Tumor embolization will devascularize the tumor and can be used adjunctively with surgical resection or as a palliative measure. Optimal embolization results in tumor devascularization with no visualization of intra-tumoral opacification while avoiding unintended vessel occlusion. Pre-operative tumor embolization for hypervascular neoplasms results in improved surgical outcome, reduced intraoperative blood loss, and facilitates tumor resection (Zahringer et al., 2005
). The following guidelines are suggested as indications for tumor embolization: (1) to control surgically inaccessible arterial feeders, (2) to decrease surgical morbidity by reducing blood loss, (3) to shorten the operative procedure time, (4) to increase the chances of complete surgical resection, (5) to decrease the risk of damage to adjacent normal tissue, (6) to relieve intractable pain, (7) to decrease expected tumor recurrence, and (8) to allow better visualization of the surgical field with decreased overall surgical complication (American Society of Interventional and Therapeutic Neuroradiology, 2001
A thorough understanding of the vessel supply, hemodynamic characteristics, venous outflow patterns, and anastomoses is essential for safe and effective treatment. A strong knowledge of regional vascular anatomy is important as complex vascular variations can often be encountered in head and neck tumors. All possible anastomoses should be comprehensively explored prior to embolization. Particular focus should be placed on identifying ECA to ICA anastomoses that carry potential for devastating unintended intra-cranial embolization.
Embolization approaches include transarterial, direct puncture, and a combination of these methods. Ideal tumor embolization is achieved with occlusion of the very small vessels within a tumor, while sparing supply to normal adjacent tissue. Liquid and particulate embolic materials are effective in penetrating small vessels, and meticulous use of these materials is essential in preventing unintended occlusions. Common practice is to begin with smaller sized embolic material to target small distal vessels and gradually increase particle size in successive injections of embolic material. If blood supply to cranial nerves is suspected, provocative testing can be performed by injecting lidocaine and observing for neurological deficit. If a deficit is elicited the micro-catheter can be re-positioned. Positioning the micro-catheter as close as possible to the tumor bed will help avoid embolization of normal structures.
Most tumor embolizations are performed via the external carotid arterial supply. Branches of the internal carotid artery may supply the tumor but in most instances risk of embolization of these branches may exceed benefit. Time to surgical resection after embolization may vary depending on tumor type, characteristics, and degree of devascularization. Embolization is often performed within 24–48
h of expected surgical resection. Some data suggest that optimal necrosis for meningiomas requires a longer period of up to 7–9
days after embolization (Kai et al., 2002
). Delay in surgical resection may cause swelling due to tumor necrosis and compression of adjacent structures.