Subtemporal Approach Research Articles

Anatomy of Inferior Temporal Arteries in Relation to Middle Cranial Fossa Structures: A Postmortem Computed Tomography Angiography Study

Abstract Objective The inferior temporal arteries (ITAs), branches of the posterior cerebral artery (PCA), are critical vascular structures encountered during subtemporal surgical approaches. Anatomical data based on multiphase postmortem computed tomography angiography (MPMCTA) are provided as a tool for preoperative surgical planning to lower the risk of ITA injury. Methods Adult (≥18 years) cases that underwent MPMCTA during 2015 to 2023 and whose cause of death did not involve the cerebral circulation were included in the study. Standardized measurements on four predefined coronal slices in relation to the posterior clinoid process (PCP) were established with references to projections in axial and sagittal planes. The main aim was to assess the presence, width, and course of anterior ITA (AITA), middle ITA (MITA), and posterior (PITA) particularly within the individual established quadrants of the middle cranial fossa. Results A total of 74 hemispheres were studied among 37 patients with the mean age of 52 ± 20.2 years. PITA was present in 98.7% of studied hemispheres, followed by MITA in 90.7% and AITA in 89.2%. The course of PITA was straight (65.8%) or oblique (34.3%), with significant difference in mean width (p = 0.050), branching angle (p < 0.001), distance to tentorial hiatus (p < 0.001), and superior petrosal sinus (p < 0.001). A pattern of PITA loop was defined as a twisting of its course within the collateral sulcus. Significant relationship between the presence of AITA and MITA (p < 0.001) along with the co-presence of AITA and PITA (p = 0.029) was found. Conclusion Knowledge of ITA characteristics and their relationship to surrounding anatomical structures is vital in subtemporal neurosurgical interventions. Preoperative inspection of the collateral sulcus and its relation to the surgical trajectory is critical to prevent PITA injury.

Microsurgical Treatment of Intracranial Dural Arteriovenous Fistulas: A Collaborative Investigation From the Multicenter Consortium for Dural Arteriovenous Fistula Outcomes Research.

First-line therapy for most intracranial dural arteriovenous fistulas (dAVFs) is endovascular embolization, but some require microsurgical ligation due to limited endovascular accessibility, anticipated lower cure rates, or unacceptable risk profiles. We investigated the most common surgically treated dAVF locations and the approaches and outcomes of each. The Consortium for Dural Arteriovenous Fistula Outcomes Research database was retrospectively reviewed. Patients who underwent dAVF microsurgical ligation were included. Patient demographics, angiographic information, surgical details, and postoperative outcomes were collected. The 5 most common surgically treated dAVF locations were analyzed about used surgical approaches and postoperative outcomes. Univariate analyses were performed with statistical significance set at a threshold of P < .05. In total, 248 patients in the Consortium for Dural Arteriovenous Fistula Outcomes Research database met inclusion criteria. The 5 most common surgically treated dAVF locations were tentorial, anterior cranial fossa (ACF), transverse-sigmoid sinus (TSS), convexity/superior sagittal sinus (SSS), and torcular. Most tentorial dAVFs were approached using a suboccipital, lateral supracerebellar infratentorial approach (39.3%); extended retrosigmoid approach (ERS) (25%); or posterior subtemporal approach (19.6%). All ACF dAVFs used a subfrontal approach; 5.3% also included an anterior interhemispheric approach. Most TSS dAVFs were ligated via ERS (31.3%) or subtemporal (31.3%) approaches. All convexity/SSS dAVFs used an interhemispheric approach. All torcular dAVFs used the suboccipital, lateral supracerebellar infratentorial approach, with 10.5% undergoing simultaneous ERS craniotomy. Angiographic occlusion rates after microsurgery were 85.5%, 100%, 75.8%, 79.2%, and 73.7% for tentorial, ACF, TSS, convexity/SSS, and torcular dAVFs, respectively (P = .02); the permanent neurological complication rates were 1.8%, 2.6%, 9.1%, 0%, and 0% (P = .31). There were no statistically significant differences in development of complications (P = .08) or Modified Rankin Scale at the last follow-up (P = .11) by fistula location. Although endovascular embolization is the first-line treatment for most intracranial dAVFs, surgical ligation is an important alternative. ACF and tentorial fistulas particularly demonstrate high rates of postoperative obliteration.

