Unmasking Cognitive Deficits After Recovery from Mild Traumatic Brain Injury

There are over 7,000 peacetime traumatic brain injury (TBI) admissions to Department of Defense and Department of Veterans Administration hospitals each year and approximately 20% of combat personnel returning from the Afghanistan and Iraq conflicts have experienced a TBI in theater. TBI has been called the "signature injury” of Operations Enduring and Iraqi Freedom. Cognitive tests are commonly used to assess the degree of injury and changes in cognitive performance with time and treatment in individuals who have suffered a TBI. However, these tests may fail to uncover some significant cognitive deficits in patients with mild TBI (mTBI) when administered in the typical resting, unstressed condition due to the ability of the individual to access their available "cognitive reserve." The implication is that this cognitive reserve can mask residual cognitive deficits and reduce the sensitivity of cognitive tests when administered in the traditional manner. This suggests the possibility of adding a physiologic stressor to the testing conditions with the goal of limiting the influence of cognitive reserve on the test results and discovering the true extent of potential cognitive deficits. The primary aim of this study is to measure cognitive function in individuals with mTBI during exposure to a mild hypoxic stress to determine if use of this stressor can uncover latent cognitive deficits not evident when exposed to testing alone.  The short term goal of this research is to develop a practical clinical test to identify latent subclinical cognitive deficits in individuals with mTBI that cannot be detected with current methods. The long term goal is to use this testing paradigm to identify those military members at risk for cogntive dysfunction following a mTBI who currently go undetected in order to promote early intervention and treatment and maximize long-term preservation of functional brain mass. Cognitive function will be measured in subjects with and without mTBI during exposure to room air and mild hypoxia in a prospective, randomized, single blind, crossover study. Data analysis will seek to determine if exposure to a mildly hypoxic environment produces more severe declines in cognitive function in subjects with a history of mTBI with apparent full recovery as compared to subjects without a history of brain injury. 

Relevance: The proposed study has the potential to expand our knowledge and understanding of the often silent, persistent, long term, disabling affects associated with a mTBI. It also offers the possibility of developing a clinical tool to assess the need for follow up care and the effectiveness of that care. Thus, this study could have a major health impact on the growing number of military members at risk for long term neurobehavioral sequelae following mTBI. 

Final Report is available on NTRL: https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB2018100...