Hello, Thanks for posting this question in HCM First of all let me tell you that a given medical problem can be due to various causes. Headache can be due to various causes too. It can be due to brain tumor, infection, problem in the blood vessels of brain, migraine and so on. Whether a patient with headache will require a brain scan largely depend upon the presence or absence of neurological deficit on neurological assessment by a neurologist. Back to your question, your headache could still be due to flu with viral infection and hence i advise you to follow the following tow paths 1. Urgent medical evaluation: This will tell us the cause of illness including the headache. A neurologist who will assess, can tell if you need a scan or not. Blood counts also will be required . Further the presence of headache in sitting and some improvement in lying down position may suggests another possibility of low CSF Pressure headache. I advise you to undergo a neurological evaluation and analysis of the CSF study and Scan. These reports will tell us the exact cause of your problem and guide us for treatment Hope this clarifies Hope this clarifies