Arteriovenous Malformation (AVM)
An arteriovenous malformation (AVM) is a congenital vascular anomaly in which brain arteries connect directly to veins without an intervening capillary network. Its most important risk is intracranial hemorrhage; the decision to treat is individualized by balancing rupture risk against procedural risk.
最終更新: 2026-06-07
Definition
An arteriovenous malformation is a congenital vascular anomaly in which brain arteries connect directly to veins without an intervening normal capillary network. Its core components are feeding arteries, a tangle of vessels called the nidus, and draining veins. Because the capillary bed is absent, high-pressure arterial blood passes directly into the low-pressure venous system, predisposing to venous hypertension and bleeding. AVMs are most common in the cerebral hemispheres (supratentorial), but posterior fossa, deep, and brainstem locations also occur.
Causes and Risk Factors
AVMs are congenital and occur in roughly one in a thousand people, usually becoming symptomatic between ages 20 and 40. Most cases are sporadic; certain inherited conditions such as hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome) may feature multiple AVMs. Associated arterial aneurysms, deep venous drainage, a single draining vein, and a prior bleed are linked to higher hemorrhage risk.
Symptoms
AVMs may present in three main ways: intracranial hemorrhage (the first sign in about half of patients), epileptic seizures, and progressive neurological deficit or headache. Seizures are particularly common with cortically located AVMs. Hemorrhage is an emergency that can present with sudden severe headache, altered consciousness, and focal neurological loss. Some AVMs are silent and found incidentally on imaging performed for other reasons.
Diagnosis
MRI is usually the first step, showing flow voids within the nidus, enlarged feeding arteries, and draining veins; susceptibility-weighted sequences may reveal prior microbleeds. When acute hemorrhage is suspected, computed tomography (CT) and CT angiography allow rapid assessment. The gold standard for detailed vascular mapping and treatment planning is digital subtraction angiography (DSA), which characterizes nidus size, feeding arteries, draining veins, and any associated aneurysms.
Spetzler-Martin Grading
The Spetzler-Martin system is a grading scheme used to predict surgical risk and scores three criteria: AVM size (small, medium, large), location in eloquent (functionally critical) brain, and the presence of deep venous drainage. The total score classifies AVMs as low (Grade I-II), intermediate (Grade III), or high risk (Grade IV-V). This grading helps weigh treatment options but does not dictate the decision on its own.
Treatment
The main goal of treatment is to completely exclude the AVM from the circulation to eliminate the risk of bleeding. The principal methods are microsurgical excision, stereotactic radiosurgery (e.g., Gamma Knife), and endovascular embolization; many cases use these methods in combination (multimodal). Microsurgery achieves high complete-removal rates in low-grade AVMs. Radiosurgery may be preferred for small or deep AVMs, but its effect appears over 1-3 years, during which bleeding risk persists. For unruptured AVMs, the choice between treatment and observation is individualized by comparing natural-history risk against procedural risk.
Prognosis
The course is closely related to the AVM's size, location, angioarchitecture, and bleeding history. After a hemorrhage, the risk of rebleeding rises markedly, so treatment is often recommended. Treatment outcomes vary by method and patient; confirming complete obliteration on follow-up imaging is important. Outcomes are individual and none can be guaranteed.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:1504-1513.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011:4045-4055.
- Spetzler RF, Kalani MYS, Nakaji P, eds. Neurovascular Surgery. 2nd ed. Thieme; 2015:791-814.
- Mohr JP, et al. A Randomized trial of Unruptured Brain Arteriovenous malformations (ARUBA). Lancet. 2014.
- Derdeyn CP, et al. Management of Brain Arteriovenous Malformations: Scientific Statement. Stroke (AHA/ASA). 2017.
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