Two commonly used particulate materials are Gelfoam (Upjohn Pharmaceuticals, Kalamazoo, MI) and polyvinyl alcohol (PVA) (PVA Foam, Cook, Inc., Bloomington, IN; Trufill, Cordis Endovascular Systems, Miami Lakes, FL; Ivalon, Inc., San Diego, CA; Contour Emboli, Boston Scientific/Target Therapeutics, Inc., Fremont, CA).^2,³ Gelfoam breaks down 72 hours after embolization, and this lack of permanence detracts from its efficacy if surgery is not performed within a few days after the procedure. Gelfoam has been used as a preoperative embolization material for neoplasms that are to be operated on within 48 hours, and for patients with epistaxis in whom the goal is to slow the bleeding sufficiently so that the body’s normal hemostatic mechanisms stop the hemorrhage. Gelfoam powder always should be used with care because its particles (approximately 50 µm) in solution act as a liquid, easily passing through tiny arteries, which may result in skin necrosis or damage to cranial nerves, or through collateral channels communicating with the intracranial circulation.

PVA is more permanent than Gelfoam, but much of the efficacy of the vascular occlusion is a result of a combination of PVA plus intravascular thrombus. The stellate-shaped particles slow the intravascular flow, and thrombus forms.²^–⁴ This thrombus may be metabolized before fibrosis occurs, however, resulting in partial or complete recanalization over weeks to months. PVA is easy to use, being supplied as uniform particles within a narrow range of size (150 to 1250 µm). In most patients with neoplasms, the smallest size (150 µm) is used because the particles can be easily injected through a small microcatheter placed selectively into tiny feeding arteries and penetrate into the tumoral vascular bed.

Because of the stellate shape of PVA particles, they do not form a tightly packed embolic mass, allowing recanalization as the interspersed thrombus undergoes lysis. Various types of beads and spheres have been produced to overcome that limitation, such as Embosphere Clear (Biosphere Medical, Inc., Rockland, MA). Their more uniform size and spherical geometry theoretically produce more complete and more permanent vascular occlusion. Similar spheres might also be filled with a chemotherapeutic or other agent for more prolonged treatment of a nonsurgical neoplasm. Microfibrillary collagen (Avitene; Avicon, Inc., Fort Worth, TX) is a hemostatic agent that may be mixed with contrast material for embolization ⁵ or mixed with other embolic agents such as PVA and ethanol.⁶

There are two broad categories of metallic coils: coils that are pushed from a catheter with a metal coil pusher or guidewire, and coils that are released by breaking a bond between the coil and the pushing wire. The latter is the type used for treating intracranial aneurysms. In head and neck lesions, metallic coils are used for occluding vessels that measure a few millimeters to 1 cm or more in diameter. Their size prohibits their moving more distally into the embolized lesion. They are best used for occluding the feeding artery after particulate embolization; the particles are embolized deeply into the lesion, with the coil producing the final occlusion of the feeding artery. Coils have been used to occlude bleeding vessels, such as in epistaxis or after trauma.

Detachable balloons with a valve mechanism to keep the balloon inflated are currently unavailable in the United States, but should be available again in late 2009. They are used primarily for fistulas with a single artery-to-vein connection. Most experience was with intracranial post-traumatic carotid-cavernous sinus fistulas, but this technique was also used for vertebral artery–vertebral venous fistulas (usually post-traumatic) or for any other type of fistula in the face or neck.⁷^–⁹ They were also used for occlusion of a parent artery leading to an unclippable aneurysm, a dissected carotid or vertebral artery producing embolization into intracranial vessels, or a carotid artery to be sacrificed at tumor surgery. Electrolytically detachable coils are used now instead of the currently unavailable detachable balloons. Many coils are usually necessary, however, to do what one balloon could accomplish, increasing the complexity and expense of the procedure.

There are numerous liquid embolic agents, the most commonly used being absolute alcohol (100% ethanol) and various tissue adhesives, including the cyanoacrylates and Onyx (MicroTherapeutics, Inc., Irvine, CA). Absolute ethanol is extremely toxic to the endothelium,¹⁰ and is highly effective at producing sclerosis of vascular lesions, such as venous and lymphatic malformations.¹¹^–¹³ Although it has also been used to treat arteriovenous malformations and dural arteriovenous fistulas, the problem with these fast-flowing lesions is the need to increase the “dwell time” of the ethanol to interact with the intima, often requiring temporary balloon occlusion more proximally. It has also been used for tumors, via endovascular and percutaneous access, particularly recurrent tumors that are surgically inaccessible.

The injection of ethanol is extremely painful, requiring deep sedation or, more commonly, general anesthesia. It is necessary to see where the embolic agent is going, and so opacification is necessary. Opacification of the ethanol with a liquid contrast agent produces dilution of the ethanol, however, decreasing its effectiveness, which is maximum if used undiluted. Metrizamide powder (Nycomed, Oslo, Norway) was used previously for opacification because a powder does not dilute the ethanol, but provides acceptable opacification. Metrizamide powder is no longer available in the United States, however.

