The Relationship Between Optic Nerve Sheath Decompression Failure and Intracranial Pressure in Idiopathic Intracranial Hypertension.

BACKGROUND:To our knowledge, there are no studies of patients with idiopathic intracranial hypertension (IIH) that address the relationship between level of intracranial pressure (ICP) and likelihood of progressive visual loss despite uncomplicated optic nerve sheath decompression (ONSD). This study investigated whether patients with IIH undergoing ONSD had a higher risk of surgical failure if opening pressure (OP) on lumbar puncture was ≥50 cm H2O compared to those with OP <50 cm H2O. METHODS:We conducted a retrospective chart review of consecutive patients with IIH who failed maximal medical therapy and underwent ONSD between January, 1992 and November, 2014, and were followed at least 3 months postoperatively. The main outcome measure was the relationship between OP on lumbar puncture and ONSD failure. We also investigated the relationship of OP with visual acuity, visual fields, age, and gender. RESULTS:During this period, 174 patients met inclusion criteria. Of the 40 patients who had an OP ≥50 cm H2O, 6 (15%) had progressive visual loss after uncomplicated ONSD, vs 6 (4.5%) of 134 patients with an OP <50 cm H2O (P = 0.032, Fisher exact test). Patients with worse visual acuity at presentation also had a higher risk of progressive visual loss after ONSD (P < 0.001, Cochran-Armitage trend test), as did men (P = 0.048, Fisher exact test). CONCLUSIONS:Patients with IIH and an OP ≥50 cm H2O had a 3-fold increased risk of failure of ONSD to prevent progressive visual loss, requiring a shunting procedure when compared to those with OP <50 cm H2O. Visual acuity at presentation and male sex also were associated with progressive visual decline after ONSD. These risk factors merit closer follow-up in the postoperative period when signs of further visual deterioration would indicate an urgent need for neurosurgical shunting.