In this paper, the authors herein discuss the indications, methods and related issues of applying neuroendoscopy to the surgical treatment of some patients with skull base chordoma. DATA AND METHODS 1. General data: Between June 2000 and June 2006, we applied neuroendoscopic surgery to treat 30 patients with skull base chordoma, including 17 males and 13 females, aged 18-55 years old, with an average of 30.5 years old. Zhang Yazhuo, Department of Neurosurgery, Beijing Tiantan Hospital, Beijing, China 2. Clinical manifestations: headache in 26 cases, other clinical manifestations included visual loss and visual field abnormality in 7 cases, cranial nerve palsy (abducens nerve and motor nerve) in 5 cases, epistaxis in 2 cases, olfactory abnormality (reduced or lost) in 6 cases, and asymptomatic in 1 case. Tumor site: 19 cases were located in the middle and upper slopes and saddle area, 6 cases had the main body of the tumor located in the middle and upper part of the slopes, one side of the paranasal sinus was prominent, and 5 cases had a wide growth of the tumor, which encroached on the middle and upper slopes and the plagiarized nose. In these cases. Tumor compression of the subcerebrum in 6 cases, the other 4 cases were hospitalized due to recurrence of chordoma of the base of the skull, which had been craniotomized 1 year earlier. Receiving already right literature classification u J, this group of cases amidship thin mainly for the saddle area type and slope type, 5 cases of extensive growth, but also to the slope of the anterior growth of the main + only l cases of tumor from the saddle area, slope to the infratemporal fossa, the middle cranial fossa growth. 4. Surgical methods: 29 cases were treated with endoscopic trans-yi butterfly approach, l case was treated with endoscopic trans-nasal butterfly. j==mandibular sinus up to the pterygopalatine fossa, and some tumors in the middle cranial fossa were resected by craniectomy under the emblematic microscope. Routine application of 30. rigid neuroendoscope with automatic flushing pump tube was. Depending on the crippling situation, the decision was made to go through one nostril or both; intraoperatively, it was decided whether to remove the middle and inferior turbinates as needed for visualization. The nasal mucosa was constricted with paranephrine cotton pads. The surgical passage was gently dilated weevil by weevil. In the pterygoid fossa, the pterygoid rustic opening (often closed when the tumor protrudes forward) is revealed, and the mucosa of the nasal septum is incised in a curved fashion within 1-2 cm above this point and lifted posteriorly downward. At this point, the soar often has revealed part of the tumor, and should try to fully reveal the tumor before gradual resection. When dealing with the tumor, the first intracapsular resection, and then as far as possible to separate the tumor border. The slope and surrounding bone should be gently mushroomed under direct vision with a grinding drill. Avoid blind chiseling, prying or breaking the bony structures of the skull base to prevent damage to the important blood vessels and nerves of the skull base. Hemorrhage in the cavity of the tumor is mainly stopped by bipolar electrocoagulation and compression hemostasis. After resection of the tumor, if the slope dura mater is not broken by tumor invasion, the dura mater should be protected by all means. If the dura is missing and the cerebrospinal fluid leaks out, the dura is sealed layer by layer with artificial dura, bio-gel, autologous eclipsed ride, floating meat tendon and so on. 5.Follow-up: 18 out of 30 patients were followed up within 6 months to 1 year after surgery, which included general clinical manifestations and neuroimaging data. 6, instrumentation: neuroendoscopy system, including camera, light source and mirror body, for the German company Rudof products, intraoperative irrigation pump for the United States circle elerus Pu Ⅱ lp 6169, intraoperative double pole Germany E out of the e company products. Results Surgical near-total resection of thigh crippling 7 cases; sub-total resection of Yu i6 inverted; partial resection of 7 cases. 24 cases of clinical performance to obtain a certain degree of improvement, 6 cases no change. All the cases recovered normal life in 7 lod after surgery. l aid the echidna had cerebrospinal fluid leakage after surgery, the leakage was terminated in 11d after lumbar big fishing cerebrospinal fluid drainage, the brisket spinal fluid nasal leakage occurred again in 20d after discharge from the hospital, and the patient was cured after repairing the dura mater again. 1 patient had nasal hemorrhage in 7d after surgery, and it was relieved by the localized compression and discharge of the loamy stuffing. Among the 18 patients who were followed up, 4 cases had tumor recurrence 10-18 months after surgery, all of which were extensive growth type tumors; 8 cases resumed normal work; 6 cases recuperated at home, 5 cases could take part of the family work, and 1 case had poor vision after surgery (Figs. 1, 2). Discussion The surgical treatment of skull base chordoma is challenging. Most of the tumors occur in the pterygo-occipital junction of the skull base, and are commonly found in the slope, saddle area, and other midline areas of the skull base. Therefore, this kind of tumor, which is characterized by the deep location of the tumor, the invasion and destruction of the important structures of the skull base, and the compression of the brain stem, poses a great challenge for surgical treatment.6 J. The treatment of chordoma of the skull base, which has been in existence for nearly a century, has progressed relatively slowly. The emergence of microscopic neurosurgical techniques, the improvement of various surgical pathways, and especially the integration of multidisciplinary application techniques have played an important role in promoting the surgical treatment of skull base chordoma.2 However, the trauma of surgery is still difficult to avoid, and the quality of postoperative survival of some patients has significantly decreased, and the postoperative recurrence rate is still relatively high. For this reason, some scholars at home and abroad have applied neuroendoscopic techniques to the surgical treatment of chordoma at the base of the skull, and achieved better results ¨’8I. Our initial attempt here has gained some experience and provided ideas for further development of this work. Correct selection of surgical indications is the key to the success of endoscopic transsphenoidal surgery for chordoma. The growth characteristics of chordoma at the base of the skull are diverse, which determines the diversity of surgical treatment means. In order to decide the surgical access and method appropriately, many scholars used