FIG 3. Patient 4.

A, Sagittal T1-weighted image (500/15/2) shows enlargement of the cervical cord and central parenchymal hypointensity. There is marked enlargement of the fourth ventricle and secondary tonsillar herniation with crowding of the foramen magnum.

B, Sagittal T2-weighted image (2500/102_eff /2) shows striking T2 prolongation within the central portion of the cord.

C, Axial T1-weighted image (583/17/2) at the C2–C3 level shows that the central cord hypointensity has an irregular margin and is not isointense with CSF.

D, Sagittal T1-weighted image (500/14/1.5) after treatment of hydrocephalus. The fourth ventricle is decompressed, the cerebellar tonsils are normally positioned, and cord caliber has returned to normal.

E, Sagittal T2-weighted image (2500/102_eff /2) shows complete resolution of previously noted parenchymal T2 prolongation. A dark line down the center of the cord (solid arrow) is presumably artifactual because of patient motion and/or truncation artifact, as other parallel lines (open arrow) are observed across the image.