Oral and general health quality of life following a subtemporal preauricular infratemporal approach with condylar fossa osteotomy in surgical skull base tumor resection.

With the capacity to provide maximal lesion exposure, the subtemporal preauricular infratemporal (SPI) approach with condylar fossa osteotomy is highly utilized in radical resection of skull base tumors. While this approach requires disruption of the temporomandibular joint (TMJ) for access, the effects of this maneuver are poorly appreciated in neurosurgery. The aim of this study was to assess the morbidity of condylar fossa osteotomies by comparing oral health quality of life (OHQOL) and general health quality of life (GHQOL) outcomes after TMJ-involving and TMJ-sparing skull base approaches. A retrospective review of the medical records of patients who underwent surgery with the SPI approach (TMJ-involving approach) for skull base chondrosarcoma (CS) by a single senior surgeon at Vancouver General Hospital between 2002 and 2022 was performed. Patients undergoing TMJ-sparing anterolateral approaches for trigeminal schwannoma (TS) during the same study period by the same surgeon were included as controls. GHQOL was evaluated using the 36-item Short Form Health Survey from preoperative and postoperative periods. Postoperative OHQOL was evaluated using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I/II screening instrument. Data regarding quality of life were available for 13 of 19 CS patients and 12 of 15 TS patients surgically managed between 2002 and 2022. CS patients demonstrated less jaw dysfunction in all parameters of the DC/TMD Axis I/II components when specifically assessing OHQOL. CS patients had a lower likelihood of temporomandibular disorder (TMD) presence on the TMD pain screener than TS patients (25% vs 45%, p = 0.40). Chronic pain scores were higher in the TS group, with significantly more patients with grade 2 or higher pain (36.4% vs 0%, p = 0.01). The mean Jaw Functional Limitation Scale (JFLS) scores were lower in CS patients than in TS patients. Both CS and TS patients demonstrated lower mean JLFS scores (0.50 and 0.81, respectively) than patients with chronic TMD (1.76), but higher mean JLFS scores than patients without TMD (0.16). The authors report novel findings regarding the impact of the SPI approach with a condylar fossa osteotomy on OHQOL and GHQOL among skull base tumor patients. Anatomical disruption of the TMJ was not associated with significant clinical TMJ dysfunction. Compared with TS patients, CS patients had even lower mean scores in TMJ-related morbidity, and both groups had lower TMJ morbidity than patients diagnosed with chronic TMJ dysfunction. Condylar fossa osteotomies can therefore be considered without concern of significant additional morbidity.

Giant tumefactive mesencephalothalamic Virchow-Robin space with triventricular hydrocephalus: a case-based systematic literature review.

The perivascular spaces of the brain are also known as Virchow-Robin spaces (VRSs). Dilated Virchow-Robin spaces in the brainstem are rare and mainly cause symptoms due to obstructive hydrocephalus, less frequently because of their size, mass effect, and impact on eloquent structures. We present a patient with giant tumefactive VRS with hydrocephalus and neurological symptoms who was treated with endoscopic third ventriculostomy (ETV) followed by microscopic cyst fenestration. On the basis of this observation, we performed a thorough review of the literature to evaluate different treatment options. An 11-year-old girl presented with a headache for 3months. The patient had a giant tumefactive mesencephalothalamic VRS with triventricular hydrocephalus. She was initially treated with endoscopic third ventriculostomy and multiple cyst fenestration. Symptomatic cyst regrowth required multiple cyst fenestrations via transcallosal transchoroidal (N = 2) and subtemporal approaches (N = 1) at the 2- and 4-year follow-ups. A literature review of these conditions allowed the detection of 12 cases (including our index case), and only 25% (3/12) of the patients underwent cyst fenestration 16.7% (2/12) required endoscopic fenestration and 8.3% (1/12) required microscopic fenestration. Giant mesencephalothalamic dVRSs are rare in the pediatric population. These patients are usually symptomatic due to obstructive hydrocephalus. Surgical options are endoscopic third ventriculostomy, ventricular shunt procedures, or direct cyst fenestration (microscopic or endoscopic). Close follow-up is mandatory owing to the risk of progression of the disease. Cyst fenestration resolves symptoms immediately, as it addresses both hydrocephalus and mass effects due to the cystic lesion in the same setting.

