Imposter behind the eye: spheno-ethmoidal mucocele mimicking meningocele with compressive optic neuropathy.

A male patient in his mid-30s presented with progressive right eye proptosis and vision loss, accompanied by retro-orbital and occipital pain. He had a history of skull base trauma and endoscopic repair for cerebrospinal fluid rhinorrhoea 7 years earlier. Imaging revealed a lesion adjacent to a cribriform plate defect, initially suggesting a non-expanding meningocele. However, intraoperatively, the lesion was identified as a spheno-ethmoidal mucocele with orbital extension. Endoscopic drainage and marsupialisation were performed, resulting in immediate resolution of proptosis and marked improvement in visual acuity. Follow-up imaging showed no residual lesion or optic nerve compression. This case illustrates a rare spheno-ethmoidal mucocele presenting as compressive optic neuropathy, emphasising the need for a broad differential diagnosis and multidisciplinary collaboration when evaluating skull base lesions.