A chronic subdural haematoma is a slow collection of old blood between the brain and its outer covering. It often follows a minor head injury, sometimes weeks earlier and sometimes forgotten, and is more common in older people and those taking blood thinners. Symptoms include headache, confusion, drowsiness, unsteady walking, weakness on one side and memory problems.

The diagnosis is made with a CT scan. If the collection is small and symptoms are mild, it may be watched. If it causes symptoms or presses on the brain, drainage is recommended. The operation uses one or two small holes in the skull, called burr holes, made under local or general anaesthesia. The blood is washed out, and a thin drain may be left in place for a day or two.

Patients are usually asked to lie flat for a period, which helps the brain re-expand. Blood thinners are reviewed and adjusted by the doctor. A repeat scan checks that the collection is clearing.

How the Procedure Can Help

Drainage relieves pressure on the brain, often with striking improvement in confusion, weakness and walking within days. It is a relatively short operation, and many patients recover well.

Risks and Considerations

Risks include recurrence of the collection, fresh bleeding, infection, seizures and anaesthesia-related problems. Returning headache, drowsiness, confusion, weakness or fits after surgery needs urgent review.