What are hypodense collections in the brain?

Q: My father was operated for removal of a chronic subdural haematoma last month. But a subsequent scan taken shows some hyper/hypodense collection in the right parietal and frontal region 2.3 cm in depth. There seems to be septation and thick membrane formation. My father is stable has no complaint whatsoever; what I should do now?

A:Blood clots outside the brain, between it and its covering called the dura, are termed subdural clots. These are especially noted in ageing persons after relatively minor injuries.When they press upon the brain, they cause a variety of problems ranging from headaches to weakness of one or other part of the body to abnormal drowsiness.They are usually removed through small holes in the overlying skull. Since these clots are often surrounded by abnormal membranes that form their envelopes and since these envelopes are often quite vascular and contain fragile blood vessels that can bleed again and again in the clot cavity.If the clot is small and does not cause significant pressure of the brain, there may be no need for further surgery. Careful observation of the patients progress by his neurosurgeon is essential. Drugs such as acetazolamide (diamox) and glycerine (medical grade) may help resolve the clot without surgery.