Intracranial vascular malformations such as arteriovenous malformation (AVM), cavernous malformation (CM), capillary telangiectasia, developmental venous anomaly (DVA), and vein of Galen malformation are congenital developmental abnormalities (except most dural and extracerebral AVMs and some CMs may be acquired) and usually take many years before they become clinically apparent. The presentation and the natural history depend on the vascular malformation subtype, location, size, and other characteristics. Some of these lesions can cause serious neurologic signs and symptoms, whereas others are typically asymptomatic and are benign.

AVMs are congenital vascular abnormalities consisting of a direct arterial to venous fistula and a normal capillary bed. While most AVMs do not have a genetic basis, hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease) is an uncommon genetic condition, which can be associated with cerebral and systemic AVMs. Symptoms of unruptured AVMs often appear in adolescence or later (most frequently in the third and fourth decades of life) and usually produce intracranial hemorrhage (intracerebral is the most common; subarachnoid hemorrhage [SAH] and intraventricular hemorrhage are less common), recurrent unilateral headache (which may resemble migraine), focal or generalized seizures, a pulsatile noise in the head called pulsatile tinnitus, progressing neurologic deficits, or, rarely, transient focal neurologic symptoms that mimic transient ischemic attacks. Not infrequently, they are discovered fortuitously, detected on cross-sectional brain imaging that is performed for an unrelated reason. AVMs are occasionally associated with a cranial or orbital bruit. They may not be observable on computed tomography (CT) imaging without contrast, except calcification, or low attenuation may be noted. Magnetic resonance imaging (MRI) is very sensitive to the detection of AVMs, with signal voids on T1 and T2 imaging and often some degree of hemosiderin. Magnetic resonance angiography (MRA) or computed tomography angiography (CTA) provides more information regarding the nature of the feeding arteries and draining veins, but an arteriogram typically is needed to evaluate the AVM in detail and aids in defining the optimal management.

CMs are well-circumscribed, angiographically occult lesions, consisting of endothelial lined caverns, and without intervening brain parenchyma. The estimated prevalence is approximately 0.5% in autopsy series. They are most commonly detected on MRI scanning, often with the cavernoma causing no neurologic signs or symptoms. When they do present with symptoms, seizures are most common, including focal or generalized seizures. Focal neurologic deficits or nonspecific headache may also occur. Symptoms are caused by small hemorrhages that occur within the lesion or at the periphery, although significant intraparenchymal
hemorrhage is rare. CT with contrast enhancement may demonstrate a characteristic mulberry-shaped lesion with calcification, although MRI typically is necessary to detect these angiographically occult lesions. MRI demonstrates a mixed increased and decreased signal lesion on both T1 and T2 imaging, with surrounding hemosiderin. They may be multiple, particularly in familial cases.

Capillary telangiectasias are anomalies of capillary-sized vessels, which characteristically are located in the brainstem or the cerebellum. They are usually asymptomatic (when associated with the syndrome of Osler-Weber-Rendu, they may be clinically recognized elsewhere in the body) and have little risk for hemorrhagic complications.

Intracranial DVAs, also known as venous malformation, are the most common vascular malformation noted on autopsy and brain imaging, found in about 2% of people. They are usually asymptomatic. Very uncommonly, they may cause seizures, focal neurologic symptoms, or trigeminal neuralgia. Rarely intracranial hemorrhage occurs, although in most cases, some other vascular malformation type—usually a CM—is found to be occurring along with the venous malformation and is the cause of the hemorrhage. They may be seen on CT with contrast as an enlarged draining vein and on MRI as a flow void, sometimes with the radial “caput medusa” appearance. On arteriography (venous phase), they are represented by a deep prominent vein of varying size and may be associated with the caput medusa pattern. Asymptomatic venous malformations have a benign prognosis, rarely causing hemorrhage or other neurologic symptoms.

Dural arteriovenous fistulae (DAVF) or dural AVMs are vascular malformations in one of the major venous sinuses. These typically acquired lesions present with clinical symptoms dependent on the site of the lesion. Lesions in the superior sagittal sinus may cause papilledema with vision loss; those in the cavernous sinus cause diplopia, exophthalmos, and vision loss; transverse/sigmoid sinus lesions may cause pulsatile tinnitus; and cortical lesions may cause seizures or neurologic deficit. Dilated veins on a CT head scan may suggest their presence, but a CT is usually normal. MRI may show the dilated veins and feeding arteries. An arteriogram is needed to characterize these lesions best and should include selective external carotid artery injection because they often receive arterial supply from the external carotid artery.