Anteromedial Petrous (Gardner's) Triangle: Surgical Anatomy and Relevance for Endoscopic Endonasal Approach to the Petrous Apex and Petroclival Region.

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.

Optimizing Workflow in Combined Petrosectomy Approaches: Surgical Technique and Case Series.

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.

A novel technique for safe percutaneous biopsy of a petrous apex lesion.

Lesions within the skull base are the most challenging targets for percutaneous biopsy due to the likelihood of encountering a critical structure along any needle trajectory. Due to ICA proximity, the petrous apex is considered unsafe. We describe a novel percutaneous CT-guided approach for biopsying a petrous apex lesion via a contralateral mandibular condylar notch (subzygomatic approach). To our best knowledge, this approach has not been reported and can be safely employed with thorough planning.

The Story of Separate Yet Connected Cholesteatomas.

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.

Aneurysmal bone cyst of the temporal bone presenting with reversible vestibular impairment.

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.

Surgical morbidity of the extradural anterior petrosal approach: the Lariboisière experience.

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.

Anterior Transpetrosal-Transtentorial Approach for Removal of a Large Petrous Apex Meningioma: 2-Dimensional Operative Video.

Video 1 demonstrates the microsurgical resection of petrous apex meningioma. Even small lesions by general rules are regarded as large due to the delicate nature of anatomic localization. The intricate relationship between the tumor and vascular supply of the brainstem and interposition of cranial nerves makes them challenging lesions to resect.1 A 67-year-old female patient presented with a 6-month history of trigeminal neuralgia in the V2 and V3 branches. She underwent gross total resection of an extraaxial homogenously enhancing dural-based tumor in the right petroclival region, consistent with a large (3-4.5 cm) petrous apex meningioma, the least frequently reported subtype of petroclival meningiomas.2,3 Skull base approaches for surgical resection of these tumors include high-speed drilling of petrous bone to create a corridor that facilitates access to the lesion.1 Preserved hearing with suprameatal extension of the infratentorial component and absence of a tumor laterally and inferiorly to the internal auditory canal provided the rationale for selecting a subtemporal approach combined with anterior petrosectomy.1,4,5 Identification of anatomic landmarks of the Kawase triangle is the key first step for determining the bony removal corridor, outlined by the greater superficial petrosal nerve, the arcuate eminence, and the petrous ridge.1,6 An important step in surgical removal is the devascularization of feeding arteries arising from the meningohypophyseal trunk.7,8 Subsequent piecemeal removal and circumferential detachment while making sure to preserve major vascular and nerve elements is crucial for successful removal. The patient consented to the procedure. The postoperative course was uneventful. The patient's trigeminal neuralgia completely regressed with no new neurologic deficit.

Otopathologic and Computed Tomography Correlation of Internal Auditory Canal Diverticula in Otosclerosis.

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.

[Diagnosis and surgical outcomes in the management of petrous bone cholesteatoma]. / Diagnostika i effektivnost' khirurgicheskogo lecheniya kholesteatomy piramidy visochnoi kosti.

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.

Sensorineural Hearing Impairment Recovery after Transmastoidal Surgery for a Petrous Apex Cholesterol Granuloma: A Case Report.

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.

Microsurgical Resection of Giant Petroclival Meningioma via the Posterior Petrosal Approach: 2-Dimensional Operative Video.

Petroclival meningiomas are challenging deep-seated lesions related to many critical neurovascular structures of the skull base.1-5 We present the case of a 45-year-old male presenting with a 3-year history of progressive headache associated gradually with multiple cranial nerves deficits and progressive tetraparesis leading to use of a wheelchair (Video 1) Preoperative magnetic resonance imaging demonstrated a mass highly suggestive of a giant left petroclival meningioma. Considering worsening of symptoms and impressive mass effect, microsurgical resection employing the posterior petrosal approach was performed. Mastoidectomy with skeletonization of semicircular canals and a craniotomy approaching both posterior and middle cranial fossae were done. Dural incision at the base of the temporal lobe was communicated to other incision in the presigmoid dura by ligation and sectioning of superior petrosal sinus. Tentorium was cut all the way toward the incisura, with attention to preserve the fifth nerve along its division and fourth nerve in the last cut. After a complete tentorium incision, the presigmoid space enlarged, exposing both supratentorial and infratentorial spaces. The lesion was totally resected employing microsurgical techniques. Postoperative magnetic resonance imaging demonstrated complete tumor resection. The patient experienced improvement of complaints and no new neurologic deficit on follow-up. The posterior petrosal approach gives great exposure and a more lateral angle of attack to the ventral surface of brainstem, allowing in this case to approach the whole tumor attachment. Informed consent was obtained from the patient for the procedure and publication of this operative video. Anatomic images were courtesy of the Rhoton Collection, American Association of Neurological Surgeons/Neurosurgical Research and Education Foundation.

