Optic Nerve Sheath Meningioma Research Articles

Does Adjuvant Gamma Knife Stereotactic Radiosurgery Have a Role in Treating Optic Nerve Sheath Meningiomas?

Meningiomas arising from or adjacent to the optic nerve sheath meningioma (ONSM) are management challenges because of their risk of visual loss. Stereotactic radiosurgery (SRS) is a minimally invasive modality that can be added as adjuvant treatment for patients whose tumor has progressed or recurred after initial resection. The authors retrospectively reviewed 2,030 meningioma patients who underwent SRS between 1987 and 2022. In total, 7 patients (4 females; median age = 49) were found with tumors originating from the optic nerve sheath. None of the patients had tumors that engulfed the optic nerve as such tumors typically undergo fractionated radiation therapy (FRT) to preserve vision. The clinical history, visual function, and radiographic and neurological findings were characterized. Outcome measures included visual status, tumor control, and the need for additional management. All patients underwent either initial gross total (n = 1) or partial surgical resection (n = 6) before SRS. Two patients with progressive tumor growth also had SRS after failing additional fractionated radiation after surgery (54 Gy, 30 fractions for both patients). The median time between the date of surgery and the SRS procedure date was 38 months. The Leksell Gamma Knife was used to deliver a margin dose of 12 Gy (range: 8-14 Gy) to a median cumulative tumor volume of 3.3 cc (range: 1.2-18 cc). The median maximal optic nerve radiation dose was 6.5 Gy (range: 1.9-8.1 Gy). After SRS, the median follow-up time was 130 months (range: 26-169 months). Two patients showed local tumor progression at 20 and 55 months after SRS. Four had stable visual function, 2 experienced improved visual acuity, and 1 patient had visual deterioration. Meningiomas arising from (but not engulfing the optic nerve) represent management quandaries after failed initial surgical removal. In this experience, salvage SRS was associated with tumor control and vision preservation in 5 of 7 patients. Additional experience with this strategy may further define the role of SRS both as a salvage and primary option.

Treatment of Meningiomas Involving the Optic Canal with Endoscopic Transnasal Decompression of the Optic Nerve

Management of patients with optic nerve sheath meningiomas (ONSM) is controversial and the treatment strategy in this patient group is still up for discussion. Transnasal endoscopic orbital and optic nerve decompression aims to reduce the pressure in the orbit and on the optic nerve and thereby prevent vision loss. This article presents material from seven cases of transnasal endoscopic orbital decompressions. The study design is a retrospective cohort study. The aim was to include all patients with a meningioma residing along the nerve sheath and who were operated using endoscopic transnasal decompression of the orbit and if needed the optic canal at Odense University Hospital. Data from the medical records were collected and pre- and postoperative eye examinations were compared. In addition, it was recorded whether there were complications to the procedure and whether additional treatments were given. In total, four women and three men were included in the study. Four out of seven patients experienced improvement in vision after the operation. One patient experienced unchanged vision and two patients experienced deterioration of vision after surgery. The current report of seven patients with ONSM shows promising results for this surgical procedure as four out of seven patients experienced improvement in their vision at follow-up examinations. The two patients, who experienced deterioration of vision, already had severely reduced vision pre-operatively, which indicates that surgery should be considered before the vision becomes significantly reduced.

Development of Magnetic Resonance-Compatible Head Immobilization Device and Initial Experience of Magnetic Resonance-Guided Radiation Therapy for Central Nervous System Tumors

PurposeWe aimed to develop and investigate positional reproducibility using a fixation device (Unity Brain Tumor Immobilization Device, UBID) in brain tumor patients undergoing magnetic resonance (MR)-guided radiotherapy (RT) with a 1.5 Tesla (T) MR-linear accelerator (LINAC) to evaluate its feasibility in clinical practice and report representative cases of central nervous system (CNS) tumor patients. Materials and MethodsQuantitative analysis was performed by comparing images obtained by placing only the MR phantom on the couch with those obtained by placing UBID next to the MR phantom. Twenty patients who underwent RT for CNS tumors using 1.5T MR-LINAC between June 2022 and October 2022 were retrospectively analyzed. Among them, five did not use UBID, whereas 15 used UBID. The positional reproducibility of UBID was evaluated using the median interfractional and intrafractional errors in the first 10 fractions. ResultsEach MR quality factor of the MR phantom with UBID satisfied the criteria presented by Elekta. Median values of median shifts in the mediolateral, anteroposterior, and craniocaudal axes for interfractional errors were 2.98-mm, 2.35-mm, and 1.40-mm, respectively. For intrafractional errors, the median values were 0.05-mm, 0.03-mm, and 0.06-mm, respectively. The median values of the median rotations in pitch, roll, and yaw for both interfractional and intrafractional rotations were 0.00°. One patient diagnosed with an optic nerve sheath meningioma received RT with motion monitoring during irradiation. In two patients, changes in the tumor cavity and residual lesions were observed in the MR images obtained using 1.5T MR-LINAC on the day of the first treatment and immediately before the 21st fraction, respectively; therefore, offline/online adaptation was performed. ConclusionThe reproducible and immobile UBID is clinically feasible in patients with CNS tumors receiving RT with 1.5T MR-LINAC. Based on our initial experience, we developed a workflow for 1.5T MR-LINAC treatment of CNS tumors.

