Orbital Cavernous Venous Malformation Mimicking Nonarteritic Anterior Ischemic Optic Neuropathy: A Case Report

This case report describes a 49-year-old woman presenting with a 20-day history of subacute, painless blurred vision and an inferior altitudinal visual field defect in the left eye, without proptosis or prior transient visual loss. Neuro-ophthalmology examination revealed left optic disc oedema, a relative afferent pupillary defect, and intact extraocular movements. Given the characteristic symptoms and visual field findings, nonarteritic anterior ischaemic optic neuropathy (NAION) was initially suspected. However, the absence of typical NAION risk factors, such as diabetes or hyperlipidaemia, prompted further neuroimaging, revealing a medial retrobulbar mass. Histopathology confirmed a cavernous venous malformation (CVM). Postoperatively, the patient’s visual acuity normalised to 20/20, optic disc oedema resolved, and visual field deficits significantly improved. This case highlights an orbital cavernous venous malformation causing compressive optic neuropathy that mimics NAION and underscores that neuroimaging is appropriate when red-flag features are present (e.g. subacute course, prior transient visual loss, persistent disc oedema, absence of vasculopathic risk factors, proptosis or choroidal folds); routine neuroimaging is not mandatory in typical NAION. Timely imaging facilitates accurate differentiation, preventing delays in surgical intervention and optimising visual outcomes. The findings align with existing evidence on CVM-induced compressive optic neuropathy and emphasise the necessity of a systematic diagnostic approach in cases exhibiting classic ischaemic optic neuropathy symptoms but lacking expected risk factor profiles.