A boy with arachnoid cyst, a fall, and temporary and reversible visual impairment

Temporal arachnoid cysts have been shown to interfere with the function of nervous structures, both cerebral cortex and cranial nerves.

In this case report we describe a boy with a left temporal arachnoid cyst with a sudden onset of visual impairment 4 days after a mild trauma to the head. A perimetry test revealed a complete nasal hemianopia of the left eye, which normalized rapidly after an emergency craniotomy with cyst fenestration 3 hours after the patient experienced the reduced vision.

The observed, reversible effect on vision is most probably caused by pressure exerted by the medial part of the cyst on the left optic nerve. We believe this is the first time such a case has been described.