Pure arterial malformations are very rare and characterized by mass-like dilated, overlapping, and tortuous arteries without arteriovenous shunting and no capillary or venous components. This distinguishes them from arteriovenous malformations and dural arteriovenous fistulas. Furthermore, the length and/or number of arterial loops do not conform to normal anatomy, as is the case with dolichoectasia.
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Epidemiology
Pure arterial malformations are uncommon, and only a few cases have been reported. Typically, these are found by chance during cranial cross-sectional imaging performed for other reasons. Due to the limited number of reported cases, strong epidemiological data is unavailable, however, the majority of cases have been diagnosed in younger individuals (adolescents and young adults) with a modest predilection for females 1,2.
Clinical presentation
Most pure arterial malformations are asymptomatic and discovered incidentally. Nonetheless, a variety of symptoms have been reported, including headaches, seizures, dizziness and hemiplegia 1,5,6.
Pathology
The key distinguishing feature of pure arterial malformations is that they are isolated to the proximal artery, without communication with veins and without arteriovenous shunting. 1,4,8. They may, however, be associated with regional aneurysms 1-3.
Their etiology is not understood and remains a source of debate 1. Possibilities include congenital dysplasia and acquired injuries (e.g. viral infections, or healed arterial dissection) 1,7.
Although pure arterial malformation can occur in any blood vessel within the brain, it most commonly affects the supraclinoid internal carotid artery and adjacent posterior communicating artery, M1 segment of the middle cerebral artery or A1 segment of the anterior cerebral artery 1.
Radiographic features
CT
The abnormality appears as a blood-density serpignious mass, often in the interpeduncular or suprasellar cistern. There may be calcification in the walls.
Vascular imaging
CT angiography, MR angiography and catheter angiography reveal dilated tortuous vessels in the the subarachnoid space without shunting on nidus 1,2. Associated aneursymal dilatation may be present.
Treatment and prognosis
The management of pure arterial malformation is still a topic of debate although the vast majority of reported cases have been treated conservatively and most remained asymptomatic 1. However, if the malformation includes a local aneurysm, surgery or endovascular treatment may be necessary 1.
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