A slower collection. A different treatment era.

What a chronic subdural hematoma is

A chronic subdural hematoma is an older collection of blood and fluid beneath the dura. On CT it is often darker than brain (hypodense). Mixed density can mean blood of different ages or recent rebleeding into an older collection.

“Chronic” describes the age of the blood. It does not mean harmless. A chronic collection can still cause headache, confusion, imbalance, weakness, or dangerous pressure.

Who is affected

Chronic collections are more common with advancing age. The brain can lose volume over time, stretching bridging veins so that a minor bump or fall is enough to start bleeding. Many patients are taking an anticoagulant or antiplatelet medicine. Some have had prior subdural bleeding, heavy alcohol use, or another clotting problem.

A remembered injury is helpful but not required. Families often recall a fall weeks earlier only after the diagnosis is made.

How it shows up

Symptoms may be gradual: a new headache, unsteadiness, a change in memory or personality, sleepiness, or “not being themselves.” Because the course can mimic dementia or a medication effect, the collection is sometimes found only after a delayed scan.

Why it can come back

Around a chronic collection, inflamed membranes can form. Those membranes may contain fragile vessels fed in part by branches of the middle meningeal artery. Continued leakage helps explain why drainage alone does not always last—and why targeting that supply can reduce recurrence.

Treatment options

The plan depends on symptoms, size, mass effect, other illness, and whether the person can be followed reliably:

• Observation for selected small, stable collections, with scheduled exams and imaging.
• Surgical drainage, often through a burr hole when the collection is liquid enough, to relieve pressure.
• MMA embolization, to reduce the blood supply of the membranes, usually as an adjunct to drainage and sometimes alone in selected patients.

Where MMA embolization fits

The 2026 SNIS guideline gives its strongest recommendation—Class I, Level A—to MMA embolization as an adjunct to surgical drainage to reduce recurrence requiring another intervention, balanced against procedural risk. Standalone MMAE is considered separately (Class IIa) in selected circumstances such as high surgical risk.

That is a substantial change in chronic subdural care. It is not a claim that every subdural bleed needs embolization, and it does not replace emergency surgery when the brain must be decompressed now. Read the MMA embolization guide and the trial evidence.