Giant tumors (≥4 cm in diameter) in the saddle region grow upward behind the visual crossover, filling the inter-foot fossa, pushing out the hypothalamus, deflating the tricuspid ventricle, and even developing into the upper slope, with a low rate of surgical total resection and many postoperative complications, which is one of the difficult problems faced by neurosurgeons nowadays. We call the area surrounded by the motor nerve, cerebral peduncle, optic bundle and optic crossings as the pedunculopontine fossa area. 56 cases of giant tumors in the pedunculopontine fossa area were treated by microsurgery with the modified wing-point approach from 1995.1 to 2009.4, and satisfactory results were achieved, which are summarized as follows. Zhang Rongwei, Department of Neurosurgery, Jinan Military General Hospital, Jinan, China 1 Data and Methods 1.1 General information There were 56 cases of giant tumors in the pedunculated fossa area, of which 37 cases were male, 19 cases were female, and the age ranged from 6 to 58 years. Female 19 cases; age 6-58 years old, average 38 years old; disease duration 1 week to l0 years, average 0.8 years. Clinical manifestations: headache, vomiting and other intracranial hypertension manifestations in 32 cases, unilateral or bilateral vision loss in 52 cases. There were 50 cases of unilateral or bilateral temporal visual field blindness, 5 cases of menstrual disorders or amenorrhea, infertility, lactation, 8 cases of decreased libido, 5 cases of acromegaly, 3 cases of gigantism, 19 cases of polydipsia, polyuria, and 11 cases of developmental retardation. There were 3 cases of ocular motility disorders and 15 cases of primary optic papillary atrophy in the fundus. 1.2 Imaging examination Imaging examination and clinical staging All the patients in this group underwent CT and MRI examination, and the tumor diameter was 4 cm in 7 cases, more than 4 cm in 49 cases, and the largest one was 5 cmx6 cmx6.2 cm. Among them, there were 13 cases of partial cystic degeneration, and 8 cases of stroke; the third ventricle was partially compressed in 38 cases, and completely compressed with symmetric enlargement of the lateral ventricles in 18 cases. The tumor progressed to the upper slope in 11 cases, and invaded to the cavernous sinus in 9 cases; CT scan had scattered or peripheral calcification in the pedunculopontine fossa area in 15 cases. Preoperative diagnoses: pituitary tumor in 27 cases, craniopharyngioma in 15 cases, meningioma in 9 cases, optic cross glioma in 2 cases, germ cell tumor in 2 cases, and misshapen tumor in 1 case. In all cases, MRI was reviewed 1 week to 1 month after surgery to compare with preoperative MRI and observe the tumor resection. Postoperative pathological diagnosis: 25 cases of pituitary tumor, 14 cases of craniopharyngioma, 9 cases of meningioma, 2 cases of optic cross glioma, 3 cases of hypothalamic glioma, 2 cases of germ cell tumor, 1 case of misshapen tumor. 1.3 Surgical methods Under general anesthesia, the modified Yasargil pterygoid approach was used to open the cranium from the right side in this group of cases. Under the operating microscope, the lateral fissure pool and the basal cerebral pool were dissected sequentially, and if there was cystic degeneration, the cyst was first broken and the fluid was discharged to obtain space, and the tumor was not cut in a hurry, and the 5 anatomical gaps in the saddle area were firstly fully dissected to reveal the tumor. Try to identify the relationship between the tumor and the optic nerve, optic cross, optic tract, internal carotid artery, anterior cerebral artery, middle cerebral artery, posterior communicating artery, arterial nerve and pituitary stalk. In principle, the tumor should be resected in blocks according to the order of the first, second, fifth and third gaps, first in the saddle and then on the saddle. For the tumor protruding into the part of the third ventricle, don’t blindly underdraw and resect it, and the tumor can be scraped with a circular scraping spoon within the package feel to maximize the protection of the function of the hypothalamus. After complete resection of the tumor, it should be rinsed, hemostasis and press the jugular vein , no bleeding before closing the skull. 