Tumors of the third ventricle in children (literature review).

Tumors of the third ventricle are rare and account for 0.6–0.9 % of all pediatric brain tumors. Tumors of the third ventricle are divided into primary tumors, such as choroid plexus papillomas and ependymomas, and secondary tumors, such as craniopharyngiomas, optic nerve gliomas, pineal tumors, and meningiomas. Choroid papilloma is a common tumor, the treatment of which is mainly based on microsurgical resection. Apart from the many treatment options for craniopharyngiomas, microsurgery is the preferred treatment option. Ependymomas also have several treatment options, with microsurgical removal considered the first line of treatment.

Gross-total resection in optic nerve sheath meningiomas: minimally invasive and cosmetic pleasing.

The optic nerve sheath meningioma (ONSM) is one of the most challenging tumors in orbital surgery. From the perspective of mental health and patient needs, we analyzed the necessity and importance of the endoscopic transnasal approach (ETA) combined with optic nerve transection (ONT) in gross-total resection (GTR) in ONSM patients with residual vision and aim to broaden the use of ONT for specific people. The authors included patients with ONSMs who were treated between 2014 and 2022. We divided those cases into two groups named ETA group and lateral orbitotomy approach (LOA) group. We present the application of ETA and analyze the preoperative indication of the ONT and compared the advantages and disadvantages between ETA and LOA. The degree of tumor resection was based on imaging and surgical evaluation. A total of 23 patients with ONSM were included. Sixteen patients underwent ETA, and seven underwent LOA. Among ETA cases, GTR was achieved in 14 patients with ONT and most patients maintained normal eye movement function (75%) and morphology (93.75%). In the ETA group, 14 patients experienced vision loss, while two other patients saw improvements in vision. And proptosis was alleviated (5.20 ± 2.34 vs 0.27 ± 0.46, p < 0.0001). Six patients with blindness and proptosis of the LOA group resulted in GTR with ONT and ophthalmectomy. Although intracranial extension and recurrence included no cases in the two groups, a significant psychological gap was presented due to cosmetic problems. Under the premise of reducing damage and improving aesthetics, the selection of ETA combined with ONT to gross-total resect ONSMs successfully provides a minimally invasive access with acceptable complications. As an important adjunct to GTR in the surgical treatment of ONSM, the scope of ONT application should be expanded to relieve the patient's psychological burden.

Radiation therapy for optic nerve sheath meningiomas: Local control and treatment related visual changes

ObjectiveOur primary objective is to evaluate the local control of optic nerve sheath meningiomas (ONSMs) treated with ionizing radiation and related visual changes after treatment. Our secondary objective is to describe the clinical characteristics and perform an analysis of the treatment impact on the functional status of this group of patients. MethodsWe present our series of 19 patients treated with ionizing radiation therapy at our radio-neurosurgery unit between 2016 and 2022. The setting, ophthalmological follow-up, morbidity, and survival are analyzed and discussed. ResultsPatients were followed up, and the impact of treatment on local disease control, visual alterations of the affected eye, and functional status of the patient were analyzed. The progression-free survival (PFS) median was 60 months (95% CI 50.3–69.6 months). The estimated PFS rates at 48 and 66 months were 100% and 66%, respectively. At diagnosis, nine (47.3%) eyes were in amaurosis and ten (52.6%) with vision. Of the ten patients without amaurosis at the time of diagnosis, three (30%) maintained unchanged visual acuity, and seven (70%) had decreased visual acuity; three of them developed amaurosis during the first year after treatment (p = 0.018). ConclusionsUsing ionizing radiation therapy is a successful treatment for the local control of ONSMs. This therapeutic modality can compromise the visual acuity of the affected eye and improve dyschromatopsia and campimetry defects. The life prognosis is good for these patients, with a zero mortality rate, but their vision prognosis is poor.

