This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Source of chronic subdural hematoma is: September 2011 
Select and explain. 
A. Aerial, B. Venous, C. Capillaries, D. None of the above
B: Venous
Answer: B: Venous 
Explanation: Ans. B: Venous Chronic subdural haematomas usually occur in the elderly and are more common in those on anti-coagulant or anti-platelet agents. There is usually but not always a history of minor head injury in the weeks or months prior to presentation. It is thought that small bridging veins tear and cause a small acute subdural haematoma which is clinically silent As the haematoma breaks down it increases in volume, leading to a mass effect on the underlying brain