Choosing a reasonable surgical approach to effectively prevent damage to important intracranial and skull base structures, reduce postoperative complications, and maximize the resection of skull base tumors is of great significance in improving the quality of patient’s survival. Skull base tumors include tumors in the anterior, middle, posterior and lateral skull base. Tumors in the nasal cavity, nasopharynx, parapharyngeal space, paranasal sinuses, pterygopalatine fossa, temporal fossa, infratemporal fossa, and temporal bone of the skull base can invade upward to the bone of the skull base, and even destroy the dura mater to form tumors of intracranial and extracranial communication. The key to the surgical outcome of skull base tumors is whether the tumor can be completely removed at one time within a relatively safe range. Due to the complex anatomical structure of the skull base region, the dense concentration of neurovascular structures and the complex and important functions of the structures, as well as the narrowness of the surgical field, the treatment of skull base tumors has always been a great challenge for neurosurgeons. Therefore, in order to cut the tumor as completely as possible without increasing the damage of important structures, it is necessary to choose the surgical access reasonably according to the condition. 1.1 Frontal approach and extended frontal approach Usually, the frontal approach is from the right frontal approach, or according to the bias side of the tumor to determine the approach, often take the coronal incision in the hairline to turn the frontal scalp forward and downward under the capitellar tendon membrane, and then the bone flap and the flap are separated, and when separating the skin flap, the supraorbital nerves and blood vessels inside the supraorbital foramen are retained; according to the requirements of the surgery, the supraorbital rim, the nasal bone and the bilateral frontal bones can be removed, and the surface of the anterior cranial fossa is exposed sufficiently. It can fully expose the bottom surface of the anterior cranial fossa. Common tumors include olfactory groove meningioma, saddle node meningioma, frontal lobe meningioma, pituitary tumor, optic nerve glioma and so on. 1.2 Frontotemporal and frontotemporal orbital-zygomatic approach Lift the frontotemporal flap forward and downward, free the bone flap, abrade the pterygoid crest, and truncate the zygomatic arch when needed, which can fully expose the floor of the anterior middle cranial fossa. The frontotemporal orbital-zygomatic approach can further expand the exposure, especially for the tumors that invade into the orbital and cavernous sinus areas and the temporal fossa, inferotemporal fossa, and pterygopalatine fossa of the cranial base. Common tumors include pterygoid crest meningiomas, cavernous sinus tumors, invasive pituitary adenomas, and intracranial and extracranial communication tumors. 1.3 Facial middle lifting approach: take the lip-dental groove incision, pass the nasal columella, cut the pyriform foramen, and lift the upper lip, nose and soft tissues of the middle part of the face upward together. It is commonly used in patients with anterior cranial fossa bottom to nasal cavity and paranasal sinuses. 1.4 Mid-face lifting + frontal coronal dissection approach Lift the mid-face and then make a frontal coronal dissection. Commonly used for tumors communicating inside and outside the anterior cranial fossa floor. 1.5 Maxillary partial resection + orbital content enucleation + frontal coronal dissection approach On the basis of frontal coronal dissection approach, the maxillary part invaded by the tumor is resected, and at the same time, the intraorbital tumor and orbital content invaded by the tumor are removed. This approach is commonly used for malignant tumors that communicate internally and externally at the base of the anterior cranial fossa and infiltrate and destroy the orbit. 1.6 Maxillary externally rotated + nasal externally rotated + frontal coronal incision approach According to the site of tumor occurrence and the scope of invasion, maxillary maxillectomy, lower maxillectomy, lateral maxillectomy or total maxillectomy with nasal externally rotated is used respectively, and then tumors involving the nasal cavity are resected together through frontal coronal incision. Tumors involving the nasal cavity, maxillary sinus, nasopharynx, pterygopalatine fossa, and bilateral sieve sinuses are common. 