Aneurysm is not a real tumor, as we know from its Latin or English name Aneurysm, it has nothing to do with tumor, but we just conventionally call it an aneurysm. In common parlance, an aneurysm is a bulge in the wall of an artery, which is somewhat like a blown up balloon with thin walls, and will rupture and bleed if it cannot withstand the pressure and rush of arterial blood flow. Because most of the larger intracranial arteries are located in the subarachnoid space, and aneurysms tend to occur in these larger arteries, aneurysm rupture often causes spontaneous subarachnoid hemorrhage (SAH), which can be combined with intracerebral and intraventricular hemorrhage in severe cases. The mortality rate for the first rupture of an aneurysm is 40-45% and doubles for the second bleed within a short period of time, making it one of the most dangerous diseases in neurosurgery. Direct craniotomy of aneurysm is an important way of aneurysm treatment. Exposure of Aneurysms Craniotomy is performed at the appropriate site. If the aneurysm is on the main trunk of the aorta, direct exposure can be performed according to the anatomical location. If the aneurysm is on the end of the artery, the aneurysm-carrying artery can be identified first and then gradually searched along this artery as seen on the angiogram. If the patient has a history of bleeding, the aneurysm is often surrounded by signs of arterial bleeding, which are easily identified. Once the adjacent area of the aneurysm is exposed, the proximal and distal ends of the aneurysm-carrying artery should be freed first, then the neck of the aneurysm should be exposed, and finally the body of the aneurysm should be exposed. This makes it easier to control sudden rupture and bleeding of the aneurysm. The order of arterial exposure during surgery for common aneurysms is as follows: (1) Aneurysms of the cavernous sinus segment of the internal carotid artery and the ophthalmic artery segment require exposure of the internal carotid artery or the common carotid artery in the neck first. (2) For posterior communicating aneurysms or aneurysms of the bifurcation of the internal carotid artery, the intracranial segment of the internal carotid artery should be exposed first. (3) For anterior communicating artery aneurysms, the intracranial segment of the internal carotid artery is exposed first, followed by the A1 segment. (4) For middle cerebral artery aneurysm, the intracranial segment of the internal carotid artery should be exposed first, followed by the middle cerebral artery. 2.Aneurysm Dissection and Clipping (Aneurysm Neck Dissection and Clipping) is not necessary to free and handle the aneurysm. However, sometimes the aneurysm covers the neck or the artery carrying the aneurysm and the aneurysm has to be dissected first. Special care should be taken in this case because the top wall of the tumor is thin and can easily rupture and bleed. Sometimes there are blood clots or adhesions on the surface, and separating them during dissection can cause bleeding, so special care should be taken. These operations can be performed with temporary blockage of the tumor-carrying artery. For those with intracerebral hematoma, the hematoma should be removed first, and then the aneurysm should be treated. 3.Aneurysm clamping or resection (1) Aneurysm Neck Clipping. This is the most ideal method in aneurysm surgery, which not only excludes the aneurysm from blood circulation, but also preserves the smooth blood flow of the aneurysm-carrying artery. The arachnoid is cut around the neck of the aneurysm with sharp instruments such as knives and scissors, avoiding tearing the arachnoid with blunt instruments. A blunt-tipped probe is then gently inserted into both sides of the aneurysm neck to explore a channel for the arterial clamp to pass through. After the aneurysm neck is clamped closed, the position of the arterial clamp should be checked to see if it is satisfactory, if the nerves or small vessels are mistakenly clamped, and if the aneurysm-carrying artery is twisted or narrowed by the aneurysm neck clamp. If the position of the artery clip is not satisfactory, it should be removed and repositioned until it is satisfactory. Aneurysm neck treatment can be performed with temporary blockage of the aneurysm-carrying artery, especially if the aneurysm has serious adhesions, thin wall and wide neck. (2) Aneurysm Neck Bipolar Coagulation and Clipping. When the aneurysm neck is too wide to be directly clipped, bipolar coagulation forceps can be used to gently clip the aneurysm neck and electrocauterize it under low current before clipping. When electrocoagulating the neck of the aneurysm, make sure that the bipolar electrocoagulation forceps hold all the neck of the aneurysm, squeeze and release it during electrocoagulation, and inject saline to prevent the tip of the forceps from adhering to the wall of the aneurysm. For aneurysms clamped by the above two methods, a needle should be used to puncture the aneurysm to exclude residual blood and to verify whether the neck of the aneurysm has been clamped. If the aneurysm is refilled after the blood is removed by puncture and the puncture needle keeps bleeding, it means that the aneurysm neck has not finished clamping or there are other blood supplying arteries in the aneurysm, and should be treated accordingly. (3) Arleurysm Thrombectomy and Neck C1ipping after removal of thrombus mechanized material. When the size of aneurysm is large (such as large or giant aneurysm) and there is sclerotic plaque in the neck, the aneurysm-carrying artery can be temporarily blocked, the aneurysm body can be cut, and the thrombus mechanized material or sclerotic plaque can be removed by suction or ultrasonic suction, and then the neck can be clamped. (4) Aneurysmectomy. Generally, only the neck of the aneurysm is clamped and the body of the aneurysm does not need to be removed. For large or giant aneurysms, the aneurysm can be freed and resected after the neck is clamped in order to relieve the compression of the neurovascular vessels by the aneurysm. However, when the aneurysm wall is tightly adhered to the important neurovascular structures, it should not be forcibly removed, and a small piece of the aneurysm wall can be left behind. (5) Electrocoagulation of aneurysm (Aneurysm Coagulation). For small (1~2mm) aneurysms without neck or abnormal bulging of the arterial wall (except for thin walled aneurysms), the aneurysm can be coagulated and crumpled by bipolar electrocoagulation forceps under low current. (6) Tubular clip closure of aneurysms (Aneurysm Clipgraft). A specially designed tubular artery clip (Sundt clip) is used, which is placed over the artery and the aneurysm neck is clamped closed. It is used when the neck of the aneurysm cannot be freed under direct vision due to surgical access or other reasons, especially if there is a breach in the aneurysm-carrying artery. The disadvantage of this method is that the nerve and vascular tissues adjacent to the aneurysm neck may be mistakenly clamped, and Sundt tubular clamps are available in various sizes, with diameters of 2.5~4.0 mm and lengths of 5~7 mm. 4.Aneurysm Trapping Ligation of the aneurysm carrier artery, including the blood supply and drainage artery of the aneurysm, so that it is isolated from the arterial system. This method is used for aneurysms whose necks cannot be clamped or are not suitable for clamping, aneurysms whose necks cannot be clamped during surgery, and spindle or interlaminar aneurysms. There are two surgical methods: (1) intracranial and extracranial isolation, in which the arterial ligation site is one outside the skull (such as the carotid or vertebral arteries in the neck) and one distal to the intracranial aneurysm. (2) Intracranial isolation, in which the aneurysm-carrying artery is ligated in the proximal and distal parts of the aneurysm, respectively. This method also blocks some blood circulation pathways in brain tissue when dealing with aneurysms, so it is only suitable for patients with good collateral circulation. However, it should be noted that even if there is good collateral circulation, cerebral ischemia may still occur in patients after surgery due to interference from arterial spasm and other factors. 5.Aneurysm Thrombosis The following methods are used to promote the formation of thrombus inside the aneurysm to occlude the aneurysm and prevent rebleeding. It is suitable for those who cannot clamp the aneurysm neck. Since this method is not as reliable as aneurysm neck clamping, the possibility of aneurysm enlargement and hemorrhage due to recanalization of the aneurysm lumen still exists. (1) Spring-ring method: A detachable spring-ring (such as GDC) is inserted into the aneurysm through an endovascular cannula (see endovascular interventions for details). (2) Electrocoagulation method: A fine copper wire of 0 or 1 mm in diameter is inserted into the aneurysm through a specially designed needle via open or stereotactic drilling method. Because of the negative charge of blood cells and fibrinogen, they can be adsorbed on the positively charged copper wire and form a thrombus. Connecting the copper wire to the positive DC (O,2~0,4mA, 30~60min) can accelerate the thrombus formation. (3) Coagulant injection method: Inject bio-glue or non-toxic plastic mucus into the aneurysm cavity to promote thrombus formation and occlusion of the aneurysm. The speed of injection should be slow and the amount should be moderate (the volume of aneurysm should be calculated according to angiography), so that the adhesive will not flow into the aneurysm-carrying artery and cause cerebral embolism. 6.Aneurysm Wrapping is suitable for: ①Aneurysms that cannot be clamped, resected or isolated, such as pike aneurysms. (2) Aneurysms that are subject to internal coagulation. Reinforcing materials include special gauze sheets, cotton sheets, muscle sheets and gelatin sponges, etc., which can be applied together with biogel to improve the efficacy. 7.Other: (1) Aneurysmectomy Followed by Vascular Reconstrution: After the aneurysm is removed, the two disconnected ends of the aneurysm-carrying artery are reanastomosed. This procedure is used for giant aneurysms and spindle-shaped aneurysms. It requires good collateral circulation because the aneurysm-carrying artery needs to be blocked for a long time. (2) Aneurysmorrhaphy: After resection of the aneurysm, the neck of the aneurysm is sutured or the gap in the aneurysm-carrying artery is repaired with an autologous vein graft. (3) Suction Decompression: Followed By neck Clipping: The aneurysm body can be punctured with a scalp needle or the internal carotid artery of the neck can be punctured with a needle, and blood can be suctioned with a syringe to reduce the tension of the aneurysm and shrink the aneurysm to facilitate clamping. This reduces the tension of the aneurysm and reduces the size of the aneurysm to facilitate clamping.