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Discussion

  • Arteriovenous malformations (AVMs) are congenital vascular lesions that consist of direct communication of arteries to veins with no intervening capillary bed.  As a result, there is direct shunting of blood with subsequent dilation of the feeding arteries and early draining veins. AVMs are usually solitary unless seen in association with other syndromes, such as Osler-Weber-Rendu or Wyburn-Mason. 

  • The most common initial symptom is related to acute intracranial hemorrhage, although larger AVMs often present with seizures. The rate of hemorrhage is 3% per year. The risk of rebleeding after an initial event is 6% during the first year. Other symptoms include headaches, neurologic deficits, and mass effect. AVMs usually do not become clinically apparent until 20 and 40 years of age.

  • Eighty percent of AVMs are parenchymal. Ten percent are durally based with an external carotid artery blood supply and usually are acquired lesions. There are 3 subtypes that depend on the blood supply: pial, dural, and mixed pial-dural types.  Aneurysms are associated with the feeding arteries in approximately 10% of cases. 

  • AVMs can be visualized with angiography, computed tomography, or magnetic resonance imaging.  MRI/MRA is the study of choice for detection of AVMs, but arteriography is superior for treatment planning. Serpiginous high and low signal (depending on flow rates) within feeding and draining vessels is best seen on MRI/MRA. AVMs replace but do not displace the brain tissue. There is no mass effect, except when complicated by hemorrhage and edema. Adjacent parenchymal atrophy is common due to vascular steal and ischemia.

Treatment

  • Embolization, sterotactic radiosurgery, microvascular surgery

Key Points

  • AVMs usually present with acute intracranial hemorrhage (50%) or seizure (25%).

  • Peak presentation is between 20-40 years of age, with 25% occurring in childhood/adolescence.

  • MRI/MRA can noninvasively evaluate arteriovenous malformations and their complications. However, angiography may be necessary for treatment planning.

  • The classic imaging finding is multiple flow voids with arteriovenous shunting and minimal or no mass effect. Hemorrhage, old and new, is also common.

  • Treatment includes embolization, radiosurgery, and also surgical resection.

References

  • Grossman, RI and Yousem, DM. Neuroradiology: The Requisites. 3rd edition, Mosby, Philadelphia, 2003.
  • Brant and Helms. Fundamentals of Diagnostic Radiology. 3rd edition, Lippincott Williams and Wilkins, Philadelphia, 2006.
  • Osborn, AG. Diagnostic Neuroradiology. Mosby, St. Louis, 1994.

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