Hello! I read your question carefully and understood your concern. In my opinion the dizzy spells and fainting are caused by a low blood pressure, which causes a low blood flow to the brain during these episodes. I don t think that there is anything to do with a brain tumor. It doesn t cause low blood pressure. I would recommend to consult with your cardiologist and have some changes in your treatment for high blood pressure. I would also recommend to measure your blood pressure during sitting position and standing up position, to see if there is any decrease in blood pressure to confirm an orthostatic hypotension which can be the cause of these problems. Hope to have been of help! Greetings! Dr. Aida