Which statement about testing for subarachnoid hemorrhage is true?

Which statement about testing for subarachnoid hemorrhage is true?

• A. CT is the most sensitive test for detecting SAH
• B. MRI is always more sensitive than CT
• C. Lumbar puncture is never used
• D. Angiography is not helpful

Answer: (A)

Non-contrast CT head is the best initial test for suspected subarachnoid hemorrhage because it quickly shows blood in the subarachnoid space. Its sensitivity is highest early, approaching 100% within the first six hours after bleed, but declines after that, so a negative CT later on does not completely rule out SAH if clinical suspicion remains. MRI can detect SAH as well, but it’s less reliable in the acute setting and not the preferred first test in the emergency evaluation. Lumbar puncture is used when CT is negative or inconclusive to look for CSF xanthochromia or red blood cells, indicating SAH. Angiography helps locate an aneurysm or other vascular source after SAH and guides treatment, rather than serving as the initial diagnostic test for SAH itself.

Non-contrast CT head is the best initial test for suspected subarachnoid hemorrhage because it quickly shows blood in the subarachnoid space. Its sensitivity is highest early, approaching 100% within the first six hours after bleed, but declines after that, so a negative CT later on does not completely rule out SAH if clinical suspicion remains. MRI can detect SAH as well, but it’s less reliable in the acute setting and not the preferred first test in the emergency evaluation. Lumbar puncture is used when CT is negative or inconclusive to look for CSF xanthochromia or red blood cells, indicating SAH. Angiography helps locate an aneurysm or other vascular source after SAH and guides treatment, rather than serving as the initial diagnostic test for SAH itself.