[The Anterior Transpetrosal Approach].

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.

The otologic approach in the management of posterior petrous surface meningiomas.

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.

[Giant petrosal meningioma invading the fourth ventricle: total removal of a recurrent tumor after eighteen years. Neurosurgical nuances. Case report and literature review]. / Gigantskaya meningioma zadnei poverkhnosti piramidy visochnoi kosti s porazheniem IV zheludochka: total'noe udalenie retsidiviruyushchei opukholi cherez 18 let. Neirokhirurgicheskie nyuansy. Sluchai iz praktiki i obzor literatury.

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.

Skull Base Tumor Mimics.

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.

[Role of helical computed tomography in petrous bone trauma: about 12 cases at the University Hospital Ibn Rochd of Casablanca]. / Place du scanner hélicoïdal dans le traumatisme du rocher: à propos de 12 cas au Centre Hospitalier Universitaire Ibn Rochd de Casablanca.

Temporal bone injuries occur in 14-22% of skull fractures occurring due to head trauma. The purpose of this study is to understand the role of helical computed tomography in petrous bone trauma and to show the different types of fractures and the associated lesions. We conducted a retrospective study of 12 patients with petrous bone trauma (including 10 men and 2 women) over a period of 14 months. The average age of patients was 30, ranging from 18 to 42 years. High-resolution multi-slice computed tomography of petrous bone without contrast agent injection, with infra-millimeter slices thickness of 0.6mm every 0.3mm, allowed to detect the following fractures: 8 extralabyrinthine transverse fractures; 1 extralabyrinthine longitudinal fracture; 2 translabyrinthine fractures and 1 oblique fracture. The associated lesions were dominated by: 5 ossicular lesions; 4 cases of temporal bone involvement and 2 cases of geniculate ganglion involvement. High-resolution computed tomography can confirm the presence of a fracture, show the orientation of the fracture line and specify the different structures affected. It can be performed for emergency assessment or after a period of observation.

Pediatric Petrous Apex Lesions: A Radiological Classification and Diagnostic Algorithm.

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.

RHINOGENIC MENINGITIS CAUSED BY CONGENITAL PETROUS APEX CHOLESTEATOMA: SIMULTANEOUS SURGICAL TREATMENT THROUGH TRANSOTIC AND TRANSSPHENOIDAL APPROACH.

A 66-year-old male patient was admitted due to high fever, severe headaches and disturbance of consciousness. Meningitis was confirmed by lumbar puncture and intravenous antimicrobial therapy was started. Since he had undergone radical tympanomastoidectomy 15 years before, otogenic meningitis was suspected, so the patient was referred to our department. Clinically, the patient manifested watery discharge from the right nostril. Microbiological analysis verified Staphylococcus aureus in a cerebrospinal fluid (CSF) sample acquired by lumbar puncture. Radiological work-up, including computed tomography and magnetic resonance imaging scans, showed an expanding lesion of the petrous apex of the right temporal bone disrupting the posterior bony wall of the right sphenoid sinus with radiological characteristics indicating cholesteatoma. Those findings confirmed rhinogenic meningitis caused by expansion of the petrous apex congenital cholesteatoma into the sphenoid sinus, allowing nasal bacteria to enter the cranial cavity. The cholesteatoma was removed completely by the simultaneous transotic and transsphenoidal approach. Since the right labyrinth was already non-functional, there was no surgical morbidity after labyrinthectomy. The facial nerve remained preserved and intact. The transsphenoidal approach enabled removal of the sphenoid portion of the cholesteatoma and two surgeons met together at the level of the retrocarotid segment of the cholesteatoma, completely removing the lesion. This case represents an extremely rare condition in which a petrous apex congenital cholesteatoma expanded through the petrous apex to the sphenoid sinus, causing CSF rhinorrhea and rhinogenic meningitis. According to available literature, this is the first case of petrous apex congenital cholesteatoma causing rhinogenic meningitis successfully treated with the simultaneous transotic and transsphenoidal approach.