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A 52-year-old man with a history of hypertension and a 30 pack-year smoking history presents to the emergency department following the sudden onset of a severe, bilateral headache. He denies nausea, vomiting, and head trauma. His temperature is 38°C, heart rate is 110 bpm, and blood pressure is 162/91 mm Hg. He is alert and oriented to place and time. His left pupil is dilated and nonreactive to light. A noncontrast computed tomographic (CT) scan of the head shows diffuse hyperdensity within the subarachnoid space. A CT angiogram is performed that demonstrates a left posterior communicating artery aneurysm, and the patient undergoes further workup with digital subtraction angiography.

Subarachnoid hemorrhage and aneurysm

What is the clinical presentation of subarachnoid hemorrhage (SAH) and how is it diagnosed?

Nearly all patients with SAH present with a sudden, severe headache that is classically described as “the worst headache of my life.” As many as 20% to 50% of patients have a “sentinel” headache within the days to weeks before the SAH.1,2 The headache is typically diffuse, but is lateralized in approximately a third of patients. Common associated symptoms include nausea, vomiting, and meningismus. Depending on the severity of the SAH, patients may have impairment in consciousness that ranges from drowsiness to coma and occasionally focal neurologic deficits. A diagnosis is most often reached by noncontrast head CT scan (Figures 23-1, 23-2, 23-3), which is 95% sensitive within the first 6 to 12 hours following the onset of symptoms. A negative CT in the presence of strong clinical suspicion, however, warrants a lumbar puncture to directly assess for the presence of blood or blood breakdown products in the cerebrospinal fluid.3

Figure 23-1.

Noncontrast CT of a patient with diffuse subarachnoid hemorrhage.

Figure 23-2.

Noncontrast CT of a patient with subarachnoid hemorrhage involving the frontal sulci, as well as right temporal intraparenchymal hemorrhage.

Figure 23-3.

Noncontrast CT showing diffuse subarachnoid hemorrhage more prominent on the left than the right.

What are the etiologies of a SAH?

Table 23-1 shows the etiologies of SAH. Aneuryms are responsible for the vast majority of nontraumatic SAHs.

Table 23-1.aEtiologies of Subarachnoid Hemorrhage

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