Location-based selection of the surgical approach to preserve the hippocampus in lesion-associated temporal lobe epilepsy

Background and objectivesSurgical resections for lesions associated with intractable temporal lobe epilepsy (TLE) offers good seizure outcomes.However, the necessity of hippocampectomy in addition to lesionectomy is controversial, especially when the hippocampus is not involved by the lesion. Lesionectomy alone, preserving the hippocampus by an appropriate surgical approach, might offer good seizure outcomes while maintaining neurocognitive function. In the present study, the aims were to examine the surgical strategy for lesions associated with TLE and to present how to select surgical approaches to preserve the hippocampus. MethodsA total of 22 consecutive lesion-associated TLE patients who underwent lesionectomy alone were retrospectively reviewed. The surgical approach, transsylvian, transorbital, subtemporal, supracerebellar transtentorial, or transcortical approach, was selected based on the location of the lesion. Postoperative seizure outcomes were classified by the Engel classification. Neurocognitive outcomes were assessed before and after surgery if possible. The pathology, the extent of resection, and lesion recurrence were reviewed. ResultsThe transsylvian approach was selected in six patients, the transorbital approach in one patient, the subtemporal approach in three patients, the supracerebellar transtentorial approach in five patients, and the transcortical approach in seven patients. Eighteen of 22 (81.8 %) patients achieved Engel’s class I or II good seizure outcomes. No patients had neurocognitive deterioration after surgery. Twelve patients had various types of brain tumors, and ten patients had non-tumorous lesions. Gross total resection was achieved in 21 patients. All patients had no recurrence. ConclusionFor patients with lesion-associated TLE, lesionectomy alone by the appropriate surgical approach offers satisfactory seizure outcomes while preserving hippocampus.

Postoperative dysgeusia following microsurgical resection for acoustic neuroma: a systematic review and meta-analysis.

To determine the collated rate of postoperative dysgeusia after microsurgical intervention in acoustic neuroma patients. The systematic review with meta-analysis was undertaken following PRISMA guidelines. A thorough search of PubMed/Medline, the Cochrane Database of Systematic Reviews, and Epistemonikos was undertaken for studies published up until May 16, 2024 reporting postoperative taste disturbance rates after microsurgical intervention for acoustic neuroma. The methodological quality of the included studies was assessed via the Methodological Index for Non-Randomized research (MINORS) tool. Using MedCalc (v. 20.215) software, the random-effects model was developed for proportional meta-analysis. Eight studies, encompassing 2,402 patients (mean age = 49.06 years; 48.54% female population), were included in the analysis. The overall pooled rate of postoperative dysgeusia following microsurgical management of acoustic neuroma was 23.7% (95% CI: 9.266-42.359, p < 0.0001). When stratified by surgical approach, the rate of postoperative dysgeusia for the retrosigmoid approach was 18.8% (95% CI: 2.821-44.461, p < 0.0001). Postoperative dysgeusia data stratified for other major microsurgical approaches (subtemporal and translabirynthine approaches) was not reported by any of the included studies. Our systematic review and meta-analysis calculated a collated rate of almost 25% and recognized postoperative dysgeusia as a common complication following microsurgical management of acoustic neuromas. These results highlight the significance of preoperative counselling and the development of strategies that minimize the likelihood of harm to the chorda tympani nerve during microsurgical intervention for acoustic neuroma.

Neck Clipping via Subtemporal Approach

The subtemporal approach offers the advantages of a wide surgical field in the anteroposterior direction and easy access to the proximal basilar artery. This approach can be adapted to treat low-positioned aneurysms using a tentorial incision, known as the subtemporal transtentorial approach. However, a disadvantage of the subtemporal approach is the risk of injury to the temporal lobe. To mitigate this risk, it is important to ensure proper positioning, adequate cerebrospinal fluid drainage, preservation of the bridging veins, and intermittent retraction of the temporal lobe.

SupraPetrous InfraTemporal Approach: A Supplemental Approach to Supracerebellar Infratentorial for Inferior Amygdala and Hippocampal Head Access-A Cadaveric Study With Case Illustrations.

