AVM is a congenital abnormality of the intracranial vascular bed, in which the capillary network between the arterioles and veins is defective and the arterioles are connected by fistulas, resulting in the arterioles flowing directly into the veins, leading to the gradual enlargement and distortion of the arterioles into clusters and the development of cerebral AVM. AVM is most common in young people, with the highest incidence between the ages of 20 and 40. AVM occurs in more than 90% of the supratentorial and 9.2% of the infratentorial. The AVM is a wedge-shaped lesion with the base in the cerebral cortex and the tip extending into the brain and even into the ventricles.
Major clinical manifestations.
1. The most important symptom of cerebral AVM is hemorrhage, which is a weak malformed vessel wall that ruptures by the impact of pulsatile blood flow, resulting in subarachnoid hemorrhage or intracerebral hematoma. The clinical manifestations are sudden and severe headache with nausea, vomiting and some degree of impaired consciousness. Since AVM is mostly venous bleeding, the amount of bleeding is less than aneurysm rupture, and the incidence of cerebral vasospasm is also low, only 8.3%-12%, but repeated bleeding is one of its characteristics.
2. The incidence of epilepsy is second only to hemorrhage, and can be the first symptom of those without hemorrhage.
3. Vascular headache is another important symptom. 20% of patients have a long history of headache before the onset of the disease, which is caused by the stimulation of the trigeminal nerve on the dura mater.
Imaging manifestations of cerebral AVM.
1.CT scan: focal high and low or low mixed density shadow can be seen, and the boundary of the lesion is clear and irregular after enhancement, and thick drainage veins can be seen nearby.
2.MRI examination: It is the preferred imaging examination means for AVM. The lesion is low signal or no signal, which is manifested as vascular “flow-void phenomenon”.
3.Digital subtraction angiography (DSA): DSA is still the most reliable method to diagnose AVM, which can clarify the AVM site, blood supply artery and drainage vein.
At present, the treatment of AVM mainly includes microsurgery, neurointerventional treatment and stereotactic radiosurgery, and most of the larger AVMs should be treated by combined treatment.
Microsurgery.
Microsurgery is the preferred radical treatment for AVM. Surgical resection of the malformed vascular mass can eliminate the risk of AVM rupture and bleeding. Surgical resection is indicated for
(i) arteriovenous malformations with hematoma or recurrent bleeding;
(ii) Intractable seizures that cannot be controlled by medication;
(iii) intractable headache that cannot be relieved. For large high blood flow lesions, staged surgery or staged embolization, or a combination of both methods, should be used.
Neurointerventional treatment.
Neurointerventional treatment has the advantages of being effective and minimally invasive and is suitable for.
① Deep brain AVMs in important functional areas;
② High blood flow or large AVM;
③ Small and medium-sized AVMs can be treated with neurointerventional therapy to make the malformed vascular mass disappear.
For large AVMs, more than 50% to 70% of the malformed vascular mass can be embolized at one time to prevent bleeding; residual malformed masses can be surgically removed or treated by stereotactic radiosurgery.
Stereotactic radiosurgery.
At present, it mainly includes gamma knife (γ knife) or linear gas pedal stereotactic (X knife), which is suitable for
① lesions less than 3 cm in diameter;
②AVM in the deep brain;
(iii) residual lesions after surgery or embolization. The disadvantage is that rebleeding cannot be prevented for six months after irradiation.