Sodium tetradecyl sulfate (Sotradecol) 3% also is an excellent sclerosing agent, is less painful on injection than ethanol, and may be opacified, although it seems to be less effective than ethanol for venous malformations, and is not considered to be an acceptable alternative. Doxycycline, a tetracycline-like antibiotic, is an effective agent at producing sclerosis of venous, lymphatic, and other slow-flow vascular malformations in which there is an adequate “dwell time.” Tetracycline has been associated with darkening of the tooth enamel in young children, so this drug is usually reserved for patients older than 11 years, after the formation of the permanent teeth. Povidone-iodine (Betadine) can also be injected into lymphatic malformations, with less pain than with alcohol and with good success.

Cyanoacrylates such as isobutyl-2-cyanoacrylate (IBCA) or N-butyl-2-cyanoacrylate (NBCA) produce polymerization of rapidly flowing blood within seconds. They not only produce immediate thrombosis and have tissue adhesive properties, but they also initiate a giant cell inflammatory reaction of the vessel wall.¹⁴ These embolic liquids are excellent for lesions with rapidly flowing blood, such as an arteriovenous malformation or an arteriovenous fistula. Neoplasms have slow flow, so there is no need to use these agents, which are associated with more risk than particulate materials injected intra-arterially or other agents injected percutaneously.

The newest “liquid” agent is Onyx, which is an ethylene vinyl alcohol copolymer containing dimethyl sulfoxide as the agent facilitating absorption through endothelial barriers.¹⁵ This tissue adhesive is a needed new addition to the armamentarium of the neurointerventionalist because it slowly permeates into tiny vessels feeding a vascular lesion, “creeping” into these feeders during fluoroscopic visualization and control, without the rapid setup time of the cyanoacrylates.^15,¹⁶

Any embolization procedure with a liquid agent should be approached with trepidation because occlusion of the end-arteries to the face, tongue, and cranial nerves may lead to necrosis, and intracranial embolization may occur as the liquid passes through tiny collateral channels to vessels feeding normal structures. Liquid embolization should be performed only when superselective catheterization can be done directly into the direct feeders to the lesion, or with percutaneous puncture of the lesion and direct visualization of the flow of the agent,¹⁷ to prevent unwanted extension to the blood supply of vital structures.

Provocative Testing to Ensure the Safety of Embolization

Two important techniques help to ensure the safety of vascular occlusion at the skull base. The first involves the injection of lidocaine (Xylocaine) 1% without preservatives into an arterial feeder that is considered a candidate for embolization, to predict the potential of permanent cranial nerve palsy from the embolization procedure.¹⁸ This provocative test anesthetizes the cranial nerve if there is blood supply leading to it from the vessel catheterized. Critics of this test suggest that a false-positive test may occur because a liquid anesthetic can be injected into the capillary bed, whereas particles used for embolization stop short of terminal arterioles so that devascularization is rare. It is likely that a negative test result is truly negative and reassuring.

The second provocative test is the temporary balloon occlusion test (BOT) of the internal carotid or vertebral artery, with the addition of blood flow measurement for precise quantification of the potential effects on cerebral blood flow during temporary or permanent occlusion of the artery during surgery or endovascular therapy. Carotid or vertebral artery occlusion might be necessary during the surgical removal of a skull base tumor, during the temporary occlusion of a major intracranial artery during surgical clipping of an aneurysm, for the thrombosis of an unclippable aneurysm via occlusion of the parent artery, or if carotid occlusion has to be performed to close a carotid-cavernous sinus fistula or any other type of traumatic vascular lesion.

First, a complete angiographic evaluation of all cerebral vessels is performed to evaluate their contribution to the particular lesion and the adequacy of collateral flow via the anterior and posterior communicating arteries. If communicating arteries are present, the traditional BOT is performed, consisting of occlusion of the internal carotid artery (ICA) with a nondetachable balloon catheter placed at the level of the future permanent occlusion. After systemic heparinization, the balloon is inflated, and the patient is evaluated for 30 minutes. Careful neurologic examinations are performed throughout the occlusion period, with special emphasis on the neurologic functions subserved by the vessel that is being tested. If the patient develops a neurologic deficit, the balloon is immediately deflated. If the patient has no neurologic deficit from the carotid occlusion, it is assumed that blood flow is adequate for permanent occlusion to occur. Such a qualitative test does not provide precise quantification of the blood flow to the hemisphere at risk, however. Blood flow values greater than 20 to 25 mL/100 g of tissue per minute allow normal neuronal function, with values less than that precipitating neuronal dysfunction. It is conceivable that blood flow values slightly greater than 20 to 25 mL/100 g/min would leave the patient without symptoms while on the angiography table, but superimposed intraoperative or postoperative hypotension, decreased cardiac output, or decreased oxygenation might precipitate cerebral infarction.

Different methods have been used during temporary occlusion to evaluate the physiologic effects of the BOT on cerebral blood flow to predict the risk of cerebral infarction after definitive occlusion. These methods include electric studies such as evoked potentials or electroencephalography,¹⁹ measurements of arterial stump pressures distal to the site of temporary occlusion,²⁰ induced hypotensive challenges, and transcranial Doppler studies. Also, several cerebral blood flow imaging methods, including xenon-enhanced CT (Fig. 136-1),²¹ single photon emission computed tomography (SPECT), positron emission tomography, and MRI and CT perfusion studies, have been used to evaluate cerebral blood flow during BOT to determine the potential risk of ischemia after permanent occlusion.^22,²³ We prefer to use SPECT because it adds little to the basic BOT and easily provides the needed information. After the balloon has been inflated for a short time, the radionuclide is injected intravenously, and the patient is scanned a few hours after the completion of the angiographic study (the radiopharmaceutical “sticks” to the brain tissue during its initial circulation in proportion to the blood flow to that tissue).

