Cavernous Malformations

1. Epidemiology and Natural History

Cavernous malformations (or cavernous angiomas) affect both sexes equally. Estimates of lesion prevalence vary between 0.02 and 0.9% depending on the criteria and methods utilized for definition. Patients typically present in the second to fourth decades of life. Familial forms, characterized by multiple lesions and an autosomal-dominant inheritance pattern, are well described and prevalent in the Hispanic population.

The natural history of cavernous malformations is not well defined. Cavernous malformations are known to be dynamic lesions that change in size and imaging characteristics with time. New lesions are also known to develop over time. Subclinical microhemorrhages are thought to be very common. Previously asymptomatic lesions have a 1 % annual incidence of hemorrhage. Once symptomatic, cavernomas rupture at an annual rate of 4.5%. Hemorrhage occurs commonly in the familial forms, deeply located lesions, lesions with associated venous malformations, in pregnant patients, and in patients who have received whole brain irradiation.

2. Pathological Characteristics

Cavernous malformations represent a lobulated collection of dilated endothelial-lined sinusoidal spaces. There is normally no intervening brain parenchyma. They are low-flow lesions that expand by internal thrombosis and hemorrhage within the sinusoidal spaces. Hemorrhage in various stages may be found within the lesion. Neighboring brain is well demarcated by hemosiderin stained, gliotic borders. The walls of the malformation lack smooth muscle and elastic lamina and are thus not true arteries or veins. Venous malformations are found in association with cavernous malformations in 15% of cases. Eighty percent of lesions are supratentorial but may occur at any location. Multiple lesions are demonstrated in 5080% of cases.

3. Clinical Manifestations

Seizures are the most common manifestation of supratentorial cavernous malformations. Surrounding hemosiderin and gliosis is thought to be responsible for this epileptogenicity. Symptomatic hemorrhage and headache are the next most common presentions. Cavernous malformations are also frequently found incidentally in radiographic studies performed for other indications.

4. Diagnosis

Cavernous malformations cannot be visualized with angiography and are best delineated by MRI. With MRI, cavernous malformations appear as a central focus of mixed signal intensity representing hemorrhage of various stages ("popcorn-like") surrounded by a hypointense rim of hemosiderin from multiple microhemorrhages (Fig. 14).

5. Treatment

Cavernous malformations that are asymptomatic are not generally treated because of their low risk of hemorrhage (~1%/year). Microsurgical resection is indicated for symptomatic supratentorial lesions. Brain stem cavernous malformations are considered for surgical resection when there is repeat hemorrhage, progressive neurological deficit, and superficial location. Stereotactic radiosurgery remains an experimental treatment option.

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