Surgical treatment of craniopharyngioma has always been a major challenge for neurosurgeons. The goal of surgical treatment is total resection of the tumor. 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 to the surrounding structures, and the experience of the surgeon. The achievement of good surgical outcome depends more on the treatment decision and surgical technique of the neurosurgeon. There are several surgical approaches for the surgical treatment of craniopharyngioma. The choice of surgical approach depends on the site of the tumor, its growth pattern and the experience of the surgeon, and should be made on the basis of adequate preoperative evaluation. Choux (1991) reported a collaborative study of 415 cases: unilateral inferior frontal approach accounted for 46%, pterygoid point approach accounted for 27%, transdiscal sinus approach accounted for 8%, transventricular approach accounted for 3%, and bilateral inferior frontal approach accounted for 3%. The bilateral inferior frontal approach accounted for 2.6%, and the transcallosal approach accounted for 0.7%. The inferior frontal approach is suitable for intra-saddle craniopharyngioma, especially for cystic tumors or small solid tumors growing anteriorly, with good conditions of the anterior visual interval; the anterior longitudinal approach is mainly suitable for supra-saddle and anterior third ventricle tumors, and tumors entering the three ventricles can be resected through the end plate; the pterygoid approach is mainly suitable for supra-saddle tumors growing in the skull base, which can be exposed from multiple angles; the transcallosal approach is suitable for intraventricular and protruding ventricle tumors; the transcallosal approach is suitable for intra-ventricular tumors and tumors entering the ventricles. The transcallosal approach is suitable for intracerebroventricular and ventricular tumors; the transsphenoidal approach is suitable for lesions with limited growth in the pterygoid saddle; the infratemporal approach is suitable for a few tumors growing mainly toward the slope and the pontocerebellar angle. The pterygopoint approach, the inferior frontal approach and the anterior longitudinal approach are the most common surgical approaches for craniopharyngioma. 1.Subfrontal approach The patient is placed in supine position with the head above the level of the heart and the head frame is fixed. A coronal incision is made within the hairline, and the skin incision on the surgical side should be low, usually choosing a unilateral right frontal opening. The bottom of the flap is turned to the superior border of the frame, taking care to protect the supraorbital nerve. A right frontal bone flap is made, medially to the midline, anteriorly to the supraorbital rim to fully reveal the base of the anterior cranial fossa, and laterally to the level of the keyhole and pterygoid point to increase lateral exposure. The dura is cut along the superior orbital rim in an arc, and the dura is turned toward the skull base. The lateral fissure pool is explored along the lateral aspect of the anterior cranial fossa, and the arachnoid membrane of the lateral fissure pool is cut to release cerebrospinal fluid. After the cerebral pressure decreases until the brain tissue is satisfactorily collapsed, the frontal lobe is lifted posteriorly and superiorly with a fixed retractor brain plate to reveal the saddle area, and care is taken to avoid excessive stretching to damage the frontal brain tissue during the operation. The ipsilateral olfactory nerve is freed to the olfactory bulb and protected. The arachnoid membrane of the suprasellar pool is sharply separated to fully expose the optic nerve, optic cross and internal carotid artery. The arachnoid membrane on the surface of the tumor is cut and further separated in the anterior space of the optic cross. At this time, care is taken to protect the perforating vessels of the anterior circulation and not to blindly cauterize them. If the tumor is collapsed, the tumor wall or saddle septum should be cut open to further separate and remove the tumor. Craniopharyngioma is not rich in blood supply, do not over cauterize the tumor during resection and pay attention to identify and protect the pituitary stalk and pituitary gland. The separation of the tumor can be performed in the first gap or the second gap, or the end plate can be opened as needed and separated along the wall of the tumor as much as possible, so that the optic nerve, optic cross and internal carotid artery can be easily protected and the residual tumor can be avoided. The subfrontal approach is a more familiar route for neurosurgeons. The advantages are that it is simple to operate, the conditions and technical requirements are not high, and it is easy to master. The disadvantages are: (1) the frontal sinus needs to be opened, and there is a possibility of cerebrospinal fluid nasal leakage; (2) the supraorbital nerve and olfactory nerve are easily damaged; (3) the lateral aspect of the pterion and the posterior aspect of the optic cross are poorly exposed, which cannot meet the needs of multi-angle operation and poorly expose the large and complex tumors; (4) the end plate is not fully exposed, and the operation in the three ventricles is limited. 