Supplementary Material for: A cavernous sinus meningioma in a child with progressive bilateral visual loss ultimately attributed to unsuspected optic nerve sheath meningiomas

Introduction: Pediatric optic nerve sheath meningiomas (ONSMs) are rare in children and have an aggressive presentation in the pediatric population often resulting in rapid vision decline. Here, we report a case of right cavernous sinus meningioma (CSM) with delayed diagnosis of concomitant bilateral ONSM, ultimately leading to permanent bilateral blindness. Case presentation: A 7-year-old boy with a history of right trochlear nerve palsy and amblyopia presented with worsening right eye vision. An MRI revealed a right CSM that was resected however the patient experienced progressive visual acuity decline from 20/60 right eye and 20/40 left eye to light perception right eye and 20/400 left eye, along with bilateral optic atrophy appreciated on optical coherence tomography. Repeat evaluation of the brain MRIs revealed bilateral ONSM characterized by a tram-track appearance. Visual acuity remained unimproved 3 years after optic canal decompression with optic nerve sheath fenestration followed by proton beam radiation.Conclusion: Pediatric ONSM is rare, with high risk of permanent blindness in children. Intracranial meningioma and unexplained painless vision loss should prompt careful evaluation of orbital neuroimaging for this condition.