Endoscopic Prelacrimal Approach and Modified Endoscopic Denker’s Approach to the Middle Cranial Fossa

Objectives: To analyse clinical, surgical and postoperative outcome perspectives of tumors occupying both middle and posterior cranial fossa. Materials and Methods: This retrospective cohort study includes 23 patients operated for tumors involving both middle and posterior cranial fossa in our department between August 2016 and August 2020. Each patient was evaluated for age, sex, co morbidities, tumour histopathology, clinical presentation, radiological characteristics, surgical and outcome characteristics. Unpaired t- test and chi-square test was used for statistical analysis. P < 0.05 was considered statistically significant. Results: The mean age was 46 years (range 40–57 years), with the majority of patients being female (56.5%). Most tumors (65.3%) were trigeminal schwannoma, with the remaining being vestibular schwannoma (21.7%), facial schwannoma (8.7%) and epidermoid (4.3%). The most commonly used surgical approach was the retrosigmoid approach (30.4%) and combined approach (30.4%). Gross total resection (GTR) was done in 14 patients while subtotal resection (STR) was done in 9 patients. STR was significantly associated (p<0.05) with persisting cranial nerve deficit and tumour progression. Midbrain compression, internal carotid artery and cavernous sinus involvement were significantly (p<0.05) associated with STR. Conclusions: Trigeminal schwannoma is the most common tumour involving both middle and posterior cranial fossa. Combined approach for such tumours is required in tumours having significant size in both middle cranial fossa and posterior cranial fossa. The intent of surgery is to achieve a gross total resection (GTR) but adhesions and involvement of critical brain structures results in STR.

Sir, Clear cell meningioma (CCM) is a rare variant of meningioma with an aggressive clinical course and usually occurs in the cerebello pontine angle (CPA) or cauda equina.[2,3] We report a case of CCM occurring in CPA that mimicked a trigeminal schawannoma by the virtue of its dumbbell shape and erosion of petrous bone. A 14-year-old female presented with left-sided facial numbness and heaviness for 2.5 months, followed by left-sided hearing loss and features of raised intracranial pressure for 2 months. A month later she developed left facial paresis of lower motor neuron type along with difficulty in swallowing and imbalance while walking with right lower limb weakness. Clinical examination revealed bilateral papilledema with left-sided trigeminal (both sensory and motor), facial (LMN type) involvement. The left glossopharyngeal, vagus, and hypoglossal nerves were involved. She had left-sided cerebellar signs with subtle right hemiparesis. Contrast-enhanced CT [Figure 1] and magnetic resonance imaging [Figures ​[Figures22 and ​and3]3] of brain revealed a lobulated mass in the left cerebro-pontine angle cistern with extension of the tumor in the middle cranial fossa in the region of Meckel's cave. Radiology showed truncation of the petrous suggesting a trigeminal schwannoma. Figure 1 Contrast-enhanced axial sections showing large lobulated dumbbell-shaped extra-axial mass in the left cerebro-pontine angle cistern with extension into middle cranial fossa in the parasellar region (white arrows). There is also erosion destruction of ... Figure 2 Axial T2 (a, b) and T1-weighted (c, d) images demonstrates large lobulated extra-axial mass in the left cerebro-pontine angle with component in the middle cranial fossa (white arrows). It is heterogeneously hyperintense on T2 and hypointense on T1-weighted ... Figure 3 Postgadolinium axial (a, b) and sagittal (c, d) images showing heterogeneous enhancement of the tumor with a tongue of tumor (white arrow) extending forward into the region of the Meckel cave She underwent a subtotal excision of the tumor through the left retromastoid approach. The lesion was grayish in color and was relatively firm and less suckable. However, CUSA was helpful. The capsule of the lesion was left. There was injury to the superior petrosal sinus and the patient succumbed to venous infarction a week later. Unfortunately, autopsy was not performed. Histopathological examination showed round to polygonal cells arranged in whorls, showing clear cytoplasm and round to oval nuclei with dispersed chromatin and insconspicuous nucleoli. There was perivascular and interstitial deposition of collagenous material in a block manner. Tumor cells tested positive for PAS and epithelial membrane antigen [Figure 4]. Features suggested clear cell meningioma, WHO grade II. Ki 67 labelling index was 2.5%. Figure 4 Clear cell meningioma (a) consisting of patternless growth of clear cells (H and E, ×200) (b) containing glycogen (PAS, ×200). (c) Tumor cells express epithelial membrane antigen. (Immunoperoxidase stain, ×400) Trigeminal schwannoma typically grows from posterior fossa into the middle cranial fossa as the lesion grows along the nerve fibers. The truncation of petrous apex suggests chronic compression and is usually seen with trigeminal schwannoma. Occasionally lymphoma or lymphohistiocytic inflammation may spread along the nerve fibers to occupy both the posterior and the middle cranial fossa thereby, mimicking a schwannoma.[1,5] Clear cell meningioma is a rare variant that is often seen in the CPA and is seen in relatively younger patients. The behavior of this variant is aggressive and is included in Grade II WHO.[2,3] Gross total resection followed by radiotherapy is the treatment for these lesions. However, lesions in the meckel's cave meningiomas in particular, are associated with more deficits following total excision.[4] Our patient had rapidly worsening symptoms over 2 months and was relatively young. The clinical features suggested an aggressive lesion rather than a schwannoma. However, the radiology showed a lesion straddling across the petrous to occupy both the middle cranial fossa and posterior fossa along with truncation of petrous suggesting a trigeminal schwannoma. The above case highlights the potential of meningiomas to grow along the nerve fibers straddling across the petrous to occupy both middle cranial and posterior fossa along with erosion of petrous mimicking a trigeminal schwannoma. Whether, such a phenomenon is limited to more aggressive meningiomas like clear cell variant remains unclear.

