Narrowing of Meckel's cave and cavernous sinus and enlargement of the optic nerve sheath in Pseudotumor Cerebri.

Objective: Pseudotumor cerebri (PTC) is a clinical entity of uncertain etiology associated with several subtle findings on magnetic resonance imaging (MRI) including posterior flattening of the globes, enlargement of the optic nerve sheath (ONS), empty sella sign. We aimed to characterize the incidence of and significance of 2 novel MRI findings: narrowing of Meckel's cave and of cavernous sinus.

Methods: Forty-six patients with a condition diagnosed as PTC based on clinical history were retrospectively reviewed, and their MRI studies were assessed for previously reported imaging findings associated with PTC. The maximal diameters of the cavernous sinuses, Meckel's caves, and ONSs were measured along with those of age-matched controls on axial T2-weighted images.

Results: The Meckel's caves and cavernous sinuses are significantly (P < 0.01) narrowed in patients (mean diameters: 0.41 and 0.25 cm) versus controls (0.54 and 0.36 cm), respectively. The ONS was enlarged in patients with a mean diameter of 0.65 cm versus 0.54 cm (P < 0.01). Meckel's cave narrowing and ONS enlargement seem to be better indicators of PTC than cavernous sinus narrowing, with sensitivities of 78.3% and 86.9% and specificities of 84.8% and 76.1% versus 60.9% and 76.1%, respectively.

Conclusions: This finding of narrowed Meckel's caves in PTC may be clinically useful as a novel imaging finding seen on routine MRI studies. Optic nerve sheath enlargement is also confirmed as an important finding in PTC.