You may worry that frequent headaches mean a brain tumor, but they're most likely migraines or tension headaches if you don't have vision loss, seizures, or other symptoms. "CT scans expose you to radiation and may miss tumors and aneurysms," says headache specialist Dr. Emily Rubenstein Engel. "MRIs are safe but expensive, and often not necessary if you meet migraine criteria and have a normal neurological exam."