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A 45-year-old man is brought to the emergency department by his wife due to the sudden onset of an excruciating headache that began 2 hours ago. He describes it as the "worst headache of my life." He also complains of nausea, photophobia, and double vision. Vital signs are temperature 37.2°C (99.0°F), heart rate 95/min, blood pressure 175/105 mmHg, and respiratory rate 16/min. His Glasgow Coma Scale score is 14. Neurologic examination reveals marked nuchal rigidity. His right eyelid is drooping, and the right pupil is dilated and minimally reactive to light. The right eye is deviated downward and outward. Which of the following is the most appropriate initial diagnostic step?

  1. A
    Lumbar puncture
  2. B
    Magnetic resonance angiography of the brain
  3. C
    Conventional cerebral angiography
  4. Noncontrast computed tomography of the headAnswer
  5. E
    Electroencephalography

Answer

Noncontrast computed tomography of the head
This patient's sudden-onset 'thunderclap' headache and nuchal rigidity are highly characteristic of a subarachnoid hemorrhage (SAH). The accompanying right-sided ptosis, mydriasis, and 'down and out' eye deviation represent an oculomotor nerve (CN III) palsy, which classically localizes the bleeding source to an expanding posterior communicating artery (PCoA) aneurysm. The most appropriate initial diagnostic test for a suspected acute SAH is a noncontrast computed tomography (CT) of the head. Noncontrast CT is fast, highly sensitive for detecting acute hemorrhage (which appears as hyperdense material in the subarachnoid spaces), and can quickly rule out large mass lesions before considering further invasive tests.

Step-by-Step Solution

1
Identify the primary clinical syndrome based on the sudden onset of a severe 'thunderclap' headache and nuchal rigidity.
The presentation is highly suspicious for an acute subarachnoid hemorrhage (SAH).
The sudden rupture of an intracranial aneurysm typically presents with an immediate, extremely severe headache.
2
Correlate the focal neurologic deficit (ptosis, mydriasis, 'down and out' pupil) with the likely etiology.
The findings indicate a right-sided oculomotor nerve (CN III) palsy, pointing to an expanding posterior communicating artery (PCoA) aneurysm.
The oculomotor nerve runs adjacent to the posterior communicating artery, making it highly susceptible to compression from an expanding aneurysm in this location.
3
Determine the standard first-line diagnostic modality for a suspected acute SAH.
Noncontrast computed tomography (CT) of the head should be ordered immediately.
Noncontrast CT is widely available, rapid, and highly sensitive for detecting acute subarachnoid blood, which appears hyperdense (bright) in the basal cisterns.

Key Concept

The initial diagnostic step for a suspected acute subarachnoid hemorrhage is a noncontrast computed tomography of the head.
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Neurosurgery

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