High-flow vascular malformations in the paediatric population are potentially life-threatening and are challenging to treat. This paper describes the management of three cases of mandibular arteriovenous malformations and reviews the contemporary management options for these serious lesions.
Almost half of all arteriovenous malformations (AVMs) occur in the head and neck. AVMs in the maxilla and mandible constitute 4–5% of all craniofacial AVMs and present a particular challenge to treat . Intraosseous AVMs of the mandible are rare, accounting for approximately 0.5–1% of all vascular malformations. Although present at birth, they may not be clinically apparent until infancy or later in childhood .
The pathogenesis of these lesions remains speculative, but it is thought that the primary abnormality originates from abnormal capillary connections between arteries and veins. The increased blood flow across the central section or nidus of such abnormal connections is presumed to result in the secondary phenomena of hypertrophied arteries and dilated veins . The resulting vascular abnormality causes significant arteriovenous shunting with increased blood flow that can result in collateralization, dilatation of existing vessels, and thickening of the adjacent vessels . Increased vascular pressure is thought to stimulate cellular hypertrophy allowing the AVM to grow in tandem with the child’s growth through progressive enlargement of the feeding and collateral vessels . These lesions do not regress spontaneously , and often expand rapidly during puberty.
Intraosseous AVMs in the maxillofacial region can be completely asymptomatic , but frequently present with facial swelling and asymmetry, mobility of the associated teeth, pain, skin discolouration, audible or palpable pulsations, and paresthesia of the lower lip and chin. Haemorrhage following the routine eruption of teeth or surgical interventions such as dental extraction or biopsy can also occur. Intraosseous high-flow AVMs may present with profuse and potentially life-threatening haemorrhage , necessitating urgent management to avert serious complications and potentially fatal outcomes.
The assessment of outcomes of intraosseous AVMs is confusing due to the various terms used to describe these lesions, with multiple studies reporting the lesions as haemangiomas . The initial classification system proposed by Mulliken and Glowacki is based on the clinical behaviour and endothelial cell characteristics, broadly classifying vascular anomalies as haemangiomas or vascular malformations . Vascular malformations can be sub-classified further as low flow (capillary, lymphatic, or venous malformations) or high flow (AVMs).
The severity of AVMs varies and the Schobinger classification has been used to clinically stage AVMs . ‘Quiescent’ lesions may remain stable for years (stage I). Rapid expansion may occur either spontaneously or may follow local trauma, attempted excision, or hormonal changes associated with puberty or pregnancy, and this is classified as stage II. Lesions that cause destruction, leading to ulceration, bleeding, necrosis, or persistent pain are stage III, and can be life-threatening. Stage IV lesions result in cardiac failure and haemodynamic decompensation and possible coagulopathy. This classification is based upon the need for intervention and on the anticipated progression of the lesion.
The optimal management of AVMs involves a multidisciplinary approach. Advocated treatments have included endovascular embolization techniques, sclerotherapy, surgical resection, or a combination of modalities. Owing to the relatively rare incidence, contemporary experience is limited to small case series and isolated case reports.
Three cases of high-flow AVMs involving the mandible in paediatric patients attending the Royal Children’s Hospital (RCH) in Melbourne are presented, to describe their presentation and to review current management approaches for these rare and challenging lesions.
An 11-year-old Polynesian male with neurofibromatosis type I, had a highly mobile left mandibular molar extracted at home by a family member. His local medical practitioner referred him to the emergency department (RCH) with prolonged haemorrhage 3 days later, due to an inability to control the bleeding with pressure packs.
On oral examination in the emergency department, torrential haemorrhage occurred spontaneously and haemoglobin was noted to be 63 g/l. The patient’s mouth was packed with gauze and he was immediately transferred to the operating room for haemorrhage control. Firm finger pressure was required to obturate the second molar socket to prevent exsanguination. Anticipating a high-flow vascular malformation, thermoplastic compound material was moulded and plugged into the socket together with the addition of overlying cotton rolls ( Fig. 1 ). The construct was secured with two circummandibular wires. The associated first molar and first and second premolars were noted to be mobile.
Eight units of packed red blood cells and intravenous fluids were administered to restore intravascular volume after a further decrease of the patient’s haemoglobin to 42 g/l. He was immediately transferred to the interventional radiology department for intravascular embolization. Via a retrograde percutaneous femoral approach, the left inferior alveolar artery was embolized with coils, and particulate Gelfoam (Manufactured by: Pharmacia and Upjohn Company 7000 Portage Road Kalamazoo, Michigan 49001 USA) was used to embolize branches of the left facial artery. To assess the effect of the emergency embolization and to remove the cotton rolls, the compound plug was removed under general anaesthesia 2 days later. Ongoing profuse haemorrhage was noted at that time. Another compound plug was then firmly inserted to re-establish haemostasis.
Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) were performed and demonstrated an extensive malformation involving the left side of the mandible, with extension across the midline to the canine region ( Fig. 2 ). Expansion of the body of the mandible with thinning and perforation of the cortex in several places was noted. Digital subtraction angiography (DSA) demonstrated that the malformation was perfused by branches of the left lingual and facial arteries, and by large branches of the right lingual artery. Brisk flow was noted with filling of the venous channels during the late arterial and capillary phase.