Figure 136-1. Xenon-enhanced CT during balloon test occlusion. This 60-year-old patient with squamous cell carcinoma invading the skull base was to undergo skull base resection and probable permanent carotid occlusion. A Swan-Ganz catheter was placed in the right internal carotid artery. Temporary blockage of the internal carotid flow for 15 minutes did not produce neurologic deficit. A, Xenon-enhanced CT scan for the production of a blood flow map (left) at the midventricular level (right) during balloon deflation reveals symmetric flows to the middle cerebral artery distributions bilaterally. B, With the balloon inflated, there is a marked reduction in the blood flow to the right middle cerebral distribution (left) relative to the left middle cerebral distribution. Flows to the right middle cerebral distribution are approximately 22 mL/100 g/min. This case was early in the authors’ experience, and a bypass procedure was not performed after permanent carotid occlusion during the skull base tumor resection. C, Postoperatively, the patient became mildly hypotensive, resulting in infarction in the distribution predicted by the temporary carotid occlusion blood flow test.

Nevertheless, these techniques have turned out to be imperfect predictors of the ischemic risk associated with permanent carotid occlusion. Clinical deficits have been reported after permanent occlusion, even when there has been a negative BOT with accompanying normal physiologic or cerebral blood flow studies. Many, if not most, of these postocclusion deficits probably are a result of marginal cerebral perfusion accompanied by hypotension or decreased cardiac output, clot propagation from the residual stump, or de novo emboli at the time of vascular occlusion.

Endovascular Treatment of Neoplasms

Paragangliomas

Paragangliomas, also known as chemodectomas or glomus tumors, are neoplasms related to chemoreceptor tissue. They usually are benign, but locally invasive and highly vascularized. Most glomus tumors originate within the temporal bone (48%), including lesions along the promontory of the middle ear (glomus tympanicum tumors) and lesions related to chemoreceptor tissue in the jugular bulb (glomus jugulare tumors). Tumors related to the vagus body (11%) in the high cervical region are called glomus vagale tumors, and tumors related to the carotid body (35%) at the common carotid artery bifurcation in the neck are called carotid body tumors. Multiple tumors are found in approximately 10% of patients (Fig. 136-2), and a familial form exists.²⁴

Figure 136-2. Multiple chemodectomas. This 38-year-old woman was one of many members of a family with chemodectomas. There is a small glomus jugulare tumor (straight arrow), a glomus vagale tumor (curved arrow), and extension of tumor along the carotid sheath to end in a carotid body tumor (arrowhead).

Glomus Tympanicum Tumor

The glomus tympanicum is a tiny tumor that usually manifests with pulsatile tinnitus and otoscopically is seen as a reddish blue mass behind the tympanic membrane. CT scanning allows the differentiation of this small tumor from an extension into the middle ear cavity of a larger glomus jugulare tumor. It also is necessary to exclude an aberrant ICA. In the former, the bony plate between the jugular foramen and the middle ear is destroyed, whereas in the latter, the posterior bony margin of the carotid canal is missing.²⁵ This tumor is usually small enough for surgery to be performed without embolization.

Glomus Jugulare Tumor

A patient with a glomus jugulare tumor usually presents with dysfunction of cranial nerves IX, X, or XI, and XII if the tumor is large. Pulsatile tinnitus also is common. Contrast-enhanced CT or MRI usually is the first diagnostic test performed, with the diagnosis generally made and the extension of the tumor shown. The tumor begins in the region of the jugular foramen and may extend inferiorly into the upper neck, superolaterally into the middle ear by destroying bone, posteromedially and posterolaterally into the posterior fossa, and anteriorly to envelop the petrous ICA. Bone destruction can be extensive, simulating a malignant tumor, as the chemodectoma spreads through the skull base. Destruction around the foramen magnum may occur, with compression of the brainstem.²⁶

The tumor is fed by multiple external carotid artery (ECA) branches, with each of these arteries feeding a specific compartment of tumor. The ascending pharyngeal (bilaterally at times) and middle meningeal (posterior division) arteries are the most commonly involved, with the stylomastoid branch of the occipital and the posterior auricular arteries providing supply less frequently (Fig. 136-3). If the tumor extends posteriorly around the foramen magnum, supply may be from the anterior and posterior meningeal branches of the vertebral artery. Intradural tumor within the posterior fossa may be fed from the anterior and posterior inferior cerebellar arteries. Tumor surrounding the high cervical or petrous portions of an ICA may parasitize tiny branches of these segments (see Fig. 136-3).²⁷^–²⁹

Figure 136-3. Glomus jugulare/vagale tumor. A and B, Cerebral angiography shows multiple enlarged external carotid branches providing most of the blood supply to this tumor (A), although there is parasitization of the vasa vasora of the high cervical internal carotid artery (B) by the circumferential tumor. C, There is complete occlusion of the distal sigmoid sinus (arrow) and nonopacification of the jugular bulb and vein.