Access to the amygdala and hippocampus (A/H) is complex. To address the limitations and invasiveness of traditional approaches, including the Transsylvian, Subtemporal, and Supracerebellar infratentorial approaches, we developed the suprapetrous infratemporal (SPIT) approach. This study describes the nuances of this approach in both cadaveric studies and clinical cases. Three unilateral exposures were performed using microscopic and endoscopic methodologies in the SPIT approach. After cadaveric investigation, this approach was successfully implemented in representative clinical cases. The SPIT approach enabled direct access to the inferior A/H, circumventing the requirement for temporal lobe retraction and detachment of the temporal lobe from the dura through a subtemporal route by drilling the upper part of the mastoid, consequently mitigating tension on the vein of Labbé. This enabled a bottom-up view because one would gain with a zygomatic osteotomy and forward projection like a mini-posterior petrosal view by using a transmastoid view, without cutting down the zygomatic arch and opening the dura subtemporally, limiting patient pain and preventing case comorbidity. The SPIT approach was performed in 2 cases of mesial temporal cavernoma presenting with seizures. The lesion was visualized intraoperatively and was successfully removed in these cases. The postoperative course was excellent with no complications, and gross total resection was radiographically confirmed with Engel Class 1a seizure freedom. The SPIT approach is a complementary approach for inferior A/H disease, combining the combined middle fossa approach modified for intradural pathology. Limited drilling of the upper aspect of the mastoid with a medial dural opening at the level of the arcuate eminence provides a direct trajectory with minimal brain retraction. Additional research encompassing a larger patient cohort and extended follow-up periods is required to substantiate the advantages of SPIT in the management of inferior A/H lesions.

Subtemporal Approach for the Treatment of Ruptured and Unruptured Distal Basilar Artery Aneurysms: Is There a Contemporary Use?

Distal basilar artery aneurysms (DBAs) are high-risk lesions for which endovascular treatment is preferred because of their deep location, yet indications for open clipping nonetheless remain. The subtemporal approach allows for early proximal control and direct visualization of critical posterior perforating arteries, especially for posterior-projecting aneurysms. Our objective was to describe our clinical experience with the subtemporal approach for clipping DBAs in the evolving endovascular era. This was a retrospective, single-institution case series of patients with DBAs treated with microsurgery over a 21-year period (2002-2023). Demographic, clinical, and surgical data were collected for analysis. Twenty-seven patients underwent clipping of 11 ruptured and 16 unruptured DBAs with a subtemporal approach (24 female; mean age 53 years). Ten patients had expanded craniotomies for treatment of additional aneurysms. The aneurysm occlusion rate was 100%. Good neurological outcomes as defined by the modified Rankin Scale score ≤2 and Glasgow Outcome Scale score ≥4 were achieved in 21/27 patients (78%). Two patients died before hospital discharge, one from vasospasm-induced strokes and another from an intraoperative myocardial infarction. These results demonstrate that microsurgical clip ligation of DBAs using the subtemporal approach remains a viable option for complex lesions not amenable to endovascular management.

The endaural subtemporal keyhole: a novel minimally invasive approach to the middle cranial fossa.

The goal of this study was to evaluate the feasibility of a minimally invasive approach to the middle cranial fossa using a novel endaural keyhole. The charts of all patients who underwent this novel minimally invasive approach to the middle cranial fossa were retrospectively reviewed. In addition, cadaveric dissection was performed to demonstrate the feasibility of the endaural keyhole to the middle cranial fossa. Six patients (5 female and 1 male; age range 47-77 years) who underwent craniotomy for CSF leak (n = 3), intracerebral hematoma evacuation (n = 2), and tumor resection (n = 1) via the endaural subtemporal approach were identified. There were no approach-related complications noted. Representative imaging from cadaveric dissection is provided with a stepwise discussion of the procedure. The endaural subtemporal keyhole craniotomy provides a novel approach to middle fossa skull base pathology, as well as a minimally invasive approach to intra-axial pathology of the temporal lobe and basal ganglia. Further research is needed to establish the limitations and potential complications of this novel approach.

Purely endoscopic subtemporal keyhole anterior transpetrosal approach to access the petrous apex region: surgical techniques and early results.

