fluoroscopic guidance. Onyx® is an FDA-approved alcohol-based liquid and cohesive embolic material now routinely used to embolize cerebral vascular lesions. Each Onyx injection takes 30 to 60 minutes.
Generally, two to three feeding arteries are used for each embolization, depending on the microcirculation and anatomical structure of the AVM. Each procedure takes approximately two to three hours and is done under general anesthesia. The patient typically spends one to two days in the intensive care unit for neurological examination and close observation of blood pressure.
Following referral to Santa Barbara Neuroscience Institute, the patient was started on keppra (levetiracetam) to prevent additional seizures, and a diagnostic cerebral angiography was performed. (The results of the brain MRI and the cerebral angiogram are illustrated in Figure 1.) The patient then underwent two Onyx® embolization procedures scheduled approximately one week apart. To reduce the perioperative risks for hemorrhage, only 30 to 45 percent of the nidus (center) of the AVM was embolized in each session.
This patient received a total of three injections through branches and feeding arteries of the right middle cerebral artery and one injection via the basilar artery and the posterior cerebral artery. Figure 2 demonstrates a microcatheter injection and portions of the nidus prior to embolization. The final angiogram shows less than 10 percent of residual nidus.
This portion of the AVM was not embolized, as it would have been at significant risk to the patient. This particular area is fed from the anterior choroidal artery. This artery carries blood not only to the AVM but also to very important normal brain structures, such as the internal capsule and the basal ganglia. Treating this portion of the AVM with surgical resection or radiosurgery would be significantly safer.
AVM Eradication Options
After the second embolization, a discussion with the patient and his family took place on two options for completely eliminating the AVM. The first option would be a craniotomy and surgical resection of the residual nidus, including most of the injected Onyx material. The second option would involve radiosurgery—utilizing either Gamma Knife®, a linear accelerator, or CyberKnife®—to deliver high-dose focal radiation to the residual nidus while shielding the rest of the brain tissue.
In this case, surgical resection was the better choice for several reasons: the patient was young and otherwise healthy; the AVM surgical risks were low after more than 90 percent of the nidus was occluded with embolic material; and the location of the AVM (right side and temporal lobe) was favorable for surgical resection.
A right-sided craniotomy and resection of the AVM was performed using standard neurosurgical and microsurgical techniques. Intraoperative advantage was taken using BrainLAB frameless navigation to localize the residual nidus and the draining veins. The procedure was uneventful. Standard AVM protocols included a postoperative angiogram to be certain the entire AVM was removed and confirm no angiographic signs of early venous drainage. Figure 3 demonstrates the postoperative angiogram without any evidence for residual AVM.
The patient recovered very well from the surgery and was discharged on postoperative day five without neurological deficits. He returned to work approximately four weeks after surgery.
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