Arteriovenous malformations - cutaneous

Arteriovenous malformations (AVMs) are rare, sporadic, destructive, fast-flowing vascular lesions with direct connection of arterial and venous vessels, which tend to worsen with time. The most common site for AVMs is the brain. Most cutaneous AVMs occur in the head and neck region, especially the cheek, becoming clinically apparent sometime between birth and adolescence. 

This chapter is set out as follows:

• The incidence is unknown
  
• Males and females are equally affected
  
• An AVM can be isolated or part of a disorder
• The most widely accepted theory of the aetiology and pathogenesis is that these lesions are due to an increase in the number of vessels caused by a defect in vascular development, particularly angiogenesis
  

• Although present at birth, only 60% of cutaneous AVMs are visible at this time; 20-30% become evident during adolescence and 10-20% in adult life
• In patients presenting under 20 years of age, lesions often start to grow and bleed, particularly at puberty or with hormonal changes
• In older patients lesions are sometimes first reported after trauma

Distribution

• Although lesions can affect any site, the head and neck are the most frequently affected. When the pinna of the ear is affected, an AVM can also usually be found on the scalp and neck

Morphology

The clinical presentation of AVMs can be varied, and the diagnosis can be easily missed in their early stages when they may take on a similar appearance to capillary malformation. Features may include:

• Red-pink macules - later on, lesions should become palpable 
• Blue-violaceous lesions or dilated veins 
• Several small lesions, often with a whitish halo 
• The presence of increased warmth, thrill or bruit  
• Pulsatile lesions - not all AVMs are pulsatile
  
• A nodule arising on a macule / patch - if a pyogenic granuloma appears over what is assumed to be a capillary malformation, one should consider the possible presence of an AVM
• Diffuse hypertrophy with increase in the size of the affected limb (Parkes-Weber syndrome) 
• Skin changes of Kaposi pseudosarcoma (Stewart-Bluefarb syndrome) 
• Lytic bone lesions
• Heart failure with multiple AVFs - rare

• The diagnosis is mainly clinical and is confirmed by Doppler ultrasound when doubt exists 

Prognosis

• Many factors affect the clinical course of AVMs, including age at diagnosis and the management approach used
• Children presenting with an exacerbation of an AVM at an early age have a poorer prognosis, with a greater number of surgical procedures, greater morbidity, and more sequelae compared with adult patients in whom changes develop during their fifth decade of life

Conservative measures

• Protection of the area, avoiding injury
• If the patient is taking oral contraceptives, these should only contain progesterone due to the proangiogenic effect of the oestrogens

Embolisation / surgery

• Are the mainstay of treatment, although partial treatment can lead to rapid worsening of the AVM