Surgical treatment of craniopharyngiomas has always been a major challenge for neurosurgeons. The goal of surgical treatment is total resection of the tumor, and the main factors that hinder the achievement of this goal are: the age and health of the patient, the way the tumor grows and its relationship with the surrounding structures, and the experience of the surgeon. The achievement of a good surgical outcome depends more on the neurosurgeon’s therapeutic decisions and surgical technique. I. Strategies and techniques of surgical approaches There are various surgical approaches available for the surgical treatment of craniopharyngioma. The commonly used ones are subfrontal approach, anterior longitudinal fissure approach, pterygoid point approach, transcallosal approach and transdiscal sinus approach. The choice of surgical approach depends on the location of the tumor, the growth pattern and the operator’s experience, and it should be made on the basis of adequate preoperative evaluation. Craniopharyngiomas are pyriform and suprasellar lesions that can grow laterally, anteriorly, and posteriorly, and are surrounded by a number of important and complex neurovascular structures, which requires that the choice of surgical access should satisfy the need for multi-angle operation. Choux (1991) reported a group of 415 cases in a collaborative study: unilateral subfrontal approach accounted for 46%, pterygoid approach accounted for 27%, transdiscal sinus approach accounted for 8%, transventricular approach accounted for 3%, bilateral subfrontal approach accounted for 2.6%, and transcallosal approach accounted for 0.7%. Subfrontal approach is suitable for intra-saddle type craniopharyngioma, especially for cystic tumors or small solid tumors growing toward the anterior part of the skull, and the condition of the anterior interspace of the optic intersection should be good; anterior longitudinal fissure approach is mainly suitable for suprasaddle type and anterior part of the third ventricle, and tumors entering into the third ventricle can be removed through the endplates; the pterygoid approach is mainly suitable for suprasaddle type tumors growing toward the base of the skull, and it can be revealed in multiple angles; transcallosal approach is suitable for intraventricular type tumors and tumors protruding into ventricle. The transcallosal approach is suitable for intracerebroventricular tumors and tumors protruding into the ventricles; the transdiscal sinus approach is suitable for lesions with limited growth in the pyriform saddle; and the infratemporal approach is suitable for a small number of tumors that grow mainly toward the slope and the pontine cerebellar angle. The pterygoid approach and the anterior subfrontal and anterior longitudinal fissure approaches are the most commonly used surgical approaches for craniopharyngioma. Subfrontal approach The patient is placed in supine position with the head above the heart level and the head frame is fixed. Coronal incision is made within the hairline, and the skin incision on the surgical side should be low, usually choosing unilateral right frontal craniotomy. Turn the base of the flap to the superior border of the frame, taking care to protect the supraorbital nerve. A right frontal flap is made, medial to the midline, anterior to the supraorbital rim to adequately expose the floor of the anterior cranial fossa, and lateral to the level of the critical foramen and pterygoid point to increase lateral exposure. The dura mater is cut in an arc along the supraorbital margin and the dura mater is flipped toward the skull base. Probe along the lateral aspect of the anterior fossa floor to find the lateral fissure pool, cut the arachnoid membrane of the lateral fissure pool to release the cerebrospinal fluid, and after the cerebral pressure decreases to the satisfaction of the brain tissue collapse, the frontal lobe is lifted upward posteriorly and superiorly with the brain plate of the fixation retractor to reveal the saddle area, and care is taken to avoid excessive retraction damage to the frontal lobe brain tissue during the operation. The ipsilateral olfactory nerve was freed to the olfactory bulb and protected, and the arachnoid membrane of the suprasellar pool was sharply separated to fully expose the optic nerve, optic cross and internal carotid artery. Cut the arachnoid membrane on the surface of the tumor, and further separate it in the anterior gap of the optic cross, at this time, pay attention to protect the perforating blood vessels of the anterior circulation, and do not blindly cauterize. Puncture the tumor, extract the cystic fluid decompression and clear diagnosis, tumor collapse, cut the tumor wall or saddle septum, further separation and resection of the tumor. Craniopharyngioma is not rich in blood supply, do not over cauterize during tumor resection, and take care to identify and protect the pituitary stalk and