A Case Report of En-Plaque Meningioma Presenting with Proptosis of the Ipsilateral Eye

Purpose: Meningioma en plaque is a rare subgroup of meningioma that usually exhibits exophthalmos as its presenting symptom. Meningioma en plaque has a female predominance. We report a case of sphenoidal meningioma en plaque in a male patient who presented with proptosis of the ipsilateral eye. Case summary: A 58-year-old man presented with proptosis of his left eye. Exophthalmometry measurements were 17 mm on the right eye and 19 mm on the left eye. His visual acuity, intraocular pressure, and extraocular movements were normal. There was no sign of lid retraction in either eye. Non-contrast-enhanced computed tomography (CT) revealed an approximately 2 cmsized, well-defined, soft tissue density mass in the lateral extraconal space of the left orbit. Contrast-enhanced magnetic resonance imaging (MRI) revealed a 3.9 x 3.7 x 2.5 cm-sized, T1 isointense and T2 iso- to hyper-intense, relatively homogeneously well-enhancing mass in the left middle cranial fossa extending to the left lateral extraconal space via the superior orbital fissure. The patient underwent Gamma knife radiosurgery for the meningioma and was postoperatively stable without complications. Conclusions: The intracranial lesion, meningioma, can easily be missed on CT imaging because meningiomas are usually isodense compared to the cerebrum. Thus, contrast-enhanced MRI should be performed in order to differentiate patients with orbital masses on non-enhanced CT scans.