Hi, Noted the history related to your friend who had a history of blood clots in brain. underwent surgery, now has headache and unable to understand, wants to know more what should be done. Surely the first thing to do is to visit a Neurosurgeon, preferably the one who operated, MRI of brain and detailed tests of blood to know the cause of bleeding or clotting in brain. To review the previous cause as this can be related to the vascular malformation or so. Second opinion of a Hematologist if needed. All these things will lead to a proper diagnosis for the cause and effect and thus allow proper management as per the case may be. Get him admitted to a Hospital for early consultations and investigations. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. T. Chandrakant, General Surgeon