2 Results 2.1 Efficacy and complications There were 46 cases of total resection and 10 cases of subtotal resection of tumors in this group, including 25 cases of pituitary tumor, 23 cases of total resection and 2 cases of subtotal resection; 14 cases of craniopharyngioma, 9 cases of total resection and 5 cases of subtotal resection; 9 cases of meningioma, all of which were totally resected; 2 cases of optic cross glioma, 1 case of total resection; 3 cases of hypothalamus glioma, 2 cases of total resection; 2 cases of germ cell tumors, 1 case of total resection; 1 case of misshapen tumor. Two cases of germ cell tumor, one case of total resection; one case of misshapen tumor, total resection. None of the cases died after surgery. The tumors were not completely resected, and 10 cases were treated with Gamma Knife or conventional radiation therapy after surgery. The symptoms of high intracranial hypertension were significantly reduced 1 week after surgery. Of the 52 cases with decreased visual acuity, 41 cases showed significant improvement in visual acuity, 8 cases showed insignificant changes, and 3 cases showed worsening of unilateral visual impairment. Lactation of l5 cases 9 cases stopped lactation after operation and 6 cases were reduced. Postoperative urolithiasis appeared in 25 cases, of which preoperative polydrinking and polyuria were aggravated in 19 cases, after treatment 5 cases of urolithiasis ceased within 1 week, and 20 cases were discharged from the hospital and needed to be applied with long-acting urolithiasis. There were 6 cases of central hyperthermia, all of which returned to normal within 1 week after surgery. Electrolyte disorders in 5 cases improved after several days of treatment. Nine cases of hypopituitarism were treated with replacement therapy. 2.2 Follow-up 52 cases were followed up for 2 months to 14 years, with an average of 3.5 years. 51 cases had a normal life, and 1 case of craniopharyngiosis died of a grand mal seizure half a year after the operation because of failure to adhere to the treatment of urolithiasis. In 4 cases with more than 2 years of follow-up, the lesions were significantly larger than those shown in MRI 1 week after surgery, which was clearly tumor recurrence. 3.Discussion 3.1 Differential diagnosis of tumors in the pedunculopontine fossa area Tumors in the pedunculopontine fossa area have not been reported in the past, and they are usually described as saddle region tumors, giant saddle region tumors, giant pituitary tumors, and giant craniopharyngiomas. Based on years of clinical experience, we have learned that when the tumor in the saddle region develops posteriorly and superiorly, filling the pedunculopontine fossa, lifting the tricuspid ventricle, and even growing to the upper slope, it is very difficult to visualize the tumor and completely resect the tumor, and many of the surgical approaches that are applicable to tumors in the saddle region are also difficult to be effective. This suggests that tumors in this region are unique in terms of surgical treatment, and the term tumor of the pedunculopontine fossa region reflects this uniqueness well. We call the area surrounded by the motor nerve, cerebral peduncle, optic tract, and optic crossings the pedunculopontine fossa region, and tumors originating from the tissues within this area are called giant pedunculopontine fossa region tumors when their growth exceeds a certain size (≥4 cm in diameter) [1]. In this group, there were 56 cases, 25 cases of pituitary tumor, 14 cases of craniopharyngioma and 9 cases of meningioma, which can be seen that the tumors in this area are mainly composed of these three kinds of tumors, accounting for 86%.The identification of the three kinds of tumors is not difficult with the combination of CT and MRI scans with the clinical manifestations and the results of endocrine examinations, and the secreting pituitary tumors have special clinical manifestations and the corresponding hormone level elevation, and even if it is a nonsecreting adenomatous tumor, the shadow imaging is mostly manifested by the pterionic saddle, pterionic sinus Even non-secretory adenomas have special clinical manifestations and corresponding elevated hormone levels, even if they are non-secretory adenomas, the imaging mostly shows the invasion of pterygoid saddle, pterygoid sinus and cavernous sinus, with irregular shape, and there may be intratumor hemorrhage, and the enhancement is homogeneous. Meningiomas without endocrine changes are mostly spherical or hemispherical in shape, with uniform enhancement and meningeal tail sign. The above three tumors confirmed by pathology in this group were correctly diagnosed preoperatively, and two cases were diagnosed as pituitary tumors and one case of craniopharyngioma, and the postoperative pathology was glioma, and the specific source was not clear, which was categorized as hypothalamic glioma, and it was questionable whether it could come from the cerebral peduncle, because gliomas in this area were rare, and the correct diagnosis was difficult preoperatively and could only be relied on the pathology. The two cases of optic crossroads glioma in our group were correctly diagnosed preoperatively, relying on the earlier visual field changes in the medical history and the relationship between the tumor and the optic crossroads of the optic nerve in the MRI fine scan. Two cases of germ cell tumors were indistinguishable from pituitary tumors on imaging, and the preoperative diagnosis was made mainly on the basis of the patient’s history of precocious puberty. one case of a misshapen tumor had a history of precocious puberty and dementia, and the MRI demonstrated an isosignal occupancy in the posterior pituitary stalk with no enhancement. 