We report a patient with an optic nerve sheath meningioma whose diagnosis and management were guided by using Gallium-68 DOTA-Tyr 3 -octreotatate ( 68 Ga-DOTATATE).
Positron Emission Tomography-Computed Tomography (PET-CT).
A 44-year old woman with no significant medical history was referred to the neuroophthalmology department for evaluation of left-sided optic nerve edema that was incidentally found on an annual eye examination.
Visual acuity was 20/20 on the right and 20/25 on the left. There was a left relative afferent pupillary defect. No proptosis was noted, and the patient had intact color vision with a full range of ocular movements. Slit lamp examination was unremarkable, while fundus examination showed swelling of the left optic disc ( Fig. 1 ). Humphrey 24-2 visual field testing showed non-specific superior and inferior visual field changes in both eyes. (Humphrey Field Analyzer; Zeiss, Germany).
Magnetic resonance (MR) scan of the brain and orbits with Gadolinium-chelate enhancement was interpreted at an outside hospital as optic perineuritis. However, review of the images in Neuro-ophthalmology was more suggestive of an optic nerve sheath meningioma (ONSM) with homogeneous intense enhancement producing the classic “tram track” appearance around the nonenhancing left optic nerve ( Fig. 3 ). There was no intracranial extension of the lesion, or any evidence of surrounding-structures invasion.
Orbit computed tomography (CT) scan with contrast enhancement was performed that revealed asymmetric enlargement/enhancement of the left optic nerve/sheath with mild retrobulbar stranding, but no calcifications were identified ( Fig. 4 ).
Given the conflicting interpretations, a 68 Ga-DOTATATE PET-CT was obtained ( Fig. 5 ) and showed an asymmetric fusiform enlargement of the left optic nerve with high curvilinear radiotracer uptake and a maximum standardized uptake value (SUVmax) of 2.4, consistent with the enhancement observed on MRI. The combination of anatomic location and uptake was suggestive of an optic sheath meningioma. The patient was referred for radiation therapy and underwent fractionated radiotherapy to the left optic nerve to dose of 50.4 Gy in 28 fractions. On follow-up exam after finishing the treatment course, optic disc edema (as shown in Fig. 2 ) showed significant improvement. There was also improvement in the visual field defects in the left eye.