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When does an adult with headaches need central nervous system imaging?

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A 32-year-old woman presents to the clinic  for evaluation of headaches, which she describes as pulsatile and throbbing, usually unilateral but involving different sides of the head at different times, and severe, causing her to miss work. They usually last between 12 and 24 hours and are associated with nausea but no vomiting and no changes in vision. They are worse around the time of her menses, have been occurring about twice a month for the past 6 months, and respond to ibuprofen. She thought they were caused by chronic seasonal allergies and sinusitis and has tried antihistamines and nasal irrigation without success. They are not affected by body position, they are not explosive, and they are not brought on by the Valsalva maneuver. She reports no other neurologic or systemic symptoms.

A detailed neurologic examination shows no deficits. However, the patient is concerned, as one of her friends was recently diagnosed with cancer. She requests imaging to “make sure there is no cancer.” Would it be appropriate to order imaging at this time?

No, it would not. Patients who have primary headache disorders without red-flag symptoms should not undergo imaging of the central nervous system (CNS) as part of their initial evaluation.1–4 (The list of potential red-flag symptoms is long but includes new onset after age 50, persistent neurologic changes, systemic symptoms or immunosuppression, sudden onset, progressive pain, positional nature, headaches precipitated by the Valsalva maneuver, and papilledema.)

Without red-flag symptoms, CNS imaging is unwarranted and may be harmful

CNS imaging may be appropriate for patients with features that increase the likelihood of structural diseases such as arteriovenous malformation, aneurysm, tumor, or subarachnoid hemorrhage. This patient, however, does not have worrisome signs or symptoms. Her symptoms are most consistent with migraine headache without aura. In patients with migraine headache without symptoms suggesting structural disease, CNS imaging is unwarranted and may be harmful.

DIAGNOSING MIGRAINE ACCURATELY

Diagnosing migraine headache can be a challenge, and up to half of all patients with migraine may be undiagnosed.5 The proper diagnosis of headache type is critical to the initial evaluation. In diagnosing migraine, one can use the mnemonic POUND4:

  • Pulsatile
  • One-day duration (4–72 hours)
  • Unilateral
  • Nausea or vomiting
  • Disabling.

If four or five of these features are present, the likelihood ratio that the patient has migraine headache is 24, making it overwhelmingly likely that is the correct diagnosis.4 With three features the likelihood ratio is 3.5. If two or fewer features are present, migraine is much less likely, with a likelihood ratio of 0.41. Thus, patients with classic symptoms of migraine can be confidently and accurately diagnosed without the need for any imaging studies.

The patient in the vignette has all five POUND criteria. If we estimate her pretest probability of migraine headache at 50% (which is actually a conservative estimate—see Guidelines and Choosing Wisely, below), then, utilizing Bayes’ theorem, the likelihood ratio of 24 would result in a 95% probability that her headaches represent migraine.

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