Purpose: To evaluate morphologic changes occurring in the retrobulbar region after optic nerve sheath decompression (ONSD) in patients with idiopathic intracranial hypertension using magnetic resonance (MR) imaging.
Design: Prospective observational study.
Methods: This study included 26 eyes of 17 patients (age range, nine to 57 years) with idiopathic intracranial hypertension who underwent ONSD. The surgery was performed through transconjunctival medial orbitotomy and by a dural window excision. After ONSD, the optic nerves were examined with MR imaging by means of 3-dimensional "constructive interference in steady state" (CISS) sequence.
Results: After ONSD, papilledema resolved in all eyes and visual functions improved in all except one. Early postoperative MR imaging (two to eight weeks after surgery) demonstrated a cyst-like fluid collection adjacent to the dural window site in nine (75%) of 12 eyes and a fibrous tissue formation in three eyes (25%). Late postoperative MR imaging (six to 15 months after surgery) demonstrated a fibrous tissue formation at the decompression site in 25 eyes (96%) and perioptic fluid collection in one eye (4%).
Conclusions: In early postoperative period after ONSD, a fluid collection adjacent to the decompression site occurs in most eyes; this finding disappears in late period. Early postoperative MR findings support the idea that ONSD functions through the cerebrospinal fluid (CSF) filtration.