Cavernous malformations are abnormal vascular structures in which there is an overgrowth of redundant blood vessels. Interestingly enough, there is also an overgrowth of redundant names for this condition: cavernous malformation, cavernous hemangiomas, and cavernous angiomas.
The blood vessels involved in cavernous malformations are often weak, imperfectly formed, and vulnerable to rupture. The vessels are immediately tangled with each other without any intervening brain tissue to separate them from one another. The compact mass of constituent blood vessels is often not supplying oxygenated blood to neural parenchyma. Histologically, the true cavernous malformation is classified by dilated thin-walled vascular channels lined by a simple endothelium and thin fibrous adventitia. Aside from blood products of various ages, gliosis and calcification are often present within the mass.
These congenital abnormalities can occur most anywhere in the central nervous system, with a tendency toward development in the brain stem and cerebral hemispheres. The lesions have been reported extracranially, as well as in nerve roots. Cavernous malformations occur in 0.1 to 0.5 percent of the general population with a familial and sporadic form.
Many cavernous malformations remain silent clinically and are diagnosed incidentally on an MRI taken for other reasons. Other cavernous malformations are prone to multiple bleeds. The lesions usually do not produce life-threatening hemorrhages, since the bleeding episodes are often separated by months or years. A hemorrhage may take place with the resulting clinical symptoms, followed by improvement as the blood is absorbed by the brain. The familial form of cavernous malformations have a more aggressive natural history with a 6.5 percent per patient, per year lesion risk of further hemorrhage following the initial bleed and neurological deterioration occurring at a rate of 15 percent per annum. The risk of further hemorrhage from the sporadic type is approximately 0.25 to 0.7 percent per year.
There is not a typical cavernous malformation presentation, but the acute or subacute onset of headaches, fits and other neurological deficits may occur.
Cavernous malformations are frequently asymptomatic lesions found coincidentally on CT, MRI or at post mortem.
Characteristically, angiography fails to delineate cavernous malformations. These lesions are considered occult to angiography.
Cavernous angiomas appear as high density regions on noncontrast CT because of associated calcification. In addition, they may enhance after IV contrast administration.
MRI offers the most sensitive means of suspecting a diagnosis of cavernous malformation. On MR, cavernous malformations are trademarked by hemisiderin surrounding various circumscribed regions of hemorrhage. The lesions have a matrix and usually appear in a round shape. As opposed to tumors, there is a complete rim of hemosiderin.
Excision or other means of removal is often curative in treating cavernous malformations.
The relative indications for surgery are to establish a tissue diagnosis and to remove the mass effect causing neurological deficit. The decision to operate on a patient with a cavernous malformation varies based on the accessibility of the lesion and the extent of the patient's presenting symptoms. There is recent evidence that radiation may obliterate the cavernous malformation mass or reduce lesion hemorrhage.