Abstract
Though persistent failure of clinical trials poses a challenge for multiple conditions, traumatic brain injury (TBI) is especially difficult to study because of its heterogeneity, complexity, unpredictable outcomes, and resistance to definition and classification. This article analyzes published discourse among researchers about the failure of two large trials for progesterone as a traumatic brain injury (TBI) treatment. The analysis specifically examines how researchers respond to trial failure and how TBI functions as a diagnostic construct. I draw on theories of kairos and multiple ontologies to argue that, while evidence-based medicine constructs TBI as a coherent entity in order to study it through randomized controlled trials, this entity breaks down in practice into multiple temporalities and spaces that are not sufficiently coordinated.