FIG 1. Aqueductal stenosis due to presumed benign tectal glioma.

Sagittal midline contrast-enhanced T1-weighted image [(SE 450/15/2)(TR/TE/excitations)] shows nonenhancing bulbous enlargement of tectum (arrowhead), obliterating aqueduct and producing severe hydrocephalus. A small gap in floor of third ventricle in front of mamillary bodies can be identified (arrow).

B. Coronal (left) and sagittal (right) T2-weighted images (FSE 5000/90/2) show no flow-void across floor of third ventricle.

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

D. Sagittal midline phase-contrast MR imaging [(2D-FISP 70/13/15°) (TR/TE/flip angle)]. Images represent a point in midsystole (left) and middiastole (right). Pulsatile CSF flow is seen within anterior of third ventricle and pontine cistern. CSF flow is rapid in anterior and slow in posterior of third ventricle, and absent through aqueduct.

E. Follow-up sagittal midline T1-weighted image (SE 450/15/2) performed after 4 years shows no changes in ventricular size and tectal mass.