Neuroendovascular Procedures for Skull Base Neoplasia

Background and Purpose: Neuroendovascular procedures are performed in skull base neoplasia with the objective of achieving preoperative embolization to increase the safety of surgical procedures by limiting intraoperative hemorrhage, reduce the need for transfusion, increase visibility in the surgical field, and shortening hospitalization length. Embolization should typically be reserved for lesions with numerous, deep, surgically inaccessible tributaries, where a significant bleed is anticipated, or the tumor is surrounded by critical neurovascular structures.

Materials and Methods: We present an evidence-based review of the perioperative process involved in endoscopic embolization of skull base tumors. This summary will outline the risk-benefit profile as well as indications and contraindications taken into consideration when determining suitability of radiologic intervention, and resultant scope of outcomes. Additional parameters including circumstances in which temporary or liquid embolic agents are more amendable, preoperative imaging features, procedural details of angioembolization, and subsequent follow-up monitoring are also discussed.

Results: Angiography often precedes embolization to establish tumor supply and collateralization as well as occluding anastomoses with coils. Additionally, it provides the interventionalist with the opportunity to become familiarized with the vasa nervorum and arteries supplying cranial nerves, as well as the tributaries supplying the tumor, thereby informing selection of an appropriate embolic agent. With encasement of large arteries like the ICA or vertebral, where inadvertent or deliberate sacrifice may be anticipated, preoperative balloon test occlusions may be utilized. The primary skull base tumors that most commonly benefit include meningioma, juvenile angiofibroma, and paraganglioma.

Meningiomas are typically-indolent tumors do not usually invade local structures in the brain, but are able to cause compressive symptoms including vision changes, headaches, seizures, and hormonal deregulation with pituitary involvement. The majority do not warrant embolization do to their superficial blood supply, with complications being either excessive ischemic necrosis leading to post-operative hemorrhage, and migratory embolization leading to neuroparenchymal or extracranial ischemia.

Juvenile nasopharyngeal angiofibromas (JNA) are characteristically benign head and neck tumors capable of exhibiting locally aggressive behavior. Angiography commonly illustrates the tumor as a high-flow lesion with dense capillary filling and shunting into prominent veins. Generally, superselective microcatheter embolization of the individual tumor feeders is preferred to arbitrary embolization from a more proximal position, to improve penetration into the tumor capillary bed and decrease likelihood of inadvertent embolization through anastomoses.

Paragangliomas are benign neuroendocrine tumors with occasional malignant capability through distant metastasis, as multicentric lesions with secretory actions have been correlated with likelihood of malignancy. The most common subtype of paragangliomas in the head and neck are carotid body tumors. DSA is used to elucidate the vascular supply of these lesions for embolization and surgical planning.

Conclusion: Neurointerventional procedures play a pivotal role in the management of skull base neoplasms. Pre-operative embolization must performed judiciously in the context of the potential harms and benefits imposed on the patient. While effective intervention can yield improved perioperative visualization with reduced tumor size and resultant blood loss, important risks for consideration include cranial nerve injury, tissue necrosis, access vessel injury, and death from inadvertent nontarget embolization.