[A case of Takayasu arteritis complicated with cavernous sinus syndrome presenting as unilateral optic nerve DWI hyperintensity].

A 47-year-old male patient with a history of Takayasu arteritis presented with prominent symptoms of left eyeball fixation, protrusion, and visual loss. Orbital magnetic resonance imaging revealed hyperintensity on diffusion-weighted imaging of the left optic nerve, with corresponding low signal on apparent diffusion coefficient maps, suggestive of acute infarction of the left optic nerve. Combined with the patient's cranial magnetic resonance imaging findings, the diagnosis of cavernous sinus syndrome was established.

Cavernous Sinus Thrombosis.

Cavernous sinus thrombosis is a potentially lethal subset of cerebral venous sinus thrombosis that may occur as a result of septic and aseptic etiologies. The overall incidence is estimated to be between 0.2 and 1.6 per 100,000 persons; and treatments include antibiotics, anticoagulation, corticosteroids, and surgery. Recent morbidity and mortality estimates are approximately 15% and 11%, respectively. Rapid identification and treatment are essential and may reduce the risk of poor outcome or death.

[Anatomy of the Cavernous Sinus].

The cavernous sinus is the crossroad of veins from various embryological origins, including the brain, eye, pituitary gland, dura, and cranium. Embryologically, the cavernous sinus is mainly formed from the pro-otic sinus; secondary anastomosis between the cavernous sinus and primitive tentorial sinus results in various anatomical variations in the drainage patterns of the superficial middle cerebral vein. Moreover, connections between the cavernous sinus and basal vein via the uncal vein, bridging vein, and petrosal vein from the superior petrosal sinus may exist. Retrograde drainage from the cavernous sinus into the cerebral veins is often observed in arteriovenous shunts involving the cavernous sinus, such as dural and carotid-cavernous fistulas, which are primarily treated using transvenous embolization. Understanding the anatomy of the cavernous sinus and its associated veins is essential for safe and reliable endovascular treatment.

Carotid Cavernous Fistula.

Carotid cavernous fistulae (CCFs) are arteriovenous shunts involving the cavernous sinus. CCFs are defined as direct or indirect. Direct CCFs are treated by deconstructive or reconstructive techniques depending on whether the affected internal carotid artery is required to perfuse the ipsilateral cerebral hemisphere, as determined by a balloon test occlusion. Indirect CCFs, or dural fistulae of the cavernous sinus wall, are most often treated with transvenous embolization. Stereotactic radiosurgery is reserved for cases of indirect CCFs that are not completely obliterated by embolization. Overall, cure rates are high with relatively low complication rates.

A quantitative comparative surgical analysis of the endoscopic transorbital approach and frontotemporal-orbitozygomatic approach for extradural exposure of the cavernous sinus.

OBJECTIVE: Recently, the endoscopic superior eyelid transorbital approach (SETA) has emerged as a potential alternative to access the cavernous sinus (CS). Several previous studies have attempted to quantitatively compare the traditional open anterolateral skull base approaches with transorbital exposure; however, these comparisons have been limited to the area of exposure provided by the bone opening and trajectory, and fail to account for the main avenues of exposure provided by subsequent requisite surgical maneuvers. The authors quantitatively compare the surgical access provided by the frontotemporal-orbitozygomatic (FTOZ) approach and the SETA following applicable periclinoid surgical maneuvers, evaluate the surgical exposure of key structures in each, and discuss optimal approach selection. METHODS: SETA and FTOZ approaches were performed with subsequent applicable surgical maneuvers on 8 cadaveric heads. The lengths of exposure of cranial nerves (CNs) II-VI and the cavernous internal carotid artery; the areas of the space accessed within the supratrochlear, infratrochlear, and supramaxillary (anteromedial) triangles; the total area of exposure; and the angles of attack were measured and compared. RESULTS: Exposure of the extradural CS was comparable between approaches, whereas access was significantly greater in the FTOZ approach compared with the SETA. The lengths of extradural exposure of CN III, V1, V2, and V3 were comparable between approaches. The FTOZ approach provided marginally increased exposure of CNs IV (20.9 ± 2.36 mm vs 13.4 ± 3.97 mm, p = 0.023) and VI (14.1 ± 2.44 mm vs 9.22 ± 3.45 mm, p = 0.066). The FTOZ also provided significantly larger vertical (44.5° ± 6.15° vs 18.4° ± 1.65°, p = 0.002) and horizontal (41.5° ± 5.40° vs 15.3° ± 5.06°, p < 0.001) angles of attack, and thus significantly greater surgical freedom, and provided significantly greater access to the supratrochlear (p = 0.021) and infratrochlear (p = 0.007) triangles, and significantly greater exposure of the cavernous internal carotid artery (17.2 ± 1.70 mm vs 8.05 ± 2.37 mm, p = 0.001). Total area of exposure was also significantly larger in the FTOZ, which provided wide access to the lateral wall of the CS as well as the possibility for intradural access. CONCLUSIONS: This is the first study to quantitatively identify the relative advantages of the FTOZ and transorbital approaches at the target region following requisite surgical maneuvers. Understanding these data will aid in selecting an optimal approach and maneuver set based on target lesion size and location.