Trigeminal schwannomas are rare neoplasms with an incidence of less than 1% that require a comprehensive surgical strategy. These tumors can occur anywhere along the path of the trigeminal nerve, capable of extending intradurally into the middle and posterior fossae, and extracranially into the orbital, pterygopalatine, and infratemporal fossa. Recent advancements in endoscopic surgery have suggested a more minimally invasive and direct route for tumors in and around Meckel's cave, including the endoscopic endonasal approach (EEA) and endoscopic transorbital superior eyelid approach (ETOA). The authors assess the feasibility and outcomes of EEA and ETOA for trigeminal schwannomas. A retrospective multicenter analysis was performed on 25 patients who underwent endoscopic surgical treatment for trigeminal schwannomas between September 2011 and February 2019. Thirteen patients (52%) underwent EEA and 12 (48%) had ETOA, one of whom underwent a combined approach with retrosigmoid craniotomy. The extent of resection, clinical outcome, and surgical morbidity were analyzed to evaluate the feasibility and selection of surgical approach between EEA and ETOA based on predominant location of trigeminal schwannomas. According to predominant tumor location, 9 patients (36%) had middle fossa tumors (Samii type A), 8 patients (32%) had dumbbell-shaped tumors located in the middle and posterior cranial fossae (Samii type C), and another 8 patients (32%) had extracranial tumors (Samii type D). Gross-total resection (GTR, n = 12) and near-total resection (NTR, n = 7) were achieved in 19 patients (76%). The GTR/NTR rates were 81.8% for ETOA and 69.2% for EEA. The GTR/NTR rates of ETOA and EEA according to the classifications were 100% and 50% for tumors confined to the middle cranial fossa, 75% and 33% for dumbbell-shaped tumors located in the middle and posterior cranial fossae, and 50% and 100% for extracranial tumors. There were no postoperative CSF leaks. The most common preoperative symptom was trigeminal sensory dysfunction, which improved in 15 of 21 patients (71.4%). Three patients experienced new postoperative complications such as vasospasm (n = 1), wound infection (n = 1), and medial gaze palsy (n = 1). ETOA provides adequate access and resectability for trigeminal schwannomas limited in the middle fossa or dumbbell-shaped tumors located in the middle and posterior fossae, as does EEA for extracranial tumors. Tumors predominantly involving the posterior fossa still remain a challenge in endoscopic surgery.

Advances in microscopic and endoscopic surgical techniques have outpaced traditional classification and transcranial surgical strategies, especially with reference to the treatment of trigeminal schwannomas (TSs). A modified TS classification is proposed and appropriate surgical strategies are discussed. The cases of 93 patients who underwent surgical treatment in Beijing Tiantan Hospital in the previous 6 years were analyzed retrospectively, and a literature review was conducted. Classification is based on surgical direction. Tumors were classified as follows: type A, backward orientation, located in the orbit or orbit and middle cranial fossa (8 cases, 8.6%); type B, upward orientation, located in the pterygopalatine fossa, infratemporal fossa or pterygopalatine fossa, infratemporal fossa, and middle cranial fossa (23 cases, 24.7%); type C, forward and backward orientations, located in the middle cranial fossa, posterior cranial fossa or both (58 cases, 62.4%); and type D, located in multiple regions (4 cases, 4.3%). 91.40% of patients underwent gross total resection (GTR) with 29 cases receiving endoscopic resection of whom 93.10% (27/29) experienced GTR. The 93 cases were satisfactorily divided into four types, according to tumor location and surgical orientation, enabling safe and effective removal by appropriate surgery.

