USMLE PRACTICE QUESTION OF THE WEEK

Question for March 6, 2026

A 28-year-old woman comes to the ED with sudden severe headache, nausea, and vomiting. She describes it as the “worst headache of my life.” She has no medical history. BP is 152/92 mm Hg. Exam shows nuchal rigidity but no focal neurologic deficits. Noncontrast CT head is negative.

Which of the following is the most appropriate next diagnostic step?

A. CT angiography of the head

B. Lumbar puncture

C. MRI brain

D. MR venography

E. Transcranial Doppler ultrasonography

Get Detailed Explanation

Correct Answer:

B. Lumbar puncture

Correct Answer Explanation:

This patient likely has subarachnoid hemorrhage. A negative noncontrast CT does not exclude it. Lumbar puncture is indicated to look for xanthochromia (bilirubin degradation products). CT angiography identifies aneurysms but is performed after diagnosis.

Further Insight:

Classic triad: thunderclap headache, neck stiffness, photophobia.
Risk of rebleeding is highest in the first 24 hours.