The Eagles have announced that defensive tackle Mike Patterson's seizure during a recent practice was caused by an AVM, or arteriovenous malformation, a congenital defect that involves tangled blood vessels outside the brain. In many cases, one of the first lines of treatment for AVM is to attach coils or glue inside the AVM to help prevent it from growing. Christopher Loftus, chair of neurosurgery at Temple, said that might not be the best option for Patterson, given his young age. Instead, Loftus favored taking the AVM out surgically if it was small enough and in a favorable location.