Detection of Optic Nerve Sheath Meningioma Using Computed Tomography Somatostatin Receptor Scintigraphy: A Case Report

Optic nerve sheath meningiomas (ONSM) pose diagnostic challenges due to their rarity and imaging overlap with other optic pathway lesions. This case study presents a patient initially exhibiting decreased visual acuity, where conventional MRI failed to conclusively diagnose the underlying pathology. Employing Tektrotyd-Tc99m tomography, a novel imaging modality utilizing somatostatin analog radiotracers, enabled precise localization and characterization of the ONSM. This study underscores the importance of leveraging advanced imaging techniques in the comprehensive management of optic nerve sheath meningiomas.

Optic nerve meningioma and cloacal adenocarcinoma in a Humboldt penguin.

A 26-y-old, male, captive Humboldt penguin (Spheniscus humboldti) was euthanized following a 3.5-mo history of weakened elimination mechanics, recurrent tenesmus, intermittent hemorrhagic droppings, and a cloacal mass. Blepharospasm, of unknown cause, of the right eye was present for ~3 mo before euthanasia. Autopsy revealed a cloacal adenocarcinoma with localized coelomic carcinomatosis and distant metastases to the liver and lungs. On histopathology, a 2.6 × 1.2 × 0.5-mm, well-demarcated mass was found surrounding the right optic nerve, expanding the subdural space and wrapping the leptomeninges. The mass was composed of neoplastic spindle-to-polygonal cells consistent with a meningioma, meningothelial subtype. No evidence of neoplasia was found in the optic chiasm or brain, indicating a primary retrobulbar meningioma. Immunohistochemistry for cytokeratin AE1/AE3, vimentin, and S100 revealed robust and consistent immunoreactivity to vimentin, and weak and variable immunoreactivity to cytokeratin and S100, supporting the diagnosis. Meningiomas have been described only rarely in avian species, and we found no reports of optic nerve meningiomas in any avian species to date. The optic nerve meningioma in this case was considered a clinically incidental finding.

Orbital tumors

Orbital tumours include a variety of orbital diseases of different origins. In the case of malignant orbital tumours, early detection is important so that treatment can be initiated promptly. Neuroradiological imaging, in particular magnetic resonance imaging (MRI), plays an important role in the diagnostic of orbital tumours. In adults, lymphoproliferative diseases, inflammations and secondary orbital tumours are most frequently found, whereas in children mostly dermoid cysts, optic gliomas and capillary haemangiomas are found. Optic glioma is a pilocytic astrocytoma and accounts for two thirds of all primary optic tumours. Optic nerve sheath meningiomas mostly affect middle-aged women. In childhood, retinoblastoma is the most common intraocular tumour. This is an aggressive malignant tumour which can occur unilaterally or bilaterally. Based on the imaging findings, differential diagnoses can usually be easily narrowed down using criteria such as age of manifestation, frequency, localisation and imaging characteristics.

Optic Nerve Sheath Meningiomas: A National Surveillance, Epidemiology, and End Results (SEER) Database Analysis.

Optic nerve sheath meningioma (ONSM) is a rare optic nerve cancer with considerable morbidity. This national analysis validates previously known ONSM concepts while providing insight into novel risk factors. The Surveillance, Epidemiology, and End Results (SEER) Program was queried from 2000 to 2019 for all histologic subtypes of meningioma primary to the optic nerve. Relevant clinical and demographic variables were analyzed. Asymptotic one-sample test for binomial proportions and Cox proportional hazards modeling evaluated the significance of factor associations. A total of 51 ONSM cases were extracted. A greater proportion of cases were observed in females (N = 37, 73%, P < 0.001) and individuals with age 50 years or more (N = 29, 57%, P < 0.001); the mean number of months from diagnosis to treatment was 4.6 months (SD 4.1, range 13). Psychosocial epidemiologic parameter analysis demonstrated a greater proportion of patients with married status on diagnosis (N = 31, 61%, P < 0.001), listed total family income between $55,000 and $74,999 (N = 24, 47%, P < 0.001). Relative to cases diagnosed clinically only, cases diagnosed radiologically without microscopic confirmation experienced decreased all-cause mortality (HR = 0.041, P = 0.050). Our SEER national analysis affirms previously characterized ONSM concepts. Upon ONSM diagnosis and if needed, treatment protocols are not significantly delayed. Novel psychosocial factors for ONSM were identified, including marital status, total family income, and non-Hispanic white race. Additional ONSM diagnostics may reduce longitudinal mortality burden.

