Optic nerve sheath meningioma detected by single- photon emission computed tomography/computed tomography somatostatin receptor scintigraphy: a case report

Discussion

Although meningiomas are common intracranial tumors, ONSMs as a specific subset are infrequent, accounting for only 1–2 % of all meningiomas [14]. Since morphological imaging techniques have their limitations in differentiating meningiomas from other tumors of the optic pathway [3, 6, 14, 15], an alternative method was added to detect whether this lesion expressed somatostatin receptors. Thus SPECT/CT or positron emission tomography/computed tomography (PET/CT) imaging with somatostatin analog radiotracers are highly effective methods for detection of meningiomas [6–13].

In accordance with a few studies on ONSMs [6, 7], the case reported herein showed an intense uptake of [¹¹¹In]-pentetreotide in the last third of the intraorbital right optic nerve (Fig. 1c, d, g and h), as well as physiological pituitary uptake (Fig. 1c and d). This radiotracer presents a very high affinity for somatostatin receptor subtype 2 with high sensitivity and specificity, as well as [¹¹¹In]-octreotide. There have also been reports on using somatostatin to treat intracranial meningiomas and monitor the efficacy of the treatment [16].

Consequently, this imaging technique provides good proof so that the exact origin of certain optic nerve tumors can be identified, especially and specifically in cases of very small tumors, in order to avoid biopsy and give the best treatment available quickly. In the majority of ONSMs involving the orbit, complete surgical resection is not possible and the results of surgical decompression are poor, despite the natural progression of diseases with progressive visual loss [15]. The diagnosis of ONSM is a crucial one, because modern surgical and/or radiotherapy approaches at an early stage may allow total resection and improve the chances of preserving vision [14, 15, 17–19]. For this reason, our patient could be treated with the best adapted procedure, resulting in better visual acuity. This technique with multimodal imaging provided positive identification rapidly, and our patient was spared more permanent visual damage or intracranial growth. A surgical approach was not adapted and presented a risk in this case due to the location and the small size.

This case supports other studies [6, 7] that have demonstrated a high [¹¹¹In]-pentetreotide uptake by ONSMs, and shows the importance of making an early and noninvasive diagnosis compared to other orbital lesions, that is, optic nerve gliomas, optic nerve inflammation, non-Hodgkin lymphomas, vascular lesions, and sarcoidosis [2, 3]. In the present case, it was the most effective method to reverse the initial diagnosis of optic neuritis.