Transorbital neuroendoscopic surgery for treatment of sphenoid wing meningiomas extending to the cavernous sinus: clinical implications and a technical illustration.

OBJECTIVE: The aim of this study was to evaluate the efficacy and safety of transorbital neuroendoscopic surgery (TONES) in the management of sphenoid wing meningiomas (SWMs) with cavernous sinus and orbital invasion. METHODS: The authors conducted a retrospective review of 32 patients with SWMs treated at Gazi University using TONES from October 2019 to May 2023. The study includes clinical applications to elucidate the endoscopic transorbital approach. Surgical techniques focused on safe subtotal resection, aiming to minimize residual tumor volume for subsequent radiosurgery. Data were collected on patient demographics, tumor characteristics, surgical procedures, complications, and postoperative outcomes, including radiological imaging and ophthalmological evaluations. RESULTS: Surgical dissections delineated a three-phase endoscopic transorbital approach: extraorbital, intraorbital, and intracranial. In the clinical application, gross-total resection was not achieved in any patient because of planned postoperative Gamma Knife radiosurgery. The mean follow-up period was 16.3 months. Of 30 patients with preoperative proptosis, 25 experienced postoperative improvement. No new-onset extraocular muscle paresis or visual loss occurred postoperatively. The average hospital stay was 1.15 days, with minimal complications and no significant morbidity or mortality. CONCLUSIONS: Total resection of SWMs invading the cavernous sinus and orbit is associated with substantial risks, particularly cranial nerve deficits. TONES offers a minimally invasive alternative, reducing morbidity compared with transcranial approaches, and represents a significant advancement in the surgical management of SWMs, especially those extending into the cavernous sinus and orbit. The approach provides a safe, effective, and patient-centric approach, prioritizing subtotal resection to minimize neurological deficits while preparing patients for adjunctive radiosurgery. This study positions TONES as a transformative surgical technique, aligning therapeutic efficacy with neurovascular preservation and postoperative recovery.

Cavernous sinus metastasis in head and neck cancer: Focus on oral squamous cell cancer.

Intracranial metastatic disease is rarely found in head and neck cancer (HNC), in particular, cavernous sinus (CS) involvement is difficult to recognize, because of its rarity, not specific symptoms associated and challenging imaging features. We report our experience in 4 cases, reviewing also the English literature. We analysed data from 21 patients showing that CS metastasis is a dramatic event, with rapid onset, usually starting with neurological manifestations (ophthalmoplegia, headache and trigeminal dysesthesia) and almost unavoidable outcome (DOD in 18/21 patients). Furthermore, we assessed that the diagnostic confirmation could be difficult to perform because of the need for multiple exams and time consuming procedures. Unfortunately, usual antineoplastic therapies seem to be not effective in prolonging survival, also because patients are already weakened by primary tumour treatments. The only option that seems useful in improving outcomes is immunotherapy.

[Basic and Advanced Techniques of Anastomosis in Deep Surgical Fields:STA-SCA Anastomosis].

This article detailly describes the subtemporal-transtentorial STA-SCA bypass technique. Through temporal base drilling, copious cerebrospinal fluid evacuation before retraction, and sufficient retraction of the temporal lobe preserving the veins of the temporal base would be primodial to obtain an appropriate surgical field. Refrection of the tentrial free edge and identification of recipient SCA posterior to the entry point of the trochlear nerve into the cavernous sinus is a micro-anatomical key. Bilateral bayonet-type needle holders and forceps should be used not to shadow the surgical corridor with one's hands.

Comparison of the transarterial, transvenous, and superior ophthalmic vein approaches in the treatment of indirect carotid-cavernous fistulas.