The glomus jugulare tumor is highly vascular, which makes surgery difficult in this confined bony area. Embolization may be of great help.³⁰ Because the diagnosis generally has been made on the basis of CT or MRI before angiography, the patient is prepared with consent forms for angiography and embolization in the same sitting. The arterial feeders are mapped with high-resolution digital subtraction angiography in multiple planes, as previously described (Fig. 136-4). Selective catheterization of the multiple feeders is performed, followed by embolization of particulate material, most commonly PVA of small size (e.g., 150 µm) (see Fig. 136-4). Before injecting external carotid branches that may supply cranial nerve VII, particularly the stylomastoid artery, 1% lidocaine is injected as a provocative test to ensure that the cranial nerve is not devascularized during the embolization procedure, as previously discussed.¹⁸

Figure 136-4. Embolization of a glomus jugulare/vagale tumor. A, Global external carotid artery injection shows a large homogeneously hypervascular mass lesion within the confines of the petrous bone, extending anteriorly in the region of the carotid canal, and extracranially in the high neck, a position typical for a glomus vagale tumor. B, Selective injection of the ascending pharyngeal artery shows filling of most of the tumor from this source. Embolization of this and other branches was performed with polyvinyl alcohol particles measuring 150 to 300 mm. C, Common carotid artery injection after embolization shows lack of visualization of the hypervascular lesion, but anterior displacement of the high cervical internal carotid artery typical for the vagale portion of the tumor.

Glomus Vagale Tumor

The glomus vagale tumor originates from the vagus body high in the neck at the C1-2 level. The tumor may extend superiorly so that differentiation from a glomus jugulare tumor is difficult and may be moot. The typical appearance is that of anterior displacement of the high cervical ICA. Blood supply is from multiple branches of the ECA, particularly the ascending pharyngeal artery. The arterial supply is mapped as for the glomus jugulare tumor, although there generally are fewer sources of supply (Fig. 136-5). Potential supply from ascending and deep cervical branches of the thyrocervical and costocervical trunks and of neuromuscular branches from the ipsilateral vertebral artery also should be evaluated. The feeding vessels are catheterized and embolized to the point of fluoroscopic devascularization, particularly with tiny PVA particles (see Fig. 136-5). The lidocaine provocative test is used if there is any question regarding potential cranial nerve insult during the procedure.

Figure 136-5. Embolization of glomus vagale tumor. Most of this tumor was below the skull base, typical of a glomus vagale tumor, although a small component extended superiorly in the region of the jugular bulb. A, Global external carotid artery injection showed the homogeneous hypervascular mass. B, Selective injection was made into one branch of an enlarged ascending pharyngeal artery, showing that most of the tumor below the skull base was filled from this vessel. Other branches of the ascending pharyngeal artery were primarily responsible for the intracranial component. All these tributaries were embolized with polyvinyl alcohol particles measuring 150 to 300 mm. C, Postembolization global left external carotid injection failed to show the hypervascular mass.

Carotid Body Tumor

A carotid body tumor is a highly vascular mass occurring in the crotch between the origins of the internal and external carotid arteries, splaying them apart. There are commonly many tiny feeders from the distal common carotid and proximal internal carotid arteries that are too small to be catheterized selectively to the degree necessary to avoid reflux of particles into the ICA, although there usually are major feeders from the ECA, particularly the ascending pharyngeal, superior thyroidal, lingual, facial, and carotid body arteries (Fig. 136-6). These can be selectively catheterized, and much of the tumor may be appropriately embolized with tiny PVA particles to make surgery easier with less blood loss (see Fig. 136-6). Some surgeons do not want preoperative embolization, believing that a potential secondary inflammatory reaction from embolization makes it more difficult to define tumor planes for removal.³¹

Figure 136-6. Embolization of carotid body tumor. This 8-year-old child had MRI evidence of a carotid body tumor. No other family members were known to have a chemodectoma. A, Common carotid artery injection showed the classic separation of the internal and external carotid trunks because of the hypervascular mass between them. There were multiple twigs from the internal and external carotid arteries supplying this tumor. B, No other chemodectomas at or above the skull base were shown. C, Selective catheterization of the artery to the carotid body during online digital fluoroscopy showed a large blood supply to the tumor from this vessel, which was subsequently embolized with polyvinyl alcohol particles measuring 150 to 300 mm. Two other smaller branches of the external carotid artery were also embolized. D, After embolization, a common carotid artery injection during digital subtraction fluoroscopy failed to show the hypervascular mass.

Juvenile Angiofibroma

The usual history of angiofibroma is that of recurrent epistaxis and nasal obstruction in an adolescent boy. The tumor has a typical location adjacent to the nasal choana and within the nasopharynx and pterygopalatine fossa. The tumor may extend anteriorly through the nasal cavity or superiorly into the sphenoid sinus. Occasionally, it extends into the subtemporal fossa. Bone destruction of the lateral wall of the sphenoid sinus or of the anterior temporal fossa allows it to enter the intracranial cavity.

