Somatostatin Receptor Scintigraphy for Optic Nerve Sheath Meningiomas

Abstract

To investigate the value of somatostatin receptor scintigraphy (SSRS) in the diagnosis of optic nerve sheath meningiomas (ONSMs). Prospective, comparative case series. SSRS was used to investigate 68 orbits in 61 patients diagnosed with an orbital tumor. Patients were injected intravenously with 200 MBq of indium-111 ((111)In)-octreotide. SSRS with single photon emission computed tomography (SPECT) was performed 24 hours after injection. The (111)In-octreotide uptake in orbital lesions was determined by semiquantitative uptake-ratio analysis (lesion/brain) on attenuation-corrected transverse SPECT slices. All orbital meningiomas, including 14 ONSMs and 12 spheno-orbital meningiomas, showed high median (111)In-octreotide uptake ratios of 7.2 (range, 4.6-15.4) and 16.3 (range, 4.6-15.4), respectively. In 7 patients with a diagnosis of ONSM, the SSRS uptake ratio was significantly decreased 2.7 (1-6.8) after treatment with 54 Gy of radiotherapy. Median uptake ratios of other tumors were vascular anomalies/vascular tumors, 1.2 (range, 0.5-3.3); non-Hodgkin lymphomas, 2.9 (range, 0.9-4.2); optic nerve gliomas, 1.5 (range, 0.2-3.3); and idiopathic orbital inflammation, 1.6 (range, 1.4-1.9). By using a threshold uptake ratio of 5.9, the sensitivity of SSRS with (111)In-octreotide for ONSM was 100%, with a specificity of 97.2%. SSRS is a useful additional tool in diagnosing ONSM and has 100% sensitivity and 97% specificity at a threshold uptake ratio of 5.9.