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A 42-year-old woman presented to the ED with headache and posterior neck pain of one and a half hour’s duration. The onset of the headache was sudden and was accompanied by one episode of vomiting.

She had seen a physician two days earlier for neck pain and was told she had a “pinched nerve.”

On examination, she was an overweight female in mild distress due to her headache. The patient was fully alert and oriented with no focal neurological deficits. She resisted full flexion of her neck.

A noncontrast head CT was obtained and interpreted as normal (Figure 1).

  • What should be done next?

The next day, the official CT reading diagnosed subarachnoid hemorrhage.

  • What are the CT findings of subarachnoid hemorrhage on this CT?

Because the patient’s headache had characteristics suspicious for subarachnoid hemorrhage (SAH)—sudden onset, association with vomiting, and mild nuchal rigidity—and because CT can occasionally miss SAH, a lumbar puncture was performed in the ED. The spinal fluid was blood tinged and, after centrifugation, the supernatant fluid had xanthochromia. She was admitted to the hospital for further evaluation of SAH.

Subarachnoid hemorrhage is a potentially life-threatening cause of headache. In 85% of cases, SAH is due to leakage or rupture of an aneurysm at the base of the brain (circle of Willis). The patient classically presents with an abrupt onset of severe headache (“thunder-clap”), which may be accompanied by an altered level of consciousness, seizure, or focal neurological deficits. When there is a large hemorrhage, the gravity of illness is obvious both clinically and on CT.

When a lesser quantity of blood leaks from the aneurysm, the patient may present solely with headache. The clinical and CT findings can be subtle and the diagnosis can potentially be missed. Such misdiagnosis can have devastating consequences when the patient later suffers a massive hemorrhage causing permanent neurological disability or death.

In up to 50% of cases, a small bleed causing a “sentinel” or “warning” headache precedes a large hemorrhage by hours, days, or weeks. Half of these patients may have sought medical attention and may have been misdiagnosed, i.e., up to 25% of SAH are missed on initial presentation (Kowalski 2004, Mayer 1996). Patients with such small bleeds benefit most from prompt diagnosis and treatment because they are neurologically intact at the time of initial presentation and ...

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