OBJECTIVE: Indirect carotid-cavernous fistulas (CCFs) are abnormal arteriovenous shunting lesions with a highly variable clinical presentation that depends on the drainage pattern. Based on venous drainage, treatment can be either transarterial (TA) or transvenous (TV). The aim of this study was to compare the outcomes of indirect CCF embolization via the TA, TV, and direct superior ophthalmic vein (SOV) approaches. METHODS: The authors conducted a retrospective analysis of 74 patients admitted to their institution from 2010 to 2023 with the diagnosis of 77 indirect CCFs as confirmed on digital subtraction angiography. RESULTS: A total of 74 patients with 77 indirect CCFs were included in this study. Embolization was performed via the TA approach in 4 cases, the TV approach in 50 cases, and the SOV in 23 cases. At the end of the procedure, complete occlusion was achieved in 76 (98.7%) cases. The rate of complete occlusion at the end of the procedure and at last radiological follow-up was significantly higher in the SOV and TV cohorts than in the TA cohort. The rate of recurrence was highest in the TA cohort (25% for TA vs 5.3% for TV vs 0% for SOV, p = 0.68). CONCLUSIONS: The rate of immediate complete occlusion was higher in the TV and SOV cohorts than in the TA cohort while the rate of complete occlusion at final follow-up was highest in the SOV cohort. The SOV approach was significantly associated with higher rates of postoperative complications. Indirect CCFs require careful examination of the fistulous point and the venous drainage to provide the most effective patient-tailored approach.

Usefulness of Opening the Diaphragma Sellae Before Transecting Interclinoidal Ligament for Endoscopic Endonasal Transoculomotor Triangle Approach: Technical Nuances and Surgical Outcomes.

OBJECTIVE: Opening the oculomotor triangle (OT) and removing the posterior fossa lesion by endoscopic endonasal approach (EEA) is challenging for even an experienced endoscopic neurosurgeon. We summarize the treatment experience and technical nuances with EEA for resection of pituitary neuroendocrine tumors and cavernous sinus (CS) meningiomas invading through the OT. METHODS: Between 2018 and 2022, 8 patients, comprising 5 with pituitary neuroendocrine tumors (3 with nonfunctioning and 2 with somatotroph tumors with increased levels of growth hormone) and 3 CS meningiomas, were treated using an endoscopic endonasal transoculomotor triangle approach. The critical surgical technique is continuously opening the diaphragma sellae from medial to lateral toward the interclinoidal ligament and transecting it to enlarge the OT. We evaluated preoperative tumor size, previous surgical history, preoperative symptoms, extent of tumor resection, histopathology, and postoperative complications for all patients. RESULTS: The gross total resection (defined as complete removal) in 3 patients (38%), near-total resection (defined as >95% removal) in 4 patients (50%), and subtotal resection (defined as ≤90% removal) in 1 patient (12%) and gross total resection of tumor invading through the OT was achieved in all patients through pure EEA. Two of 3 patients with visual deficits in nonfunctioning pituitary neuroendocrine tumors improved, and the other remained stable postoperatively. One patient showed transient oculomotor nerve palsy. The growth hormone level of the 2 patients with somatotroph tumors declined to normal. For 3 patients with CS meningiomas, cranial nerve palsy improved in 2 patients, whereas the other patient developed increased facial numbness after surgery. CONCLUSIONS: The endoscopic endonasal transoculomotor triangle approach is an efficient surgical option for tumors with CS invasion and OT penetration.

MRI 3D SPACE T2WI for Pituitary Adenoma Cavernous Sinus Invasion Diagnosis.

