Cavernomas are benign lesions in the nervous system filled by blood, but under very low pressure. They can cause seizures or bleeding in the brain or spinal cord. A typical cavernoma looks a bit like a blackberry. It is filled with blood that flows slowly through vessels that are similar to like "caverns". Cavernomas vary in size, from a few millimetres to several centimetres across. They are diagnosed by MR scans and are not visible on an angiography. Some cavernomas can go undetected and cause no symptoms, while others produce symptoms such as headaches, dizziness, weakness, numbness, tiredness, memory difficulties. When these symptoms do occur, this is often due to the presence of Brain haemorrhage, Epilepsy or progressive disability, depending on the size and position of the Cavernoma.

Microsurgical removal is the mainstay of treatment. Other treatment modalities such as Stereotactic radiotherapy (a course of radiotherpay), Stereotactic radiosurgery (a single concentrated dose of radiation therapy) however, are not without risk and are often reserved for inoperable cavernomas.