Case history

An 8-year-old girl presented with swelling of the right cheek, bleeding from the gums and episodes of epistaxis since she was 2 years of age. There was no history of surgical intervention. A non-contrast computed tomography (CT) scan revealed a lytic lesion with expansion and thinning of the right maxilla with soft tissue density within the sinus. The lesion extended inferiorly up to the 14–17 alveolar margins ( Fig. 1 ). A diagnostic angiogram showed a large intraosseous AVM with multiple feeders from the right internal maxillary artery and right facial artery with a branch from the left external carotid artery ( Fig. 2 ). A large intraosseous venous sac was seen within the maxilla that corresponded with the soft tissue density mass seen on the CT scan. Venous drainage was predominantly into the cavernous sinus via the angular vein and facial vein. The patient was taken up for embolization. A direct percutaneous puncture of the posterolateral wall of the right maxillary bone was made under sedation and CT guidance ( Fig. 3 a) using a 20G spinal needle. The patient was moved to the digital subtraction angiography suite and following an angiogram with 2 ml non-ionic contrast (Ultravist 300mg% Schering, Germany) the AVM was embolized with 1 ml of 1:1 n-butyl-2-cyanoacrylate (NBCA), (histoacryl-blue; Braun, Melsungen, Germany) mixed with iodized oil (lipiodol; Laboratoire Guerbert, Roissy, France) with compression of bilateral angular veins to prevent reflux into the cavernous sinus under fluoroscopic guidance. An NBCA and lipiodol cast was seen conforming to the shape of the sac with no evidence of reflux into veins. A postembolization CT scan showed obliteration of the venous sac ( Fig. 3 b). The patient returned for a follow up visit 2 months later with a marked relief of symptoms. Mild swelling of the cheek was present. Minimal bleeding from the gums and a few episodes of epistaxis occurred during the follow up period. Diagnostic intra-arterial cranial angiography showed a residual AVM nidus fed by the right internal maxillary artery ( Fig. 4 a) . Superselective catheterization of the right maxillary artery was carried out and the nidus was embolized by polyvinyl alcohol (PVA) particles (250–355, 500 and 500–700 μm). A postembolization angiogram showed occlusion of the AVM nidus ( Fig. 4 b). The patient was discharged after 2 days and had no further bleeding in the 22 months follow up period.

Axial CT through the right maxilla. Note the expansion and thinning of the right maxilla with soft tissue attenuation in the sinus, which corresponded to the large venous sac seen on the angiogram.

Angiogram of the right external carotid artery injection, demonstrating an AVM with a large venous sac. (a) Lateral view showing multiple small feeders from the right facial artery and internal maxillary artery. (b) Anteroposterior view of superselective cannulation of the internal maxillary artery showing the large venous sac.

(a) Axial CT demonstrating direct percutaneous puncture of the posterolateral wall of the right maxilla under CT guidance. (b) Axial CT through the bone showing obliteration of the venous sac following embolization with 50% glue and lipiodol mixture (very high attenuation substance in maxilla).

(a) Follow up angiogram with superselective catheterization of the right internal maxillary artery showing residual AVM nidus fed. (b) Complete occlusion of the AVM nidus demonstrated by superselective cannulation of the right internal maxillary artery following selective PVA particle embolization.

Discussion

High flow vascular malformations (HFVMs) of the head and neck are rare and their incidence is unknown. The maxilla and mandible account for less than 10% of the HFVMs of the head and neck region. Primary bony involvement of AVMs of the head and neck occur only in tooth-bearing bones of jaw. Large intraosseus AVM of the maxilla is rare, with fewer than 60 cases of maxillary AVM reported by G allagher et al. Intraosseous maxillary AVMs may cause massive, life threatening and sometimes fatal hemorrhages .

