Abstract BACKGROUND Optic nerve sheath meningiomas (ONSM) are rare, comprising 1-2% of paediatric CNS meningiomas. Despite slow growth, ONSM often lead to vision loss in the affected eye. Diagnosis is challenging due to the tumour’s proximity to the optic nerve, complicating biopsy or complete removal. METHODS We searched our Neuro-Oncology MDT database for patients treated for ONSM between Jan 2018 and Dec 2023. We retrospectively reviewed clinical presentation and diagnostic workup that led to the diagnosis of ONSM. RESULTS 6 children aged 3-15years (mean 9 years) were identified over 5 years. 3 children were treated at GOSH, 2 at UCLH and 1 at BCH. 3/6 patients were male. 2/6 underwent a biopsy. Presenting symptoms included headache, acute visual loss and eye pain. 2/6 patients presented with bilateral vision deterioration. The average time between onset of symptoms and presentation was 8 months (range 3–15 months). Identified causes of delayed diagnosis included delayed presentation related to COVID-19 pandemic (2 patients) and impaired quality of imaging due to dental braces (1 patient). Whilst awaiting diagnosis, 2 patients lost vision completely in their affected eye. Diagnostic workup included: optic disc examination (6 patients), lumbar puncture (2 patients), angiotensin-converting enzyme (sACE) (2 patients), MRI brain and spine (6 patients), CT scan (6 patients), PET-DOTATE scan (3 patients), NF2 genetic testing (4 patients). Two patients completed PBT therapy while 1 is undergoing radiotherapy. One patient underwent an enucleation, while the rest are under surveillance. CONCLUSIONS Paediatric ONSM diagnosis remains challenging despite advanced imaging. Our review highlights the added value of CT and PET-DOTATATE when a biopsy is high-risk. CT reveals calcification in 20-50% ONSM while the role of PET-DOTATATE is related to the expression of somatostatin receptor 2 in meningiomas. Despite optimal treatment, vision loss maybe unavoidable. Early multidisciplinary consultations are advised for enhanced outcomes.