The anterior transpetrosal approach using a microscope to provide wider access to the petrous apex region has been described for radical resection of lesions of the middle and posterior skull base. The microscopic anterior transpetrosal approach (mATPA) requires a wide craniotomy and meticulous epidural procedures to minimize temporal lobe retraction. Recently, the clinical application of transcranial endoscopic keyhole approaches for minimally invasive surgery has been steadily expanding. In this study, the details of the purely endoscopic subtemporal keyhole ATPA (eATPA) for petrous apex lesions are described and its initial results are reported. Between May 2022 and May 2023, the authors performed eATPA in 10 patients with petrous apex lesions, of which 6 were meningiomas, 3 were trigeminal schwannomas, and 1 was epidermoid cyst. The surgical procedure of the purely eATPA is as follows. After a small temporal craniotomy, the endoscopic procedure is started. The anterior rim of the petrous bone and Meckel's cave are exposed via an intradural subtemporal approach. The lesion is removed with additional drilling of Kawase's triangle, cutting the superior petrosal sinus, opening Meckel's cave, and cutting the tentorium. The authors also compared the outcomes of mATPA versus eATPA for consecutive cases of petrous apex lesions. Gross-total resection was achieved in 8 of the 10 patients. The average operative time was 4 hours 13 minutes. There were 3 cases of transient abducens nerve palsy and 1 case of trochlear nerve palsy in the postoperative period. No new-onset motor deficits or CSF leakage was noted in any of these patients. Only 1 patient exhibited postoperative asymptomatic temporal lobe edema. The Karnofsky Performance Scale (KPS) scores remained unchanged or improved for all patients postoperatively. Compared with mATPA, eATPA achieved a similar extent of resection and comparable postoperative KPS scores with a significantly shorter mean operative time, much smaller temporal craniotomy, and thus less mean blood loss during surgery with lower rates of new-onset temporal lobe edema in the postoperative period. An eATPA allows a direct route to access Meckel's cave and posterior cranial fossa lesions similar to conventional mATPA, with shortening the operative time and reducing the risk of postoperative temporal lobe edema. This eATPA is considered one of the new surgical techniques that can be expected to develop in the future.

Microanatomical Investigation of the Subtemporal Transtentorial Approach

To study the microanatomic structure of the subtemporal transtentorial approach to the lateral side of the brainstem, and to provide anatomical information that will assist clinicians to perform surgeries on the lateral, circumferential, and petroclival regions of the brainstem. Anatomical investigations were conducted on 8 cadaveric head specimens (16 sides) using the infratemporal transtentorial approach. The heads were tilted to one side, with the zygomatic arch at its highest point. Then, a horseshoe incision was made above the auricle. The incision extended from the midpoint of the zygomatic arch to one third of the mesolateral length of the transverse sinus, with the flap turned towards the temporal part. After removing the bone, the arachnoid and the soft meninges were carefully stripped under the microscope. The exposure range of the surgical approach was observed and the positional relationships of relevant nerves and blood vessels in the approach were clarified. Important structures were photographed and the relevant parameters were measured. The upper edge of the zygomatic arch root could be used to accurately locate the base of the middle cranial fossa. The average distances of the star point to the apex of mastoid, the star point to the superior ridge of external auditory canal, the anterior angle of parietomastoid suture to the superior ridge of external auditory canal, and the anterior angle of parietomastoid suture to the star point of the 10 adult skull specimens were 47.23 mm, 45.27 mm, 26.16 mm, and 23.08 mm, respectively. The subtemporal approach could fully expose the area from as high as the posterior clinoid process to as low as the petrous ridge and the arcuate protuberance after cutting through the cerebellar tentorium. The approach makes it possible to handle lesions on the ventral or lateral sides of the middle clivus, the cistern ambiens, the midbrain, midbrain, and pons. In addition, the approach can significantly expand the exposure area of the upper part of the tentorium cerebelli through cheekbone excision and expand the exposure range of the lower part of the tentorium cerebelli through rock bone grinding technology. The total length of the trochlear nerve, distance of the trochlear nerve to the tentorial edge of cerebellum, length of its shape in the tentorial mezzanine, and its lower part of entering into the tentorium cerebelli to the petrosal ridge were (16.95±4.74) mm, (1.27±0.73) mm, (5.72±1.37) mm, and (4.51±0.39) mm, respectively. The cerebellar tentorium could be safely opened through the posterior clinoid process or arcuate protrusion for localization. The oculomotor nerve could serve as an anatomical landmark to locate the posterior cerebral artery and superior cerebellar artery. Through microanatomic investigation, the exposure range and intraoperative difficulties of the infratemporal transtentorial approach can be clarified, which facilitates clinicians to accurately and safely plan surgical methods and reduce surgical complications.