pituitary gland. Separation of the tumor can be performed in the first or second gap, or the endplates can be opened as needed to try to separate the tumor along the tumor wall, which facilitates the protection of the optic nerve, optic crossings, and internal carotid artery, and can avoid residual tumor. Subfrontal approach is a more familiar path for neurosurgeons. The advantages are simple operation, low conditions and technical requirements, and easy to master. The disadvantages are: (1) the need to open the frontal sinus, with the possibility of cerebrospinal fluid leakage; (2) easy to damage the supraorbital nerve and olfactory nerve; (3) poor exposure of the lateral aspect of the pterygoid plexus and the posterior aspect of the optic chiasm, which can’t satisfy the need of multi-angle operation, and poor exposure of the larger and more complex tumors; (4) inadequate exposure of the endplates, and the restriction of operation in the tricuspid ventricle. Anterior longitudinal fissure approach The patient’s position and craniotomy method are the same as that of frontal subfrontal approach, and the exposure of the midline side is larger. After the dura mater is cut open, the cerebrospinal fluid is released from the lateral fissure pool first, and the frontal lobes are separated from the longitudinal fissure after the cerebral pressure drops and the small frontal drainage veins can be pre-disconnected. Both frontal lobes are separated first to the base of the middle cranial fossa and then posteriorly to the knee of the corpus callosum to fully visualize the endplates and anterior arterial complex. At this point, a tumor protruding upward through the anterior gap of the optic crossings is often seen, and the tumor often displaces the optic crossings and anterior communicating arteries posteriorly and superiorly. The arachnoid membrane surrounding the tumor is separated and the surrounding structures are exposed. If the tumor is cystic, the periphery should be protected with cotton pads before puncture to prevent spillage and spread of cystic fluid. The outer wall of the suprasellar portion of the tumor is covered by the arachnoid membrane, which makes it easy to separate the tumor from the optic nerve and great vessels. The tumor cystic cavity is often lined with calcified deposits; in most cases the calcifications are sandy and easy to separate and remove, sometimes the calcifications are hard and require patience and careful separation. The position of the optic cross has a greater influence on the anterior longitudinal fissure approach. If the optic cross is posterior and the first gap is open, the tumor can be resected via the inferior approach to the optic cross first; if the optic cross is anterior and the first gap can not reveal the tumor, the tumor can be resected via the transendoplanar approach to the posterior optic cross or anterior and inferior part of the third ventricle. After resection of the tumor via the endplate to relieve the compression of the optic chiasm, the first gap may be opened up, which is convenient for resection of the tumor below the optic chiasm. Intraoperatively, a combination of the transoptic approach and the endplate approach is often required, as the blood vessels in the tumor peritumor can be cut off by pre-electrocoagulation, and the transoptic approach facilitates the identification and protection of the pituitary stalk. We believe that unilateral frontal flap craniotomy is sufficient and bilateral craniotomy is usually not required. Advantages of the anterior longitudinal fissure approach include: (1) adequate exposure of the anterior gap of the optic intersection, the endplate, and the anterior arterial complex; (2) transendoparietal approach facilitates the resection of tumors in the anterior and inferior portions of the third ventricle; (3) less interference with the internal carotid artery; and (4) relatively simple technical operation. The disadvantages of this approach include: (1) long working distance; (2) the operation angle and the visual field angle are parallel to each other, and the deep fine operation is affected; (3) it is easy to damage the supraoptic area penetrating blood vessels; (4) poor exposure below the optic intersection and at the base of the third ventricle; (5) poor exposure of tumors in the lateral side and slope invasion; (6) easy to injure the olfactory nerve, but it is superior to the infra-frontal approach; (7) easy to develop frontal lobe infarcts and cerebral swelling in the postoperative period; ( (8) It is necessary to open the frontal sinus, which also has the risk of cerebrospinal fluid leakage. 