OBJECTIVE: This study aims to assess the utility of magnetic resonance imaging (MRI) 3D SPACE T2-weighted imaging (T2WI) sequences in evaluating cavernous sinus invasion by pituitary adenomas. METHODS: Data were collected from patients who underwent continuous pituitary MRIexaminations at the Medical Imaging Center of our hospital from October 2019 to February 2021. Eligible cases were evaluated for sagittal and axial T1WI sequences, coronal 3D SPACE T2WI sequences, and sagittal and coronal enhanced T1-weighted imaging (T1WI) sequences using the INFINITT PACS workstation. The Wilcoxon signed-rank test for paired samples and the Mann-Whitney U test for 2 independent samples were used to statistically analyze differences in image quality scores among various groups. In addition, the sensitivity, specificity, positive predictive value, and negative predictive value of each observation index were compared with intraoperative results. RESULTS: 3D SPACE T2WI showed superior cavernous sinus imaging quality compared with contrast enhanced T1WI and T2WI plain scans (P < 0.05). The sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 90.0%, 55.60%, and 100.0%, respectively. The accuracy for pituitary adenoma invasiveness diagnosis based on cavernous sinus medial wall integrity was 94.40%. CONCLUSIONS: The imaging quality of the medial wall of the cavernous sinus on the 3D SPACE T2WI plain scan sequence surpassed that of contrast enhanced T1WI TSE-enhanced scans and T2WI TSE plain scans. The continuous observation of the medial wall of the cavernous sinus using this sequence holds great diagnostic value for assessing cavernous sinus invasion by pituitary adenomas. This strategy is more reliable than traditional MRI observation indicators.

Carotid-cavernous fistula: A potential treatable cause of bilateral abducens palsy and conjunctival hyperemia.

OBJECTIVE: Carotid cavernous fistulas (CCFs) represent uncommon and anomalous communications between the carotid artery and the cavernous sinus. MATERIALS AND METHODS: Case report RESULTS: We present the clinical details and successful management of a previously healthy 44-year-old patient who presented with one-month worsening headache, bilateral abducens palsy and conjunctival injection. Imaging modalities including magnetic resonance imaging (MRI) with contrast and digital subtraction angiography (DSA) facilitated the diagnosis of CCF. The patient underwent endovascular coiling of the CCF, leading to neurological recovery and symptom remission. CONCLUSION: This case highlights the importance of promptly CCF diagnosis in patients with multiple cranial nerve palsies and conjunctival hyperemia. Moreover, it emphasizes the efficacy of endovascular coiling in achieving symptom remission.

Hormone Concentration Measurement in Intracranial Dural Arteriovenous Fistulae.

OBJECTIVE: Intracranial dural arteriovenous fistulae (DAVFs) represent a subset of cerebral vascular malformations associated with significant morbidity and mortality. In Japan, DAVF exhibits sex-based differences in anatomical distribution, with female predominance in the cavernous sinus (CS) and male predominance in the transverse sinus (TS). Nevertheless, the pathophysiology of DAVF is not fully understood, and hormonal influences are hypothesized to play a role in its development. This study aimed to investigate changes in the concentrations of sex steroid hormones between intracranial and peripheral sampling sites in patients with CS- and TS-DAVF. METHODS: We recruited 19 patients with CS-DAVF (n = 12) and TS-DAVF (n = 7) in this study. Blood hormone measurements were obtained from peripheral and jugular bulb samples during endovascular intervention. Hormone concentrations were analyzed using enzyme-linked immunosorbent assay kits, and statistical analyses were performed. RESULTS: Our study revealed a higher prevalence of CS-DAVF in females and TS-DAVF in males, which is consistent with previous studies. Estradiol concentration was significantly lower in the jugular bulb compared with in the periphery in both patients with CS- and TS-DAVF. This decrease in estradiol was observed irrespective of the patient's sex and independent of follicle-stimulating hormone levels. CONCLUSIONS: These findings indicate a local decrease in estradiol levels within the intracranial vasculature of patients with DAVF. This suggests a potential multifactorial role of estradiol in the pathomechanism of DAVFs, warranting further investigation to understand its influence on DAVF formation and potential targeted therapies, thereby enhancing patient outcomes.

Successful surgical treatment of oculomotor palsy due to schwannoma of the cavernous sinus in a 7-year-old girl: a case report.

Oculomotor nerve schwannoma in children not associated with neurofibromatosis is a rare disease, with 26 pediatric cases reported so far. There is no established treatment plan. A 7-year-old girl presented with oculomotor nerve palsy. Surgical reduction of the tumor combined with postoperative gamma knife surgery preserved the oculomotor nerve, improved oculomotor nerve function, and achieved tumor control during the observation period of 20 months. The combination of partial surgical resection and gamma knife surgery as a treatment strategy for oculomotor nerve schwannoma resulted in a good outcome.

[Carotid-cavernous fistulas]. / Sinus-cavernosus-Fisteln.