Typically, blood supply is from the ascending pharyngeal artery (which may be bilateral and may require common carotid rather than ECA injections to visualize because of the possible origin of this vessel near the common carotid bifurcation), and the internal maxillary artery and its branches, particularly the ascending and descending palatine arteries (Fig. 136-7). Tumor may remain extracranial and receive supply from collaterals of the petrous and cavernous segments of the ICA.³²^–³⁴ Intracranial extension may be supplied from the middle meningeal and accessory meningeal branches of the internal maxillary artery, and from branches of the petrous and cavernous internal carotid arteries. Because the middle meningeal, accessory meningeal, and foramen rotundum arteries supply cranial nerves within the cavernous sinuses,³³ it is preferable to catheterize the internal maxillary artery beyond the origin of the accessory meningeal artery for particulate material embolization (150 µm) of tumors that are purely extracranial (see Fig. 136-7). Supply from the middle meningeal and accessory meningeal arteries should be embolized with care, usually preceded by a lidocaine test. Other arteries are catheterized and embolized as necessary. Such embolization usually dramatically decreases the blood loss at the time of surgery.³²^–³⁵

Figure 136-7. Embolization of angiofibroma of the nasopharynx. This 15-year-old boy was seen with nasal bleeding. A and B, Common carotid artery injection (A) showed the classic appearance of an angiofibroma of the nasopharynx, fed primarily by the internal maxillary artery, with a dramatic degree of vascularity of the tumor (B). Catheterization of the internal maxillary artery was performed beyond the middle meningeal and accessory meningeal arteries, for embolization with polyvinyl alcohol particles, initially by use of 150 µm for the tiniest peripheral tumor branches, followed by 300 to 500 µm for the larger feeders. C, Embolization resulted in a dramatic decrease in vascularity of the tumor on follow-up angiography.

Meningiomas

Meningiomas are the most common intracranial nonglial tumors, accounting for approximately 20% of all primary intracranial tumors. They originate from the arachnoid, occur most often in patients 30 to 69 years old, and predominate in women. Their most common locations are over the cerebral convexities and in the parasagittal and parafalcine regions (50%), but meningiomas originating from various sites along the skull base and tentorium account for at least 40% of the cases.

Meningiomas derive their primary blood supply from arteries supplying the meninges. External carotid branches, such as the middle meningeal and ascending pharyngeal arteries, play a significant role in this supply, but dural branches of the intracranial carotid, ophthalmic, and vertebral arteries also are significant. As meningiomas grow, they may parasitize pial branches of the cerebral circulation.

Whether to embolize a meningioma in a given location depends on the risk-to-benefit ratio of the intervention and the ability to catheterize the appropriate blood supply selectively.^36,³⁷ Frontobasal meningiomas involve the orbital roof, the olfactory groove, and the planum sphenoidale. Their blood supply is primarily from ethmoidal branches of the ophthalmic arteries. Because of the potential risk to vision, selective catheterization of an ophthalmic artery and subsequent embolization usually is not performed. Sphenoid wing and middle cranial fossa tumors may derive significant blood supply from the middle meningeal artery. If so, selective embolization of the middle meningeal artery, taking care to place the microcatheter above the origins of the branches supplying the cranial nerves, may be a valuable preoperative intervention, especially because the location of this tumor may make control of the blood supply difficult at surgery.

Cavernous sinus meningiomas have various potential sources of blood supply from branches supplying the dura in this region. The inferolateral trunk from the C4 portion of the ICA frequently represents a major supply to meningiomas in this region, and, if enlarged, may be selectively catheterized with a microcatheter. If catheterization is impossible, a nondetachable balloon may be placed in the ICA above the origins of the dural branches, and embolization with tiny particles performed.^38,³⁹ Other sources of blood supply include the accessory meningeal and the middle meningeal arteries. Both of these latter vessels provide blood supply to the cranial nerves, so there is the potential of cranial nerve injury if these vessels are embolized. Provocative testing with the use of 1% lidocaine can be performed, and catheterization beyond the origins of the cranial nerve blood supply.

If a microcatheter with an inner diameter of 0.014 inch is used, 150-µm particles can be used to penetrate the meningioma; these particles usually are too large to penetrate the vessels supplying the cranial nerves. Gelfoam powder with particles of 40 to 60 µm behaves more like a liquid, and has a greater potential of producing cranial nerve palsies and passing through dangerous anastomoses. True liquids, such as cyanoacrylates and ethanol, carry too high a risk for cranial nerve injury or passage into anastomotic channels to be used as a preoperative agent. Occasionally, for patients with recurrent, nonoperative tumors requiring shrinkage for palliation of mass effect, absolute ethanol can be used, acknowledging the higher risk of cranial nerve injury (Fig. 136-8). Meningiomas in this region may infiltrate the ICA or middle cerebral artery. If en bloc resection of the tumor, including the ICA, is contemplated, preoperative occlusion of the ICA with a detachable balloon may be performed.³⁹

Figure 136-8. Embolization of a recurrent intracranial meningioma with alcohol. A 65-year-old woman had recurrence of a meningioma around the right middle cerebral artery. A, Right internal carotid artery angiography showed the “stain” of the meningioma wrapping around the middle cerebral artery and deriving blood supply from tiny feeders from that vessel. B, Right external carotid artery study showed a significant supply from the right middle meningeal artery. C, Selective catheterization of the right middle meningeal artery was performed, and angiography revealed its selective supply. D, To stop the tumor from occluding the middle cerebral artery, it was elected to perform embolization of the tumor. Small amounts of absolute alcohol were slowly infused into the tumor, which produced occlusion of the tiny feeding branches over a 15-minute period. An alternative therapy might have been gamma knife irradiation to stop the tumor growth.

