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.
Highlights
The subarachnoid space (SAS) around the optic nerve in the orbit can be detected by the fat saturation pulse sequence adapted for T2-weighted imaging.[1,2]
The optic nerve sheath (ONS) diameter can be estimated by measuring the outer diameter of the SAS
The SAS can be observed in normal subjects, and dilation of the SAS is associated with idiopathic intracranial hypertension or hydrocephalus presenting with increased intracranial pressure.[2,3,4,5]
Summary
SUMMARY: The subarachnoid space around the optic nerve can be detected by fat-saturated T2weighted MR imaging of the orbit, and dilation of this space reflects increased intracranial pressure. The SAS can be observed in normal subjects, and dilation of the SAS is associated with idiopathic intracranial hypertension or hydrocephalus presenting with increased intracranial pressure.[2,3,4,5] Because increased intracranial pressure causes dilation of the SAS around the optic nerve, the outer diameter of the SAS may decrease in patients with CSF hypovolemia or intracranial hypotension. Observation of such collapse of the SAS provides suggestion of decreased CSF volume or pressure in CSF hypovolemia. We report 3 cases of CSF hypovolemia in which the diameters of the SAS around the optic nerves were measured by MR imaging before and after epidural blood patch treatment
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