How to image your patient with headaches

Based on the knowledge we have accumulated so far, we can use an algorithm to organize our approach to assessing a patient with headache:

1. Take a detailed history and perform a neurologic examination.
2. Generate a preliminary diagnosis.
3. Analyze for red flags.
   1. If there are none present, ask if the presentation satisfies the criteria for a primary headache disorder.
   2. If there are red flags present or if the presentation does not satisfy the criteria for a primary headache, consider a diagnosis of secondary headache.
4. Order appropriate diagnostic testing.

Most headache patients you will encounter have normal neurological examination and a primary headache disorder. These patients do not need further testing to establish a diagnosis.

However, sometimes there is a pressure for further testing that is created by the expectation of reassurance beyond your word or expertise, as expressed by the patient, family, or your community of colleagues. It is important to avoid unnecessary testing! Therefore, it is important to understand when certain tests are indicated, and when they are not.

Additional diagnostic evaluation is needed in cases that do not meet the criteria for a primary headache disorder, or which are associated with unusual or worrisome features, such as the red flag symptoms.

Here are the top ten reasons for ordering diagnostic imaging for your patient with headache:

1. The headache characteristics are different from what your patient usually experiences.
2. The headaches occur with increasing severity or frequency.
3. The headaches differ from the typical International Headache Society diagnostic criteria for that headache type.
4. You identify the presence of an abnormality on the neurological examination.
5. Your patient is experiencing seizures.
6. The headache is sudden or severe (thunderclap headache) or radiates to the neck and you need to rule out subarachnoid hemorrhage.
7. Your patient is suffering from refractory headaches.
8. The headaches always occur ipsilaterally.
9. Your patient has a co-existing medical condition, such as the human immunodeficiency virus (HIV).
10. Your patient presents with red flags (remember SNOOPP).

Computed tomography (CT)

Computed tomography, or CT, is faster, more readily available, and is used often in emergent situations. Emergent imaging, perhaps with a thunderclap headache, trauma, or when determining safety before lumbar puncture can be accomplished with a CT. CT is also superior for assessing bony lesions.

Magnetic resonance imaging (MRI)

Magnetic resonance imaging, or MRI, on the other hand, is preferred for looking at soft tissue and brain parenchymal structures, and ruling out structural abnormalities. These include tumors, vascular lesions, infections, Arnold-Chiari malformations, pituitary masses, intracranial hypotension, or hydrocephalus.

Angiography / venography

CT / magnetic resonance angiography (MRA) or venography might be needed to further assess vessels and vascular lesions.

While there are no hard and fast rules about when to not image a patient, it is well documented that without focal neurologic examination abnormalities, the yield of imaging decreases.

When a patient has an established headache pattern for years, for instance a typical migraine, and has not had significant changes, they can often be treated without imaging. Many studies have looked for patterns in migraine and tension headache patients using imaging and there are generally no differentiating factors when the neurologic examination is normal.

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