomy of the anterior part of the temporal bone and the histological structure of the dura mater. In addition, it is necessary to learn operative techniques for venous preservation, accurate hemostasis at each step, and prevention of cerebrospinal fluid leakage. In this article, the anatomy and surgical techniques that are required for a beginner to master the anterior transpetrosal approach are explained step by step.

Abstract: Petrous apex cephalocele (PAC) is a rare type of cephalocele. It is usually asymptomatic. It can be unilateral or bilateral. Bilateral cases are less common. They are etiologically and clinically different entities from unilateral ones. A 56-year-old female patient presented to the hospital with the complaint of a severe nonspecific headache. She has been examined in ear nose throat, ophthalmology, and finally neurology clinics. Bilateral PAC was incidentally found in magnetic resonance imaging (MRi) examination. Headache was associated with PAC because no additional pathology could explain the clinical symptomatology. There is a proven relationship between empty sella and PAC. Regarding PAC less than 50 cases are known. Our paper aims to contribute to the literature by exhibiting etiologic and clinic differences between unilateral and bilateral PAC. It highlights the relationship between PAC and broad sella that is a different entity from empty sella and shows this remarkable radiological appearance. The authors presented our case accompanied by clinical and MRi findings., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 by Mutaz B. Habal, MD.)

Many different benign and malignant processes affect the central skull base and petrous apices. Clinical evaluation and tissue sampling are difficult because of its deep location, leaving imaging assessment the primary means for lesion evaluation. Skull base lesions demonstrate a variety of confusing appearances on imaging, creating diagnostic dilemmas. It is important to be familiar with imaging appearances of common mimickers of malignant neoplasm in the skull base. This article familiarizes readers with imaging characteristics of various anatomic variants and benign pathologies that mimic malignant neoplasms, in hopes of increasing confidence of diagnosis, decreasing unnecessary procedures, and allaying patient fear., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objective: To evaluate the effectiveness of surgical treatment of patients with petrous bone cholesteatoma (PBC) depending on the localization of the pathological process., Material and Methods: The analysis of surgical treatment using various surgical approaches and its results in 32 patients with PBC, depending on the type, localization in petrous bone and intraoperative findings, is presented. Patients with supralabirint PBC underwent extended atticoantromastoidotomy with tympanoplasty and mastoidoplasty with automaterials ( n =19), labyrinthectomy ( n =4), subtotal petrozectomy with labyrinthectomy and suturing of the external auditory meatus (EAM) ( n =2). In infralabirint and infralabirint-apical PBC, a transotic approach was used with Rambo suturing of EAM ( n =9). The pre-sigmoid approach was performed in 1 patient. With an extradural subtemporal approach, PBC of apical localization was removed in 1 case., Results: After surgical treatment, hearing remained at the same level in 15 (47%) patients, 14 of them had deafness. In the early postoperative period, a temporary increase in bone conduction hearing thresholds by 10-20 dB was detected in 14 (44%) patients with their gradual recovery over 3 months. Deafness in the postoperative period developed in 3 (9%) patients after removal of supralabirint cholesteatoma. In the early postoperative period, 3 (9%) patients developed systemic dizziness, which was stopped after 3 months. In 25 (78%) patients, the function of the facial nerve in the early postoperative period remained at the same level, of which 14 (44%) were normal, and 11 (34%) had the same degree according to the House-Brackmann (HB) classification. Improvement of function by one degree of HB classification was observed in 4 (12.5%) patients on average 5 months after surgery., Conclusion: An adequate personalized choice of surgical treatment methods allowed mainly to preserve the function of hearing and facial nerve. In cases of deterioration of facial nerve function in the postoperative period, gradual improvement was observed for 3-10.5 months with further positive dynamics.

The authors present a patient and neurosurgical nuances of total resection of recurrent meningioma of posterior surface of petrous bone 65´35´30 mm. The tumor captured two critical zones of posterior cranial fossa with unusual frontal growth and spread from the surface of petrous bone to the fourth ventricle. The neoplasm filled the ventricle without lesion of ependyma. Extensive fibrous meningioma of posterior surface of petrous bone was totally excised 18 years ago. MRI was annually carried out for 5 years. Surgical nuances that ensured total extraction of tumor without cytoreduction were as follows: 1) en-bloc resection of tumor from the fourth ventricle due to smooth surface of tumor and minimum number of adhesions with cerebellum; MR-confirmed CSF strip between the tumor edges and walls of the ventricle; no signs of hydrocephalus in subtotal ventricular tamponade; 2) unusual frontal tumor growth under 45º required appropriate angular traction of tumor with minimal rotation; 3) traction was followed by sequential appearance of 3 segments of tumor: petrous, apertural and ventricular; 4) topography of the area of lateral eversion of the fourth ventricle was established by identifying the narrowing (constriction) of tumor; 5) in extracting the tumor from the fourth ventricle, we performed minimal rotation to avoid damage to ventricular walls and lateral aperture due to difference between the larger and smaller diameters (by 6 mm) of ovoid ventricular segment of tumor; 6) no CSF leakage following appearance of ventricular segment (tumor enlargement) indicated integrity of ependyma of the fourth ventricle. Histological examination confirmed fibrous meningioma. Fast and complete regression of focal symptoms was observed after surgery. A 3-year follow-up after surgery revealed no signs of tumor recurrence.