A DIFFUSION TENSOR IMAGING STUDY ON THE RELATION BETWEEN SYMPTOM SEVERITY, WHITE MATTER INTEGRITY, AND COGNITIVE FUNCTION AMONG THE MTBI POPULATION

Abstract

The population of young adults who have sustained a mild traumatic brain injury (mTBI) has been growing steadily in recent years. As a result, there is a higher prevalence of symptoms that range from behavioral irregularities to abnormalities in brain anatomy and physiology. There are microstructural alterations of nerve tracts in the form of axonal injury that can lead to cognitive deficits after an individual experiences an mTBI. Despite this knowledge and an ever-growing number of cases, little research has focused on the direct link between the structural changes of the brain, how these symptoms present themselves, and the cognitive deficits that follow (specifically in executive functioning). The present study takes into consideration the neurological and behavioral components of mTBIs and aims to determine the extent to which symptom severity and brain structure are associated with cognitive ability. A total of 38 participants (20 healthy controls (HCs) and 18 post-mTBIs) completed a series of tasks (self-report questionnaires, computerized assessments), followed by a neuroimaging session using magnetic resonance imaging (MRI). Symptom severity was measured using the Rivermead Post Concussion Symptoms Questionnaire (3-RPCSQ) and cognitive ability, in the form of executive function, was measured using a computerized Wisconsin Card Sorting Test (WCST). Diffusion tensor imaging (DTI) data from the cingulum bundle (believed to play a large role in executive functioning) were collected and analyzed to quantify fractional anisotropy (FA), a measure of axonal integrity. We hypothesized that the cingulum bundle would show reduced FA following mTBI and that symptom severity in conjunction with FA would significantly predict cognitive ability. Results showed that FA was associated with objective measures of cognitive function, but symptom severity is not predictive of cognitive ability. Additionally, FA in the right cingulum significantly predicted cognitive ability, in that reduced FA correlated with poorer executive functioning on the WCST. The findings of this thesis demonstrate how the white matter tracts known as the cingulum bundle remain a significant, neural predictor of executive function. When affected by an mTBI, microstructural alterations in brain integrity and imbalances in the energy needs of the brain can eventually lead to the manifestation of common clinical symptoms.