CSF pressure, papilledema grade, and response to acetazolamide in the Idiopathic Intracranial Hypertension Treatment Trial

Previous reports suggest an association between the degree of optic nerve head edema and CSF pressure (CSFp) in idiopathic intracranial hypertension (IIH). We hypothesized that CSFp would be associated with Frisén papilledema grade (FPG) and other clinical features, and that FPG would modify the CSFp response to acetazolamide in participants in the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT). In the IIHTT, eligible patients underwent lumbar puncture (LP) prior to enrollment and were randomly assigned to one of two treatment groups: acetazolamide plus supervised diet or placebo plus supervised diet. Trial eligibility required baseline CSFp ≥250 mm H₂O or ≥200 mm H₂O with compelling clinical or imaging IIH findings. Associations between CSFp and FPG and other clinical features were examined at baseline. The effect of acetazolamide on 6-month change in CSFp was examined in those with low FPG (grades I–III) and those with high FPG (grades IV–V) at baseline. All 165 enrolled subjects had a baseline LP and 85 had an LP at 6 months. There was an association between CSFp and FPG at baseline: CSFp was more elevated in subjects with high FPG (378 ± 90 mm H₂O, n = 50) than in subjects with low FPG (331 ± 77, n = 115, p = 0.002). At 6 months, acetazolamide had a similar effect on CSFp in subjects with high FPG (−79.9 mm H₂O) and in subjects with low FPG (−50.9 mm H₂O, p = 0.50). We found a modest association between CSFp and FPG. Acetazolamide had a beneficial effect on CSFp regardless of baseline FPG.