Spotlight On: Headache, MRI and Brain Imaging
What to know about your headache before getting a brain scan
by Benjamin Frishberg MD, Clinical Professor of Neuroscience (Voluntary), UCSD, The Neurology Center, Carlsbad CA
I must have a brain tumor!
Isn’t that the worry of the many people who suffer from bad headaches? I often hear patients ask me how they can have such severe headaches and not have something seriously wrong in the brain. There is also a general feeling in the public that if you have bad headaches, you must have a brain imaging study done. In the past, a CT scan would suffice, but now that patients are researching on the internet and they all seem to want to have an MRI!
We understand that patients want answers, and as physicians, we know that the key to the diagnosis is the history. Sharing your symptoms and the answers to our questions about symptoms allows us to make an appropriate diagnosis, and determine if any further testing is necessary. To start, we separate headache disorders into primary and secondary headaches. Primary headaches refer to headache disorders that do not have a structural cause. These include migraine headache, tension type headache, and cluster headache. Secondary headaches, on the other hand, are caused by an underlying disease process and include such things as a brain tumor, aneurysm, sinusitis, meningitis, concussion, and high pressure in the brain.
When we evaluate a headache patient, we are looking for “red flags”; certain aspects of the history or findings on the examination that suggest the headache may be a secondary headache. Some of our red flags clearly indicate a serious issue, but many of these red flags just indicate the patient is not typical and may need further studies. On the other hand, we also look for headache features that help us confirm the headache is primary in which case neuroimaging is usually not necessary. For more information on these red flags, check out this article on the American Migraine Foundation website by Dr. Todd Schwedt.
When is it considered medically necessary to have a brain imaging study?
When there are significant findings on the physical examination such as:
- swelling of the optic nerve
- abnormal reflexes
- weakness on one side of the face or body
- unsteady gait
- double vision
- vision loss
- abnormalities of the pupils
In certain situations such as:
- new headache in a person with cancer
- headaches in people who are immunosuppressed
- headaches that are becoming worse
- new headache in people over age 50
- no better with prescribed medicine
- persistent headache after head injury.
- persistent fever
Brain imaging will often be ordered based on a headache that does not meet criteria for migraine, or has features that in the opinion of the provider is worrisome. There are few clear-cut “rules.”
When is it not medically necessary to have a brain imaging study?
- In people who meet the criteria of migraine, have no abnormal findings on examination, and who have not had a significant change in the headache pattern DO NOT need to have an imaging study. This was first stated in 1994 as part of an imaging guideline by the American Academy of Neurology, and has been adopted as an evidence based guideline. This has been restated in the Choosing Wisely guideline in 2013 here.
- People with mild intermittent headaches which are unchanged and have no red flags usually do not need to have any studies done. 90% of the US population has a headache at some point.
As headache is such a common problem, primary care providers see the clear majority of sufferers and make decisions about evaluation and treatment. They often refer to neurologists in more difficult or unusual cases. Many doctors bow to patient pressure to obtain a scan, and many practice defensive medicine and order a scan despite the guidelines. If a scan is ordered to evaluate a headache disorder, MRI with contrast is preferred as it is a more sensitive test than CT and does not involve any radiation. However, as it is so sensitive, there are often abnormal findings unrelated to the headache that may lead to further testing. The most common abnormalities are small spots in the brain that may be mistaken for Multiple Sclerosis. These spots are seen in up to 30% of all migraine patients, and are usually an incidental finding with no clinical significance.
Bottom Line: If you have migraine, which is often a severe and disabling headache, you do not need to have a CT or MRI, and can rest assured that the likelihood of having a serious abnormality in the brain is probably no different from your next-door neighbor who does not have migraine. If however, you are suffering from new headaches, headaches that are increasing in frequency and intensity, or have a major change in your headache pattern; make an appointment to discuss this with your care provider.