Objective: The purpose of this study was to determine if orbital and cerebral CT can be used to distinguish normal patients from those with pseudotumor cerebri, and to correlate CT findings with the severity of visual impairment.
Subjects and methods: Seventeen patients with a clinical diagnosis of pseudotumor cerebri were compared with 20 age- and sex-matched control subjects. Thin-section coronal and axial CT scans of the orbit and whole-brain axial CT scans were available for all subjects. The diameter of the optic nerve sheath, the degree of reversal of the optic nerve head, the presence and degree of empty sellae, and ventricular and sulcal sizes were evaluated without knowledge of whether or not the subject had pseudotumor cerebri. The same parameters were compared for two subgroups of patients with pseudotumor cerebri: those with mild vision loss and those with severe vision loss.
Results: Patients with pseudotumor cerebri had significantly larger optic nerve sheaths than did control subjects (6.5 +/- 0.83 mm vs 5.4 +/- 0.69 mm). Radiologic evidence of papilledema with reversal of the optic nerve head was found in 12 of 17 patients compared with one of 20 control subjects. An empty sella was seen more frequently and to a greater degree in patients with pseudotumor cerebri than in control subjects (16 vs seven). Eight of nine patients with severe vision loss and four of eight patients with mild to moderate vision loss had reversal of the optic nerve head; the degree was greater in the group with severe vision loss. No difference in ventricular size or sulcal enlargement was seen between any of the groups. The opening CSF pressures of the two groups with vision loss were not significantly different (348 +/- 80 mm H2O vs 391 +/- 98 mm H2O).
Conclusion: In addition to the role of CT in excluding intracranial disease as a basis for the clinical syndrome of pseudotumor cerebri, thin-section CT of the orbits reveals a constellation of findings, including enlarged optic nerve sheaths, reversal of the optic nerve head, and empty sellae in patients with pseudotumor cerebri. Furthermore, severe vision loss in these patients correlates with more frequent and more severe reversal of the optic nerve head.