Traumatic brain injury (TBI) represents one of the most significant health risks related to military duty; rapidly becoming the "signature injury" of the Iraq and Afghanistan conflicts. TBI patients often experience multiple cognitive problems, with disturbances in memory, attention, and executive functions among the most common. Disturbances in memory as well as attention are particularly problematic, as disruption of these relatively basic cognitive functions may exacerbate or cause additional disturbances in executive function, communication and other more complex cognitive domains. These cognitive deficits, especially when memory is affected, significantly impact day-to-day functioning and are the source of lingering disability and distress to the affected individuals. However, despite advances made in TBI care, treatment of cognitive deficits in TBI lag behind, forcing clinicians to provide treatment without the guidance of evidence-based scientific data. This proposal aims to begin the process of providing clinicians with evidence-based guidelines for pharmacological management of Veterans with TBI suffering from persistent cognitive deficits following their injuries. This aim will be accomplished by conducting a clinical trial in Veterans suffering from moderate to severe posttraumatic memory impairment following TBI. Specifically, this proposal will evaluate the efficacy and safety of rivastigmine transdermal patch, an intermediate-acting cholinesterase inhibitor, in this population.

The investigators hypothesize that rivastigmine transdermal patch will be more effective than, and equally safe as, placebo in the treatment of moderate to severe posttraumatic memory impairment in Veterans with TBI when tested in a randomized, multi-site, parallel design, placebo-controlled trial, at a 12-week endpoint. The exploratory hypothesis states that compared to placebo, rivastigmine patch will be more effective and equally safe in the treatment of patients who will continue in a randomized, placebo-controlled phase for a total of 26 weeks. To test these hypotheses we will evaluate the effect and the safety of rivastigmine 9.5 mg/24 hours (10cm2) transdermal patch in 138 Veterans who meet or exceed the criteria for closed, non-penetrating, mild TBI and who present at baseline with moderate to severe memory impairment. Memory impairment will be defined as a Total Recall index (Trials 1-3) of the Hopkins Verbal Learning Test-Revised (HVLT-R) that is at least 25% lower than the intelligence-adjusted expected score, as assessed by the Wechsler Adult Intelligence Scale - Fourth Edition (WAIS-IV) Information and Vocabulary subtests. The study consists of a screening period, one-week single-blind, placebo run-in phase, and a 12-week double-blind acute treatment phase (Phase I). Subjects will be randomized 1:1 to rivastigmine transdermal patch 9.5mg/24 hours (10cm2) or matching placebo. During Phase I, there will be an initial 4-week titration period followed by an 8-week continuation phase. Following the 12-week acute treatment phase, randomized patients will continue in the double-blind phase (Phase II) for additional 14 weeks or until study treatment period ends. Recruitment stage ended 2.25.16. Efficacy will be determined by comparing the proportion of patients in each treatment group who are classified as responders at week 12. Secondary measure of functional capacity assessing the impact of memory improvement on real-world functioning, other measures of cognitive domains affected in TBI, namely attention, working and episodic memory and executive functions, as well as measures of mood and quality of life will be examined. Study findings will contribute to the body of evidence needed to establish standards of care for Veterans with posttraumatic memory impairment and other cognitive deficits.