fig 2.

Hydrocephalus secondary to aqueductal stenosis.

A, Spin-echo T1-weighted image at 400/12. When compared with normal appearance in fig 1, there is clockwise rotation of the chiasm, the mammillopontine distance is decreased, the mammillocommissural distance is increased, and the third ventricular floor is concave with consequent counterclockwise rotation of its line.

B, Following endoscopic third ventriculostomy, there is a significant improvement but not normalization of midline appearance. The change in ventricular size was minimal and difficult to appreciate in the axial plane.