Fusiform dilatation of the outer contour of a dissected anterior cerebral artery revealed by magnetic resonance cisternography in a patient with simultaneous cerebral infarction and subarachnoid hemorrhage.

A 46-year-old man presented with right hemiparesis. Cranial magnetic resonance (MR) imaging revealed both an acute cerebral infarction in the territory of the left anterior cerebral artery (ACA) and a thin subarachnoid hemorrhage in the left superior frontal sulcus. MR angiography revealed stenosis at the A2 segment of the left ACA. MR cisternography was, therefore, performed on day 12 after admission using sagittal, 3-dimensional, heavily T2-weighted images. Fusiform dilatation of the outer contour was confirmed by MR cisternography at the region of narrowing identified by MR angiography. This case indicates that the combination of MR cisternography and angiography can be useful for detecting ACA dissection.