2. Anterior longitudinal approach The patient’s position and craniotomy method are the same as that of inferior frontal approach, but the exposure of the midline side is larger. After the dura is cut, the cerebrospinal fluid is also released from the lateral fissure pool first, and then separated from the longitudinal fissure after the brain pressure drops and the frontal lobe collapses, and the small frontal lobe drainage vein can be pre-cut. Both frontal lobes are separated first to the base of the middle cranial fossa and then posteriorly to the knee of the corpus callosum, fully exposing the end plate and anterior arterial complex. At this point, the tumor is often seen to protrude upward through the anterior space of the optic cross, and the tumor often displaces the optic cross and anterior communicating artery posteriorly and superiorly. The arachnoid membrane surrounding the tumor is separated to expose the surrounding structures. If the tumor is cystic, the surrounding area should be protected with a cotton pad before puncture to prevent spillage and spread of the cystic fluid. The outer wall of the suprasellar portion of the tumor is covered by the arachnoid membrane, which makes the separation of the tumor from the optic nerve and large blood vessels easy. There are often calcified deposits in the cystic cavity of the tumor. In most cases, the calcification is gritty and easy to separate and remove, but sometimes the calcified mass is hard and requires 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 interval is open, the tumor can be resected first through the inferior optic cross approach; if the optic cross is anterior and the first interval cannot reveal the tumor, then the tumor behind the optic cross or the anterior lower part of the three chambers can be resected through the end plate approach. If the tumor cannot be revealed in the first interval, then a transendoscopic approach can be chosen to remove the tumor behind the optic cross or in the anterior and inferior part of the tricompartment. The blood supply vessels on the tumor envelope can be cut by pre-electrocoagulation, and the transcranial approach below the optic cross can facilitate the identification and protection of the pituitary stalk. We believe that a unilateral frontal flap approach is sufficient to meet the need, and generally no bilateral approach is needed. The advantages of the anterior longitudinal approach are: (1) it can fully expose the anterior gap of the optic cross, the end plate and the anterior arterial complex; (2) the transendocranial approach facilitates resection of the tumor in the anterior lower part of the three ventricles; (3) there is less interference with the internal carotid artery; and (4) the technique is relatively simple. The disadvantages of this approach are: (1) long working distance; (2) parallel operation angle and field of view angle, deep fine operation is affected; (3) easy to damage the supraoptic area penetrating vessels; (4) poor exposure below the optic cross and the base of the three ventricles; (5) poor exposure of tumor with lateral and slope invasion; (6) easy to damage the olfactory nerve, but better than inferior frontal approach; (7) easy to develop postoperative frontal lobe infarction and brain swelling; ( (8) need to open the frontal sinus, and also have the risk of cerebrospinal fluid nasal leakage. 3.Transcallosal-clear septal space-interdome approach The patient is placed in a supine position with the head elevated and tilted upward at 30 degrees, and the head frame is fixed. A unilateral skin incision is made, with the posterior border at the coronal suture and slightly over the midline medially (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 about 0.5 cm above the midline to facilitate the contralateral retraction of the superior sagittal sinus. The dura is cut and turned toward the midline, and the dura is pulled contralaterally with sutures to facilitate vertical manipulation. The brain surface in this area is generally free of thick draining veins, and if larger draining veins are found, the direction of entry can be adjusted back and forth, so the longitudinal diameter of the bone window cannot be too small. The hemispheres are held apart laterally and the corpus callosum is revealed by strict midline sharp separation, and the anterior part of the corpus callosum is incised longitudinally for about 2 cm to enter the interstitial space of the septum pellucidum. Further separate the two sides of the septum pellucidum, the inferior border of which is the fornix, and carefully separate the bilateral fornix to enter the third ventricle. Good spatial orientation is required to perform this approach, otherwise it is easy to get disoriented, remembering that the general working direction is the vertical direction from the coronal suture to the line connecting the two auricles. The lateral ventricles can often be entered when separating the hyaline septal space. It is often not certain which lateral ventricle is