Ectopic brain in the orbit with congenital adduction deficit and simultaneous abduction

An 11-month-old girl was referred to us with enophthalmos and restriction of ocular movement in the right eye. There was restriction of supraduction and adduction with synergistic divergence on left gaze. MRI revealed a multiloculated cystic mass in the right inferior orbit. There was an atrophic and misinserted inferior rectus muscle and only a vestigial right medial rectus muscle. Excisional biopsy of the orbital cystic mass was performed. Microscopic examination disclosed that the mass was brain tissue composed of arachnoid tissue, brain parenchyma, choroid plexus, and dura mater. Our report describes a rare case of ectopic brain in the orbit that was combined with anomalies of the extraocular muscles.