Symposium on Cerebrovascular DiseasesNatural History, Evaluation, and Management of Intracranial Vascular Malformations
Section snippets
INCIDENCE
Population data are scant regarding the overall incidence of intracranial vascular malformations; however, they are apparently about 1/7 as common as intracranial saccular aneurysms.3 In a large autopsy series, the overall frequency of detection of AVMs was 1.4% (46 AVMs among 3200 brain tumor cases).4 In that series, 12.2% of patients were symptomatic. A population-based study from Olmsted County, Minnesota, reported that the age- and sex-adjusted incidence for intracranial vascular
ARTERIOVENOUS MALFORMATIONS
Arteriovenous malformations are congenital lesions that occur most commonly in the supratentorial region. These space-occupying vascular lesions consist of multiple arteries and veins, connecting as a fistula without an intervening normal capillary bed. Typically, AVMs are single lesions, except when associated with hereditary hemorrhagic telangiectasia.6 The histology includes clusters of normal or dilated arteries and abnormal veins with calcification and occasionally some prior hemorrhage.
CAVERNOUS MALFORMATIONS
A CM is typically a small mulberry or “popcornlike” lesion in the brain, spinal cord, or nerve roots that consists of a tangle of intertwined clusters of sinusoidal vascular channels. The overall frequency of CMs, also called cavernous angiomas, cavernomas, or cavernous hemangiomas, was approximately 0.4% in a large autopsy study of 4069 people.66, 67 A retrospective review of MRI scans reported a detection rate of 0.4% to 0.9%.68, 69 Cavernous malformations are uncommon in children,70 with
VENOUS MALFORMATIONS
A VM is physiologically important to brain tissue because it provides normal venous drainage. Venous malformations are thin-walled venous channels with normal intervening neural tissue. Computed tomography with contrast enhancement shows a large draining vein, although non- contrast-enhanced CT results are usually normal. Magnetic resonance imaging is sensitive; it shows a flow void and may show a radial pattern, the so-called classic caput medusae pattern.96 Arteriography is required rarely
DURAL ARTERIOVENOUS FISTULAS
Dural arteriovenous fistulas (DAVFs), also called dural AVMs, involve a vascular malformation of the wall of one of the major venous sinuses.1, 103 Venous outflow obstruction, sometimes associated with sinus thrombosis, can precede formation of some DAVFs. Head CT typically does not detect DAVFs, although dilated veins may suggest their presence; MRI also may detect these lesions, showing the diagnostic dilated veins and feeding arteries in an appropriate location, but is not sensitive.
CAPILLARY TELANGIECTASIAS
On pathological examination, capillary telangiectasias are somewhat enlarged ectatic capillaries found typically with other vascular malformations.1, 77, 80 They are detected frequently and were the second most common intracranial vascular malformation in one series.1 Capillary telangiectasias are noted often in the posterior fossa or spinal cord and have an overall frequency of about 0.1%.1 They are extremely unlikely to cause symptoms, although there are case reports of patients with
CONCLUSION
Intracranial vascular malformations are seen commonly in clinical practice, particularly as CT and MRI are performed increasingly. The range of symptoms and signs at presentation is myriad. Natural history depends on lesion type, location, size, and overall hemodynamics. Management decisions are often complex. A multidisciplinary approach including neurosurgery, radiosurgery, interventional neuroradiology, and vascular neurology is most useful in determining the best management strategy.
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