Microinvasive surgical techniques (minimally invasive) are the direction of medical development in the new century, and neuroendoscopy is the most important component of microinvasive neurosurgery. Endoscopy has been used in surgery for decades, but due to the limitation of optical technology and production process, there is no endoscopic equipment suitable for neurosurgery for a long time. In recent years, with the development of high-tech technology, high-definition, multi-purpose, flexible and convenient neuroendoscopes have been introduced, making neurosurgery easy, safe and convenient. The lesions in the skull base, intracerebral, and intracerebral ventricles can be removed under microinvasive conditions, and surgeries that used to require shunts can be replaced by endoscopic fistulotomy; surgeries that used to require craniotomy can be replaced by surgery through a single nostril, thus increasing the cure rate and reducing complications and medically induced injuries. After the 1990s, Europe and the United States, Japan and Korea began to apply neuroendoscopy in the diagnosis and surgical treatment of clinical neurosurgical diseases, and its scope of application has gradually expanded. In China, this work started late but developed rapidly. In recent years, dozens of hospitals have introduced neuroendoscopic systems, mainly for the treatment of intracerebroventricular and deep brain cystic lesions and hydrocephalus. Endoscopy-assisted surgical microscopy is applied to carry out locked-hole surgery, so that total resection of tumor is near possible with maximum protection of brain tissue. Application of neuroendoscopic surgery for intracerebral hemorrhage, saddle area tumor, skull base tumor, intracerebroventricular tumor, transnasal-ptero-skull base, transventricular neuroendoscopic surgery neuroendoscopic technology combined with stereotactic technology will become one of the main treatment tools in neurosurgery, which will greatly improve the treatment of ventricular system lesions, deep brain cystic tumor, skull base tumor, spinal cord cavernous disease, disc herniation and other cerebrospinal lesions . However, for substantial tumors and intracranial aneurysms in the deep brain, especially in the skull base, most hospitals still use conventional surgical access or expanded skull base access. The development of neurosurgery requires the best treatment effect and the least medical damage. The best way to protect the structural integrity of tissues is to leave them untouched or unexposed as much as possible. In recent years, with the advent of high-technology, high-definition, versatile, flexible and convenient neuroendoscopes have been introduced, making it possible to replace microscopic surgery in some aspects of endoscopic surgery. We have carried out research on the clinical application of neuroendoscopy from the following aspects 1. obstructive hydrocephalus The treatment of obstructive hydrocephalus, which used to be treated by ventriculo-abdominal shunt, requires a ventricular shunt tube to be placed in the ventricle and abdominal cavity through a subcutaneous tunnel. Due to the inevitable shunt tube failure and shunt tube length limitation, the catheter often needs to be replaced several years after surgery, which affects the therapeutic effect. The new therapy inserts an endoscope of only 6mm in diameter into the ventricles, inserts a special balloon catheter into the three ventricles through the tube of the endoscope, creates a fistula at the bottom of the three ventricles, and makes a permanent orifice after balloon expansion to recreate the ventricular circulation. If the blockage of the midbrain aqueduct is not serious, the aqueduct can also be opened directly, so that the hydrocephalus improves and the symptoms are relieved without leaving any foreign body in the body. 2.Intracerebroventricular tumor The rise and perfection of neuroendoscopic technology in recent years has provided a good prospect for the treatment of intracerebroventricular tumor. The location of intracerebroventricular tumor is deep, and the surgical access has to traverse long distance of normal brain tissue, which is challenging for neurosurgeons. Intraoperative cuts and strains on normal brain tissues are minimized, and damage to deep-side important structures, such as the thalamus, basal ganglia, and fornix, is minimized. The application of neuroendoscopy can reduce brain tissue damage, and with the help of the fine endoscopic display system, the blood supplying arteries, draining veins and surrounding structures on the tumor tegument can be clearly identified during the treatment of the lesion, so that the risk and mortality of intracerebroventricular tumor surgery have been greatly reduced. If the intracerebroventricular tumor causes narrowing and obstruction of the cerebrospinal fluid circulation pathway, it can also be treated simultaneously. The choice of surgical access depends on the location, nature and characteristics of the lesion. Generally, the puncture sites of ventricular puncture and drainage can be used, such as the puncture sites of the frontal horn, temporal horn, occipital horn and triangle of the lateral ventricle. If the tumor is located in the interventricular foramen, the tumor can be seen after the endoscope enters the ventricle. Exploration of the tumor supply artery and drainage vein is important for the success of the procedure. For lesions in the third ventricle, not only resection or biopsy can be performed, but also fistula of the third ventricular floor and evacuation of conduit obstruction can be performed. When removing the tumor, generally the tumor is firstly excised in a block within the capsule, then the boundary between the tumor and the brain tissue is separated and gradually removed. 3. Hypertensive cerebral hemorrhage 70% of intracerebral hematoma is caused by hypertension, and its mortality rate is about 80%. The traditional method to remove intracerebral hematoma is to open the skull, cut the brain tissue and remove the hematoma, which may add new damage to the primary damage caused by hemorrhage. In recent years there has been interest in different types of microinvasive techniques and an emphasis on stereotactic endoscopic intracerebral hematoma aspiration. We combine neuroendoscopy with stereotactic techniques to treat spontaneous intracranial hematomas. Endoscopic surgical removal of intracerebral hematoma is performed only by skull drilling, and the surgical objectives are: (1) to reduce intracranial pressure; (2) to avoid secondary brain tissue damage; and (3) to shorten the recovery period. 4.Anterior skull base tumor Endoscopic transsphenoidal approach for pituitary tumor has become a fairly mature surgical technique. This approach can also treat some anterior skull base tumors, craniopharyngioma, hollow pterygoid saddle, cerebrospinal fluid leak repair, cavernous sinus, surgery of optic nerve and treatment of slope lesions. Due to the wide and variable view of the endoscope itself, the surgical approach using the transnasal endoscope can reveal an area no less than 2 cm wide, from the saddle base to above the foramen magnum, but care should be taken to avoid damage to the internal carotid artery in both sides of the exposure. Pituitary tumors, craniopharyngiomas, chordomas, cholesteatomas, and meningiomas in this space can be exploited with this surgical approach. It should be noted that adequate visualization is a prerequisite for successful tumor removal. The advantage of endoscopic transsphenoidal approach is that the tumor can be removed to the maximum extent while preserving the normal structure of the patient’s nose, and the patient can resume life on the day of surgery, shortening the hospital stay and reducing complications. Based on the endoscopic anatomical study of skull base and brain pool, our department started to apply neuroendoscopy to perform triple ventriculostomy for obstructive hydrocephalus, endoscopic removal of intracerebral hematoma and intracerebral hematoma, and treatment of intracerebral cystic lesions in 2003, and endoscopic resection of pituitary tumor, saddle area tumor, skull base tumor and endoscopic resection of intracerebral tumor in 2004. He has achieved excellent results in all cases.