subtentorial arteriovenous malformation resection

AVM under the cerebellum accounts for about 7% to 18% of intracranial AVM. More common in the cerebellum and the midline, but the upper, lower, lateral, deep, cerebellum and pons of the cerebellar hemisphere can occur. 1 Cerebellar hemisphere upper AVM: located above the cerebellar horizontal groove. Smaller people are more common in the front of the cerebellum, and large ones can reach the horizontal ditch. The blood supply artery is mainly derived from the ipsilateral or bilateral superior cerebellar artery, and the branches of the anterior cerebral artery and the posterior cerebral artery are also available for blood. The output vein has the cerebellar superior vein, the cerebellar anterior central vein, the superior iliac vein and the lateral midbrain vein, etc., and can also be introduced into the cerebellum and the straight sinus by a single paracentral vein. 2 AVM in the lower part of the cerebellar hemisphere: blood supply belongs to the area of the inferior cerebellar artery, and a small number may also have blood supply to the anterior cerebellar branch. Small people are sometimes located only in the tonsils, and large ones can extend to the second and even the second half of the moon. The drainage vein is injected up or down into the cerebellar central vein and merges into the straight sinus. 3 cerebellar sacral AVM: most commonly involved in the upper or lower half of the cerebellar vermis. The upper iliac crest is the upper cerebellar artery and the arteries that extend to the top of the fourth ventricle. In its deep part, it may have a genus on the upper cerebellum and drain the vein to the superior iliac vein. The lower iliac crest often supplies blood from the inferior cerebellar artery. Sometimes branches of the anterior cerebellar artery in the choroid plexus also participate. 4Cerebellar ganglion AVM: The lesions are mostly outside the brain and can also reside in the brain. The extra-cerebral person is located in the subarachnoid space; the brain is located in the ventral side of the cerebellum, which may involve the quadrilateral, the semilunar, and the small nodule. It belongs to the blood supply range of the anterior cerebellar artery. Large people can also supply blood from some branches of the superior cerebellar artery and the inferior cerebellar artery. The output vein is mainly the lateral crypt or the lateral pons vein, and finally leads into the vein or the great cerebral vein. 5 pons AVM: rarely seen. The blood supply artery can be derived from the superior cerebellar artery and the basilar artery. Often located outside the pons, the deformed blood vessels are mostly outside the pia mater and can be removed in the subarachnoid space. Some can be deep into the pons, the deformed vascular group is located under the pia mater, surgery will have certain difficulties, the resection should be carefully considered, because the postoperative often has a poor prognosis. 6 giant posterior fossa AVM: can occupy the entire cerebellar hemisphere. The blood can be supplied by the bilateral arteries, and the output vein is difficult to see. It may be drained up to the great cerebral veins, and the lateral sinus is introduced into the sinus, and the midline is introduced into the straight sinus. Since the successful re-excision of cerebellar AVM in 1932, only sporadic surgical treatments have reported long-term mortality and disability rates. It was not until the 1980s that there were more reports of AFM surgery in the posterior cranial fossa, and the curative effect was continuously improved. In 1986, Drake reported that 51 cases were removed in 66 cases, the operative mortality rate was 15%; in the same year, Batjer reported 32 cases, the operative mortality rate was 7%; in 1988, Yasargil reported that 68 cases died in only one case. At present, under the microsurgical operation, it is not difficult to remove the AVM of the cerebellar hemisphere, that is, the AVM of the larger cerebellar vermis and the midline is not left with severe ataxia, or even the cerebellopontine angle AVM of the pons It can also be safely removed without damaging the function of the cranial nerves and brainstem. Treatment of diseases: cerebellar stenosis, meningioma Indication Suboccipital arteriovenous malformation is suitable for: 1. Superficial medium and small AVM. 2. Medium and small AVM with a history of bleeding. 3. AVM in the cerebellopontine angle of the subarachnoid space and the brainstem. Contraindications 1. Large AVM without obvious symptoms. 2. AVM under the pia mater in the bridge brain. Preoperative preparation 1. The volume of the posterior cranial fossa is small. The important structures such as the brain stem, the posterior cranial nerve and the vertebral-basal artery cannot be damaged or excessively pulled. Therefore, the design of the incision is very important when the skull is opened. It must be accurately positioned before surgery. Surgical approach to meet the needs of surgical operations. 2. Under the occipital cranium, the neck should be reached. The skin preparation must include the full head, neck and shoulders. Surgical procedure According to the location of the deformed vascular mass, the blood supply artery, the output vein, and the relationship with the surrounding tissue, the corresponding surgical steps were taken. In the following, the surgical procedures of the AVM, the upper axillary-based AVM, and the cerebellar pons AVM next to the midline of the lower cerebellum are introduced as representative. 