The cerebral arteriovenous malformation is a vascular condition characterized by the presence of abnormal, direct connections between the cerebral arterial and venous circulatory system, thus bypassing the capillaries.
A small group of people with cerebral arteriovenous malformations (CAVMs) remain asymptomatic and are diagnosed accidentally . However, a vast majority of patients present with symptoms ranging from mild headaches to severe life-threatening hemorrhages .
The most common feature in CAVMs is intracerebral hemorrhage, being present in nearly 50% of patients with this disease. These hemorrhages result from rupture of the abnormal arteriovenous connections in the brain. The annual risk of rupture is 2-4%, but it may be as high as 30% in a few patients .
Seizures are the second-most common clinical feature seen in these patients, being present in about 15-40% of the diseased population  . Around 10-50% patients may present with headaches . There are no specific patterns to the seizures and headaches in these patients, owing to the heterogeneity in location and function of the CAVMs .
Based on the location of the CAVMs, patients may present with certain other neurological features, which include: motor deficits like muscle weakness, sensory deficits in the form of numbness, pain, and paresthesias, memory and learning disabilities, ataxia, apraxia, aphasia, vision abnormalities, dizziness, mental confusion, and hallucinations.
In view of intracerebral hemorrhages being the most common presentation, the initial test of choice in CAVMs is a brain computed tomography (CT scan) . Unruptured connections are usually seen as areas of mixed enhancement with surrounding edema and mass effect. A quarter of cases may show calcification in these areas.
If the patient presents with seizures and a brain CT scan is negative, a magnetic resonance imaging (MRI) of the brain must be done. CAVMs appear hyperintense (‘flow-voids’) on T2 images owing to the turbulence of blood present within these connections. The sensitivity of MRI is around 80-95%, increasing with the use of gadolinium enhancement.
The key investigation to study the CAVM location, size, and associated areas are digital subtraction angiography (DSA) . CAVMs are usually wedge-shaped, with the arteries appearing enlarged and tightly packed, along with an accompanying tortuous and dilated venous circuit. DSA may also be useful in detecting arteriovenous malformations with a diameter of less than 1 cm, termed the micro-arteriovenous malformations.
A suitable alternative to DSA is CT and MR angiograms, that may be used for follow-up after treatment. They are, however, unreliable in detecting micro-arteriovenous malformations.
Routine blood tests, in the form of a complete blood count (CBC), blood grouping, coagulation studies, must be performed to rule out other causes of intracerebral hemorrhages. These tests may also be beneficial when taking the patient up for surgery. Hemorrhage in young adults may warrant a toxicological screening for drugs.
An electroencephalogram (EEG) may be needed in patients who have seizures as their first complaint. Visual fields need to be examined in patients reporting ocular symptoms.
Other tests that may be performed include functional imaging scans such as functional MRI, positron emission tomography, and magnetoencephalography . These may help in localizing the functionally important cortical areas. Superselective Wada testing may be performed before surgery.