Onyx Embolization for Complex AVMs
At age 7, Courtney McGrath experienced numbness in her arm and leg. An MRI revealed that she had an
arteriovenous malformation (AVM) about the size of a lemon, 6 cm by 6 cm, in her motor cortex. Until about a year ago, it would have been very difficult to remove this lesion without causing paralysis on the left side of the body.
Fortunately, when Courtney came to Harborview, the cerebrovascular team could offer hope for a better outcome.
Courtney’s doctors began treatment with onyx embolization as a way to make surgery safer. Onyx is an embolic agent approved by the Food and Drug Administration in 2005 to close off an AVM partially in preparation for surgery or radiosurgery. Compared to n-BCA, the previous standard for embolic agents, onyx polymerizes more slowly and can be delivered with greater precision into the AVM.
After several onyx treatments, Courtney’s doctors were able to remove her AVM during a complex and difficult operation lasting about 16 hours. Follow-up angiograms indicate that the lesion was completely obliterated.
"The decision to treat an unruptured AVM begins with a careful risk assessment," said
Dr. Laligam Sekhar, Courtney’s neurosurgeon at Harborview. "Only three percent of these malformations bleed per year, but the consequences can be devastating. After a single bleed, nearly 33 percent of patients either die or have significant disability."
An AVM is a malformation involving a direct connection of arteries and veins. Although usually present at birth, it may not be diagnosed until the patient suffers a bleed. Other possible symptoms are recurrent, bad headaches, seizures and impaired brain function. Depending on the size and location of the AVM, three treatment modalities are available: microsurgery, Gamma Knife radiosurgery and endovascular embolization.
Surgical resection is advised if the AVM is located in a superficial portion of the brain or spinal cord because it immediately eliminates the risk of a bleed. Additionally, with advances in endovascular and microsurgical techniques, the cerebrovascular team at Harborview can also operate on some very large AVMs located in superficial or deep parts of the brain, which previously could not be treated safely. But, for other deeply located AVMs, radiosurgery with the Gamma Knife is a better option than microsurgery, to avoid damage to critical areas of the brain.
Endovascular embolization is performed preoperatively to make surgery safer or to provide a smaller target for radiosurgery. An interventional neuroradiologist inserts small catheters through the groin into the carotid artery. When the tip of the catheter reaches the tiny blood vessels of the AVM, an embolic agent is delivered, which begins to seal off the blood vessels.
Embolization is frequently done in stages to avoid sudden changes in blood pressure that may result in hemorrhage.
Related Articles