The National Aeronautics and Space Administration (NASA) Science Mission Directorate In- Space Propulsion Technology office is sponsoring NASA Glenn Research Center (GRC) to develop a 4 kW-class Hall thruster propulsion system for implementation in NASA science missions. Tests were performed within NASA GRC Vacuum Facility 5 at background pressure levels that were six times lower than what has previously been attained in other vacuum facilities. A study was conducted to assess the impact of varying the cathode-to-anode flow fraction and cathode position on the performance and operational characteristics of the High Voltage Hall Accelerator (HiVHAc) thruster. In addition, the impact of injecting additional xenon propellant in the vicinity of the cathode was also assessed. Cathode-to-anode flow fraction sensitivity tests were performed for power levels between 1.0 and 3.9 kW. It was found that varying the cathode flow fraction from 5 to approximately 10% of the anode flow resulted in the cathode-to-ground voltage becoming more positive. For an operating condition of 3.8 kW and 500 V, varying the cathode position from a distance of closest approach to 600 mm away did not result in any substantial variation in thrust but resulted in the cathode-to-ground changing from -17 to -4 V. The change in the cathode-to-ground voltage along with visual observations indicated a change in how the cathode plume was coupling to the thruster discharge. Finally, the injection of secondary xenon flow in the vicinity of the cathode had an impact similar to increasing the cathode-to-anode flow fraction, where the cathode-to-ground voltage became more positive and discharge current and thrust increased slightly. Future tests of the HiVHAc thruster are planned with a centrally mounted cathode in order to further assess the impact of cathode position on thruster performance.

Cholesteatoma of the petrous bone extending into the intracranial region is an unusual occurrence. Most cases have been attributed to secondary extension of a primary epidermal blastomatous malformation of the temporal bone into the middle or posterior fossae. Within the past two and a half decades, intracranial extension of acquired aural cholesteatoma has been recognized as a likely alternative to this mechanism. Recent literature has rejoined this observation by considering both primary and secondary cholesteatoma of the petrous bone as a single group, petrosal cholesteatoma. The present study is presented to analyze the clinical presentation, imaging findings, and surgical treatment of six patients with acquired aural cholesteatoma extending into the intracranial region. Findings in this study are compared with the extant literature on congenital and acquired cholesteatoma of the petrous bone. This study proposes that petrosal cholesteatoma is a valid anatomical construct; however, the pathogenesis of petrosal cholesteatoma is still important in understanding the clinical presentation and management of cholesteatoma that extends beyond the usual confines of the middle ear and mastoid. Retrospective case review conducted at a tertiary referral center. From 1985 to 1999, 477 patients were surgically treated for acquired aural cholesteatoma. Patients with intracranial extension of cholesteatoma were studied. Clinical presentation, imaging studies, operative findings, surgical treatment, and postoperative results were evaluated. Six cases in a series of 477 patients with acquired aural cholesteatoma had intracranial extension of disease. In this series, the most frequent pathway for intracranial extension was supralabyrinthine through the supratubal recess into the middle cranial fossa. A less frequent pathway was via the retrofacial air cells into the posterior cranial fossa. Surgical access for removal of intracranial cholesteatoma was accomplished through several approaches including translabyrinthine, transcochlear, retrolabyrinthine, and middle cranial fossa. In two patients who had reoperation for possible residual disease, one was free of residual disease and one was found to have residual cholesteatoma in the region of the horizontal facial nerve. Acquired aural cholesteatoma can extend into either the middle or posterior cranial fossae. In this study, cholesteatoma extended into the middle fossa through the supratubal recess along the labyrinthine facial nerve and into or above the internal auditory canal. A less frequent path is through the retrofacial air cells into the posterior fossa. Intracranial acquired cholesteatoma is generally small and presents with complaints related to underlying otitis media rather than the neurological deficits that are often associated with primary petrous bone cholesteatoma. While computed tomography and magnetic resonance imaging are both required to differentiate congenital petrous cholesteatoma from other lesions of the petrous bone, computed tomography of the temporal bone is usually sufficient to diagnosis and define intracranial extension of acquired aural cholesteatoma. These lesions can be completely excised rather than exteriorized.