3.2 Surgical points of giant tumors in the pedunculopontine fossa region In the past, there have been many reports on the surgical approaches for giant saddle region tumors, including transsphenoidal approach, subfrontal transsphenoidal approach, transsphenoidal approach, enlarged transsphenoidal approach, subfrontal one-pterygoidal point combined approach, subfrontal epidural approach in two cases, transcallosal approach, combined mediastinal fissure one-frontal subfrontal approach, and transventricular foramen approach, [2, 3, 4]. The transsphenoidal approach is obviously not suitable for large tumors in the pedunculopontine fossa region, and the transfrontal, longitudinal fissure, and ventricular approaches are not optimal because they are difficult to visualize the pedunculopontine fossa region, and they can cause great damage to the hypothalamus and optic pathways. We used the modified Yasargil wing point approach for right sided craniotomy, and appropriately enlarged the incision and bone flap posteriorly on the basis of the Yasargil wing point approach, and achieved satisfactory clinical results, with 46 cases of total resection of the tumor and 10 cases of subtotal resection, with a total resection rate of 82%. There were no major complications and no surgical deaths except for postoperative urolithiasis in some patients. In practice, we have the following experiences to improve the total resection rate of huge tumor in the inter-foot fossa area and reduce postoperative complications: (1) The access position should be low enough, the skin flap should be turned down as much as possible, and the posterior can exceed the zygomatic arch if necessary, the muscle flap should go to the zygomatic arch on both sides, and the retraction should be tight, and the crest of the pterygoid bone should be ground down to prevent occlusion. (2) Thoroughly dissect the lateral fissure up to the frontal-parietal junction, carefully dissect each arachnoid pool at the base of the brain, release cerebrospinal fluid for decompression, and for patients with combined hydrocephalus, decompression of the right ventricle can be done by fine-tube puncture. (3) Dissect the interstices at the base of the brain under high magnification microscope, reveal the tumor and the important structures in the interstices, and identify the structures that may be displaced and deformed such as the pituitary stalk, and do not cut the tumor in a hurry. (4) Cut the tumor in chunks within the peritoneum in the order of the first, second, fifth and third interspaces, first in the saddle and then on the saddle, and finally remove the tumor peritoneum. (5) Use the wall of the suction tube and the side of the bipolar electrocoagulation forceps to briefly pull the nerves and blood vessels alternately, so as to minimize the pulling injury. When finally removing the part of the tumor that presses toward the base of the third ventricle, we do not force to remove it together with the tumor peritoneum, but scrape the tumor tissue within the peritoneum in order to protect the hypothalamus and pituitary stalks that have residual function. 3.3 Intraoperative protection of the pituitary stalk For huge tumors in the pedunculopontine fossa area, how to resect the tumor while maximally protecting the peritumoral brain tissues and reducing complications is a great challenge. With the increase of the total tumor resection rate, the occurrence of postoperative complications will increase. One of the most common causes of postoperative complications is damage to the pituitary stalk. Destruction of the pituitary stalk results in prolonged dysuria with severe water and electrolyte disturbances. The incidence of postoperative permanent dysuria in giant pituitary adenomas has been reported to be higher than that of normal adenomas, which is related to the infiltration of giant pituitary adenomas into the pituitary stalk and the subthalamus. Permanent dysuria is a difficult clinical problem to manage . The retention rate of the pituitary stalk in total resection of craniopharyngioma via the wing-point approach has been reported to be 36.5-63% [5]. Cao Dongbiao et al[6] reported