3.Transcallosal-hyaline septal space-intercallosal approach The patient is placed in supine position, the head is elevated and tilted upward by 30 degrees, and the head frame is fixed. A unilateral skin incision was made, with the posterior border at the coronal suture and the medial side slightly over the midline (no more than 1 cm). Two bone holes were drilled along the midline, with the posterior border of the bone flap to the level of the coronal suture, medially crossing the midline by about 0.5 cm to facilitate retraction of the superior sagittal sinus to the contralateral side. The dura mater is cut and flipped to the midline, and the dura mater is pulled open to the contralateral side with sutures to facilitate vertical manipulation. The brain surface in this region is generally free of coarse draining veins, and if larger draining veins are found, the direction of entry can be adjusted anteriorly and posteriorly, so the longitudinal diameter of the bone window should not be too small. Strict midline sharp separation, the hemisphere to the lateral retraction, downward separation reveal reveal the corpus callosum, longitudinal incision of the anterior corpus callosum of about 2 cm, into the interstitial cavity of the pellucid septum. The septum lucidum is further separated on both sides, and the inferior border of the septum lucidum is the fornix, which is carefully separated bilaterally to enter the third ventricle. Good spatial orientation is required to perform this approach, otherwise it is easy to become disoriented, remembering that the general direction of work is vertically from the coronal suture to the line of the bicuspid auricular canal. Separation of the septum pellucidum often allows access to the lateral ventricle, and it is often not possible to be certain which ventricle has been accessed; the position of the interventricular foramen can be used to localize the approach. If the tumor is cystic, puncture is feasible. The aspiration of cystic fluid must be slow, and the wall of the cyst should be decompressed slowly to prevent tension injury of the brain tissue. It is important to distinguish whether the tumor is a completely triple intraventricular type or whether it is protruding from below. Tumors protruding into the ventricles have arachnoid structures on the surface. There is a band of glial proliferation between the wall of the tumor capsule and the wall of the ventricle, which should be strictly separated at this interface. After resection of the posterior pole of the tumor, the superior opening of the cerebral aqueduct is visible, and the anterior and inferior parts of the third ventricle can be revealed by retracting the knee of the corpus callosum anteriorly. The basilar artery can be seen after resection of the tumor protruding into the ventricle, and care should be taken to protect the branches of the basilar artery and the surrounding arachnoid membrane, and the pituitary stalk can not be confirmed in general. The advantages of transcallosal-hyaline septal space-intercallosal approach include: (1) under direct vision, the visual field is fully revealed; (2) it can avoid the damage of the blood vessels of the Willis ring; (3) it is conducive to the total resection of the tumor, and the technical operation is easy to master. The disadvantages are: (1) long working distance; (2) easy to damage the hypothalamus structure, can not recognize the pituitary stalk; (3) poor exposure of the anterior and inferior parts of the three chambers, the pterygoid saddle and the lateral lesions; (4) unskilled operation, easy to get lost; (5) postoperative patient reaction, the risk of ventriculitis and obstructive hydrocephalus, delayed hospital discharge. The patient should take the supine position, elevate the shoulder of the same side, and fix the head frame. Elevate the head 15 degrees above the heart level to facilitate venous return. The neck is stretched and the head is angled backward and downward so that the frontal zygomatic process is in a high position, and the head is rotated to the contralateral side by 25-35 degrees. The skin incision starts 1 cm anterior to the ear screen at the superior border of the zygomatic arch and arcs upward to 2 cm adjacent to the midline hairline, with the incision always within the hairline. An interfascial flap was taken in the temporal region, and the temporalis muscle was retracted posteriorly and inferiorly. The flap was reniform, with the frontal bone window near the base of the anterior cranial fossa to increase exposure of the anterior interspace of the optic cross, and the temporal side near the base of the middle cranial fossa, with the pterygoid crest abraded to the pterygoid tuberosity. The dura mater was cut with the pterygoid crest as the center, and the arachnoid of the lateral fissure pool was sharply separated to adequately release cerebrospinal fluid for decompression. Continuing the deeper separation along the lateral fissure pool to the bifurcation of the internal carotid artery, the frontal lobe was retracted with an automated brain plate to reveal the structures and lesions in the saddle region. The separation of the suprasaddle pool followed a three-step surgical dissection method, in which the