The goal of treatment for cerebral arteriovenous malformations is to prevent bleeding, reduce or correct “brain theft,” improve blood supply to brain tissue, relieve neurological dysfunction, control epilepsy, and improve patient life. The current treatment methods include conservative treatment, microsurgical resection, intravascular interventional embolization and stereotactic radiation therapy, as well as a combination of these methods.
Conservative treatment: For those who are older, have only epileptic symptoms or are located in important functional brain areas and deep brain lesions or have extensive lesions that are not suitable for surgery, conservative treatment should be used. The main purpose of conservative treatment is to prevent or stop bleeding and rebleeding, control epilepsy, and relieve symptoms, etc.
(1) Maintain a normal routine: avoid strenuous exercise, mood swings and exertion, keep bowel movements smooth, and lower blood pressure appropriately in hypertensive patients. For those with bleeding, absolute bed rest for 1 to 6 weeks.
(2) Anti-epileptic treatment: choose anti-epileptic drugs according to the type of epilepsy and adhere to regular medication for a long time to control seizures. Phenytoin sodium, phenobarbital or paracetamol can be preferred for grand mal seizures and limited seizures, phenytoin sodium, carbamazepine, nitrazepam and sodium valproate can be used for psychomotor seizures, and ethosuximide, sodium valproate and clonazepam can be used for aphasic petit seizures. Generally, a gradual reduction of the drug dosage is considered only after 2 to 3 years of complete seizure control.
(3) Symptomatic treatment: Those with bleeding can be treated symptomatically as subarachnoid hemorrhage. Those with increased intracranial pressure may be given dehydrating agents such as mannitol to reduce intracranial pressure. If the hematoma is large and the increase in intracranial pressure is severe, surgical removal of the hematoma is appropriate. Select different drugs for symptomatic treatment according to the patient’s symptoms to reduce the patient’s symptoms, etc.
(4) Prevention of rebleeding: Coagulant drugs such as aminomethylbenzoic acid and aminohexanoic acid can be tried to prevent rebleeding, but their efficacy needs to be further confirmed.
2.Microsurgical resection: The application of microsurgical techniques has greatly improved the surgical total resection rate of cerebral AVM. So far, surgical resection is still one of the best methods to completely treat this disease.
Selection of AVM surgical resection cases.
① Those with a history of intracranial hemorrhage and cerebral angiogram showing AVM of grade 1 to 3.5, including those located in functional brain area, medial side of brain, lateral fissure area, corpus callosum, lateral ventricle, paraventricular area, intra-striatal capsule thalamus area, cerebellar hemisphere and cerebellar earthworm should be considered for surgical resection. However, lesions located in and around the hypothalamus, brainstem and pontocerebellar horn of the cerebellum must be treated with caution; it is not easy to survive after hemorrhage, and surgical injury may have extremely serious consequences.
②No history of intracranial hemorrhage, located in superficial non-functional areas of the brain, anterior and middle frontal, parietal and medial occipital lobes, etc., avm with a diameter <5 cm, can be selected for surgical excision.
③No history of intracranial hemorrhage, but with the following symptoms: intractable epilepsy or severe progressive neurological deficits that have failed to be controlled by medication, etc., lesion resection may help to improve symptoms.
④Large-type, high-flow AVMs with lesion resection within 1 to 2 weeks after endovascular intervention to embolize part of the main blood supply artery.
⑤ Patients with acute intracranial hemorrhage should undergo emergency surgery when intracerebral hematoma leads to brain herniation formation and endangers life, and in general, removal of the hematoma and reduction of intracranial pressure are the main priority to save life, unless cerebral angiography has been performed before surgery, and AVM resection can be considered. Generally, after the general condition and neurological function have improved and stabilized, cerebral angiography should be performed for further examination, and AVM resection should be performed under the premise of adequate preparation. At present, 3D-CTA has important reference value in determining the site and size of AVM lesions in the acute stage of hemorrhage and helps to guide the removal of hematoma, and the examination is non-invasive and can be completed in just a few minutes, even when the patient is on the way to the operating room for preoperative preparation.
(6) Elderly patients, those whose cardiopulmonary function is difficult to tolerate anesthesia and surgery, and those with serious disorders of other systems for which AVM resection would not help improve quality or duration of survival should be considered contraindications.
(7) The possible complications and sequelae of the surgery that may affect the patient’s occupation, especially AVM that has not bled out and is occasionally found without any clinical manifestation, must let the patient and his relatives fully understand the purpose and consequences of the surgery and make the treatment choice after weighing the pros and cons.
3.Endovascular interventional embolization: Endovascular treatment began in the 1960s and is mainly used for deep AVMs that are difficult to be treated surgically, so that the lesion can be reduced or completely occluded to facilitate surgery or radiation therapy. However, as a means of treating AVM alone, endovascular treatment still has great limitations, and only a few cases with a small number of blood supplying arteries and simple structures can be cured by simple embolization therapy. The cure rate by embolization alone is reported to be about 10%-15%, and another 50% of lesions can be reduced to the extent that they can be treated with radiotherapy or surgery. Therefore, embolization is often used as an adjunct to surgery or radiation therapy. The main risks of endovascular treatment are.