that the retention rate of pituitary stalk in resection of giant pituitary adenoma was 65.38%, and the incidence of postoperative diuresis was 61.54%. In this group, there were 25 cases of postoperative diuresis, with an incidence rate of 43%. Patients with meningiomas could see the compressed pituitary stalk posteriorly or laterally after resection of the tumor, and patients with malformations could see tumors protruding from the posterior aspect of the pituitary stalk into the intercalary fossa, and the pituitary stalks were very well protected intraoperatively. In the remaining 46 patients, the pituitary stalk could be identified in 8 cases, and in 9 cases, the pituitary stalk was vaguely identified by longitudinal vascular pattern, and these patients did not suffer from dysuria or transient dysuria after surgery; more patients could not identify the pituitary stalk intraoperatively, which could be attributed to the invasion and destruction of this structure and the hypothalamus by the tumor itself on the one hand, and to the fact that the tumor was so large that it had caused the pituitary stalk and the posterior-superior displacement of hypothalamus, which was flattened into a single body with the basement of brain tissue, and could not be identified. The tumor is so large that it causes the pituitary stalk and hypothalamus to shift posteriorly and superiorly to the fundus tissue, flattening it out and preventing recognition. How to identify and protect the pituitary stalk and hypothalamus during surgery, we learned that: (1) fully reveal the inter-foot fossa area, not as good as cutting the tumor, fully dissect the five gaps under high magnification microscope, and carefully identify the pituitary stalk before cutting the tumor, and then the pituitary stalk will be well protected. This was done in 12 cases in this group. If the tumor is not adequately exposed , the pituitary stalk is easily injured by mistake when resecting the tumor. Therefore, adequate exposure under direct vision is important to protect the pituitary stalk. (2) Tumor removal in sequence, we cut the tumor in the order of the first, second, fifth and third interspace, so that the possibility of injury to the pituitary stalk is small, according to the law of displacement of the posterior pituitary lobe and pituitary stalk of the tumor in the saddle region, this order is opposite to the possibility of displacement. With the gradual resection of the tumor, the saddle septum tension is reduced, and then expand the range of resection of the saddle septum, and resect the saddle septum to the medial part of the optic nerve and the upper edge of the cavernous sinus on both sides, so as to resect the tumor protruding to the pars pallidum. There is a border between the tumor protruding to the saddle and the subthalamus, and the interface is the tumor-like saddle septum and the arachnoid membrane in between, which is easy to separate under the operating microscope. In some cases, there is an irregular band of adhesion between the tumor and the inferior thalamus, which should be sharply separated without tearing or pulling. With the resection of the tumor, the gap becomes larger and the anatomical relationship is clearer, which is conducive to the protection of the pituitary stalk and other structures. (3) Craniopharyngiomas, especially those originating from the pituitary stalk and nodal region, the pituitary stalk itself becomes part of the tumor cystic wall, which is not easy to identify intraoperatively, and may be resected as the tumor cystic wall.Yasargil et al.[7] pointed out that the pituitary stalk can be identified from the many longitudinal blood vessels on the surface of the pituitary stalk, and we first released the cystic fluid for decompression, and then carefully identified the cystic wall, which was twisted and stretched due to the compression of the tumor and turned thin or pale, and the pituitary stalk could be recognized from the numerous longitudinal vessels. Due to the distortion, elongation, thinning or paleness of the tumor, the pituitary stalk loses its normal color and characteristics, and the area with a high concentration of longitudinal blood vessels is likely to be the pituitary stalk, which should be protected. In this group, 6 cases of craniopharyngioma belonged to this situation. (4) For patients who cannot identify the pituitary stalk, especially for giant pituitary tumors, when finally cutting the part of the tumor that presses toward the base of the third ventricle, we do not force to resect the tumor together with the tumor envelope, but scrape the tumor tissue within the envelope, so as to protect the flattened and elevated pituitary stalk and hypothalamus, and at