CAMS1 patient may have a neurocutaneous AVM in the nose

or retina and a brain parenchymal AVM.

Molecular Classification

The identification of underlying causal genes in familial forms

of CVMs has allowed the definition of an ever-increasing

number of these disorders at the molecular level. Specific

mutations in some genes (e.g., CCM1/KRIT1, CCM2/MGC4607,

CCM3/PDCD10) cause autosomal dominantly inherited

cavernous malformation syndromes (CCM1, CCM2, and

CCM3). Some patients with brain AVMs also have cutaneous

capillary malformations attributable to RASA1 gene

mutations. Hereditary hemorrhagic telangiectasias (HHT)

result from several mutations, among them the endoglin gene

(ENG) in HHT1. Whether cavernous and venous malformations

are "molecularly distinct" or only "phenotypically distinct"

lesions that result from the same CCM gene mutations is

controversial.

Functional Classification

Endovascular radiologists have proposed a functional, highly

practical system that divides all CVMs into 2 basic categories:

(1) CVMs that display arteriovenous shunting and (2) CVMs

without AV shunting. The former category includes AVMs and

arteriovenous fistulae; the latter is basically everything else

(venous, capillary, cavernous malformations). The former are

amenable to intervention; the latter are either left alone or

treated surgically.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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