The Idiopathic Intracranial Hypertension Treatment Trial: Design Considerations and Methods

Background: The objectives of this study were to present the rationale for the main aspects of the study design and describe the trial methodology for the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT). Methods: Eligible candidates with mild visual field loss (automated perimetric mean deviation [PMD] 22 to 27 dB) were randomized to receive either acetazolamide or matching placebo tablets. Randomized participants were offered participation in a supervised dietary program. The primary outcome variable, PMD, was measured at 6 months. Additionally, cerebrospinal fluid from subjects and serum from study participants and matched controls were collected for genetic analysis and vitamin A studies. An ancillary optical coherence substudy was added to investigate the changes of papilledema in the optic nerve head and retina that correlate with Frisen grading, visual field deficits, and low-contrast visual acuity. Results: The randomized trial entered 165 participants from March 17, 2010, through November 27, 2012, from the United States and Canada. The primary outcome (month 6) visits were successfully completed by June 15, 2013. Blood specimens were obtained from 165 controls without IIH to investigate vitamin A metabolism and genetic markers of potential risk factors for IIH. Conclusions: The IIHTT is the first randomized, double-masked placebo-controlled trial to study the effectiveness of medical treatment for patients with IIH. (C) 2014 by North American Neuro-Ophthalmology Society