(1) Intraoperative bleeding, with an incidence of 7% to 11%, often occurs during catheter delivery and may be due to inaccurate positioning of the embolization material to embolize the vein, and often requires emergency surgery if this occurs.
②The embolization may involve the normal blood supply artery and lead to ischemic complications.
(iii) Recanalization after treatment.
(iv) Intraoperative vasospasm leading to difficult retrieval, catheter adhesion to the vessel, and disconnection, requiring emergency surgical management. The development of super-selective catheter technology and the application of various new technologies have improved the efficacy of endovascular treatment, especially in the prevention of ischemic complications.
4, stereotactic radiation therapy: radiation therapy is a therapy carried out in the past 20 years, with important γ-knife, χ-knife, proton beam, linear gas pedal, etc.. It is the use of contemporary advanced stereotactic and computer systems to intracranial targets, using a high dose of irradiation, radiation from multiple directions, multi-angle precise aggregation of the target, causing radiobiological response, so as to treat the disease method. However, clinical observation in recent years shows that the occlusion rate after radiotherapy increases year by year, and the occlusion rates in the 2nd, 3rd and 4th years after radiotherapy are 32%, 50% and 80%, respectively. It is generally believed that the occlusion rate after AVM treatment is closely related to the volume of cerebral AVM and the radiation dose received. Since the possibility of hemorrhage and radioactive reaction of brain tissue during the complete occlusion of the malformed vascular mass after radiation therapy still becomes the main factor limiting its application, the length of this time is very important to evaluate its efficacy.
Radiotherapy is not effective for lesions >3 cm and has a high complication rate; therefore, it is currently used mainly for avm with diameters <3 cm, deep and aggressive locations, lesions located in major functional areas, not easily operable, or difficult to treat endovascularly and for complementary treatment of residual lesions after craniotomy and endovascular embolization. Radiation therapy is easily accepted by patients because it does not require craniotomy and has a short hospital stay. However, less than 25% of all brain avm are fully suitable for radiation therapy.
5.Comprehensive treatment: microsurgery, intravascular interventional embolization and stereotactic radiosurgery have been widely used in the treatment of cerebral AVM, but for large, giant AVM or lesions located in important structures or deep brain, it is difficult to achieve ideal efficacy with a single treatment method. In recent years, studies on the combined application of two or three treatments have shown to significantly improve the cure rate and reduce the disability and mortality rates of AVMs.
Small (<3 cm in diameter) and superficial AVMs are treated surgically, while small (<3 cm in diameter) and deep lesions are treated radiosurgically. For AVM >3cm in diameter, endovascular embolization should be performed first. If the AVM disappears completely, no further treatment is needed, but follow-up is required; if the diameter is still >3cm, lesions with high surgical risk are temporarily treated conservatively, and radiotherapy is not advocated; lesions that are reduced in size and superficial in diameter <3cm can be surgically resected, and deep ones are treated radiosurgically.
(1) Interventional embolization plus surgical resection: The combined application of these two methods is the most widely carried out at present. Preoperative embolization can reduce the volume of AVM, blood flow and intraoperative bleeding, especially the obstruction of deep blood supply artery is beneficial to the separation of vascular mass and total resection. Preoperative fractionated intravascular embolization has a greater significance in preventing intraoperative and postoperative cerebral hyperperfusion phenomena. It is generally believed that surgery is most appropriate 1 to 2 weeks after embolization, while revascularization occurs with NBCA embolization, which is more common after 3 months, so surgery can be delayed appropriately. In conclusion, endovascular interventional embolization has been an important adjunct before surgical resection of AVM.
(2) Interventional intravascular embolization plus stereotactic radiotherapy: The application of stereotactic radiosurgery, γ-knife, χ-knife, etc. (hereinafter referred to as radiotherapy) for the treatment of cerebral AVM has the advantages of non-invasive, small risk and short hospital stay, but the efficacy of single radiotherapy is inferior to the combined treatment of both. Intravascular embolization before radiotherapy can reduce the size of AVM, decrease the radiation dose, and reduce the radiation response of surrounding brain tissue, which can improve the cure rate. Endovascular embolization can also occlude AVM complicated by aneurysm and associated large arteriovenous fistula, reducing the risk of rebleeding during radiotherapy observation. However, embolization before radiotherapy can make the residual AVM mass more irregular in shape, which makes it difficult to accurately estimate the target volume of AVM and calculate the radiation dose.
(3) Stereotactic radiotherapy plus microsurgical resection: large cerebral AVM can also be treated with stereotactic radiotherapy as an adjunct before surgical resection. After radiotherapy, thrombosis within the AVM mass is formed, the volume is reduced, the number of vessels is decreased, and intraoperative bleeding is low. Converting large AVM into a lesion with low complications facilitates surgical operation and improves the success rate of surgery. Surgery, in turn, removes large AVMs that cannot be occluded by radiotherapy, improving the cure rate.