1. Cerebellar tonsil AVM resection (1) The cranial fossa was opened in the median incision. (2) After cutting the dura mater and the arachnoid membrane of the occipital cistern, the thick lower saphenous vein of the main drainage can be seen, and some abnormal vascular clusters exposed on the surface can be seen at the cerebellar tonsil. (3) Separation of the boundary between the deformed vascular mass and the cerebellar surface under the drainage vein that protects the expansion and flexion. After revealing the deep vascular mass covered by the surface of the brain, the cerebellum retractor is used to retract the cerebellum outwards. . (4) Separate the trunk of the blood supply artery (posterior inferior cerebellum) to the distal end to find the branch of the artery supplying the AVM. (5) The blood supply artery is blocked and cut by a blood vessel clip or a wire. Keep the main output vein. (6) Continue to dissociate along the boundary line between the AVM and the cerebellum, while the vascular group is turned outward while separating, until all the blood supply artery and the small drainage vein are completely freed. When all the deformed vascular masses are turned out to be connected only to the main drainage vein, all the veins associated with the lesion are ligated and the lesions are completely removed. (7) Close the blood and close the skull. 2. Upper axillary AVM resection (1) It is very important to choose the incision. There are 3 kinds of incisions to choose from. Each has its own advantages and disadvantages. It should be determined according to the specific conditions of the lesion. 1 After lifting the temporal lobe, the "L" shape cuts the cerebellum and enters the surgical field from the front of the cerebral horn of the cerebral pons. It is the most reasonable way to deal with lesions at the anterior end of the cerebellar midline, but this incision is limited when dealing with large AVMs that extend to the contralateral and posterior portions. 2 under the pillow through the small brain curtain approach. It is convenient to treat the lesions on the opposite side and the back of the upper palate, but the observation of the blood supply artery is not from the front but from the top, so it is not as good as the former. 3 under the cerebellum approach. It is convenient to operate on the left or right side of the lesion, but the output vein from the dorsal aspect of the cerebellum to the cerebellum is a disadvantage. In order to clearly reveal the surgical field, the cranial forehead should be retracted in multiple directions. (2) The lesion can be seen through the different surgical approaches to the upper cranial area of the cerebellum and the dorsolateral side of the pons. The AVM at this site is almost exclusively supplied by the superior cerebellar artery. Drainage veins vary greatly, most of which are the upper iliac veins that flow into the great cerebral veins or straight sinus. The position is in the midline, and it is not in the midline but in the midline. It is introduced into the upper sinus or lower sinus through the vein. If the surgical operation requires a drainage vein in the field of view, the vein is easily damaged, causing massive bleeding. (3) Along the trunk of the superior cerebellar artery, look for branches that supply blood to the deformed vascular group, and clip and cut them one by one. (4) After completely dissipating the abnormal vascular mass, the drainage vein was cut off and all the lesions were removed. (5) Close the skull after hemostasis. 3. Cerebellar ganglion AVM resection (1) Incision of the posterior cranial fossa of the U-shaped side, or other incision of the cerebellopontine approach. Because the main part of the deformed vascular mass is located under the cerebellum and close to the pons, so no matter what kind of incision is used, the cerebellar hemisphere should be easily pulled inward and backward to facilitate sufficient field exposure. (2) After craniotomy, as with the removal of the cerebellar cerebral horn tumor, the cerebellum is first pulled to the inner and rear with a serpentine retractor to reveal the cerebellopontine angle of the cerebellum. (3) After the cerebral horn of the cerebellum is exposed, it can be seen that some vasospasm formed by the blood supply artery and the drainage vein surrounds the V and VII, VIII cranial nerves. The difficulty of surgery is: 1 the thickening of the blood supply artery, it is difficult to identify which is the trunk of the blood supply artery, and which is the branch of the blood vessel that enters the deformed blood vessel group. 2 The main blood supply artery of this AVM is the inferior cerebellar artery, which has a long stroke and is complex and variable. Starting from the ventral side of the cerebral ventricle, it is wound to the outside, and after forming a small sputum near the VIIVIII cranial nerve, it is divided into the medial branch and the lateral branch. The medial branch (ie, the anterior branch) passes the anterior pompon to the underside of the cerebellum, and the lateral branch (ie, the posterior branch) turns to the horizontal groove behind the pompon. There are many small branches distributed on the pons on the trunk before the branch. These branches are already complicated, and the deformed vascular mass is more complicated. For this reason, the bifurcation point of the inner and outer branches is followed to the direction of the basilar artery along the artery to be seen. The proximal side of this point is the trunk of the inferior cerebellar artery. Then turn the gaze to the inner ear hole, find the artery that enters it, and then trace it to the brain stem side. This path is the path of the anterior cerebellar artery. The person who goes to the deformed vascular group from this path is the blood supply artery. There are two kinds of drainage veins of malformed vascular mass, which are respectively on the ventral and dorsal sides of the cerebellum. If there is a small branch that obstructs the view, it can be cut off for surgery. (4) After clearing the blood supply artery of the non-main trunk, one of them is clipped and cut off. For the deformed blood vessels that are difficult to separate between the cranial nerves, it is not appropriate to separate them, and some of them may remain. A blood vessel that is not easily peeled off or a deformed blood vessel that enters the brain stem may be adhered to the side of the pons, and a part of it may be left in isolation. (5) The drainage vein was ligated and cut, the deformed vascular group was removed, and the skull was closed after careful hemostasis. complication Intracranial hematoma is prone to occur after surgery, and should be carefully observed. Once the delay or surgical rescue is not timely, the consequences are more serious than those on the screen.