Fig 1.

Noncontrast head CT examples of SAH. Perimesencephalic SAH: axial image from a noncontrast head CT demonstrates acute SAH in the prepontine and interpeduncular cistern, consistent with a perimesencephalic pattern of SAH (A). Sulcal SAH: axial image from a noncontrast head CT demonstrates acute SAH in the left precentral sulcus and in the sulci overlying the left middle frontal gyrus, consistent with a sulcal pattern of SAH (B). Diffuse SAH: axial image from a noncontrast head CT demonstrates acute SAH in the bilateral Sylvian fissures, overlying the sulci of the bilateral temporal lobes, consistent with a diffuse pattern of SAH. Note also intraventricular hemorrhage within the third ventricle (C). Isolated IVH: axial image from a noncontrast head CT demonstrates acute intraventricular hemorrhage casting the right lateral ventricle (D).