BACKGROUND: Carotid cavernous fistulas (CCFs) are rare but clinically significant vascular anomalies characterized by abnormal connections between the cavernous sinus and arteries. This overview presents a comprehensive analysis of anatomy, classification, clinical presentation, diagnosis, imaging, and therapy of CCFs. The cavernous sinus, a central venous structure in the brain, is of critical importance for understanding CCFs due to its proximity to key structures such as the internal carotid artery and cranial nerves. CLASSIFICATION: CCFs are classified into direct and dural types, with direct fistulas typically being high-flow and dural fistulas being low-flow. The symptomatology varies greatly and can range from noises in the head, diplopia, red eye, tearing, to blurred vision and headaches. The diagnostic assessment requires a combination of detailed medical history, neurological and ophthalmological examination, and the use of imaging techniques. METHODS: In imaging, computed tomography (CT) and magnetic resonance imaging (MRI) are crucial for depicting the anatomical structures and blood vessels, while digital subtraction angiography (DSA) is considered the gold standard for accurate representation of the fistula. The treatment of CCFs is complex and depends on the type of fistula, location, and clinical condition of the patient. CONCLUSION: This overview emphasizes the importance of precise diagnosis and individualized therapy to achieve optimal results and avoid complications. Ongoing developments in medical imaging and treatment techniques will continuously improve the treatment outcomes of patients with CCFs.

Transmaxillary approach for resection of maxillary division trigeminal schwannoma at foramen rotundum.

BACKGROUND: The foramen rotundum and anterior cavernous sinus have traditionally been accessed by transcranial approaches that are limited by the high density of critical neurovascular structures. The transmaxillary approach provides an entirely extradural route to the foramen rotundum and anterior cavernous sinus. METHOD: This patient with neurofibromatosis and facial pain with trigeminal schwannoma at the foramen rotundum was successfully treated by transmaxillary resection of the tumor. This approach allowed for a direct extradural access to the pathology, with bony decompression and tumor resection, avoiding transcranial routes. CONCLUSION: The transmaxillary approach provides a safe and entirely extradural corridor to access smaller localized skull base lesions at and surrounding the cavernous sinus.

Off-label use of large diameter Concerto fibered coils through a 0.017 inch microcatheter for transvenous embolization of indirect carotid-cavernous fistulas: two case reports.

BACKGROUND: A carotid-cavernous fistula is an abnormal communication between the arteries and veins within the cavernous sinus. While conservative management may be prudent in low risk cases, many patients require intervention and endovascular embolization has evolved as the preferred method of treatment. Embolization can be performed via either the transarterial or transvenous approach. One major challenge of the transvenous approach is the complex and variable compartmentation of the cavernous sinus, which often requires the use of low profile microcatheters to navigate and reach the fistulous point. Fibered coils are also preferred when performing transvenous embolization of carotid-cavernous fistula, as they are of higher thrombogenicity and allow for faster occlusion of the fistula. However, most low profile (0.017-inch) microcatheters are not able to deploy fibered coils based on the manufacturer's instructions. CASE PRESENTATION: We present two successful cases of off-label use of Medtronic Concerto fibered coils via a 0.017-inch microcatheter during transvenous embolization of carotid-cavernous fistula in a 60-year-old and an 80-year-old Chinese female, respectively. CONCLUSION: Our case series highlight the possibility of deploying large diameter (up to 10 mm) Concerto fibered coils through a low profile (0.017-inch) microcatheter in an off-label manner for transvenous embolization of indirect carotid-cavernous fistula.

Multi-center application of a convolutional neural network for preoperative detection of cavernous sinus invasion in pituitary adenomas.

OBJECTIVE: Cavernous sinus invasion (CSI) plays a pivotal role in determining management in pituitary adenomas. The study aimed to develop a Convolutional Neural Network (CNN) model to diagnose CSI in multiple centers. METHODS: A total of 729 cases were retrospectively obtained in five medical centers with (n = 543) or without CSI (n = 186) from January 2011 to December 2021. The CNN model was trained using T1-enhanced MRI from two pituitary centers of excellence (n = 647). The other three municipal centers (n = 82) as the external testing set were imported to evaluate the model performance. The area-under-the-receiver-operating-characteristic-curve values (AUC-ROC) analyses were employed to evaluate predicted performance. Gradient-weighted class activation mapping (Grad-CAM) was used to determine models' regions of interest. RESULTS: The CNN model achieved high diagnostic accuracy (0.89) in identifying CSI in the external testing set, with an AUC-ROC value of 0.92 (95% CI, 0.88-0.97), better than CSI clinical predictor of diameter (AUC-ROC: 0.75), length (AUC-ROC: 0.80), and the three kinds of dichotomizations of the Knosp grading system (AUC-ROC: 0.70-0.82). In cases with Knosp grade 3A (n = 24, CSI rate, 0.35), the accuracy the model accounted for 0.78, with sensitivity and specificity values of 0.72 and 0.78, respectively. According to the Grad-CAM results, the views of the model were confirmed around the sellar region with CSI. CONCLUSIONS: The deep learning model is capable of accurately identifying CSI and satisfactorily able to localize CSI in multicenters.

