[Imaging of subarachnoid hemorrhage]

Even if acute subarachnoid hemorrhage (SAH) accounts for only 5% of strokes, its diagnosis is very important because its clinical consequences can be tragic. Recent technological advances in medical imaging have improved diagnostic and therapeutic management of patients with SAH. Nonenhanced CT of the head is the initial imaging modality in suspected SAH for the detection of ruptured intracranial aneurysms. Digital subtraction angiography (DSA) remains the reference exam. Multidetector row CT angiography may potentially replace DSA in the emergency setting, as it provides image data that allows evaluating aneurysmal morphology, the neck size or the visualization of vessels in the vicinity of the aneurysm. For SAH unrelated to aneurysm rupture (15% of cases), MRI and MRA can be added to the diagnostic work-up in order to exclude other differential diagnoses such as venous thrombosis or angiitis. Finally, transcranial color-coded duplex sonography, CT, or MRI are used in clinical practice in order to detect aggravating factors of SAH like hydrocephalus or vasospasm.