Imaging & Monitoring

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Key points

  • MRI is the best test for diagnosing and monitoring CCM; CT scans can be used to quickly check for large bleeds.
  • If you have new or worsening neurological symptoms, contact your care team. MRI may be recommended for evaluation. Stable lesions may be monitored according to a schedule determined with your care team.
  • Having many CCM lesions on MRI may suggest a familial (genetic) form of the disease — discuss genetic testing with your doctor if this applies to you.

When reviewing your MRI, your care team focuses on several important things:

  1. Number of lesions: One CCM vs. many can point toward sporadic or familial disease.
  2. Signs of recent bleeding: Edema (swelling) and blood signal changes on T1 sequences.
  3. Associated DVA: A nearby developmental venous anomaly is common with sporadic CCM and matters for surgery planning.
  4. Changes over time: New lesions, growth, or new swelling compared to prior scans.

When the diagnosis is uncertain

Sometimes a CCM can look like other conditions — including a small arteriovenous malformation (AVM), a hemorrhagic tumor, or simply old microbleeds from high blood pressure or aging. In these cases, follow-up imaging after the blood has resolved often clarifies the diagnosis. Biopsy is rarely needed but may be considered if a lesion is growing or showing dense contrast enhancement suggesting a tumor.

The 2025 consensus guidelines note that tiny dark spots on susceptibility sequences alone (without any of the typical CCM features) may be cerebral microbleeds — not CCM. These are more common with aging, high blood pressure, or amyloid angiopathy. Genetic testing can help tell the difference if the situation is unclear.

“Innumerable CCMs”

When many small lesions are present, the 2025 guidelines recommend that radiologists avoid using the word “innumerable,” which can cause unnecessary anxiety. Instead, reports should give an estimated range (such as “more than 100 lesions”) or describe burden as mild, moderate, or severe. If you see this language in your report, ask your doctor what it means for your care.

Tests such as CT angiography (CTA), MR angiography (MRA), and catheter angiography look at blood vessels. CCM lesions are usually not visible on these studies.

Catheter angiography is not generally recommended for CCM. It may be used only if there is concern that the lesion could be an AVM rather than a CCM, since AVMs and CCMs require very different treatment approaches.

When to get repeat imaging

You should get an MRI if you develop new or worsening neurological symptoms. This should happen as soon as possible — ideally within 2 weeks of symptom onset. In an emergency, a CT scan may be done first to look for large bleeds, but MRI should follow.

Routine scheduled scans

There is no single recommended schedule that fits everyone. Routine MRI can be useful to track lesions that have previously bled, grown, or changed. The decision about how often to image should be made together by you and your neurologist or neurosurgeon, based on your specific situation.

Recent research suggests that small, silent changes on surveillance MRIs may sometimes predict a future symptomatic bleed — though how this should affect treatment decisions is still being studied.

After surgery

If you have surgery to remove a CCM, your doctor will order follow-up MRIs to confirm the lesion was fully removed and to watch for any regrowth. An MRI within 72 hours after surgery gives useful information, though it is not perfect at confirming complete removal. Long-term surveillance — typically annual MRIs for at least 5 years — is recommended. This is especially important for children, who have higher rates of recurrence.

If you develop new neurological symptoms during pregnancy or while breastfeeding, an MRI without contrast is considered safe and is recommended. Gadolinium contrast is generally avoided during pregnancy unless absolutely necessary.

Strong recommendation · Class I

Brain MRI is the only imaging test strongly recommended for diagnosing and monitoring CCM.

Strong recommendation · Class I

MRI for CCM must include a susceptibility-weighted sequence (SWI or similar) to determine whether there is one lesion or many.

Strong recommendation · Class I

Brain imaging should be done as soon as possible after new symptoms. CT may be used first in an emergency, but MRI is preferred and should follow ideally within 2 weeks.

Strong recommendation · Class I

If you have had prior brain radiation and develop a new severe headache, seizure, or neurological deficit, an MRI is indicated because radiation can cause CCM to develop.

Not generally recommended · Class III

Catheter angiography is not routinely recommended for CCM unless an AVM needs to be ruled out.

Two specialized techniques are being studied but are not yet used for standard clinical care:

  1. QSM (Quantitative Susceptibility Mapping): Measures iron content as a way to track blood leakage over time. Being developed as a marker of disease activity in drug trials.
  2. DCE Permeability Imaging: Measures how leaky the blood vessel walls are. Also used in research and drug trials. Not yet available for routine care.

Functional MRI (fMRI) and diffusion tensor imaging (DTI) may also be used before surgery to map important brain areas and pathways, helping surgeons plan a safer approach.

Updated 5/27/26.

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