It is classified as a group of vascular malformations, where a collection of dilated blood vessels form a tumor.
The terms cavernoma, cavernous hemangioma, cavernous angioma, and cavernous malformation are used interchangeably and appear equally frequent in the literature. The terms cavernoma, cavernous angioma, and cavernous hemangioma suggest that it is a neoplastic lesion, which is inaccurate as cavernous malformations are true vascular malformations.
The term cavernous hemangioma is also confusing as cavernous hemangiomas in the cavernous sinus or in the orbit; both are slow-growing neoplastic diseases unrelated to vascular malformation
In its sporadic form, CA occurs as a solitary hemorrhagic vascular lesion or as clustered lesions associated with a developmental venous anomaly. In its autosomal dominant familial form (Online Mendelian Inheritance in Man #116860), CA is caused by a heterozygous germline loss-of-function mutation in one of three genes—CCM1/KRIT1, CCM2/Malcavernin, and CCM3/PDCD10—causing multifocal lesions throughout the brain and spinal cord.
Cavernous malformations (cavernous angiomas, cavernomas, cavernous hemangiomas) are well-defined, grossly visible lesions that may reach a significant size. They are composed of a compact mass of sinusoidal-type vessels immediately in apposition to each other without any recognizable intervening neural parenchyma.
Cavernous malformation (CCM)s are benign, low-flow vascular lesions with thin elastic endothelial walls that lack adventitial smooth muscle and frequently present with little intervening brain parenchyma.
Microscopically, cavernous angiomas consist of sclerotic, variably calcified compact vessels in a honeycomb pattern.
Unlike telangiectasis and arteriovenous malformation these lesions do not contain interstitial parenchyma.
The cells that form the vessels do not form the necessary junctions with surrounding cells and the structural support from the smooth muscle is hindered causing leakage into the surrounding tissue.
It is the leakage of blood, known as a hemorrhage from these vessels that causes a variety of symptoms known to be associated with this disease.
CMs were difficult to diagnose in the pre-MRI era. They are invisible on angiogram and thus the term AOVM (angiographically occult arteriovenous malformation) was sometimes used. However, the venous angioma sometimes seen in association with a CM was visible on angiogram, and thus believed to be the source of the hemorrhage seen, even though in reality it was the CM that had hemorrhaged. Thus, venous angiomas were sometimes treated, also with radiosurgery, a management that was soon aborted 9).
The introduction of MR imaging increased the number of diagnosed CMs as a CM that has hemorrhaged has a typical appearance on MR images (MRI). An unruptured CM cannot, however, be seen. Consequently, a CM diagnosed in a patient with an earlier normal MRI does not necessarily represent a denovo CM. It may be a CM that was present but invisible on an earlier scan that now can be seen due to an earlier hemorrhage with sequel signals depicted on MRI 10).