Atypical orbital primary optic nerve sheath meningioma with severe disfiguring proptosis: an alternative surgical approach

Primary optic nerve sheath meningioma is generally a benign tumor. In rare instances, however, the growth rate and intraocular and intracranial extensions can be highly aggressive, especially in children, leading to poor prognosis. Here, we reported a case of a 24-year-old woman who presented with left eye swelling for 3 years. This was associated with blurred vision, retrobulbar pain, and redness. On examination, the left eye was severely proptosed with complete ophthalmoplegia. Magnetic resonance imaging showed an extensive tumor occupying the whole left orbital cavity with a disfigured eyeball. However, no intracranial extension was observed. Interestingly, complete surgical excision was feasible via transconjunctival anterior orbitotomy without bone removal. The histopathological examination confirmed the diagnosis of optic nerve sheath meningioma. Adjunct radiotherapy was given. On a follow-up after 2 years, left enophthalmos with esotropia was observed.

Primary Tumours of The Optic Disc and The Optic Disc Sheath

Primary optic nerve and optic nerve sheath tumors constitute approximately 8% of intraorbital tumors and although most of them are benign, they are manifested by findings that significantly affect visual function such as vision loss, visual field defect and proptosis. Tumors originating from the optic nerve trunk are mostly benign optic nerve glioma, but rarer tumors such as ganglioglioma, medulloepithelioma, hemangioblastoma, melanocytoma and high-grade glioblastomas such as malignant optic nerve glioma can also be detected. Tumors originating from the optic nerve sheath usually have optic nerve sheath meningioma (ONSM), of those with intraorbital and intracanalicular origin are classified as primary and intracranial ONSMs are classified as secondary tumors. Optic glioma, ONSM, and hemangioblastomas can be seen sporadically or as a component of Type 1 and Type 2 Neurofibromatosis (NF) and Von Hippel-Lindau (VHL) syndromes, respectively. Treatment with systemic chemotherapy, surgical resection and radiotherapy methods should be considered when progressive vision loss, visual field defect and cosmetically intolerable proptosis develop in optic nerve and nerve sheath tumors, which can have a quiet course for years in terms of visual function. While systemic chemotherapy is accepted as the main treatment method in optic gliomas, more successful results are obtained with specialized treatment methods such as stereotactic fractionated radiotherapy in ONSMs.

Role of hypofractionated stereotactic radiotherapy for primary optic nerve sheath meningioma.

Optic nerve sheath meningiomas (ONSM) are rare tumors potentially causing visual deficits. This study aims to report the anatomic and visual outcomes of patients with primary ONSM treated with hypofractionated stereotactic radiotherapy (HF-SRT). Data of 36 patients treated with HF-SRT between 2008 and 2019 were retrospectively collected. The clinical target volume (CTV) was equal to the gross tumor volume and a 2 mm was added for the planning target volume. All responses other than progression were accepted as local control (LC). The VA grading was performed under 3 groups to provide an even distribution; 20/400 or worse, 20/40-20/400, and 20/40 or better. Median HF-SRT dose was 25 Gy and the median CTV was 1.94 cc. After a median of 106 months of follow-up, the tumor regressed in 23 (64%), was stable in 9 (25%), and progressed in 4 (11%) eyes. The overall rate of LC was 89% with 2-, 5-, 10-, and 15-year rate of 100%, 94%, 84%, and 84%, respectively. Treatment-related late toxicity rate was 11%. The VA was stable in 27 (75%) eyes, improved in 5 (14%) eyes, and worsened in 4 (11%) eyes, respectively, after HF-SRT. Female gender was the only independent predictor of an improved VA. Hypofractionated stereotactic radiotherapy is a safe and satisfactory treatment option for primary ONSM without severe toxicity. It may be advisable to commence treatment before an established visual deficit of 20/400 or worse occurs, to make the most of the functional benefit.

Diagnostic Pearls in Case of Optic Nerve Sheath Meningioma

Diagnostic Pearls in Case of Optic Nerve Sheath Meningioma

Optic Nerve Sheath Meningiomas: Solving Diagnostic Challenges with 68Ga-DOTATOC PET/CT.

