Diagnostic Approach for Subarachnoid Hemorrhage

Initial Evaluation and Diagnostic Workup

When CTA is negative in a patient with confirmed subarachnoid hemorrhage, the pattern of hemorrhage should guide further diagnostic workup, according to the American Heart Association, as cited in Stroke and the Journal of the American College of Radiology 1, 2
The American College of Radiology recommends that CTA has limited sensitivity for aneurysms <3 mm in size, and overlying bone can be problematic with CTA, especially at the skull base, as noted in Stroke 1, 2

The American Heart Association suggests that 3D rotational angiography should be included in the diagnostic workup as it is more sensitive than 2D angiography for detecting vascular pathology, as cited in Stroke 3
The quality of CTA interpretation depends on radiologist experience, and vessel tortuosity can decrease the specificity of CTA, leading to misinterpretation, according to the American Heart Association, as noted in Stroke 5
Small aneurysms (<3 mm) may be missed by CTA, as reported in Stroke and the Journal of the American College of Radiology 1, 2

The American Heart Association recommends careful monitoring of blood pressure, particularly in patients with liver dysfunction who may experience increased bioavailability of nimodipine, and systolic blood pressure >160 mm Hg may be associated with increased risk of rebleeding, as cited in Stroke 4

MRI with fluid-attenuated inversion recovery, proton density, diffusion-weighted imaging, and gradient echo sequences may be helpful when CT scan is negative, as suggested by the American Heart Association, as cited in Stroke 1, 4
The American College of Radiology recommends that DSA with 3D rotational angiography should be included in the diagnostic algorithm for patients with persistent clinical suspicion despite negative initial imaging, as noted in Stroke and the Journal of the American College of Radiology 1, 6