68Ga-DOTANOC PET-CT is a Valuable Tool for Diagnosing an Optic Nerve Sheath Meningioma-A Case Report and Literature Review

Background: Optic nerve sheath meningiomas (ONSM) are one of the most common tumors affecting the optic nerve. Since operative decompression is known to cause visual loss, a biopsy diagnosis is usually unavailable. Though high-resolution MRI can delineate the tumor extent well, another reliable, non-invasive diagnostic method is desirable. Most meningiomas express somatostatin receptors and PET tracers based on ligands such as ⁶⁸Ga-DOTATATE have high sensitivity in detecting them.

Observations:  We describe the clinical presentation of a patient who presented with a history of recently noticed visual loss. We describe the imaging findings in MRI and the confirmation of the diagnosis with a ⁶⁸Ga-DOTANOC PET scan before we decided on radiation therapy.  The lesion was distinctly seen within the intraorbital area with a maximum standardized uptake value of  2.77. We also review the literature which compares the utility of this modality in comparison to MRI in ruling out alternative diagnoses.

Lessons: Imaging with somatostatin receptor ligands like ⁶⁸Ga-DOTANOC is a valuable tool in the non-invasive diagnosis of orbital lesions. It helps in differentiating meningiomas from other benign and malignant conditions. ⁶⁸Ga-DOTANOC scan should be considered in all patients with equivocal imaging findings in meningiomas.