Symptoms

Arteriovenous malformations

Arteriovenous malformations (AVMs) are fast-flow malformations characterized by abnormal collections of arteries and veins that directly communicate (shunts), thus bypassing the high-resistance capillary bed (Image 9.9). The shunts comprise the epicenter of the AVM, called the nidus. Intracranial AVMs are more common than extracranial AVMs.

Image 9.9 Arteriovenous malformations.

Areas affected by extracranial AVMs in decreasing frequency are the head and neck, limbs, trunk, and viscera. AVMs may be apparent at birth but are often misdiagnosed initially as a capillary malformation or infantile hemangioma due to pink staining in the overlying skin.

Although arteriovenous malformations are present in neonates at birth, they often suddenly become obvious when the patient is older because of various stimuli such as trauma, pregnancy, or puberty. Progression may also occur following biopsy or surgical intervention (e.g., ligation, partial surgical excision).

Common symptoms include pain, overgrowth of the involved body part, changes related to decreased blood flow (ischemia), bleeding, and heart failure. Bleeding is usually minor, but it may be very serious; it typically occurs with dental work in patients with arteriovenous malformation of the dental arcade. Schobinger's staging (stages 1-4) is commonly used to describe the degree of progression (Table 9.2).

Table 9.2

As an AVM grows, it can become more masslike, causing ulceration of the overlying soft tissue, bleeding, pain, or heart failure. Lower-extremity AVMs often develop curious, dry, brown-violaceous-colored plaques.