AVMs

Arteriovenous malformations (AVMs) are congenital vascular abnormalities characterized by direct arterial-to-venous connections that bypass the capillary bed. The central nidus is a tangle of abnormal vessels that receives high-flow arterial inflow and drains into venous channels. AVMs can occur in many organs, most commonly in the brain and spinal cord, but may also involve the eyes, skin, lungs, liver, and retina.

In the brain, AVMs may be asymptomatic or present with headache, seizures, focal neurologic deficits, or intracranial hemorrhage, which can be life-threatening. Spinal AVMs can cause back pain, progressive weakness, sensory loss, or myelopathy. Cutaneous AVMs appear as redness or warmth; visceral AVMs can produce organ-specific symptoms such as high-output heart failure.

Diagnosis typically begins with noninvasive imaging such as magnetic resonance imaging with MR angiography or computed tomography angiography, followed by digital subtraction angiography (DSA), which provides detailed mapping of feeding arteries and draining veins critical for treatment planning.

Management is individualized and depends on size, location, venous drainage, prior rupture, and risk to eloquent brain tissue. Unruptured or small, low-risk brain AVMs may be observed. Treatment options include endovascular embolization to reduce flow, microsurgical resection to remove the nidus, stereotactic radiosurgery to obliterate the lesion over months to years, or a combination of these approaches. The choice balances rupture risk against procedural risks.

Untreated brain AVMs carry a risk of rupture and hemorrhage, commonly cited as about 2-4% per year, with higher risk after a prior bleed. Outcomes vary with lesion characteristics and treatment efficacy. Most AVMs are sporadic, though some are associated with hereditary hemorrhagic telangiectasia (HHT).