entered, and the position of the interventricular foramen can be referred to for localization. If the tumor is cystic, puncture is feasible. The aspiration of cystic fluid must be slow, and the cyst wall must be slowly decompressed to prevent tensional damage to the brain tissue. It is important to distinguish whether the tumor is completely intraventricular type or protrudes from below. Tumors that protrude into the ventricles have arachnoid structures on the surface. There is a glial proliferation zone between the tumor capsule wall and the ventricular wall, which should be strictly separated at this interface. After resection of the posterior pole of the tumor, the superior port of the cerebral aqueduct can be seen, and the anterior lower part of the three ventricles can be revealed by drawing the knee of the corpus callosum forward. After resection of the tumor protruding into the ventricles, the basilar artery can be seen. Attention should be paid to protect the branches of the basilar artery and the surrounding arachnoid membrane, and the pituitary stalk generally cannot be confirmed. The advantages of the transcallosal-hypophyseal septal gap-interdome approach are: (1) under direct vision, the visual field is fully exposed; (2) it can avoid the injury of the Willis ring penetrating vessels; (3) it facilitates total tumor resection and the technical operation is easy to master. The disadvantages are: (1) long working distance; (2) easy to damage the hypothalamic structures and cannot identify the pituitary stalk; (3) poor exposure of the anterior lower part of the three chambers, the pterygoid saddle and lateral lesions; (4) unskilled operation, easy to lose direction; (5) postoperative patient reaction, the risk of ventriculitis and obstructive hydrocephalus, delayed discharge. 4. Pterygopoint approach The patient is placed in a supine position with the ipsilateral shoulder padded and the head frame fixed. The head is elevated 15 degrees above the level of the heart to facilitate venous return. The neck is extended and the head is angled posteriorly downward so that the frontal zygomatic process is in an elevated position and the head is rotated 25 to 35 degrees to the opposite side. The skin incision starts 1 cm in front of the ear screen at the upper edge of the zygomatic arch and arcs upward to 2 cm next to the midline hairline, with the incision always inside the hairline. The interfascial flap was taken in the temporal region and the temporalis muscle was retracted posteriorly and inferiorly. The flap is kidney-shaped, with the frontal bone window near the base of the anterior cranial fossa to increase exposure of the anterior visual cross space, and the temporal side near the base of the middle cranial fossa, with the pterygoid crest abraded to the pterygoid pterygoid. The dura was cut with the pterygoid crest as the center, and the arachnoid membrane of the lateral fissure pool was sharply separated to fully release the cerebrospinal fluid for decompression. Continue to separate deeper along the lateral fissure pool to the bifurcation of the internal carotid artery, and retract the frontal lobe with an automatic cerebral plate to reveal the structures and lesions in the saddle area. The separation of the suprasellar pool followed a three-step surgical anatomy, first sharply cutting the arachnoid membrane of the ipsilateral optic nerve and optic cross pool, releasing cerebrospinal fluid, and lifting the frontal lobe again to fully expose the anterior optic cross space and the end plate; then, sharply separating the arachnoid membrane between the optic nerve and internal carotid artery, pulling the temporal lobe backward to expose the lateral gap of the internal carotid artery, exposing the cerebellar curtain margin, arteriolar nerve, posterior communicating artery, and interpeduncular pool; finally. The frontal lobe was further retracted to fully expose the A1 segment of the anterior artery, the anterior communicating artery, the anterior medial aspect of the contralateral optic nerve and the ipsilateral posterior bed process. Due to the influence of the pathological and anatomical features of the tumor, structures such as the optic nerve, optic cross, internal carotid artery and anterior artery will be displaced and distorted, and the corresponding anatomical gaps will be changed, some shrinking or even disappearing, and some opening up. The end plate is easy to open during the pterygopoint approach, but the visual field after entering the three ventricles is not well exposed, especially the ipsilateral ventricular wall is poorly exposed, and opening the end plate can be used as an adjunct to the pterygopoint approach to resect the tumor. The separation of the tumor should follow the principle of easy first and then difficult, that is, the operation should start from the easiest separation from the surrounding structures. The surgical operation should try to utilize all anatomical gaps and avoid operating in blind areas of the operative field. The large blood vessels tolerate the pulling better than the nerve structures, therefore, the blood vessels can be pulled appropriately during