Cavernous Malformations

Epidemiology

Accounting for 8% to 16% of all cerebral vascular malformations, cavernous malformations are found most commonly in cerebral hemispheres when they occur intracranially. Risk factors for cerebral cavernous malformations are not yet known, but familial syndromes exist.

Pathology

A cavernous malformation is a well circumscribed bluish-purple, unencapsu-lated lobular mass with the surrounding brain frequently discolored by previous hemorrhage. It is hypothesized that malformation growth results from rupture of thin-walled vessels with repeated re-endothelialization of cavities, growth of new vessels as part of hematoma organization, and production of additional fibrous scar tissue. Hemorrhage is believed to occur in 8% of cases.

Clinical Features

Although most adult cases of cavernous malformation are discovered with minimal or no symptoms, children with cavernous malformations often are symptomatic.

Seizure, hemorrhage, or progressive neurological deficit are the typical symptoms that lead to detection of cavernous malformation. Most episodes of bleeding are minor, and many times may occur undetected. Fatal hemorrhages have been reported in cases of malformations located in the posterior fossa. Chronic irritation from hemosiderin is the likely explanation for associated seizures. Occasionally, a cavernous malformation may lead to a progressive neurological deficit, and, thus, can mimic symptoms of a neoplasm. Multiple cavernous malformations usually are seen in familial disorders in an autosomal dominant distribution.

Treatment

Since the risk factors for cavernous malformation are not yet elucidated, no standard treatment is described for children with diagnosed cavernous malformation. In children who have experienced a bleed, early excision is recommended, since the hematoma can help define the lesion and aid in its complete excision. The annualized hemorrhage rate following a known event ranges from 1% to 4% per year. Therefore, excision for accesible lesions is recommeded. Excision of hemosiderin-stained brain should be considered for children who have experienced a convulsion or have more intractable seizures. Malformations located within the brainstem or basal ganglia should be approached cautiously, if at all.

Small cavernous malformations may be difficult to localize, therefore, stereotac-tic CT or MR guidance can be an excellent tool to localize the lesion intraopera-tively (Chapter 2, Fig. 8). Intraoperative stereotactic CT or MR guidance can allow the neurosurgeon to make a more safe and thoughtful entry through the cortex to reach the malformation. Although radiosurgery has been used in some pediatric cases, long-term effectiveness is lacking and repeat hemorrhages are known to have occurred following radiosurgery treatment.

Outcome

Once the malformation has been completely excised, the majority of patients are completely relieved of their symptoms.

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