A cluster of thin-walled vessels resembling a mulberry, filled with slow-moving blood. Cavernomas leak rather than burst. Many cause nothing at all; some cause seizures or repeated small bleeds.
Because the blood inside a cavernoma is at low pressure, a bleed is usually small and contained rather than catastrophic. What it produces depends entirely on location: a cavernoma in the temporal lobe may cause seizures, one in the brainstem may cause double vision, numbness or weakness from a bleed that would pass unnoticed elsewhere.
Many are found by chance on MRI and never do anything at all.
MRI is the test. Specific sequences show the characteristic appearance and reveal old blood products, and often detect additional cavernomas that were not suspected — important, because multiple lesions raise the possibility of a familial form worth discussing with the family. Catheter angiography is typically normal, since these lesions are angiographically occult.
Surgical removal is considered when a cavernoma has bled more than once, when it causes seizures that medication does not control, or when it produces progressive neurological problems. The decision rests heavily on where it sits: an accessible lesion in a quiet part of the brain is a different proposition from one deep in the brainstem, where the approach itself carries real risk.
For a cavernoma found incidentally and causing no symptoms, observation with periodic MRI is usually right. Radiosurgery has a limited and debated role.
Where a cavernoma is the clear cause of epilepsy, removing it — along with the stained brain around it — offers a good chance of seizure freedom, and that benefit often justifies surgery even when the bleeding risk alone would not.
That is usually the right question, and often the answer is no. Send the scans and you will get a straight opinion — including when the safest course is to do nothing and watch.