Computed tomography angiography (CTA) of the brain is a reasonable test to consider when evaluating select patients for subarachnoid hemorrhage after a negative non-contrast computed tomography of the brain. The benefits and risks of CTA of the brain need to be considered by the treating physician.
Acute onset headache is a common presenting complaint in the emergency department and failure to diagnose a subarachnoid hemorrhage is associated with significant morbidity.(1) Recently, clinical decision rules have been proposed that have a sensitivity of up to 98-100% and specificity up to 28%. (2) Traditionally, the standard of care is for a patient to have a noncontrast computed tomography scan (NCCT) and, if negative, then a lumbar puncture (LP). Because of limitations in the sensitivity of NCCT to
detect subarachnoid hemorrhage, lumbar puncture may be necessary to be reasonably confident that a subarachnoid hemorrhage is not missed, particularly in higher risk patients. Lumbar puncture has been shown to be 100% sensitive and have a negative predictive value of 100% for SAH. (3)