arachnoid membrane of the ipsilateral optic nerve and optic-crossing pool was first sharply clipped, cerebrospinal fluid was released, and the frontal lobe was again lifted to fully reveal the anterior optic-crossing interspace, and the endplates; then, the arachnoid membrane between the optic nerve and the internal carotid artery was sharply detached, and the temporal lobe was retracted posteriorly to reveal the posterolateral internal carotid artery hiatus and to expose the cerebellar pontine rim, the motoneural nerve, posterior communicating artery, and the interpeduncular pool; and, finally, the The frontal lobe was further retracted to fully expose segment A1 of the anterior artery, the anterior communicating artery, the anteromedial aspect of the contralateral optic nerve, and the ipsilateral posterior bed processes. Due to the influence of tumor patho-anatomic features, structures such as optic nerve, optic cross, internal carotid artery and anterior artery will be displaced and distorted, and the corresponding anatomical gaps will be altered, with some shrinking or even disappearing, and some opening up. The endplates are easy to open in the wing point approach, but the visual field is not well revealed after entering the tricuspid ventricle, especially the ipsilateral ventricular wall is poorly exposed, and the opening of the endplates can be used as an auxiliary means of resecting the tumor in the wing point approach. The separation of the tumor should follow the principle of first easy and then difficult, i.e., start the operation from the easiest to separate from the surrounding structures first. Surgical operation should try to utilize all anatomical gaps and avoid operating in the blind area of the surgical field. When separating the tumor, it is inevitable to pull the peripheral neurovascular structures, and the large blood vessels are more tolerant to pulling than the neural structures, so the blood vessels can be pulled appropriately during the operation, avoiding the pulling of the neural structures, and, of course, in the case of significant atherosclerosis, the operator should also minimize the interference with the internal carotid artery. The operation should be patient; there is less space to operate in the beginning, and as the tumor is separated and resected, the space will become larger, and the tumor protruding into the third ventricle may be trapped, and the tumor at the pedunculopontine pool may be moved forward with the fluctuation of the cerebrospinal fluid. Many technical errors may occur during the wing-point approach, and common technical errors are as follows: (1) Injury to the frontotemporal branch of the facial nerve: when making skin, fascia, and muscle incisions, the operator must be familiar with the travel of the motor branch of the facial nerve innervating the frontalis muscle. It is difficult for the operator to find this facial nerve branch during surgery. Separation under the capitellar tendon membrane, excessive retraction and electrocautery are all prone to cause injury. Generally speaking, separation close to the surface of the deep temporal muscle fascia can avoid injury, and excessive separation between the capitellar tendon membrane and the anterior superficial temporal muscle fascia should be avoided. The superficial temporal artery should also be given enough attention, and its thick branches should be preserved as much as possible. (2) Inappropriate bone flap position: this is an error that should be avoided diligently and can be completely avoided with careful planning. Inadequate abrasion of the pterygoid crest and the fact that the frontal bone window margin is not close to the base of the skull impede the exposure of the deeper structures. (3) Inadequate decompression of brain tissue: Adequate brain tissue decompression is necessary for safe and effective retraction of brain tissue and exposure of the area below the third ventricle and the suprasellar region. If high intracranial pressure is found prior to clipping the dura, available measures include hyperventilation, lumbar puncture to release cerebrospinal fluid, and injections of mannitol, diuretics, and steroids. If this is not effective, the head can be repositioned to facilitate venous return, and the frontal horn of the lateral ventricle can be punctured to release ventricular fluid. After opening the dura mater, the cerebrospinal fluid should be fully released in the lateral fissure pool and the internal carotid artery pool, and the brain tissue should be pulled with an automatic retractor after the brain tissue is collapsed satisfactorily. (4) Improper use of automatic retractor: automatic retractor position is too deep or too shallow, poor exposure of deep structures, frontal retractor placed near the ipsilateral olfactory bulb is good; automatic retractor force is too large or frequently adjusted, resulting in swelling or hemorrhage of the brain tissue Pteronasal