Isolated cerebral varices: clinical observations and literature review

The aim of the study is to present rare clinical cases of isolated cerebral varices, summarize scientific literature data on their diagnosis and treatment.The article describes 2 clinical observations of isolated cerebral varix, presents a literature review of this topic, as well as treatment tactics for patients with this pathology.In the first clinical observation, in a male 72‑year-old patient isolated cerebral varix was interpreted as distal saccular aneurysm of the right middle cerebral artery per computed angiography data. Surgical treatment was performed: from subtemporal approach in the area of the floor of the middle cranial fossa, cerebral varix, inflow and outflow veins were visualized. The inflow and outflow veins were clipped, aneurysm was resected and sent to histological examination. The patient was discharged on day 8 after surgery. Histological examination of the cerebral varix wall showed typical components for a venous wall, in particular, individual smooth muscle fibers, absence of elastic membrane.In the second clinical observation, in a female 59‑year-old patient magnetic resonance (MR) imaging, MR angiography and MR venography in the projection of anterior basal parts of the left temporal area showed an aneurysmal malformation transitioning into the superficial middle cerebral vein. Taking into consideration venous pathogenesis of the vascular lesion, dynamic observation of the patient was chosen.Isolated cerebral varix is a rare vascular pathology without a specific clinical and instrumental picture. To avoid erroneous diagnosis and determine further treatment tactics, additional examinations are recommended: MR imaging, MR angiography and MR venography.

Coexistence of anterior choroidal artery and posterior cerebral artery retia mirabilia presenting with subarachnoid hemorrhage: illustrative case.

A rete mirabile is a rare vascular anomaly, with posterior cerebral artery (PCA) involvement being especially rare. Its pathogenesis has been speculated as a remnant of "distal annexation" between the primitive anterior choroidal artery (AchA) and the PCA at this site, but the exact mechanisms remain unclear. A 29-year-old man presented with subarachnoid hemorrhage. Arteriovenous malformation in the medial temporal lobe was initially suspected, but an arteriovenous shunt was not detected. First, conservative treatment was administered; however, rebleeding occurred 1 month later. Carotid angiography revealed a network-like cluster of blood vessels at the choroidal point of the AchA, suggesting a rete mirabile; these vessel clusters led to the persistent temporo-occipital branch of the AchA. Furthermore, an aneurysm was detected at the junction between the rete mirabile and the persistent temporo-occipital branch of the AchA. Additionally, vertebral angiography demonstrated a rete mirabile at the P2 segment. These findings suggested the coexistence of AchA and PCA retia mirabilia. Consequently, the aneurysm was clipped using a subtemporal approach to prevent re-rupture, and the postoperative course was uneventful. This first report of coexisting AchA and PCA retia mirabilia supports the remnant of distal annexation between the primitive AchA and the PCA as the reason for rete formation at this site.

10159-STMO-7 INTRAOPERATIVE MRI SURGERY FOR POSTERIOR FOSSA LESIONS

Abstract Background: Intraoperative MRI (iMRI) is an important modality in brain tumor surgery to identify residual tumors, however, it is problematic due to patient positional limitations. In this study, we investigated the usefulness of iMRI for posterior fossa lesions. Materials and Methods: Of 320 cases of brain tumors removed using iMRI from June 2016 to April 2023, 24 cases of posterior fossa lesions were included. Tumor type, approach method, imaging availability, tumor removal rate, and complications were examined retrospectively. Results: Tumor types included 8 gliomas, 5 epidermoid cysts, 4 meningiomas, 3 metastatic brain tumors, 1 schwannoma, and 3 others. Eleven patients underwent midline suboccipital approach in the supine position, 8 patients underwent lateral suboccipital approach, 2 patients underwent occipital transtentorial approach, and 2 patients underwent anterior transpetrosal approach in the supine position. transpetrosal approach in 2 cases and subtemporal approach in 1 case. iMRI showed residual lesion in 14 of 24 patients. More than half of the gliomas and epidermoid cysts had intraoperative residual disease, whereas only one meningioma did. Total resection was achieved except for one case of intentional residual schwannoma and two cases of glioma. Discussion: iMRI requires the upper body to fit within a gantry, and it is difficult to image in the park bench position. However, various approaches is possible by using a supine-lateral or semi-prone position. In the concorde position, where the fourth ventricle and upper cerebellum are approached, it is useful to insert a mat in the anterior thoracic and raise the upper body. For tumors in the dorsal brainstem and upper cerebellum, the occipital transtentorial approach was used. iMRI is effective in the removal of all tumors, including gliomas in intramedullary tumors and epidermoid cysts in extramedullary tumors. Conclusion: iMRI can be used in posterior cranial fossa lesions.