Posterior fossa meningiomas include lesions in the clival, petroclival, and paraclival regions, and lesions involving the petrous bone, cerebellopontine angle, jugular foramen, and foramen magnum. The dural blood supply depends on their location, and these tumors may be embolized in the same manner as described for supratentorial tumors.

Other Neoplasms

Hypervascular solid masses involving the face and neck, other than those previously discussed, are uncommon. Occasionally, a hypervascular thyroid tumor receiving its blood supply from the superior and inferior thyroidal arteries is amenable to embolization. The inferior thyroidal artery is a branch of the thyrocervical trunk, and the superior thyroidal artery usually is the first branch of the external carotid; both generally are easy to catheterize. Selective lingual or facial angiography and injections into the thyrocervical and costocervical trunks should be done to evaluate tumor extension or other sources of blood supply. Embolization usually is performed with particulate materials.

Intra-arterial Chemotherapy

Endovascular techniques permit the selective perfusion of high concentrations of chemotherapeutic agents directly into a tumor, while minimizing systemic side effects. This technique has been used for advanced primary head and neck tumors, and metastatic tumor to cervical lymph nodes.⁴⁰ A new delivery technique involves intra-arterial injection of ethylcellulose microspheres containing chemotherapeutic agents. These biodegradable microspheres can remain in the tissue for weeks while they slowly release their anticancer drugs.⁴¹

Lesions of Vascular Etiology

Epistaxis

Epistaxis may result from trauma, tumor, coagulopathy, or a congenital vascular malformation, such as in hereditary hemorrhagic telangiectasia (or Osler-Weber-Rendu disease). The most common cause is spontaneous bleeding, with or without hypertension, from small vessels along the nasal septum and superior margins of the nasal cavity. Spontaneous bleeding from the anterior aspect of the nasal cavity usually is self-limited and does not require endovascular therapy, but posterior nasal hemorrhage (20%) is more inaccessible and more difficult to manage clinically. Cautery, ligations of the internal maxillary arteries, and nasal packing may be ineffective. Nasal packing may be associated with pulmonary or cardiac problems in elderly patients; embolization may be an effective and rapid therapy.

In all patients, bilateral selective internal and external carotid angiography should be performed to visualize the feeders to the bleeding site (Fig. 136-9).^42,⁴³ Superselective catheterization of internal maxillary artery, facial, and ascending pharyngeal vessels is performed with a microcatheter for angiography. If a bleeding site is found, all feeders and potential collaterals to the site are embolized by moving the microcatheter distal to branches potentially feeding cranial nerves such as the middle meningeal and accessory meningeal arteries. If no bleeding site is found, distal internal maxillary artery and facial artery embolization is performed bilaterally to ensure hemostasis (see Fig. 136-9).^32,⁴⁴^–⁴⁷ Particles 150 µm provide excellent hemostasis, and there is no risk of devascularizing normal facial tissues. Distal rather than proximal vascular occlusion decreases the chance of recurrent bleeding from collateral circulation. With the development of coaxial microcatheter systems and the heightened awareness of functional facial vascular anatomy, success rates of 91% to 97% with complication rates of 0% to 3% have been reported.⁴⁶

Figure 136-9. Embolization for epistaxis. A 69-year-old woman had recurrent epistaxis requiring nasal packing. A and B, Selective left external carotid artery injection (A) showed a hypervascular area in the region of the superior aspect of the left side of the nose (arrow in B). Embolization of polyvinyl alcohol particles, 150 µm, was performed under the control of digital subtraction angiography road-mapping. C, Postembolization study showed occlusion of the distal internal maxillary artery and no site of bleeding. Clinically, there was no recurrent epistaxis.

Facial Arteriovenous Fistulas

Arteriovenous fistulas may occur after direct facial trauma or from iatrogenic trauma such as facial surgery or image-guided biopsy.⁴⁸ Temporomandibular joint or maxillary sinus surgery may result in an arteriovenous fistula (Fig. 136-10). Arteriovenous fistulas also may be congenital in origin. Whatever the cause, selective angiography defines the site of the fistula, which generally is easy to occlude with an appropriately sized detachable balloon (see Fig. 136-10),⁷ or with detachable coils. Metallic coils also may be used to pack the venous and arterial sides of a fistula via superselective arterial or venous approaches. To do so, a catheter with a nondetachable balloon is introduced from one femoral artery and placed proximal to the fistula, to be inflated to provide flow control so that the coils do not get swept downstream. A second catheter is introduced via the other femoral artery and placed proximal to the fistula. This second catheter is a guiding catheter with a lumen that accommodates a microcatheter that is manipulated across the fistula into the venous side. Coil occlusion is performed during proximal balloon inflation, progressively pulling the microcatheter back to occlude the arterial side.

Figure 136-10. Iatrogenic facial arteriovenous fistula with embolization. Surgery had been performed on the left maxillary antrum for chronic sinus disease. One month postoperatively, a large pulsatile mass was noted below the left temporomandibular joint. A and B, Selective left internal maxillary artery injection showed an arteriovenous fistula with a large venous varix. C, A detachable balloon was placed at the site of the fistula (arrow denotes metallic marker on balloon) to produce complete occlusion of the fistula.

