Hello. Thanks for asking from HCM. I can understand your concern. Headache with nausea, vomiting and weight loss could be due to variety of reasons. To reach upto some conclusion, we need more details of your complaint like your age, any history of tuberculosis or TB (if you are from developing country) in you or your family, any history of fever, any other neurological symptom like weakness/numbness/visual blurring, any history of diabetes or HIV. You can provide these details by asking another question. Now coming to your complaint and analysing details, it can be inferred that you are not having any lesion (according to CT) and brain infection (according to CSF). But there are few other investigations beside your clinical history which can help like MRI brain (more specific than CT) to rule out any lesion. Examination of your abdomen to rule out abdominal diseases like abdominal mass, liver disease, intestinal disease (ulcerative colitis/Crohn disease/colitis). You can ask your doctor about this. Regarding headache due to spill tap, it can occur due to negative pressure created as a result of loss of brain fluid (CSF). It is treated by ; bed rest ; keeping head at lower level than chest] ; drinking 2.5 to 3 litre fluids daily ; painkiller like Diclofenac sodium after proper prescription Hope it will help you. Take care. Thanks.