Cerebral cavernous malformations (CCMs) are groups of tightly packed, abnormal small blood vessels with thin walls. They may be present in the brain or spinal cord. The vessels contain slow-moving blood that's usually clotted. CCMs, which look like a small mulberry, can create problems in the brain or spinal cord due to leaking of blood in some people.

The clusters can vary in size from less than a quarter of an inch (0.6 centimeter) to 3 to 4 inches (7.6 to 10.2 centimeters). CCMs can run in families, but most often they occur on their own.

CCMs are one of several types of brain vascular malformations, which contain abnormal blood vessels. Other types of vascular malformations include:

  • Arteriovenous malformations (AVMs)
  • Dural arteriovenous fistulas
  • Developmental venous anomaly (DVA)
  • Capillary telangiectasias.

It's common to have both a DVA and a CCM.

CCMs may leak blood and lead to bleeding in the brain or spinal cord (hemorrhage). Brain hemorrhages can cause many signs and symptoms, such as seizures.

Depending on the location of the cavernous malformation in a person's nervous system, CCMs can also cause stroke-like symptoms. Bleeding in the spinal cord can cause difficulty with movement or feeling in the legs and sometimes arms, as well as bowel and bladder symptoms.


CCMs may exist without apparent symptoms. Seizures may occur when there is a CCM on the outer surface of the brain.

A wide variety of signs and symptoms may occur when CCMs are found in the brainstem, basal ganglia and spinal cord. For example, bleeding in the spinal cord may cause bowel and bladder symptoms or trouble with movement or feeling in the legs or arms.

Generally, signs and symptoms of CCMs may include:

  • Seizures
  • Severe headaches
  • Weakness in the arms or legs
  • Numbness
  • Difficulty speaking
  • Problems with memory and attention
  • Problems with balance and walking
  • Vision changes, such as double vision

Neurological issues can progressively worsen over time with recurrent bleeding. Repeat bleeding can happen soon after an initial bleed or much later. In other cases, a repeat bleed may never occur.

When to see a doctor

Seek medical help immediately if you experience any symptoms of seizure, or signs and symptoms that suggest a CCM or brain bleeding.


Most CCMs are known as "sporadic form." They occur as a single formation without an apparent cause and without any family history. The sporadic form often has an associated developmental venous anomaly (DVA), which is an irregular vein with a witch's broom appearance.

However, roughly 20% of affected people have a genetic (inherited) form of the disorder (familial cavernous malformation syndrome). In many cases, such people can identify similarly affected family members, most often with multiple malformations. A diagnosis of the inherited form can be confirmed by genetic testing. Genetic testing is often recommended for people who have:

  • MRI evidence of multiple CCMs without a DVA
  • A family history of CCMs

Radiation to the brain or spinal cord may also result in CCMs 2 to 20 years afterward. Other rare syndromes may be associated with CCM.

Risk factors

While most CCMs occur with no clear cause, the inherited form of the condition can cause multiple cavernous malformations, both initially and over time.

To date, research has identified three genetic variants responsible for inherited cavernous malformations, to which almost all familial cases of cavernous malformations have been traced.

Familial CCMs are inherited through a mutation in one of these genes:

  • KRIT1, also called CCM1
  • CCM2
  • PDCD10, also called CCM3

It isn't fully understood why these mutations lead to CCM. These genes are thought to work together to communicate between cells and reduce leaking from blood vessels.


The most concerning complications of CCMs stem from recurrent bleeding, which may cause a hemorrhagic stroke and lead to progressive neurological damage.

Bleeding is more likely to recur in people with prior diagnosed hemorrhages. They're also more likely to happen again with malformations located in the brainstem.

Cavernous malformations care at Mayo Clinic

Dec. 14, 2022
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