point approach after the operation may occur in the following surgical complications related to the operation: (1). Facial swelling: it tends to be noticeable and does not require special treatment and usually subsides 1 week after surgery. (2). Injury to the frontotemporal branch of the facial nerve: incomplete eyelid closure, loss of frontal lines, how to prevent this complication has been described earlier. (3). Temporal muscle atrophy: temporal muscle fiber injury, deep temporal artery injury, improper temporal muscle tone and denervation can cause temporal muscle atrophy, excessive cauterization and pulling of temporal muscle should be avoided during surgery. Temporalis muscle atrophy not only affects cosmetic appearance, but also affects the patient’s quality of life. (4). Ocular subsidence and fluctuant proptosis: when cranial orbital zygomatic approach is used, care should be taken to preserve part of the orbital apex connected to the orbital spine to form an orbital bone flap, and not to overbite the lateral orbital wall. The greatest advantage of the wing point approach is the ability to visualize the lesion from multiple angles, followed by the shortest working distance, which facilitates the identification and protection of the pituitary stalk. The main disadvantage of the wing point approach is that the technique is complicated and the doctor should have skillful microscopic operation; secondly, the wing point approach is not as good as the anterior approach in revealing the end plate, and the internal carotid artery may be occluded after the operation for the patients with serious atherosclerosis. 5.Transsphenoidal approach Surgical operation method is the same as transsphenoidal pituitary adenoma resection. The transsphenoidal approach is the earliest approach used in craniopharyngioma surgery. Since there is no need to open the skull and pull the brain tissue, the operation is safe and less damaging. Surgery can relieve the compression of the tumor on the optic nerve and the anterior pituitary gland, and improve the symptoms of visual impairment and endocrine disorders. However, because craniopharyngiomas tend to grow upward toward the saddle, are tough and prone to cystic degeneration, calcification, and adhesion, it is difficult to remove the tumor completely by the transsphenoidal approach. However, with the increasing maturity of neuroendoscopic techniques, reports of transsphenoidal approach for resection of craniopharyngiomas are beginning to increase. We believe that the transsphenoidal approach can be used as a complementary approach to craniopharyngioma resection. Strategies and techniques of tumor resection According to the size of the tumor, we usually classify craniopharyngiomas into four types, those less than 2 cm are small, those between 2 and 4 cm are medium-sized, those between 4 and 6 cm are large, and those more than 6 cm are giant. For small craniopharyngiomas, it is relatively easy to completely resect the tumor, regardless of whether the tumor is cystic or solid, and whether it is located in the saddle, suprasellar or intracerebral ventricle. From clinical practice, in most cases, solid craniopharyngiomas are easy to be completely resected, while cystic craniopharyngiomas are less easy to be completely resected because of their more pronounced adhesion to the surrounding neurovascular structures. Most neurosurgeons believe that total resection of large and giant craniopharyngiomas is very difficult, and postoperative complications are numerous and serious. However, Choux does not think so. He believes that there is no obvious relationship between tumor size and the degree of tumor resection, and that the distal part of the tumor is mostly cystic, which can be resected without obvious adhesions. We believe that the key to successful and complete resection of the tumor is surgical exposure, and the biggest obstacle to surgical exposure of craniopharyngioma is the important neural and vascular structures in the saddle region itself. Surgical resection of lesions growing forward and downward and laterally is relatively easy, and exposure of lesions growing backward and upward is difficult. For cystic craniopharyngioma, the first step is to puncture and remove the cystic fluid, the process should be slow, after the removal of the cystic fluid, the tumor will collapse to the center, at this time, do not rush to remove the cystic wall, you can pull the collapsed pouch of cystic wall to separate up to the total resection of the tumor, if the cystic wall is removed early in the piecemeal process, the cystic wall may be retracted deeper resulting in the tumor residue. If the total resection is difficult to complete, the cystic wall of the tumor is thin and scattered with small calcified spots. In this case, the cystic wall is thin and brittle, and the fractured cystic wall fragments are often tightly adhered to the deep neurovascular structures.