Arachnoid cyst accompanied by proptosis and unilateral high myopia.

An 8-year-old boy presented with proptosis of the left eye. On ophthalmic examination,unilateral axial elongation of the left eye was evident.Computed tomography and magnetic resonance imaging revealed an arachnoid cyst in the left middle cranial fossa, which expanded the bone and deformed the posterolateral wall of the left orbit. The lesion was observed with serial examinations and reviewed by a neurosurgeon and a radiologist. After 6 months of follow-up, there was no progression of the cyst. We believe this is the youngest reported case of an arachnoid cyst associated with isolated proptosis in the setting of unilateral high myopia. Neuroimaging should be considered in cases of prominent or progressive proptosis in the context of unilateral axial myopia in order to detect other possible etiologies.