the operation to avoid pulling the nerve structures, of course, in the case of obvious atherosclerosis, the operator should also minimize the interference with the internal carotid artery. The operation should be patient. At the beginning, there is less space for operation, and as the tumor is separated and resected, the space will become larger, and the tumor protruding to the three ventricles may be trapped, and the tumor at the interpeduncular pool may move forward with the fluctuation of cerebrospinal fluid. Many technical errors may occur during the pterygopoint approach, and the 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 to detect this branch of the facial nerve during surgery. Separation under the capitellum, excessive traction and electrocautery can easily cause injury, and generally speaking, separation close to the surface of the deep fascia of the temporalis muscle can avoid injury. The superficial temporal artery should also be given sufficient 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 by careful planning. Inadequate grinding of the pterygoid crest and the frontal bone window margin not close to the skull base impede the exposure of deep structures. (3). Inadequate brain tissue decompression: Adequate brain tissue decompression is necessary to safely and effectively retract brain tissue and expose the subventricular and suprasellar regions. If high intracranial pressure is found prior to dural clipping, available measures include hyperventilation, lumbar puncture to release cerebrospinal fluid, and injection of mannitol, diuretics, and steroid hormones. If this does not work, the head may be repositioned to facilitate venous return and the frontal horn of the lateral ventricle may be punctured to release ventricular fluid. After opening the dura, cerebrospinal fluid should be released sufficiently in the lateral fissure pool and internal carotid artery pool, and brain tissue collapse should be satisfied before retracting brain tissue with an automatic retractor. (4). Improper use of the automatic retractor: the position of the automatic retractor is too deep or too shallow, poor exposure of deep structures, frontal retractor placed near the ipsilateral olfactory bulb is good; excessive force of the automatic retractor or frequent adjustment, resulting in brain tissue swelling or hemorrhage Possible surgery-related complications after pterygoid approach are: (1). Facial swelling: it is often obvious, no special treatment is needed, and will generally subside 1 week after surgery. (2). Injury to the frontotemporal branch of the facial nerve: incomplete eyelid closure and loss of frontal lines. (3). Temporal muscle atrophy: temporal muscle fiber injury, deep temporal artery injury, improper temporal muscle tension and denervation can cause temporal muscle atrophy, and excessive cautery and pulling of the temporal muscle should be avoided during surgery. Temporal muscle atrophy not only affects the cosmetic appearance, but also affects the patient’s quality of life. (4). Eye subsidence and fluctuating proptosis: When cranial orbital zygomatic approach is performed, attention should be paid to retaining part of the orbital apex connected to the orbital spine to form an orbital bone flap and not to excessively occlude the lateral orbital wall. The greatest advantage of the pterygopoint approach is the ability to reveal 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 pterygopoint approach is that it is technically complex and the surgeon must be skilled in microscopic operation; secondly, the pterygopoint approach does not reveal the endplate as well as the anterior approach, and the internal carotid artery may be occluded after surgery in severe atherosclerosis. 5.Transpalpebral sinus approach The operation method is the same as that of transpalpebral sinus pituitary adenoma resection. The transsphenoidal approach is the earliest approach used for craniopharyngioma surgery. Since there is no need to open the cranium and pull the brain tissue, the operation is safe and less damaging. However, because craniopharyngioma grows up to the saddle and has a tough texture, and is prone to cystic degeneration, calcification and adhesions, it is difficult to remove the tumor completely with the transsphenoidal approach. However, with the increasing maturity of neuroendoscopic techniques, reports of transsphenoidal approach for craniopharyngioma resection have started 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 tumor, we usually classify craniopharyngiomas into four types: small ones less than 2 cm, medium ones between 2 and 4 cm, large ones between 4 and 6 cm, and huge ones over 6 cm. For small craniopharyngioma, regardless of whether the tumor is cystic or solid, and regardless of whether it is located in the saddle, suprasellar or intracerebroventricular, it is relatively easy to be completely resected. From clinical practice, in most cases, solid craniopharyngiomas are easy to be completely resected, while cystic craniopharyngiomas have more obvious adhesions to the surrounding neurovascular structures and are not easy to be completely resected. Most