If your doctor is not able to diagnose cluster headaches based solely on your symptoms and physical exam, other tests may be done to rule out other conditions. In addition to imaging tests (such as an MRI or CT scan), these tests may include:

• Blood and urine tests. Blood tests may be done to find out whether you have conditions associated with cycles of headaches such as low thyroid function (hypothyroidism) or inflammation of blood vessels in the temple (giant cell arteritis).
• Electroencephalogram (EEG). This test may be useful for people who have seizures associated with their headaches. But it is not often used, because other tests provide more helpful information about the causes of headaches.
• Lumbar puncture (spinal tap). This test is done only if there is a serious question about your diagnosis. It is done when you have a fever and a stiff neck to rule out meningitis, an infection around the brain and spinal cord.