FIG 3. Aqueductal stenosis.

A. Midline sagittal T1-weighted image (SE 550/14/2) in patient with moderate hydrocephalus shows distal aqueductal stenosis (arrow).

B. Proton-density axial image (SE 2200/20/1) at level of lateral ventricles shows moderate hydrocephalus but no periventricular edema, indicating acute obstructive hydrocephalus.

C–D. Sagittal midline phase-contrast MR imaging (2D-FISP 70/13/15°). Images represent a point in mid-systole (C) and middiastole (D). Craniocaudal pulsatile flow is seen through floor of third ventricle.