Dural Arteriovenous Fistulas

Dural arteriovenous fistulas represent direct communications between small arterial channels within the dura and the underlying dural sinus or veins draining into that sinus. Two types of dural arteriovenous fistulas are considered: fistulas that involve the transverse and sigmoid sinuses and fistulas involving a cavernous sinus.

Transverse and sigmoid sinus dural arteriovenous fistulas are acquired lesions, probably resulting after sinus thrombosis and increased venous pressure, which opens tiny arteriovenous shunts in the dura, with or without subsequent sinus recanalization.⁴⁹ Increased flow in the transverse and sigmoid sinuses produces a subjective bruit. The prolonged high flow may lead to intimal hyperplasia of the sinus wall, stenosis, and recurrent occlusion. Persistent or recurrent occlusion of the transverse and sigmoid sinuses produces increased outflow in the contralateral sinuses. Compromise of this venous drainage produces retrograde flow into cortical venous channels, venous hypertension, and tissue congestion, resulting in neurologic deficits.⁵⁰ Further venous hypertension may lead to intraparenchymal or subarachnoid hemorrhage.⁵¹ The arterial supply to a transverse and sigmoid sinus dural arteriovenous fistula is from multiple ECA branches bilaterally, particularly the occipital arteries and the tentorial branches of the internal carotid arteries. Meningeal branches of the vertebral arteries also may be involved.⁵²

If the patient complains of only a mild bruit but is otherwise asymptomatic, the risk-to-benefit ratio does not warrant treatment. In patients in whom the bruit has become so severe that the patient is incapacitated, treatment may be undertaken. The presence of cortical venous outflow, with or without neurologic deficit, indicates a high-risk lesion that should be managed with endovascular techniques. Lesions producing neurologic deficit, dementia, and previous hemorrhage require management.

Arterial embolization alone may be only palliative, with multiple other dural sources increasing in size as the primary feeders are occluded. Embolization with particles is particularly discouraging; if only the arterial side is embolized, a tissue adhesive such as Onyx (Fig. 136-11), or alcohol, may be very effective. Another solution is a combination of arterial and venous approaches. After decreasing the arterial flow rate with particle embolization, coils are deposited in the transverse and sigmoid sinuses via a transvenous approach (usually transfemoral venous catheterization of the jugular bulb with a large guiding catheter, through which a smaller catheter is manipulated into the transverse sinus for coil deposition along the length of the transverse and sigmoid sinuses).⁵³ If transfemoral venous access is impossible, intraoperative exposure of the sinus for coil packing may be necessary. Some transverse and sigmoid sinus dural arteriovenous fistulas are complex; recurrences are frequent, and therapy may require the combined expertise of the interventionalist and the surgeon over multiple sessions.

Figure 136-11. Anterior temporal fossa dural arteriovenous fistula treated with intra-arterial Onyx infusion. A, A 52-year-old man presented with a spontaneous hemorrhage in the left temporal lobe. The differential diagnosis was a “cryptic” arteriovenous malformation or a dural arteriovenous fistula, such as from the superior petrosal sinus. B, Selective middle meningeal artery injection showed early filling of the vein of Labbé (arrow) from multiple middle meningeal artery feeders. As a soccer goalie, this patient might have had a skull base fracture and a traumatic arteriovenous fistula. C, Onyx was infused into the middle meningeal artery, leaving a “cast” of the tantalum-containing compound. D, Subsequent external carotid angiogram did not show the fistula; it was not shown on follow-up angiography 1 year later.

The etiology of cavernous sinus dural arteriovenous fistulas is unclear. They are most common in elderly women and manifest with symptoms of proptosis, chemosis, conjunctival injection, decreased vision, and occasionally cranial nerve palsies. The blood supply is from the external carotid and ICA branches to the dura of the cavernous sinus. These lesions behave differently than transverse and sigmoid sinus dural arteriovenous fistulas because they may close spontaneously or after angiography, or subsequent to air travel with its barometric changes. Intermittent compression of the ipsilateral carotid artery may produce closure of the fistula. Progressive loss of vision or cortical venous drainage requires therapeutic intervention. ECA embolization with particles may lead to closure, in contrast to transverse and sigmoid sinus dural arteriovenous fistulas. Inferior petrosal vein catheterization via a transvenous femoral approach permits the deposition of coils or rarely a tissue adhesive into the cavernous sinus, which is highly effective management with a low complication rate.

Facial Vascular Malformations

Venous malformations of the face manifest as bluish lesions that may distend with the Valsalva maneuver. Although they are congenital, they usually are dormant until some type of factor, such as local trauma, causes them to enlarge.^54,⁵⁵ MRI studies show lesional hyperintensity on T2-weighted sequences, and the size and the extent of the lesion. Management is for cosmetic purposes. Percutaneous puncture allows the deposition of sclerosing agents. Absolute ethanol is more effective than sodium tetradecyl sulfate, but produces more swelling and is much more painful on injection, requiring deep sedation or anesthesia.¹⁰^–¹³

Arteriovenous malformations of the face are rare. If surgery or irradiation of a facial arteriovenous malformation is impossible for cosmetic reasons, embolization may be undertaken as a palliative treatment. In such a case, ethanol can be injected intra-arterially, particularly with flow control to keep the agent in proximity to the endothelium for as long as possible (Fig. 136-12). The major complication is flow of the ethanol into the tiny arteries feeding the skin and cranial nerves, producing necrosis. Even with flow control, the rapid flow in the arteries feeding the malformation usually sweeps the ethanol into the venous system for dilution, preventing such complications.