68Ga-DOTATOC PET could be a noninvasive, highly sensitive, and specific technique for the challenging diagnosis of optic nerve sheath meningioma (ONSM). Our objective was to report the use and results of 68Ga-DOTATOC PET in suspected ONSM. Twelve subjects who underwent 68Ga-DOTATOC PET for suspected ONSM in our department were retrospectively included. Standardised clinical and radiological data were collected. The PET examination results were classified as positive or negative, and lesion standardised uptake values (SUVmax) were recorded. 68Ga-DOTATOC PET confirmed positive uptake in six cases (SUVmax > 5), leading to ONSM diagnoses followed by radiation therapy in patients with vision loss. Six 68Ga-DOTATOC PET scans were considered negative (SUVmax < 5); these comprised one case of neurosarcoidosis, one cavernous malformation, and four uncertain diagnoses, leading to further investigation. 68Ga-DOTATOC PET was helpful in tumour volume delineation before radiation therapy, leading to a decrease in dose exposure. Noninvasive 68Ga-DOTATOC PET should be performed before treating nonhistologically proven meningiomas with radiotherapy or stereotactic radiosurgery, particularly in cases of uncertain diagnosis with MRI, which characterises most ONSM cases. PET SUVmax thresholds to distinguish meningioma from nonspecific uptake in other lesions need to be adapted to ONSM. 68Ga-DOTATOC PET improves the intraorbital lesion diagnostic approach and therefore impacts therapeutic management.

The treatment efficacy of radiotherapy for optic nerve sheath meningioma.

Optic nerve sheath meningioma (ONSM) is a rare benign tumour that accounts for approximately 2% of all orbital tumours. Radiotherapy has gradually become an important treatment for ONSM because of its good effect in preserving or improving vision. We aimed to explore the effect of radiotherapy on tumour control and vision preservation/improvement in patients with ONSM. Forty-three patients with primary ONSM treated in our institution from 2015 to 2021 were enrolled. The irradiation dose was from 50.4 to 54 Gy with 28-30 fractions. We evaluated the tumour volume on MRI or CT, and visual acuity before and after the radiotherapy. Thirty-four patients (79%) experienced a vision decrease at diagnosis. The mean duration of follow-up was 54.1 months (ranges: 18-93, median: 56). Among 25 patients who had tumour evaluation using MRI, 16 patients (37.2%) showed stable tumours, 7 patients (16.3%) had tumour shrinkage, but 2 patients (4.7%) experienced tumour progression. Among the 39 patients performing vision acuity evaluation, 16 patients (37.2%) had vision improvement or recovery. 16 of the 23 patients without vision improvement demonstrated severe visual loss at diagnosis. Two patients had evidence of tumour progression during the follow-up. Additionally, 4 (10.2%) patients had dry eyes, 7 (17.9%) patients experienced watery eyes, and 3 (7.7%) patients had eye swelling. Patients with vision loss for more than 12 months had a lower possibility of vision recovery than those with vision loss for less than 12 months. Radiotherapy such as IMRT, VMAT, and 3D-CRT plays an important role in the treatment of ONSM. The probability of vision recovery is lower in patients with severe vision loss at diagnosis or the duration of vision loss is more than 12 months.

Ophthalmic Manifestation in Neurofibromatosis Type 2

Neurofibromatosis type 2 (NF2) is a genetically determined tumor-predisposing syndrome. Ocular manifestations include cataracts, epiretinal membranes, retinal hamartomas, optic disk gliomas, and optic nerve sheath meningiomas. Moreover, optic disk edema, optical atrophy, motility disorders, pupil and lid dysfunction, and neurotrophic keratitis can be observed as indirect signs. An observational study was conducted with the aim to collect clinical data and describe the most frequent NF2 ocular manifestations. Fourteen patients affected by NF2, according to the Manchester criteria, were enrolled. All patients underwent complete ophthalmologic and orthoptic evaluation and a spectral domain optical coherence tomography. Ocular manifestations were present in all patients. The slit lamp evaluation of the anterior segment highlighted cataracts in five patients, keratitis in two patients, corneal leukoma in two patients, and corneal pannus in one patient. Fundus oculi and OCT evaluation identified epiretinal membranes in four patients, vitreoretinal tufts in three patients, optic nerve edema in one patient, and retinal hamartoma in one patient. Moreover, the orthoptic evaluation identified different types of ocular motility disorders in seven patients. This is a descriptive study of a rare disease with poor previous literature. Clinical data are shown, emphasizing the role of NF2-specific ophthalmological and orthoptic findings to help establish an early diagnosis.