1.7 Mandibulotomy external rotation approach This approach is suitable for tumors invading nasopharynx, parapharyngeal space, oropharynx, infratemporal fossa and so on. 2.1 Pituitary adenoma Pituitary adenoma is a benign tumor occurring in the anterior lobe of the pituitary gland, and it is also one of the most common intracranial tumors, accounting for about 10-15% of intracranial tumors. transnasal pterygoid sinus approach is the main surgical method nowadays. Surgery can be accomplished with neuroendoscopic assistance and/or combined surgical microscopy. The availability of neuronavigation techniques allows for safer surgery and more complete tumor resection. For aggressive pituitary adenomas, some patients can take the expanded transsphenoidal approach, which was firstly proposed by Weiss. Compared with the traditional transsphenoidal approach, the expanded transsphenoidal approach extends forward over the saddle node, backward over the saddle dorsum, and resects the inferior wall of cavernous sinus on one or both sides, which exposes the tumor without pulling the brain tissues, and avoids the damage of important nerves and blood vessels. This approach can also resect tumors involving cavernous sinus, suprasellar region, anterior cranial fossa base, and slope tumors. For pituitary adenomas that are tough, protrude into the third ventricle, have rich blood flow, invade one or both cavernous sinuses and encircle the cavernous sinus segment of the internal carotid artery, or have multidirectional invasion, we strive for the transnasal butterfly approach combined with the infra-frontal or trans-flanking point approach. In transsphenoidal surgery, the midline must be mastered, and the distance from the midline must be constantly estimated when resecting tumors far from the midline. Damage to the internal carotid artery should be avoided in transsphenoidal surgery. Cerebrospinal fluid leakage should be prevented in transsphenoidal surgery for large and giant pituitary adenomas, and if it occurs, it should be repaired with muscle plasma in time. 2.2 Saddle node meningioma usually takes unilateral or bilateral subfrontal approach, the anterior edge of the bone should be as low as possible in the operation, directly to the bottom of the anterior cranial fossa, in order to ensure that the frontal lobe base is unnecessarily overstretched during the operation, and the frontal sinus is open during the craniotomy, attention should be paid to closure, in order to prevent the cerebrospinal fluid leakage. Cook reported three cases of saddle node meningiomas resected by the transnasal butterfly approach and concluded that the transnasal butterfly approach, combined with intraoperative microDoppler detection and endoscopic assistance, could safely and minimally invasively resect relatively small saddle node meningiomas confined to the midline.Laws successfully resected seven cases of saddle node or pterion plateau meningiomas by the enlarged transnasal butterfly approach, with no recurrences or serious complications. For saddle node meningiomas growing toward the posterior longitudinal fissure, the transmedial approach can be chosen, and the incision is across the midline. Preoperative cerebral angiography should be performed to understand the intracranial vascular condition, and if the horizontal segment of the anterior cerebral artery on one side is underdeveloped or occluded, or the anterior communicating artery is very short, the artery should not be cut off in the operation, so as to avoid the occurrence of acute cerebral infarction. For the tumor to one side and to the back of the saddle, the wing point approach can be used to remove the pterygoid crest, and the operation can make full use of the optic cross-pool and the internal carotid artery inner and outer pool space to fully release the cerebrospinal fluid, and minimize the damage to the hypothalamus, the internal carotid artery and the optic nerve as much as possible. First intratumoral resection, trying to reduce the size of the tumor, in order to facilitate the early identification, isolation and protection of important peritumoral structures. In general, the pituitary stalk is located posteriorly or laterally behind the tumor. When the anterior part of the tumor is resected, lifting the tumor envelope from the surface of the saddle septum anteriorly and inferiorly, and gradually turning over to resect the remainder of the tumor, the pituitary stalk can be protected to the maximum extent. If the tumor is tough, or if the tumor encircles the optic nerve, and it is difficult to remove the tumor completely, microscopic endotumor resection should be performed first to dissect its relationship with the optic nerve and the pituitary stalk, so as not to increase the new damage to the optic nerve, and to achieve the purpose of optic nerve decompression, and the damage to the optic nerve caused by heat conduction should be paid attention to during the operation. 