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Case 21

Arteriovenous malformation

Michael Crouch

A lady with five days of severe headache

This middle aged lady presented with five days of severe headache and vomiting. She was found to have a mild left homonymous hemianopia. Seventeen years earlier she had developed seizures of the left leg, which were successfully controlled with phenytoin.

Findings

Non contrast enhanced scans demonstrated an area of increased density in the right parietal region associated with a focal area of calcification.

After contrast injection a huge number of serpiginous dilated afferent and efferent feeding vessels are demonstrated, extending into a strongly enhancing nidus.

The first image above demonstrates the enlarged right anterior cerebral artery feeding the AVM, and the second (not shown previously), the large vein draining forwards in the midline. Large veins are also visible over the convexity of the right hemisphere.

Diagnosis

Large right parietal arteriovenous malformation (AVM)

Discussion

AVMs are the most frequent of the vascular malformations of the brain. They usually present with either bleeding, seizures, progressive neurological deficit or headaches.

Most become symptomatic during the second or third decade of life (and 80% by the end of the 4th decade). the yearly rate of first haemorrhage is approximately 2-3%. For each bleed there is an average risk of 10% mortality.

Histologically the lesions consist of vascular clusters that form direct arteriovenous shunts without any intervening capillary network.

Angiography is mandatory to confirm the diagnosis, to map the afferent arteries and efferent veins and to determine the speed of blood flow through the malformation and to decide the best alternative of treatment depending on size, location and calibre of vessels.

Surgical resection is considered the treatment of choice for small AVMs. Other alternatives include embolisation and stereotactic radiotherapy.

References

Taveras & Ferruci. Radiology Vol 3. Lippincott, Philadelphia 1992.

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