AVmalformaties

AVmalformaties, or arteriovenous malformations (AVMs), are abnormal tangle-like connections between arteries and veins that bypass the capillary bed. Cerebral AVMs are the most studied form, but AVMs can occur in the brain, spinal cord, or other organs.

They create high-flow shunts and a nidus of abnormal vessels. The lack of a capillary bed leads to fragile venous channels that are prone to rupture, causing hemorrhage, seizures, or neurologic deficits, especially if located in eloquent brain regions.

Diagnosis typically begins with MRI and MR angiography or CT angiography; digital subtraction angiography is the gold standard for mapping feeding arteries, the nidus, and draining veins needed for treatment planning.

Classification often uses the Spetzler-Martin grading system, which assigns points for lesion size, eloquence of adjacent brain, and deep venous drainage, yielding grades 1 through 5 that guide treatment risk. Other schemes describe venous drainage and architecture.

Treatment is individualized and may be multimodal. Small, accessible AVMs may be cured with microsurgical resection; endovascular embolization can reduce nidus size or be used before surgery; stereotactic radiosurgery can control or obliterate others over months to years.

Observation is considered for incidental, low-risk lesions in some patients. Complications of treatment include stroke or hemorrhage from the procedure, radiation effects, or partial obliteration leaving residual AVM.

Epidemiology: AVMs are uncommon, with a baseline population incidence around 1 per 100,000 per year. Most are congenital and sporadic; they may be associated with hereditary hemorrhagic telangiectasia in a minority of cases.