SURG-29. APPROACH SELECTION FOR COMPLEX, MULTI-COMPARTMENTAL PETROCLIVAL MENINGIOMAS: A SYSTEMATIC REVIEW OF ENDOSCOPIC AND TRANSCRANIAL APPROACHES TO AN EXCEEDINGLY DIFFICULT CLASS OF SKULL BASE LESIONS

Abstract INTRODUCTION Petroclival meningiomas are among the most formidable and technically challenging tumors in skull base surgery owing to their deep-seated location and proximity to critical neurovascular structures. Herein, we seek to understand why skull base surgeons preoperatively plan the staged excision of petroclival meningiomas. METHODS Three databases were queried per PRISMA to identify studies describing the indications for staging surgical resection of petroclival meningiomas. RESULTS Fourteen studies describing 187 patients (59.3% female, age range: 5 – 81 years) met inclusion criteria. The most common presenting symptom at diagnosis was headache (24.6%). Other common symptoms included cerebellar signs (16.0%) and gait disturbances (13.4%). Petroclival meningiomas were most commonly observed extending to the cavernous sinus (52.88%) and meckel’s cave (49.04%). With respect to critical neurovasculature, the trigeminal nerve was involved in a majority (54.59%) of petroclival meningiomas, while other relevant cranial nerves with tumor involvement included the facial (16.22%) and vestibulococcular (12.43%). Additionally, the most commonly involve vascular structures were the basilar (2.16%) superior cerebellar arteries (1.62%). Of the 187 patients who underwent surgical resection of petroclival meningioma, 144 (77%) underwent surgery involving a single stage, while 43 (23%) underwent surgery in which a two-stage approach was used. The most common single-stage approaches were the retrosigmoid (n = 35) and transpetrosal (n = 22), while the most common approaches employed in a multi-stage fashion were the subtemporal (n = 6), pterional (n = 5), and suboccipital (n = 4) approaches. To clarify, these approaches were each performed as one half of a two-stage surgery involving a second, separate approach. CONCLUSION Common approaches used in multi-stage procedures included the retrosigmoid, anterior petrosectomy, posterior petrosectomy, orbitozygomatic, translabrynthine, and various combinations thereof. Indications for performing surgery in this manner include coexistence of lesion in both middle and posterior skull base compartments, absence of meaningful hearing function, tumor size, and surgeon preference.

Quantitative Anatomical Comparison of Surgical Approaches to Meckel's Cave.

