Hi. A brain tumor normally does not show up in sinus x-rays. A cranial CT scan is the usual procedure which is used to check for the presence of masses in the brain. But I think you should first have yourself checked by a neurologist or an internal medicine specialist, before prematurely concluding that you have a brain tumor. The light headed feeling and sharp pains (headache?) are too non-specific to be readily attributed to the presence of a brain tumor.