Surgical interventions in idiopathic intracranial hypertension - a comprehensive multi-center study of outcome and the role of treatment indication

Background: Surgical intervention is recommended in idiopathic intracranial hypertension (IIH) for fulminant or treatment-refractory cases, yet data on outcomes remain limited, particularly regarding indication-specific effects. This study evaluated outcomes and indications for surgery in IIH, aiming to identify predictors of favorable or adverse results. Methods: A retrospective multi-center study was conducted by the Danish-Austrian IIH Consortium (DASH-IIH). Databases from three centers (Vienna, Odense, Copenhagen) were screened for people with IIH (pwIIH) fulfilling revised Friedman criteria who underwent surgery and had ≥6 months of follow-up. Outcomes at six months included visual function, headache improvement (≥50%), papilledema resolution, and severe adverse events. Multivariable regression was used to adjust for confounders. Results: Of 1310 pwIIH, only 3.6% required surgery overall. Thirty-six pwIIH were included (100% female; mean age 32.5 years; median BMI 37.0; median CSF opening pressure 41 cmH₂O). Of these, 27 (75%) underwent CSF diversion and 9 (25%) optic nerve sheath fenestration (ONSF). The primary indication for surgery was acute visual deterioration in 83.3% and refractory headache in 16.7%. Visual function improved in 41.7%, papilledema resolved in 89.7%, and headache improved in 30.6%. No significant differences in outcomes were found between CSF diversion and ONSF. Importantly, no visual improvement occurred in cases operated for headache alone, and the odds of headache improvement were significantly lower in this group (OR 0.11, p=0.012). Conclusion: CSF diversion and ONSF are effective in IIH with acute visual threat, improving vision and, to a much lesser extent, headache. Refractory headache alone appears insufficient indication for surgical intervention.