This case is a 15-year-old male, presenting with headaches, right face, and arm numbness, and ataxia. MRI (magnetic resonance imaging) revealed a large right sided dumbbell shaped lesion, extending into the middle and posterior fossa with compression of the brainstem consistent with a trigeminal schwannoma. Treatment options here would be a retrosigmoid suprameatal approach or a lateral presigmoid approach. Given the tumor extension into multiple compartments, a presigmoid craniotomy, combining a middle fossa approach with anterior petrosectomy, and retrolabyrinthine approach with posterior petrosectomy were used to maximize the direct access corridor for resection. The petrous apex was already expanded and remodeled by the tumor. Nerve fascicles preservation technique is paramount to the functional preservation of the trigeminal nerve. The extent of resection should be weighed against the anatomical functional integrity of the nerve. Near total resection is considered if that means more nerve preservation. Postoperatively, the patient had a slight (House–Brackman grade II) facial droop, which resolved over days and developed right trigeminal hypesthesia at several weeks. This case is presented to demonstrate a combined petrosectomy technique for resection of lesions extending into both the middle and posterior cranial fossa with near total resection and trigeminal nerve preservation.The link to the video can be found at:https://youtu.be/kA9GyFhL1dg.

Ruptured dermoid cyst consisting of two adjacent masses with different components in the middle and posterior cranial fossa

Trigeminal schwannomas with middle and posterior fossa extension are difficult to treat, particularly after prior surgery or stereotactic radiosurgery (SRS). A minimally invasive interdural approach such as the endoscopic lateral transorbital approach (ELTOA) may offer safer access in these settings. We present the case of a 33-year-old woman with a history of partial resection of a left trigeminal schwannoma through a pterional approach and adjuvant SRS, who developed progressive left V1 paresthesia and trigeminal neuralgia. Neurological examination revealed hypoesthesia in V1-V2. Magnetic resonance imaging (MRI) demonstrated a dumbbell-shaped mass occupying the left middle cranial fossa, with a cystic component extending into the posterior fossa through Meckel's cave, displacing the brainstem. Given symptom progression and mass effect, reoperation was indicated. An ELTOA, performed through a superior eyelid-crease incision, was selected to exploit a surgically naive interdural corridor parallel to the tumor axis, thereby minimizing brain retraction while providing direct access to Meckel's cave and the posterior fossa. Postoperatively, the patient developed a transient cranial nerve IV palsy, her trigeminal neuralgia resolved, and she was discharged on postoperative day 5. Postoperative MRI demonstrated complete resection and decompression of the middle and posterior cranial fossae. This report demonstrates that the ELTOA is a feasible and safe reoperative strategy for trigeminal schwannomas in previously operated or irradiated corridors, reducing morbidity while achieving effective decompression.

INTRODUCTION: Trigeminal schwannoma is a rare central nervous system tumor and involves multi-compartmental skull base. Recently, endoscopic transorbital approach (ETOA) has been emerging technique as a minimally invasive surgery. METHODS: Between Sep. 2016 and Feb. 2022, we performed ETOA in 50 patients with trigeminal schwannoma at four tertiary hospitals. There were 15 men and 35 women with the mean age of 46.9 years. All tumors were classified type A (mainly involving the middle cranial fossa), type B (mainly posterior cranial fossa), type C (dumbbell-shaped tumor involving middle and posterior fossa), type D (Extracranial type). Type D tumors were also classified the ophthalmic division (D1), maxillary division (D2), mandibular division (D3). RESULTS: In this study, overall gross or near total resection was performed in 45 of 50 patients (90.0%). Median follow-up period was 21.9 months ranging from 1 to 61.7 months. There was no regrowing or recurrence during the follow-up period. Based on the classification, there were 17 tumors with type A, 1 type B, 19 type C and 13 type D. In particular, seven tumors were belong to D1, one D2, and five D3. For type A tumors, GTR/NTR was achieved with ETOA in 16 of 17 patients (94.1%). 18 of 20 patients with type C received GTR/NTR. For type D tumors, GTR was achieved in 5 of 7 patients who underwent ETOA. CONCLUSIONS: This study showed that trigeminal schwannomas can be effectively treated with a minimally invasive ETOA in all types of tumor except tumors mainly involving posterior fossa (type B). Especially, trigeminal schwannoma involving orbit (D1) or infratemporal fossa (D3) can be successfully removed with ETOA alone or combined ETOA with the endoscopic endonasal approach.

