Cerebral cavernous malformations, occur when blood vessels in the brain don’t form correctly. Tiny blood vessels, known as capillaries, group together and grow with extremely thin walls that can easily leak. These are known as lesions.
These clusters of blood vessels can be less than 1/4 inch to 3 to 4 inches in size. Cavernous malformations can occur anywhere in the body and when they form in the brain, they are known as cerebral cavernous malformation and cause symptoms. 
Symptoms of Cerebral Cavernous Malformation
Approximately 25 percent of people with CCM never experience any related medical problems. Other will have serious symptoms like:
- Seizures (ranging in severity, duration and intensity),
- Headaches (ranging in severity, duration and intensity),
- Paralysis,
- Hearing or vision changes, and
- Bleeding in the brain (cerebral haemorrhage that may damage surrounding brain tissue)
While adults are most often diagnosed with CCM, people of all ages may be affected by cavernous malformations, and approximately 25% of all diagnosed cavernous malformations are found in children.
Cavernous malformations usually are not diagnosed until they start causing symptoms. When possible symptoms appear, your doctor may recommend a magnetic resonance imaging (MRI) scan, which remains the best way to diagnose cavernous malformations.