A novel classification for guiding the surgical approach for cranio-orbital lesions: a single institution case series of 45 cases and a literature review.

We aim to share our experience of the removal of cranio-orbital lesions (COLs) and propose a novel classification to guide the tailored approach selection. We retrospectively reviewed 45 consecutive patients with COLs who underwent surgery performed by the same neurosurgeon between November 2010 and November 2022. The surgical approach was selected according to the anatomical region classification of the COLs. For lesions limited to space A (lateral superior orbital fissure, SOF), the pterion or extended pterion approach (PA or EPA) was used. For lesions limited to space B (extraconal compartment medial SOF, and cavernous sinus CS) and C (intraconal compartment, medial SOF, and CS), the pretemporal transcavernous approach (PTCA) was used. For lesions limited to space D (intraconal compartment and optic canals), the subfrontal approach (SA) was used. For lesions extending into the infratemporal fossa (ITF), the cranio-orbito-zygomatic approach (COZA) was used. For lesions involving pterygopalatine fossa (PPF), the endoscopic transnasal approach (ETNA) was used. We analyzed the clinical manifestations, imaging data, surgical approaches, surgical outcomes, neurological outcomes, and follow-up data. Gross total resection was performed in 35 patients (35/45, 77.8%). SA, PA, EPA, PTCA, COZA, and ETNA were performed in 9, 9, 10, 10, 6, and 1 case(s), respectively. Progression of the residual tumor was observed in 6 cases (1 adenoid cystic carcinoma and 5 meningiomas). Surgical approach selection plays a vital role in patient prognosis. This novel classification based on the involvement of anatomic space could help surgeons select an appropriate approach to remove the COLs.

The learning curve for cavernous sinus surgery illustrated by symptomatic intracavernous aneurysm clipping through a pretemporal transcavernous approach.

OBJECTIVE: The anatomy of the cavernous sinus (CS) has been well studied in the laboratory for decades; however, performing surgery in and around the CS is still a challenge. To reveal the learning curve for CS surgery via the pretemporal transcavernous approach (PTTC), surgical procedures were examined. The authors proposed 4 levels of surgical difficulty in opening the walls of the CS through this approach. Details of the approach were illustrated by surgical videos of symptomatic intracavernous aneurysm clipping. METHODS: Four levels of surgical difficulty were proposed. The higher the level, the more the CS walls were opened. Pathologies corresponding to each level of difficulty in and around the CS were categorized in each level together with explanations. From 2015 to 2021, 5 patients with symptomatic intracavernous aneurysms (diplopia due to compressive cranial neuropathy) underwent the PTTC at the authors' institute and served as representative cases in opening the walls of the CS. All CS cases from 2009 to 2021 were reviewed and categorized to demonstrate the learning curve. RESULTS: Four levels of surgical difficulty are as follows: level 1, a basic Dolenc extradural approach, which involves opening the anterior third of the superior and lateral walls of the CS; level 2, mobilizing the internal carotid artery (ICA) and opening the proximal dural ring to enter the roof of the CS and treat lesions around the clinoid and upper cavernous ICA; level 3, opening the entire aspect of the superior and lateral walls of the CS, which involves opening the oculomotor triangle and peeling the lateral wall of the CS to the tentorial incisura; and level 4, mobilizing cranial nerves III, IV, and V1 to gain access to the supra-/infratrochlear triangles to have proximal ICA control and opening the posterior wall as the last step to enter the posterior fossa. Surgical steps were described and illustrated with surgical videos of symptomatic intracavernous aneurysm clipping. CONCLUSIONS: The learning curve for CS surgery is long. The authors use 4 levels of surgical difficulty to describe applications of the PTTC in CS surgery. This approach serves as an effective workhorse in treating CS pathologies with low morbidity and high success rates when performed by experienced neurosurgeons.