Fractionated Stereotactic Radiotherapy for the Treatment of Optic Nerve Sheath Meningiomas: Preliminary Observations of 33 Optic Nerves in 30 Patients with Historical Comparison to Observation with or without Prior Surgery

Primary tumours of the optic nerve and its sheath

“…25,29 The characteristic features of optic nerve sheath meningiomas include the presence of calcification surrounding the nerve (which occurs in 20-50%), tubular enlargement of the nerve, and a bulbous enlargement of the optic nerve at the apex with distal tubular enlargement. The appearance of the optic nerve on coronal section is a hypodense area surrounded by a dense peripheral ring.…”

“…32,33 To date, the only long-term data reflect the results after treatment using conventional fractionated radiation therapy; 34 however, there is increasing evidence that stereotactic or conformal fractionated radiation therapy may result in improved visual outcome with fewer complications. 29,[35][36][37] I recommend that patients with optic nerve sheath meningiomas who have good visual function be followed without intervention until or unless they begin to experience progressive loss of vision, at which time I recommend stereotactic or conformal fractionated radiation therapy, whereas patients who present with significant visual loss should be given the option to undergo radiation therapy immediately. In such patients, the progression of visual loss may be extremely slow, occurring over many years.…”

Primary optic nerve sheath meningioma

“…This led the authors to conclude that an early initiation of RT is advisable. In the study of Andrews et al, 33 although there was a 92% rate of improved or stable vision, there was 13% toxicity. It was left unexplained which patients experienced toxicity, particularly important because there were 9 of 30 patients with intraorbital ONSM and 1 in whom ONSM extended intracanalicularly, all other ONSM being more extensive.…”

“…With the use of MRI it is nowadays easier to differentiate ONSM from sarcoidosis, 23 optic neuritis, [24][25][26][27][28] schwannoma, hemangiopericytoma, hemangioma, hemangioblastoma, metastasis, and glioma. [29][30][31][32] Ancillary tests such as 111 -In-Octeotride scintigraphy 33 or 3D ultrasound coronal C-scan imaging 34 hold promise for future studies, as recently shown.…”

“…These results could have been better if cases with pretreatment mild or moderate visual loss were represented more, because patients with marked improvement after SFRT are likely those having visual acuities ranging from 20/40 to 20/30, which may allow a greater potential for good treatment results, as reiterated recently by Richards et al, 79 Landert et al, 80 and Sitathanee et al 82 Nevertheless, the results of SFRT were accompanied with extremely low toxicity, which, in cases without significant extension outside the orbit, is negligible. Toxicity in 2 studies 33,43 could be attributed rather to undisclosed predisposing factors and more extensive tumors in which planning was rather difficult, and accompanied with dose inhomogeneities leading to its occurrence. Also, a recent report 83 of a case with radiation retinopathy occurring 2 years after SFRT (optic nerve dose, 54 Gy in 30 daily fractions; optic nerve head dose, 48-54 Gy; posterior retina dose, 27.8-48 Gy) for pONSM located intraorbitally and intracanalicularly did not provide additional information on this matter.…”