2.3 Cavernous sinus meningioma and middle cranial fossa meningioma Cavernous sinus meningioma adopts wing point approach or fronto-orbital zygomatic approach, and the surgical incision should be as low as possible, and the cerebral angiography should be performed before the surgery to understand the blood supply of the tumor, and embolization can be performed if there is blood supply from the external carotid artery. After the tumor is exposed under the surgical microscope, the outer part of cavernous sinus is resected first, and when the inner part of the sinus is resected, there is more bleeding, and hemostasis can be performed while cutting the tumor, and hemostasis can be performed by filling with hemostatic gauze, thrombin, gelatin sponge, and so on. During surgery, the III, IV and VI cranial nerves in the lateral wall of cavernous sinus should be protected, and tumors invading the internal carotid artery should be handled with great care to prevent rupture and hemorrhage.Sen et al. reported that saphenous vein grafts were given to reconstruct the internal carotid artery after resection of tumors invading the internal carotid artery, and the patency rate was up to 86% at the 18-month follow up.Selchar also reported that there were 25 cases of benign tumors invading the cavernous sinus, and 21 cases were completely resected without operative deaths. cases were completely resected and there were no operative deaths. For cavernous sinus tumors that develop to the cerebellar vermis or to the subventricular, the cerebellar vermis should be incised during surgery, and an ultrasonic suction or laser knife should be used to resect the tumor, and cranial nerves III, IV, and VI and the brainstem should be protected. For the management of meningioma in the middle cranial fossa, the wing point approach or temporal approach should be taken according to the location of the tumor. Preoperative cerebral angiography should be performed to know the blood supply of the tumor and the blood supplying artery from the external carotid artery should be embolized. The surgical incision should be low enough to facilitate adequate exposure of the base of the middle cranial fossa, and the tumor should be resected in pieces intraoperatively, and protection of Labbe’s vein is important in patients with tumors in the dominant hemisphere. After surgery, the dura that is invaded by the tumor should be resected together and the dura should be repaired artificially. 3. Surgical access for tumors of the posterior cranial fossa floor 3.1 Tumors of the rocky slope region and tumors of the pontine cerebellar angle The main lesions in the slope region are chordoma and chondrosarcoma. Chordoma is a rare tumor of the skull base, which accounts for 1% of intracranial tumors, is a remnant of the spinal cord of the embryo, and rarely metastasizes. The prognosis is poor, with a 10-year survival rate of 18 to 35 percent. Chondrosarcomas are more common tumors that arise from primitive mesenchymal or embryonic cells, often in the cartilage of the skull base. The best treatment for these tumors is surgery plus radiation therapy, and the easiest surgical access is transnasal butterfly microscopic surgery and endoscopic surgery, which has been reported in the literature to be effective in endoscopic resection of tumors. Its complications include internal carotid artery injury, cranial nerve injury, and cerebrospinal fluid leakage. Tumors in the rocky oblique region include meningioma, cholesteatoma, chordoma and chondrosarcoma. Surgical methods include transmural, enlarged middle cranial fossa, and transnasal butterfly. The transnasal butterfly should consider the pterygoid sinus pneumatization and the relationship between the internal carotid artery and the tumor. Transnasal butterfly resection of tumors in the slope area makes full use of the anatomical gap (nasal cavity and sinuses) to reach deep structures without craniotomy and pulling brain tissues, while reducing complications. Endoscopes have a much wider field of illumination and are able to compensate for the deficiencies of microscopy. However, transsphenoidal surgery alone is limited for tumors that extend laterally to both sides of the slope such as chondrosarcoma, where the lesion extends beyond the cavernous sinus or carotid arteries, and these lesions usually require a staged approach, which can be performed by a combination of craniotomy and endoscopic surgery. Surgical approaches including transsphenoidal, transsphenoidal, anterior or distal lateral to the ethmoid sinus are generally based on the surgeon’s preference and the characteristics of the tumor. Kassam et al. reported a group of 17 endoscopic resections of lesions in the slope region via an expanded naso-pterygoid approach, the results of which were evaluated by the score of the Kassam’s Behavioral Scale, the degree of resection of the lesion, and complications, of which 11 (79%) of 14 patients with significant preoperative neurologic symptoms improved, with a total resection rate of 59% and a subtotal resection rate of 41%, and with complications that included cerebrospinal fluid leakage ( Complications included cerebrospinal fluid leakage (24%), tension pneumonitis (6%), and intracranial hematoma (6%), and permanent functional impairment in one case. The endoscopic enlarged transnasal butterfly approach (EEE) is considered to be a safe and effective surgical approach for lesions in the slope region.