the same time protect the blood supply of the area, thus reducing the chances of postoperative urolithiasis. (5) When separating the pituitary stalk, it should be very gentle and try to preserve the integrity of the pituitary stalk. For the pituitary stalk that is closely adhered to the tumor, it should be carefully separated under high magnification microscope, and the saddle septum (or the tumor wall) can be left around it when separation is difficult. Unipolar electrocoagulation is forbidden for stopping the bleeding around the hypothalamus and pituitary stalk and it should be stopping the bleeding by bipolar electrocoagulation with a small electric current. It is very important to protect the blood supply of the pituitary stalk, which is mainly supplied by the pituitary stalk arteries from bilateral posterior communicating arteries or posterior cerebral arteries, and these blood vessels may be adherent to the pituitary adenoma or involved in the tumor’s blood supply, and they should be protected by careful freeing under the microscope. 3.4 Intraoperative protection of optic nerve function The huge tumor in the pedunculopontine fossa compressed the optic nerve for a long time, resulting in the optic nerve being compressed into a thin sheet, and the adhesion with the tumor caused the optic nerve to be obviously atrophied, and most of them had serious visual field impairment, and some of them had only weak vision and narrow field of vision left. The preservation and improvement of residual vision is also one of the important aims of surgery. Through the practice of this group, we experienced that the following points should be noted for optic nerve protection in microdissection of giant tumors in the inter-foot fossa region: (1) Fully reveal the optic nerve, optic cross and optic bundle, clarify the relationship with the tumor under direct vision, and protect them before removing the tumor. (2) Remove the tumor in pieces within the periphery under direct microscopic vision in the first gap, which will make the compressed bilateral optic nerves and optic crosses fully decompressed, touch the optic nerves as little as possible, especially prevent the suction device from accidentally aspirating the optic nerves. (2) When surgical operations are performed in all gaps and retraction of the optic nerve, optic cross and optic bundle is required, continuous hard retraction is strictly prohibited, and we borrowed Yasagil’s method of alternating brief retraction with the wall of the suction tube and the lateral side of the bipolar electrocoagulation forceps, so as to minimize retraction injury. (3) Separate the optic nerve from the tumor wall carefully from the interface between the tumor envelope and the surrounding tissue structure, i.e., the subarachnoid space layer, some of the tumor wall and the lower part of the optic nerve have irregular band adhesion, which should be sharply separated, not torn or pulled, and when separation is difficult, it can be residual in its periphery of the tumor wall, and should not be forcibly separated. (4) It is very important to protect the blood supply of the optic nerve. The blood supply of optic nerve mainly comes from the superior anterior pituitary artery, which sends out several branches from the medial wall of the upper section of ICA bed protrusion. These small arteries tend to follow the surface of the tumor forward and backward, and are distributed in the base of the optic nerve and optic nerve cross, and these blood vessels may be adhered to the wall of the pituitary tumor, or participate in the blood supply of the tumor. Normal pituitary blood supply mainly comes from the superior and inferior pituitary arteries, and the study of Liu Yunsheng et al [8] showed that the blood supply of large and giant pituitary adenomas also comes from the neovascularization of arteries that are in close contact with the tumor, nerve trophoblastic vessels, and dural blood vessels, and the blood vessels supplying the tumor are mainly on the top of the tumor wall, and the cut-off of the tumor supplying tubes in the area of the tumor wall does not cause the damage to the optic nerve, the optic nerve and the optic nerve and optic cross inferior colliculus and other structures. When separating the tumor from the proximal optic nerve, bipolar electrocoagulation and cauterization should be used sparingly, and when bipolar cauterization of tumor hemorrhage must be used, a weak current should be used while cooling with water rinsing to avoid thermal damage to the optic nerve. After resection of the tumor, the internal carotid artery and optic nerve should be covered with popovine cotton pads for 3-5 min to relieve vasospasm caused by surgical operation.