to classify chordomas according to the tumor imaging characteristics and clinical manifestations, but in our group, we mainly based on the tumor site, scope and bony structure changes shown by MRI and CT to decide how to operate. The application of neuroendoscopic technique is mainly considered in two cases, one is that the main part of the tumor can be better resected simply by neuroendoscopy, mainly by using the natural lumen and trying to choose the route with a short path and relatively few bony obstacles. In this group, 29 cases were purely transnasal, and the extent of the revealed tumor was gradually expanded. In another case, part of the tumor was resected by microsurgery first, and then the tumor deep in the dead zone of the microscopic field was resected by neuroendoscopy. In this group, there was one case of resecting the tumor at the base of the middle cranial fossa under the microscope, and the endoscopy was coordinated with the resection of the infratemporal fossa, the pterocephalic sieve and the maxillary sinus, and the tumor in the anterior part of the slope. Therefore, we believe that the current range of cases in which neuroendoscopy is applied to chordoma of the skull base can include (1) transnasal butterfly approach and expanding to the periphery with this as the center, which is suitable for tumors in the pterygoid sieve sinus, the middle and upper slopes, with growth mainly toward the anterior side; (2) trans-oral pharyngeal approach, which is suitable for tumors located in the lower slopes, the foramen magnum of the occiput, and the upper cervical vertebrae in the anterior side; and (3) combined use of the endoscopy and the microscope, which is mainly taken into consideration that the tumor grows (3) The combination of endoscopy and microscopy is mainly considered because the tumor growth is so extensive that it is difficult to completely remove the tumor by one method alone. The selection of such indications is also relative, and with the advancement and improvement of technology, the scope of endoscopic resection of skull base chordoma may be more extensive. An important goal of neuroendoscopy in skull base surgery is to minimize surgical trauma while allowing greater lesion visualization.2,13j One of the key techniques for surgical resection of skull base chordomas is to increase tumor visualization and reduce the extent of nonrectal blind excision of the tumor to avoid injury to important neurovascular vessels. However, the growth characteristics of this tumor make it extremely difficult to adequately visualize the tumor. In our group, neuroendoscopic transnasal butterfly tumor exposure was applied as the main method, which caused less damage to the surgical path. In order to prevent damage to important structures during the surgery, ‘when gradually expanding the tumor exposure, the deep bony components, such as the bone around the pyriform foramen, the medial wall of the maxillary sinus, the bone of the saddle base of the pterygoid sinus, and especially the bone of the slope, were carefully abraded, mainly with a high-speed abrasive drill. Because of the relatively wide field of view projected by the neuroendoscope, the milling drill is operated within the field of view of the endoscope, and its operation can be clearly guided by a monitor. With the step-by-step resection of the tumor during surgery, the operating cavity can be further expanded. Most tumors invade into the surrounding bone and cause bony destruction, which needs to be carefully identified under the endoscope and carefully abraded until the normal bone is removed, but it is not necessary to forcefully remove the bone that is connected to the important structures. In this group, the pathological bone of the tumor was more obvious when it was removed endoscopically alone, so extra care should be taken here to prevent the bone fragments from puncturing important blood vessels. Hemostasis is still based on bipolar electrocoagulation and compression, preferably with single-handled scissor-type bipolar forceps. The practice of this group shows that the wide-angle, angle-forming, localized irradiation of the lesion, and monitor observation of neuroendoscopy are suitable for the operation of deep luminal lesions and cause less damage to the surgical access. Careful operation is the key to preventing surgical complications to obtain a good prognosis u4 a citation. Chordoma of the skull base can invade extensively around the saddle region, slope, optic canal, internal carotid artery bulge, and cavernous sinus, and it is often difficult to find the border during surgery, so careful intraoperative manipulation is necessary to prevent damage to these structures, especially when the bone has been extensively destroyed, and the fragmented bone should be carefully removed. Due to the wider field of view of endoscopy, the tumor and surrounding structures seen endoscopically may not be reached by conventional instruments and must be adequately prepared. The appropriate lesion should be treated with angled instruments (including bipolar and suction) that can be applied at depth. Because endoscopic grinding is very convenient, we do not advocate violence such as chiseling, prying, and rigid retraction during deep skull base manipulation, which is essential to prevent injury to these structures. Intraoperatively, it is common for the dura mater to be invaded by the tumor, and after resection of the tumor, there can be a more obvious defect, and it is very important to closely reconstruct the dura mater to prevent cerebrospinal fluid leakage. It is routinely repaired with multiple layers of artificial dura mater, autologous fat, and muscle mashing. We found that it is quite important for the artificial dura mater to adhere flatly and be exactly firm during bioadhesion. Further improvement of the technique is necessary to extend the scope and improve the quality of the procedure. There have been many applications of neuroendoscopic techniques in deep skull base surgery o7’8, 12, 13J. A large number of cases have amply confirmed that this method is less invasive, with relatively good visualization and clear vision. The results of the present group support this view. It should be noted, however, that neuroendoscopy is a developing technology, and there is much room for development and growth, both in terms of instrumentation and the technique itself. First of all, the flexibility of neuroendoscopy in deep manipulation should be further improved, and electronic endoscopy may play a good role in terms of clarity and flexibility. The topic of reconstructive smelling after extensive destruction of the skull base remains an important topic, and the method of reconstruction of the ear salary is still flawed and needs to be continuously improved.