Bilateral idiopathic optic nerve sheath meningocele: A case report and literature review.

Optic nerve (ON) sheath meningocele is an enlargement of the ON sheath, consisting in a cerebrospinal fluid collection along the perineural space of the optic nerve. It should be considered primary when it is not associated with orbital-cerebral neoplasm or with cranio-orbital junction malformations. Here, we report a case of bilateral primary idiopathic ON meningocele with gradual vision loss, treated with acetazolamide, which showed a maintained visual recovery and partial improvement during a 6-month follow-up period. The literature review retrieved eight cases of primary idiopathic ON sheath meningocele: ON sheath fenestration is considered in patients with progressive and severe vision loss, otherwise, acetazolamide treatment is indicated with good results on symptoms control, as confirmed in our case report.