Meckel's cave is a challenging surgical target due to its deep location and proximity to vital neurovascular structures. Surgeons have developed various microsurgical transcranial approaches (MTAs) to access it, but there is no consensus on the best method. Newer endoscopic approaches have also emerged. This study seeks to quantitatively compare these surgical approaches to Meckel's cave, offering insights into surgical volumes and exposure areas. Fifteen surgical approaches were performed bilaterally in six specimens, including the pterional approach (PTA), fronto-temporal-orbito-zygomatic approach (FTOZA), subtemporal approach (STA), Kawase approach (KWA), retrosigmoid approach (RSA), retrosigmoid approach with suprameatal extension (RSAS), endoscopic endonasal transpterygoid approach (EETPA), inferolateral transorbital approach (ILTEA) and superior eyelid approach (SEYA). All the MTAs were performed both with 10 mm and 15 mm of brain retraction, to consider different percentages of surface exposure. A dedicated navigation system was used to quantify the surgical working volumes and exposure of different areas of Meckel's cave (ApproachViewer, part of GTx-Eyes II, University Health Network, Toronto, Canada). Microsurgical transcranial approaches were quantified with two different degrees of brain retraction (10 mm and 15 mm). Statistical analysis was performed using a mixed linear model with bootstrap resampling. The RSAS with 15 mm of retraction offered the maximum exposure of the trigeminal stem (TS). If compared to the KWA, the RSA exposed more of the TS (69% vs. 46%; p = 0.01). The EETPA and ILTEA exposed the Gasserian ganglion (GG) mainly in the anteromedial portion, but with a significant 20% gain in exposure provided by the EETPA compared to ILTEA (42% vs. 22%; p = 0.06). The STA with 15 mm of retraction offered the maximum exposure of the GG, with a significant gain in exposure compared to the STA with 10 mm of retraction (50% vs. 35%; p = 0.03). The medial part of the three trigeminal branches was mainly exposed by the EETPA, particularly for the ophthalmic (66%) and maxillary (83%) nerves. The EETPA offered the maximum exposure of the medial part of the mandibular nerve, with a significant gain in exposure compared to the ILTEA (42% vs. 11%; p = 0.01) and the SEY (42% vs. 2%; p = 0.01). The FTOZA offered the maximum exposure of the lateral part of the ophthalmic nerve, with a significant gain of 67% (p = 0.03) and 48% (p = 0.04) in exposure compared to the PTA and STA, respectively. The STA with 15 mm of retraction offered the maximum exposure of the lateral part of the maxillary nerve, with a significant gain in exposure compared to the STA with 10 mm of retraction (58% vs. 45%; p = 0.04). The STA with 15 mm of retraction provided a significant exposure gain of 23% for the lateral part of the mandibular nerve compared to FTOZA with 15 mm of retraction (p = 0.03). The endoscopic approaches, through the endonasal and transorbital routes, can provide adequate exposure of Meckel's cave, especially for its more medial portions, bypassing the impediment of major neurovascular structures and significant brain retraction. As far as the most lateral portion of Meckel's cave, MTA approaches still seem to be the gold standard in obtaining optimal exposure and adequate surgical volumes.

Microscopic with Endoscopic Surgery via Subtemporal Approach for Cavernous Sinus Cholesteatomas

The aim of this study was to retrospectively analyze the clinical data of 16 patients with cavernous sinus cholesteatomas, explore the surgical outcomes, and summarize the surgical experience. Patients with cavernous sinus cholesteatomas underwent surgery between June 2016 and June 2022 at the Department of Neurosurgery at the First Affiliated Hospital of Soochow University. Clinical data were obtained from all patients for analysis. Common preoperative symptoms included headache, dizziness, diplopia, ptosis, and facial numbness. There were 7 patients with 2 or more symptoms. There were 13 patients with total resection and 3 patients with subtotal resection. There were 5 patients with improved postoperative symptoms, 10 patients with no significant change, and 1 patient with worse symptoms. New postoperative cranial nerve defects occurred in 4 patients. During the follow-up, all patients had favorable prognosis without progression. Using "double-scope" technique, the subtemporal approach, a surgical strategy for cavernous sinus cholesteatomas, was sufficient to completely resect the tumors.

Extradural Subtemporal Approach for Giant Multicompartmental Skull Base Chondrosarcoma-Personalized Virtual Surgical Planning and Operative Nuances: 2-Dimensional Operative Video.

Extradural Subtemporal Approach for Giant Multicompartmental Skull Base Chondrosarcoma-Personalized Virtual Surgical Planning and Operative Nuances: 2-Dimensional Operative Video.

Combined retrosigmoid and middle fossa approach for a small, superiorly located petroclival meningioma: how I do it.

Petroclival meningiomas pose significant surgical challenges because of their deep location and complex surrounding neurovasculature. The use of multiple surgical approaches can optimize safe tumor removal from multiple anatomic compartments. We describe a patient with a growing superior petroclival meningioma centered at the posterior clinoid with extension into Meckel's cave that was successfully removed with a combined retrosigmoid and subtemporal middle fossa approach. This strategy avoided the need for anterior petrous bone drilling and tentorial splitting. A combined retrosigmoid and subtemporal middle fossa approach can provide safe access to tumors spanning the supra- and infratentorial compartments.