Cardiovascular Radiology

Case 4:

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A young male presents with seizure. An MRI was performed. 
What is the diagnosis?

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Imaging Findings reveal a classic arterio-venous malformation in the left parietal region, with areas of flow void and hemorrhage and mass effect.

There are four main types of AVMs in the brain and spinal cord:  the classic arteriovenous malformation, the cavernous angioma, venous angioma and the capillary telangectasia.  The most common is the classic AVM.

As the name implies, arteriovenous malformations (AVMs) are a conglomeration of abnormal vascular channels, which shunt blood from arteries to veins without an intervening capillary network. AVMs have been likened to a vascular "bag of worms" which can cause a steal phenomena leading to ischemia and atrophy of adjacent brain.

Clinical Features
The majority of AVMs are assymptomatic until adulthood, presenting as a progressive neurologic deficit, seizure or acute intracranial hemorrhage between the ages of 20 and 40 years. One fourth of all AVMs hemorrhage within the first 15 years of life. The annual risk of intracranial hemorrhage is believed to be 2-4%, with each episode of hemorrhage carrying a 30% risk of death and 25% likelihood of long-term morbidity. The majority of AVMs are solitary, but a small number, roughly 2%, are multiple and usually associated with neurocutaneous disorders such as Osler-Weber-Rendu or Wyburn-Mason Syndromes. Their typical location is within the cerebral hemispheres. A minority (15%) occur in the posterior fossa.

The most common symptoms of an AVM are headache similar to migraine, seizures, progressive neurological deficits and hemorrhage or brain attack.   Over time as the AVM steals blood from surrounding tissues, this causes a lack of blood flow or ischemia to the surrounding brain. Progressive neurological deficits means a slow loss of specific functions (motor, sensory, vision, etc.) that is often insidious and not appreciated by the patient until the symptoms are severe.

MR Findings
MRI shows the majority of vessels as signal-void, and is capable of providing information regarding the vascular supply and venous drainage, as well as the nidus. In addition, PC technique may be helpful in determining blood flow velocities in arteries and veins involved with the AVM.

Options include microscopic surgical excision of the entire nidus, endovascular occlusion of feeding vessels and if possible the nidus itself with embolization, and stereotatic surgery.

Dr. Ashok Raghavan, Manipal Hospital, Bangalore