Eagles player Mike Patterson’s seizure may be due to arteriovenous malformation, but the condition is often treatable

Philadelphia Eagles defensive tackle Mike Patterson has been diagnosed with arteriovenous malformation after suffering a seizure on the field during practice Wednesday, according to news reports.

AVM is a flaw in the circulatory system that produces abnormal blood vessel connections in different parts of the body, but whose cause is unknown, according to the National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health. They usually form just before or after birth, and most people with the disorder live their lives with few symptoms or none at all.

In some cases AVM can manifest as a tangle of blood vessels in the brain. When blood enters the brain it usually goes through arteries, then into arterioles that branch out from the arteries, then through capillaries. But for those with AVM, the blood goes right from the arteries to the veins, circumventing the capillaries altogether, according to the Mayo Clinic. That can cause the arteries and veins to break, resulting in bleeding in the brain, which in turn can trigger a stroke. Symptoms that can occur without bleeding include confusion, headaches, blurred vision, muscle weakness, noise in the ear, trouble walking and seizures.

While rare (the NIH reports that cerebral AVMs happen in less than 1% of people), people at any age can experience symptoms. As far as treatment goes, the agency says medications can help with indicators such as headaches, seizures and back pain, but irradiation therapy and surgery are considered more permanent solutions.

If Peterson undergoes surgery there are risks, and the decision to operate is carefully weighed against possible outcomes such as seizure, stroke, hemorrhage and swelling of the brain.

A 2003 study in the journal Neurosurgery looked at how patients fared after radiosurgery for AVM; this technique is usually used on areas of the brain that are hard to reach via regular surgery. The technique uses a focused energy source to treat damaged vessels.

Researchers looked at post-surgery outcomes for 144 patientts who had radiosurgery for an AVM. Follow-up on 129 patients after an average seven years found that after surgery, most patients were shielded from the risk of hemorrhage and went on to perform their usual daily routines. On rare occasions there were complications years later that required further treatment.