neurosurgeons believe that total resection of large and giant craniopharyngiomas is very difficult, and postoperative complications are numerous and severe. He believes that there is no significant relationship between tumor size and the extent of tumor resection, and that the distal part of the tumor is mostly cystic, and this part of the tumor is usually resectable without obvious adhesions. We believe that the key to successful and complete resection of tumor is surgical exposure. The biggest obstacle to surgical exposure of craniopharyngioma is the important nerve and vascular structures in the saddle area itself. It is relatively easy to surgically remove lesions that grow downward and laterally, but difficult to expose lesions that grow backward and upward. For cystic craniopharyngioma, first of all, the cystic fluid should be removed by puncture, and the process should be slow. After the cystic fluid is removed, the tumor will collapse toward the center, at this time, do not rush to remove the cystic wall, you can separate up to total removal of the tumor by pulling the collapsed pouch-like cystic wall, if the cystic wall is removed in pieces early, the cystic wall may retract to the deeper part causing tumor residue. In such cases, the wall is thin and brittle, and the fractured wall fragments are often closely adhered to the deep neurovascular structures. The relationship between the tumor and the three ventricles, pituitary stalk and blood vessels should be correctly understood and handled during surgery. Those tumors located outside the triventricular ventricle which only elevate the bottom of the triventricular ventricle are easier to resect and will not cause serious damage to the hypothalamus; those tumors which break through the bottom of the triventricular ventricle and enter the triventricular ventricle are not easy to be completely resected and easily damage the hypothalamus; those tumors completely located in the triventricular ventricle are also easy to be completely resected, but easily damage the hypothalamus. Choux believes that the presence of non-functional glial proliferative zone is conducive to total resection of the tumor without serious hypothalamic injury. Pathologically confirmed craniopharyngiomas with significant glial proliferation bands often protrude finger-like into the brain parenchyma, and the tumor adheres significantly to the brain tissue. Therefore, we believe that in the case of obvious glial proliferation zone around the tumor, it is difficult to separate and deliver the tumor smoothly through the pterygoid point approach or inferior frontal approach, and the tumor can be removed strictly along the non-functional glial proliferation zone under direct vision through the corpus callosum-interdome approach, thus reducing the damage to brain tissue. During craniopharyngioma surgery, care should be taken to find the pituitary stalk. The pituitary stalk is easy to identify and protect during surgery for small craniopharyngiomas, but large craniopharyngiomas often displace the pituitary stalk laterally or posteriorly, making it difficult to identify intraoperatively. The surface of the pituitary stalk has characteristic striated structures formed by portal vessels, and the central saddle septum is its relatively fixed location. Hoffman and Sweet believe that the pituitary stalk should be sacrificed to eliminate the source of recurrence of craniopharyngioma, and Rougerie and Konovalov advocate preserving the pituitary stalk as much as possible, even if a small amount of tumor remains. We believe that total tumor removal is more important than pituitary stalk preservation, especially in children. We believe that the pituitary stalk should be preserved as much as possible anatomically, especially in adult patients, to reduce the complications of severe postoperative endocrine hypoplasia and to improve the quality of patient survival. The pterygopoint approach is easier to identify and protect the pituitary stalk than the inferior frontal approach and anterior longitudinal fissure approach. The pterygopoint approach can operate at multiple angles with short working distance, which facilitates sharp separation of the pituitary stalk and tumor. Intraoperative electrocoagulation should be reduced to protect the blood supply to the pituitary stalk and pituitary gland. Craniopharyngiomas often distort and displace blood vessels and rarely encapsulate or occlude large vessels. Posterior craniopharyngioma of the optic cross type may displace the A1 segment of the anterior artery anteriorly or inferiorly and displace the basilar artery posteriorly. Craniopharyngiomas often adhere to the arachnoid membrane surrounding the great vessels and generally do not adhere to the great vessels themselves, but may adhere to the perforating vessels of the ring of Willis. Vascular complications of craniopharyngioma surgery include vasospasm, internal carotid artery tears, and delayed aneurysmal dilatation of the internal carotid artery. Craniopharyngioma generally does not adhere to the brainstem or basilar artery, and the compressed brainstem can be repositioned after surgery.