CT scanning reveals a soft tissue mass, involving the maxilla or mandible, with bone erosion surrounding the teeth . Recognizing the enlarged adjacent arteries and veins is crucial in making the diagnosis and is more easily visualized in a contrast-enhanced study. On magnetic resonance imaging (MRI), these HFVMs characteristically show dilated feeding arteries and draining veins with flow voids on T2 weighted images and high signal on flow-enhanced gradient-echo sequences. The nidus of the malformation may be seen as smaller calibre curvilinear abnormalities. MR angiography (time-resolved and contrast enhanced) may further characterize the flow characteristics and haemodynamics . Catheter angiography remains the gold standard; it defines the exact angioarchitecture and directs the planning of embolic therapy .

The goal of intraosseous AVM treatment should be to eliminate the nidus and the initial segment of venous outflow. The surgical approach to a large intraosseous AVM is maxillectomy or mandibulectomy with significant intraoperative blood loss, subsequent high incidence of incomplete resection, multiple recurrences and facial disfigurement . Owing to the deforming surgical options with their potentially life threatening complications, preoperative transarterial embolization followed by surgery was the treatment of choice before the use of percutaneous direct puncture glue embolization became established in the management of introsseous AVMs . K ohout et al. reported a 60% overall success rate by combining embolization with surgical resection on a large series of 81 patients with head and neck vascular malformations evaluated over a 20-year period.

A number of embolizing agents have been used with varying success; transarterial embolization with PVA alone fails to eliminate the existence of a nidus . In 1999, K iyosue et al. reported the insertion of a transvenous coil, which caused occlusion of a mandibular AVM, resulting in a cure 2 years after treatment. F an and R esnick et al. have shown that the use of coils for embolization is linked to the risk of exfoliation of the mucosa and delayed extrusion of coils Direct injection of the intraosseous nidus and proximal draining vein with tissue adhesives followed by transarterial embolization of the feeders results in obliteration of the intraosseous AVM _. The materials of choice for embolization of large intraosseous AVMs are ethylene-vinyl alcohol co-polymer (onyx) and NBCA which can be used transarterially or by direct puncture . H an et al. reported complete disappearance of craniofacial HFVMs in 42% of their patients by direct glue puncture alone while the lesion was more than 90% devascularized in 35% of patients. In the rest of the patients, 60–70% devascularization was achieved leading to insignificant blood loss during subsequent surgical extirpation of the residual mass.

Onyx is approved by the US FDA for the embolization of brain AVMs. NBCA is not approved by the FDA and its use is limited in the USA over concerns of carcinogenicity. In contact with blood, onyx precipitates on the surface while maintaining a liquid core, lowering the risk of fragmentation and distal inadvertent embolization. It has better handling properties than NBCA, offering the user more control during embolization of even extensive AVMs and multiple nidal compartments from a single catheter position, which is not feasible with NBCA. Its ability to maintain a constant liquid core allows for longer injections and better assessment of treatment progress. Onyx causes fewer foreign body reactions or cast extrusions from sockets after loss of teeth than NBCA .

NBCA has advantages over onyx for percutaneous embolization of craniofacial AVMs. The intense inflammatory reaction to acrylic glue allows for formation of pseudocapsule around the cast over a period of time, allowing for easier surgical excision of the lesion. The increased thrombogenicity and subsequent venous occlusion appear to be a favourable result in the management of craniofacial AVMs. NBCA is less costly than onyx. Onyx causes permanent blackish discoloration of the skin, which may be cosmetically unacceptable to the patient long after the lesion is treated _.

Embolization is the preferred treatment option, but it is not without risks. Potential complications include puncture site haematoma, migration of the embolization material, stroke and infection. As the field is contaminated during transoral intraosseous injection of glue, the use of long term antibiotic therapy may prevent the complication of osteomyelitis .

In conclusion, AVMs of the facial region involving bone are difficult to treat. The intraosseous sac constitutes a major fistulous segment and is best treated by a combination of direct embolization with glue after CT guided puncture and placement of the needle and transarterial embolization with PVA particles. Because of the potential for disastrous bleeding in these patients, treatment should be offered as early as possible.