Reversible distension of the subarachnoid space around the optic nerves in a case of idiopathic hypertrophic pachymeningitis.

Idiopathic hypertrophic pachymeningitis (IHP) is a chronic inflammatory disease of unknown cause. We report a case of IHP with bilateral distended subarachnoid space (SAS) of the optic nerves and unilateral visual disturbance. We observed marked amelioration of magnetic resonance (MR) imaging findings after initiation of treatment with prednisolone. This radiological finding implicates optic nerve sheath involvement that affects cerebrospinal fluid (CSF) dynamics around the optic nerve.