The Idiopathic Intracranial Hypertension Treatment Trial: A Review of the Outcomes

Objective The Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) was the first large, randomized study on the use of acetazolamide and weight loss for treatment of idiopathic intracranial hypertension‐associated vision loss. The multicenter trial also examined a number of secondary outcomes. This review summarizes all available results of the study published in the literature since 2014. Background Prior to the IIHTT, clinicians managed idiopathic intracranial hypertension based on data from small, unmasked trials, expert opinion, and clinical experience. Due to the lack of empiric evidence, there were no official treatment protocols to guide treatment of the disorder. Methods We performed a PubMed literature search for all articles with data from the IIHTT Study Group. After review of each article and any relevant supporting literature, the results were compiled into a summary of the literature. Results The PubMed search identified 14 articles with primary and/or secondary outcome data from the IIHTT. We summarized the findings for the primary outcome of visual field outcomes in the acetazolamide treatment group compared to the placebo group, as well as secondary outcomes for the safety and tolerability of acetazolamide, cerebrospinal fluid opening pressure, quality of life, fundus photography, and optical coherence tomography. While both groups demonstrated improvement on most outcomes, acetazolamide had a greater effect even when controlling for its effect on weight loss. Conclusions As the first large, randomized, prospective trial, the IIHTT extensively expanded the available data on idiopathic intracranial hypertension treatment. Most importantly, it provided support for the safe use of acetazolamide up to 4 g daily with weight loss for effective treatment of mild vision loss in IIH, with associated improvements in papilledema, increased intracranial pressure, and quality of life.