PANCE Neurology Practice Test

Which finding on lumbar puncture supports SAH when CT is negative?

Increased opening pressure Elevated protein Xanthochromia Normal CSF glucose

Correct Answer:

Xanthochromia

Explanation:

Xanthochromia reflects breakdown products of blood in the cerebrospinal fluid and is the finding that most strongly supports subarachnoid hemorrhage when a CT scan is negative. When bleeding spills into the subarachnoid space, red cells lyse and hemoglobin is processed by the body into bilirubin, which gives CSF a yellow tint. This discoloration may not be visible immediately but becomes detectable within hours (often after about 4 hours) and can persist for days to weeks, making LP useful when CT misses the bleed. Other common LP findings like elevated opening pressure, increased protein, or normal glucose are nonspecific or not diagnostic for SAH, so the presence of xanthochromia is the best indicator that SAH occurred.

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