The surgical approach and associated anatomy of cavernous sinus tumors involving the orbital apex are discussed. Methods A frontotemporal arcuate incision with a pterygopoint approach was used in all 22 cases. When the tumor was located in the lateral aspect of the optic nerve or the lateral wall of the cavernous sinus, a temporal off-set incision was chosen. The lower bone flap was removed, the pterygoid crest was ground away, and the dura was cut to separate the lateral fissure. Depending on the location of the tumor, the anterior bed process and the superior wall of the optic canal are removed with a microdrill. The lateral wall of the cavernous sinus or orbital fascia was selected as the site of tumor protrusion and the tumor was excised in pieces. Out of 22 cases of orbital apical cavernous sinus, 17 cases were completely resected, 3 cases were nearly completely resected, 1 case was mostly resected, and 1 case was biopsied. Conclusion Detailed understanding of the surgical anatomy familiar with the cavernous sinus and orbital apical tumor is a good outcome to achieve surgical resection of the tumor. 1, Clinical data 1.1, General: female, 17 cases; male, 5 cases. Age 16-67 years old, mean age 39 years old, including 1 case under 20 years old; 2 cases from 21-30 years old; 10 cases from 31-40 years old; 4 cases from 41-50 years old; 4 cases from 51-60 years old; 1 case over 60 years old. 1.2 Main manifestations: 14 cases with proptosis and limited eye movement; 3 cases with headache; 3 cases with facial numbness; 2 cases with vision loss. 2 months-1.5 years, including 3 cases within 3 months; 9 cases between 4 months and 6 months; 6 cases between 7 months and 1 year; 4 cases over 1 year. 1.3 MR imaging and CT scan: All patients underwent MR imaging and CT scan to determine All patients underwent MR imaging and CT scan to determine the location of tumor and its relationship with surrounding structures. The tumor was located in the cavernous sinus and involved the orbital apex in 13 cases; the tumor was located in the orbital apex and involved the cavernous sinus in 4 cases; the tumor involved the cavernous sinus and orbital apex extensively in 4 cases. The tumors were located in the outer layer of the lateral cavernous sinus wall in 16 cases; in the inner cavernous sinus in 3 cases; and between the two layers of the lateral cavernous sinus wall in 3 cases. The tumors were located in the outer layer of the optic nerve in 17 cases; above the optic nerve in 3 cases; and inside the optic nerve in 2 cases. The tumor was attached to the internal carotid artery in 13 cases; partially bypassed the internal carotid artery in 6 cases; completely bypassed the internal carotid artery in 3 cases. There were 19 cases of single tumor; 3 cases of multiple tumors. There were 2 cases of partial cystic transformation and 1 case of calcification. 1.4. Surgical method: All patients underwent frontotemporal arc incision. When the tumor was located in the lateral side of optic nerve or lateral wall of cavernous sinus, a temporal biased incision was chosen. After the bone flap was removed, the pterygoid ridge was ground away, and the dura was cut open to separate the lateral fissure. Depending on the location of the tumor, the anterior bed process and the superior wall of the optic canal are abraded with a microdrill. The lateral wall of the cavernous sinus or the orbital fascia was selected as the site of tumor protrusion and the tumor was excised in pieces. When the tumor grows towards the posterior part of the cavernous sinus, it is necessary to prevent the damage to the bullae of the superficial large nerve. When separating the tumor from the internal carotid artery, vasospasm and hemorrhage should be prevented. 2. Results: 2.1 Surgical results Among 22 cases of orbital apical cavernous sinus tumors, 17 cases had total tumor resection; 3 cases had near total resection; 1 case had major total resection; 1 case had biopsy, see table. Postoperatively, 2 patients with meningioma developed incomplete actinic nerve palsy; 1 patient with metastasis had supraorbital fissure syndrome. 2.2 Follow-up All patients were followed up from 3 months to 6 months. 2 patients with actinic nerve palsy recovered completely at 3 months postoperatively. 14 patients with preoperative proptosis, 6 recovered completely at 3 months postoperatively, 6 recovered at 6 months postoperatively 2 recovered incompletely. 2 patients with trigeminal nerve dysfunction, 1 recovered at 3 months postoperatively, 1 had no change at 6 months postoperatively. 1 patient with preoperative hypotony had no change at 6 months postoperatively. 