Arteriovenous Malformation

Epidemiology

Arteriovenous malformations (AVMs) are developmental malformations of the vascular system that result in abnormal communication between arteries and veins. The primary abnormality appears to be at the level of the capillary bed. AVMs are classified as a type of vascular malformation using the classification system of Mulliken and Glowacki. AVMs also include arterial malformations and arteriovenous fistulae and are characterized as high-flow lesions. AVMs of the parapharyngeal space are not isolated and usually involve adjacent spaces.

Clinical Findings

The clinical findings can be variable depending on the extent of the lesion. The neck and craniofacial region are common sites of occurrence. On clinical examination, AVMs present as a soft tissue fullness that is compressible. Superficial AVMs may be associated with a palpable thrill or audible bruit. The overlying skin may be discolored due to dilated superficial veins. Patients with more advanced lesions may present with facial deformity, skin ulceration, or functional compromise. Patients may also present with hemorrhage that may be spontaneous or follow minor trauma such as tooth extraction. AVMs may enlarge with pregnancy. It is unclear as to whether the growth is due to direct hormonal stimulation or results secondarily from an increase in the circulating blood volume.

Pathology