Decreased diameter of the optic nerve sheath associated with CSF hypovolemia

Abstract

The subarachnoid space around the optic nerve can be detected by fat-saturated T2-weighted MR imaging of the orbit, and dilation of this space reflects increased intracranial pressure. We examined 3 patients with CSF hypovolemia with MR imaging of the orbit and measured the optic nerve sheath diameter before and after treatment. We showed that the subarachnoid space is decreased in patients with CSF hypovolemia and the usefulness of this finding.

Figures

Fig 1.

Coronal fat-saturated T2-weighted orbital MR images of cases 1, 2, and 3. In case 1, MR images showing the subarachnoid space (arrow) had collapsed and the ONS could not be detected before treatment (A) but became visible with diameter of 5.5 mm on the right and 5.8 mm on the left after treatment (B). In case 2, MR images showing the ONS diameter just behind the optic globe before treatment were 5.0 mm on the right and 4.7 mm on the left (C) and became 5.9 mm and 5.3 mm, respectively, after treatment (D). In case 3, MR images showing the subarachnoid space had collapsed, and the ONS could not be detected before treatment (E) but became visible with a diameter of 6.2 mm on the right and 6.2 mm on the left after treatment (F).