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CT-Negative Subarachnoid Hemorrhage in the First Six Hours
Tia Chakraborty1, Ali Daneshmand2, Giuseppe Lanzino1
1Mayo Clinic Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester 55905, MN, USA.
Summary
A negative head CT within six hours of a thunderclap headache does not rule out aneurysmal subarachnoid hemorrhage (SAH), especially in anemic patients. Lumbar puncture is crucial for diagnosis in such cases.
Area of Science:
- Neurology
- Radiology
- Emergency Medicine
Background:
- Aneurysmal subarachnoid hemorrhage (SAH) typically presents with thunderclap headache.
- Non-contrast head CT scans are highly sensitive for detecting SAH within the first six hours of symptom onset.
- No prior cases reported negative CT head in early SAH with anemia.
Observation:
- A 47-year-old anemic female presented with thunderclap headache, somnolence, and meningismus.
- Initial head CT within 6 hours of symptom onset was negative for SAH.
- Non-traumatic lumbar puncture revealed bloody cerebrospinal fluid, leading to repeat imaging showing intraventricular hemorrhage.
Findings:
- The patient was diagnosed with an intradural carotid artery aneurysm.
- CT angiography confirmed the aneurysm, which was successfully treated with pipeline embolization.
- The case highlights a potential false-negative result of head CT in early aneurysmal SAH due to anemia.
Implications:
- Anemia may reduce the sensitivity of non-contrast head CT for detecting SAH in the early hours after a thunderclap headache.
- Lumbar puncture remains a critical diagnostic tool for SAH, particularly in patients with significant anemia.
- This case underscores the importance of considering lumbar puncture in diagnosing SAH when initial imaging is negative but clinical suspicion remains high.
