How is aneurysmal subarachnoid hemorrhage (SAH) evaluated in the differential diagnosis of migraine headache?

Updated: Oct 21, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Helmi L Lutsep, MD  more...
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An extensive evaluation is indicated in such cases, including an initial computed tomography (CT) scan of the head without contrast. Lumbar puncture (LP) should be considered if the scan is negative, as 25% of cases are missed by CT scanning. Questions remain over whether an angiogram should be performed if the patient has normal findings on neurologic and cerebrospinal fluid (CSF) examination, as well as on CT scan or MRI.

In one study, acute, severe thunderclap headache comparable to that of SAH without the nuchal rigidity occurred in 6.3% of patients with unruptured aneurysm. Other studies have revealed that in patients with severe thunderclap headache with normal CT-scan and CSF findings, none developed SAH. [73]

In selected cases, angiography should probably be performed if an experienced angiographer is available. Patients at risk include those whose CT scan and LP are performed late after symptom onset, so that negative results are unreliable, and patients with suggestive clinical features, such as family history or past medical history of SAH, classic SAH-like symptoms, or the presence of neurologic signs (in particular a third cranial nerve palsy affecting the pupil)

In patients with unrevealing studies in whom the diagnosis of aneurysmal SAH is possible but very unlikely, MRI and magnetic resonance angiography (MRA) are screening tests. Close follow-up is appropriate if the findings of these tests are negative.

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