Mandibular arteriovenous malformation: A rare life-threatening condition depicted on multidetector CT angiography.

Arteriovenous malformation (AVM) of the mandible is a rare and potentially life-threatening condition which can lead to massive hemorrhage. The following is a description where a large mandibular AVM presented with torrential bleeding following tooth extraction for caries. An orthopantomogram (OPG) was performed which was suggestive of aneurysmal bone cyst or ameloblastoma. A computed tomography (CT) angiography revealed a large mandibular AVM with submandibular extension. It is important for both clinicians and radiologist to be aware of this type of lesion that can have life-threatening complications. It is important to define the anatomical location and the feeder vessels of the entity in detail preoperatively. This communication highlights the common differential and use of multidetector CT (MDCT) angiography along with other imaging modalities to prevent a fatal hemorrhage and arrive at a correct diagnosis.

INTRODUCTION

Arteriovenous malformations (AVMs) occur as a result of errors in vascular morphogenesis present at birth. These grow proportionately with age,[12] and manifest at any time during life due to an event like trauma, surgery, infection, etc.[3]

Mandibular AVMs are uncommon and potentially life-threatening vascular malformations.[456] Young female patients are predominantly affected. They are frequently high-flow vascular malformations.[7] Clinically, they may present with minor gingival bleeding, dental loosening, lower lip numbness, facial deformity, malocclusion and sometimes hemorrhagic shock following extraction of teeth.[8910] The radiographic appearances of these lesions are variable, ranging from a small radiolucency to markedly obvious osseous erosion of the alveolus with apparently floating teeth. Computed tomography (CT) scan and magnetic resonance imaging (MRI) are helpful imaging tools to assess the extent of the lesion into the bone, soft tissue and major vessels. We report a case of a 10-year-old female with an AVM of the left half of mandibular ramus with extension into submandibular region.

CASE REPORT

A 10-year-old female patient presented at Emergency Room of our institute with massive hemorrhage apparently from left side of mouth following tooth extraction for caries. Hemorrhage was controlled by packing the mandible and subsequent blood transfusion. The patient had no history of previous medications, blood transfusions, bleeding diathesis or hospitalization. Systemic examination was unremarkable. No obvious facial asymmetry was noted [Figure 1]. The patient was advised an orthopantomogram (OPG) which was suggestive of a large expansile radiolucent lesion with soap bubble appearance in left ramus and angle of mandible extending up to molar area [Figure 2]. Suspecting a possible aneurysmal bone cyst or ameloblastoma, a detail noncontrast CT (NCCT) followed by contrast study and CT angiography was performed. The NCCT showed a large expansile lytic lesion with cortical thinning and destruction involving the left ramus of mandible [Figure 3]. Contrast study showed an enhancing lesion with abnormal tuft of tortuous, dilated feeding vessels at the site of lesion [Figure 4]. The lesion was seen extending into left masticator space. On CT angiography, multiple arterial feeders to the lesion were seen originating from left external carotid artery with venous drainage into left external jugular vein [Figure 5]. Final diagnosis of left mandibular AVM was made.

Figure 1

Clinical photograph of the patient did not reveal any facial asymmetry

Figure 2

Orthopantomogram showing radiolucent lesion involving left mandibular ramus (white arrow head) with fine septations and soap bubble appearance

Figure 3

Noncontrast bone window settings showing expansile lytic lesion with cortical thinning involving the left mandibular ramus

Figure 4

Sagittal reconstructed computed tomography image showing tortuous arterial feeders (yellow arrow) from left external carotid artery supplying the enhancing mandibular arteriovenous malformation (AVM; white arrow)

Figure 5

CT angiography axial image showing arterial feeders (yellow arrow) from external carotid and tortuous venous channels associated with enhancing AVM (white arrow)

DISCUSSION

Approximately 51% of vascular malformations occur in the head and neck region and the male-to-female ratio is 1:1.5.[11] Extracranial AVMs of the head and neck are high-flow lesions and among the most serious of the vascular malformations because they are difficult to diagnose, treat and cure. The detection rate of AVM in the general population based on prospective data from the New York Islands study is approximately 1.34 per 100,000 persons.[12] Death occurs in 10-15% of patients who have hemorrhage and morbidity of various degrees occurs in approximately 50%.[13] Multiple imaging modalities should be used to evaluate characteristics of AVMs such as size, flow velocity, flow direction, relation to the surrounding structures and lesional contents.[14] There are no pathognomonic radiographic features to distinguish AVMs on plain radiographs. They may appear as bone erosions, sclerotic changes, periosteal reactions or a cyst-like radiolucent lesions. lesion. A sunburst effect, created by spicules radiating from the center, is often present.[14] The radiographic differential diagnosis of these lesions includes ameloblastoma, ameloblastic fibroma, odontogenic myxoma, central giant cell granuloma and metastatic malignant tumors.[10] Before performing a biopsy or surgery in a radiographically suspected case of ameloblastoma or aneurysmal bone cyst, especially in children, clinician should advise a contrast CT or MRI to rule out the possibility of an AVM to avoid sudden massive hemorrhage from the lesion and mortality and morbidity associated with it. Contrast-enhanced CT can be useful in assessing the AVMs. The drawbacks of CT are considerable exposure to ionizing radiation and limited information about blood flow.[14] Angiography is currently the gold standard diagnostic aid for determination of location and flow characteristics of vascular lesions. Angiography is useful to determine blood vessels supplying blood to the lesion, the relative venous outflow characteristics and the presence or absence of arteriovenous shunts.[11] Superselective arteriography remains an essential tool in the identification of an AVM and contributory vessels.[15] Superselective angiography is an invasive procedure and not available everywhere. CT scanning and MRI are sufficient in most cases to clarify the extent of the lesion, bone erosion and involvement of major vessels, feeder artery and draining vein. It is also invaluable if superselective arteriography and embolization of main nutrient artery is planned.[16] Due to the size and extent of the lesion in this patient and potential danger of hemorrhage, surgical intervention was advised as a choice of treatment after obtaining proximal and distal vascular control by transfemoral embolization. The patient's attendants refused any invasive procedure like arteriography and embolization and could not be convinced for any surgical intervention.

CONCLUSION

A radiograph showing lytic lesion resembling aneurysmal bone cyst or ameloblastoma in mandible in a child with history of gingival bleeding and no significant past history should raise a suspicion of mandibular AVM. The clinician should be aware of mandibular AVM before performing a biopsy, which may lead to torrential hemorrhage and even death of the patient. A preliminary CT angiography has an advantage of providing bony details along with status of feeder vessels of the lesion which is a prerequisite for surgery or endovascular intervention. Therefore, angiography remains the gold standard diagnostic aid in management of AVM.