A Patient With Exophytic Primary Optic Nerve Sheath Meningioma: Stratified Risk of Surgery Based on the Morphology.

Primary optic nerve sheath meningioma (pONSM) is one of the most challenging tumors to manage. Although surgical excision may be considered a treatment option to maintain visual function, the safety of surgery remains debatable due to the non-negligible risk of optic nerve injury. pONSM often grows concentrically around the optic nerve; however, it can also demonstrate an exophytic growth from the optic nerve. The risk of surgical excision of pONSM may vary based on the tumor's growth pattern and area of contact with the optic nerve; however, there has been no detailed report on risk stratification to date. The authors present an illustrative case of an exophytic pONSM which was removed surgically without complications, suggesting that tumor morphology may also influence the surgical risk. In this report, the imaging and intraoperative features of exophytic pONSM are presented in detail, and the risk factors for complications are discussed.

Clinical and imaging characteristics of optic nerve tumors as the differencial diagnosis of optic neuritis

Objective: To investigate the clinical and imaging features of optic nerve tumors that require differential diagnosis from optic neuritis. Methods: A retrospective case series study was conducted. Clinical data of patients diagnosed with optic nerve tumors from January 2017 to December 2021 at the Second Affiliated Hospital of Zhejiang University School of Medicine were collected. A total of 29 patients (39 eyes) with clinical and magnetic resonance imaging (MRI) findings similar to optic neuritis or optic neuropathy were included. There were 15 cases of optic nerve sheath meningioma (ONSM) (17 eyes), 4 cases of optic nerve glioma (ONG) (5 eyes), and 10 cases of infiltrative optic nerve lesions (ION) (17 eyes). All patients underwent best-corrected visual acuity (BCVA), anterior and posterior segment examinations, visual field examination, and orbital or cranial MRI examination. Patient data were observed and analyzed, treatment and follow-up information were recorded, and clinical and imaging features were summarized and compared with those of optic neuritis or optic neuropathy. Results: Among the 29 patients with optic nerve tumors, 10 were male and 19 were female, with an average age of (43.3±13.8) years and a range of 11 to 72 years. The follow-up time was 6.8 (2.0, 11.0) months, with a range of 1 to 33 months. Sixteen patients (21 eyes) with optic nerve tumors were initially misdiagnosed as having acute optic neuritis and showed poor response to steroid treatment. Of these, 9 cases (11 eyes) were ONSM, 4 cases (6 eyes) were ION, and 3 cases (4 eyes) were ONG. The diagnostic delay time was 7.1 (1.5, 12.0) months, with a range of 1 to 24 months. The main clinical symptoms of all affected eyes were acute vision loss in 23 eyes, slow vision loss in 5 eyes, transient blackouts in 4 eyes, and no obvious visual symptoms in 7 eyes. The median BCVA of all affected eyes was 0.1, ranging from light perception to 1.0. Fundus examination results showed optic disc edema in 34 eyes and normal optic disc in 5 eyes among the 39 eyes with optic nerve tumors. A total of 27 patients (33 eyes) completed visual field examinations, which revealed an enlarged physiological blind spot in 11 eyes, a concentric or tubular visual field contraction in 8 eyes, a diffuse decrease in light sensitivity in 7 eyes, an arcuate scotoma in 4 eyes, and a normal visual field in 3 eyes. All affected eyes completed orbital or cranial MRI examinations, which showed mild optic nerve thickening in 22 eyes, significant thickening in 6 eyes with distortion, and no significant thickening in 6 eyes. Contrast-enhanced T1-weighted imaging (T1WI) MRI showed optic nerve parenchymal thickening in 5 eyes, all of which were ONG, and 2 of them had optic nerve parenchymal enhancement. Optic nerve sheath thickening and enhancement without optic nerve parenchymal thickening or enhancement were observed in 28 eyes, including 17 eyes of ION and 11 eyes of ONSM. There were 6 eyes with no obvious optic nerve thickening, which were all ONSM, showing mild or significant thickening and enhancement of the optic nerve sheath without optic nerve parenchymal thickening or enhancement. Conclusions: Optic nerve tumors can present with ophthalmic clinical features similar to optic neuritis, such as optic disc edema, and demonstrate MRI findings that resemble those of optic neuritis. Therefore, differentiation between the two is crucial, based on differences in their natural course and response to steroid therapy.

PO-1153 Visual outcome after fractionated stereotactic radiotherapy for optic nerve sheath meningioma

PO-1153 Visual outcome after fractionated stereotactic radiotherapy for optic nerve sheath meningioma