3. Discussion The literature on surgical resection of orbital apical cavernous sinus tumors has not been reported in China, and most reports attribute the lesions related to the orbital apical cavernous sinus to purely intraorbital or cavernous sinus lesions. However, current neuroimaging can clearly demonstrate a communicating lesion between the cavernous sinus and the orbital apex. From the microsurgical anatomy, the cavernous sinus and the orbital apex are two closely related structures, with the kinetic, talipes, adductor, and ophthalmic branches of the trigeminal nerve traveling within the cavernous sinus into the supraorbital fissure, the optic nerve and ophthalmic artery entering the orbit by the optic canal, and the knee of the internal carotid artery traveling intracranially through the orbital apex. Therefore, tumors in the orbital apex may enter the cavernous sinus through the superior orbital fissure and optic nerve canal or destroy the bone, and tumors in the cavernous sinus may also erode into the orbit, resulting in orbital symptoms such as proptosis, visual impairment and limited eye movement. In contrast, early headache and facial numbness of cavernous sinus tumor are not obvious and are overlooked. The key to surgical resection of orbital apical cavernous sinus tumor is to reveal the tumor, prevent damage to the optic nerve and remove the tumor. In general, only epidural approach is used for orbital cavernous sinus tumor, and it is difficult to remove the lesion completely. In our group of 22 patients, only 2 cases of small meningioma used the epidural approach, while 20 cases used the subdural approach. After the epidural grinding of the pterygoid crest, the dura was cut open and the lateral fissure was separated to reveal the internal carotid artery and the beginning of the middle cerebral artery in the anterior bed process, and if the tumor broke through the subdura, the lesion entering the anterior and middle cranial fossa was removed first. For tumors that enter the orbital apex, the anterior bed process and the superior wall of the optic canal are removed by subdural abrasion. In order to evaluate the indication of cavernous sinus tumor surgery, Sekhar et al. classified cavernous sinus tumors into grade V according to the imaging features of cavernous sinus tumors: grade I, the tumor is confined to the cavernous sinus and encircles the internal carotid artery; grade II, the tumor involves more than 2 neural structures of the cavernous sinus interstices and partially encircles the internal carotid artery; grade III, the tumor completely encircles the internal carotid artery, but Grade IV, the tumor wraps around the internal carotid artery causing stenosis or occlusion; Grade V, the tumor involves the cavernous sinuses bilaterally. It is considered difficult to surgically remove the tumor in grade III and IV, and there is no indication for surgery in grade V. In this group of patients, 18 cases were grade II cavernous sinus tumors and 4 cases were grade III. The lateral wall of the cavernous sinus is a double-layered membrane structure, with the outer layer tough and thick continuous with the dura mater and the inner layer thin and soft with the periosteum, and the arteriolar, talocrural and trigeminal nerve branches 1 and 2 travel between the double-layered membrane in the lateral wall, and the abducens nerve, internal carotid artery and sympathetic plexus are located in the internal carotid artery. These cranial nerves, along with the dura mater and bone structures of the skull base, form surgical anatomical gaps, which are summarized by Van lovern et al. as nine cavernous sinus surgical triangles, which are used to resect tumors in the cavernous sinus. The commonly used triangles are the Parkindon’s triangle with the abducens nerve and the ophthalmic branch of the trigeminal nerve as the two sides and the bedrock ligament as the bottom side. Mullen’s triangle with the ophthalmic and maxillary branches of the trigeminal nerve on both sides and the foramen ovale and foramen ovale on the bottom side. The lateral cavernous sinus triangle with the mandibular and maxillary branches of the trigeminal nerve on both sides and the line connecting the foramen ovale and foramen ovale at the base. Since it is not easy to damage the motoneurotic nerve and optic nerve from these triangles to the cavernous sinus, there are few postoperative complications. Except for small grade I-II cavernous sinus tumors via epidural approach, 20 patients in our group took subdural approach. After the dural incision, it is necessary to separate the lateral fissure and reveal the internal carotid artery and proximal end of middle cerebral artery in the upper part of anterior bed process, if the tumor protrudes into the cavernous sinus into subdural, the tumor in middle and anterior cranial fossa should be removed first, and the tumor entering the orbital apex should be abraded to remove the anterior bed process and the upper wall of optic nerve canal. The common postoperative complication of cavernous sinus tumor is oculogyric nerve palsy, which is mostly caused by excessive intraoperative strain on the oculogyric nerve and tumor involvement, and for lighter oculogyric palsy, it can be recovered within 2 weeks, and for larger tumor and severe intraoperative strain on the oculogyric nerve, it can be recovered from 3 months to 6 months after surgery. In one of our patients, the articulating nerve was severed intraoperatively, and the articulating nerve palsy recovered 1 year after the nerve anastomosis was performed. Due to the involvement of the ophthalmic branch of the trigeminal nerve, there can be corneal foreign body sensation, itching and dryness. Especially for patients who cannot be reset after proptosis, antibacterial eye ointment is applied to the eye to prevent the occurrence of keratitis. When grinding the upper wall of the optic canal and anterior bed protrusion, prevent the occurrence of cerebrospinal fluid leakage. For patients with postoperative cerebrospinal fluid leak, continuous lumbar puncture drainage can be used, and for those who do not heal from cerebrospinal fluid leak, secondary surgical repair should be performed.