Figure 136-12. Facial arteriovenous malformation (AVM) embolized with intra-arterial alcohol. This 38-year-old woman had a long history of a bilateral facial AVM, and had undergone multiple embolization procedures in the past. A, Left external carotid artery study showed an enormous AVM involving the soft tissues of the mandibular region. Two balloons were placed for flow control, one in the external carotid artery and one in the left facial artery. The latter was a balloon surrounding a catheter with a lumen, through which 100% alcohol was injected. The balloon in the facial artery kept the alcohol in contact with the AVM endothelium, whereas the proximal balloon prevented reflux into other external carotid artery branches and into the internal carotid artery. B, Postembolization study showed a marked reduction in visible AVM. Three more procedures on the left and three on the right were performed over the subsequent 9 months, markedly reducing the facial deformity.

Hemangiomas of the Face and Neck

Hemangiomas have a proliferative phase followed by involution, so that 90% of hemangiomas that are present at birth regress by early childhood.⁵⁵ Therapy for infantile or early childhood hemangioma is necessary only if there is airway obstruction, such as from hemangioma of the tongue or subglottic tissues. Even if the hemangioma is in the periorbital region and interferes with normal eye function, time should be allowed for regression, followed by eye muscle and cosmetic surgery. In adolescents or adults, problems may be simply cosmetic, although the hemangioma may infiltrate surrounding tissues such as the alveolar ridge, resulting in hemorrhage when eating, or narrow the airway or esophagus. If there is a slow arterial component, embolization with PVA particles can be performed. If there is primarily a capillary or venous component, direct puncture of the lesion with the instillation of a sclerosing agent, such as absolute ethanol or sodium tetradecyl sulfate, may be effective. In most patients, embolization is followed by surgical removal.

Pseudoaneurysms

Cranial trauma resulting in cavernous carotid artery laceration usually produces a carotid-cavernous sinus fistula, although a pseudoaneurysm may be formed instead, with enlargement over time, erosion into the sphenoid sinus, and rupture, producing massive life-threatening epistaxis. Emergency balloon occlusion of the ICA may be necessary because the lack of a true arterial lining of the pseudoaneurysm predisposes to recanalization after intra-aneurysmal coil or balloon placement.

Rapid hyperextension of the neck with contralateral head rotation forces the high cervical ICA against the lateral mass of C2, or stretches a vertebral artery at C1-2 between its contained segments within the C2 foramen transversarium and the dura at the foramen magnum,⁵⁶ resulting in arterial dissection and subsequent pseudoaneurysm formation. Surgical repair may be difficult, necessitating the use of endovascular techniques. Because the pseudoaneurysm lacks a true arterial wall, frequently has a wide neck, and may contain semisoft clot of variable age, successful occlusion with intra-aneurysmal balloons or coils usually is impossible. The endovascular placement of a stent across the neck of a pseudoaneurysm is the preferred method of management; the combination of stenting and intra-aneurysmal coil placement may be even more successful. If necessary, occlusion of the parent artery with balloons⁵⁷ or coils placed above and below the aneurysm is definitive, but should be preceded with the BOT and assessment of cerebral blood flow after carotid occlusion via collateral channels.

Inadvertent biopsy of an aberrant carotid artery in the middle ear cavity has been reported, leading to severe otorrhagia and massive epistaxis. These lesions generally are best handled by trapping with balloons or coils proximal and distal to the aneurysm (Fig. 136-13).⁵⁸

Figure 136-13. Pseudoaneurysm of an aberrant right internal carotid artery after biopsy with balloon occlusion. This 6-year-old child had a reddish mass behind the tympanic membrane. A biopsy of the mass was performed by an otolaryngologist, producing rapid blood loss through the myringotomy. The ear was packed, and the patient was sent for evaluation. A, Right common carotid angiography showed the arcuate appearance of the petrous portion of the right internal carotid artery characteristic of an aberrant internal carotid artery extending into the middle ear cavity, with a pseudoaneurysm extending laterally representing the site of biopsy. B, A releasable balloon was placed above the aneurysm in the horizontal portion of the petrous segment (arrow marks distal margin of balloon). A second balloon was placed in the high cervical carotid artery for trapping of the aneurysm. Excellent cross-flow from left to right through the anterior communicating artery prevented neurologic sequelae after carotid occlusion.

Tinnitus-Producing Fibromuscular Dysplasia of the Carotid Artery

Fibromuscular dysplasia of the ICA, which usually occurs at the level of C2, is one of the many causes of pulsatile tinnitus. Vascular webs that characterize this entity may be stretched by angioplasty,⁵⁹ and stent placement may be necessary to prevent recurrence.

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Interventional Neuroradiology of the Skull Base, Head, and Neck

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