Malignant Mimics of Trigeminal Schwannoma

Trigeminal nerve schwannomas (TNSs) are rare lesions that typically present with symptoms of trigeminal neuropathy or other cranial nerve palsies. These lesions classically have a dumbbell shape, with an anterior component within Meckel's cave and posterior component extending into the posterior fossa through the porus trigeminus. Surgical resection of TNSs can often be achieved via an extradural subtemporal approach to Meckel's cave without an anterior petrousectomy, even for tumors with a significant posterior fossa component, as the tumor often erodes a portion of the petrous apex.1 We present the case of a 53-yr-old female presenting to our institution with complete trigeminal neuropathy secondary to a right-sided, previously resected and radiated TNS. Serial imaging demonstrated an interval growth of significant residual tumor despite multiple adjuvant therapies, and, thus, the patient was recommended to undergo additional surgical resection. The lesion was approached through a right-sided subtemporal approach to Meckel's cave,2 with a plan to utilize an anterior petrousectomy only if difficulty resecting the posterior fossa component of the tumor was encountered. Intraoperatively, the posterior fossa component was found to be densely adherent to the adjacent brainstem, likely secondary to prior surgery and radiation therapy, and, thus, an anterior petrousectomy was performed. Postoperatively, the patient had stable trigeminal neuropathy without any new neurological deficits and a magnetic resonance imaging (MRI) confirmed a gross total resection. In the accompanying video, we hope to demonstrate the steps and nuances of both the subtemporal approach to accessing Meckel's cave and anterior petrousectomy when employed for the resection of TNSs. The patient in question provided formal consent for the making of this video.

Two primary surgical approaches, the transcranial approach (TCA) and the endoscopic endonasal approach (EEA), offer distinct advantages and disadvantages, but studies have yet to compare their outcomes for trigeminal schwannoma (TS) resection systematically. A retrospective review of TSs between 2013 and 2023 was performed, with clinical characteristics, surgical outcomes, and follow-up data collected and analyzed. The patients were divided into two surgical groups, and tumours within each group were further classified according to the Samii system into middle fossa (type A), dumbbell-shaped involving middle and posterior fossae (type C), and extracranial with intracranial extension (type D), excluding posterior fossa (type B). A total of 101 patients (44 via EEA, 57 via TCA) were included. The two groups exhibited comparable baseline characteristics, except for the prevalence of dizziness in the pooled data (types A, C, and D). In pooled data and type A tumours, the EEA was associated with a statistically significant differences in higher gross total resection rate, shorter operative time, lower intracranial infection rate, and greater improvement in facial numbness. EEA was also significantly associated with a lower neurological deficits and higher Karnofsky Performance Scale scores in pooled data. Both approaches resulted in similar outcomes for type C tumours. EEA was advantageous for type D tumours in the infratemporal fossa, pterygopalatine fossa, and medial orbital regions, and no neurological deficits were observed. The optimal outcome of the surgical approach and minimization of morbidity for these complicated lesions depend on the meticulous selection of cases.

Trigeminal schwannomas (TSs) are intracranial tumors that can cause significant brainstem compression. TS resection can be challenging because of the risk of new neurologic and cranial nerve deficits, especially with large (≥ 3cm) or giant (≥ 4cm) TSs. As prior surgical series include TSs of all sizes, we herein present our clinical experience treating large and giant TSs via microsurgical resection. This was a retrospective, single-surgeon case series of adult patients with large or giant TSs treated with microsurgery in 2012-2023. Seven patients underwent microsurgical resection for TSs (1 large, 6 giant; 4 males; mean age 39 ± 14years). Tumors were classified as type M (middle fossa in the interdural space; 1 case, 14%), type ME (middle fossa with extracranial extension; 3 cases, 43%), type MP (middle and posterior fossae; 2 cases, 29%), or type MPE (middle/posterior fossae and extracranial space; 1 case, 14%). Six patients were treated with a frontotemporal approach (combined with transmastoid craniotomy in the same sitting in one patient and a delayed transmaxillary approach in another), and one patient was treated using an orbitofrontotemporal approach. Gross total resection was achieved in 5 cases (2 near-total resections). Five patients had preoperative facial numbness, and 6 had immediate postoperative facial numbness, including two with worsened or new symptoms. Two patients (28%) demonstrated new non-trigeminal cranial nerve deficits over mean follow-up of 22months. Overall, 80% of patients with preoperative facial numbness and 83% with facial numbness at any point experienced improvement or resolution during their postoperative course. All patients with preoperative or new postoperative non-trigeminal tumor-related cranial nerve deficits (4/4) experienced improvement or resolution on follow-up. One patient experienced tumor recurrence that has been managed conservatively. Microsurgical resection of large or giant TSs can be performed with low morbidity and excellent long-term cranial nerve function.

Endoscopic Endonasal Resection of Schwannoma of Pterygopalatine Fossa