Computerised Eye Tracker Assessment in Young Adults with Mild Traumatic Brain Injury

Abstract

Mild traumatic brain injury (mTBI) is a common and under-reported injury with high personal and economic impact, and recent research suggests that mTBI involves both spinal and brain injury. Current mTBI diagnostic criteria is subjective and prone to bias, which reduces diagnostic accuracy and complicates management. Computerised assessments are a useful and objective way to assess broad aspects of cognitive function after mTBI. As part of this thesis, a battery of computerised eye tracker assessments (CEAs) was designed and assessed for reliability. The finalised CEA battery included six refined and reliable assessments—egocentric localisation, fixation stability, pursuit, saccades, the Stroop test, and the vestibulo-ocular reflex (VOR). Two experiments using the validated CEA battery were performed, evaluating the role that afferent spinal proprioception could have on CEAs. The first study altered proprioceptive drive using cervical vibration and assessed spinal function using the flexion relaxation ratio (FRR) in control and mTBI participants. Vibration resulted in significant differences between the mTBI and control groups for many CEA outcomes, and the FRR was worse in mTBI indicating spinal dysfunction. Secondly, we assessed if one session of chiropractic intervention to modify aberrant proprioception could alter CEA outcomes in young adults with long-term mTBI symptoms (persistent postconcussion syndrome, PPCS). This single-blind randomised controlled trial found differences following chiropractic intervention for fixation, pursuit, Stroop, and the VOR. Finally, as we had accumulated equivalent baseline CEA data from control, mTBI, and PPCS, across the three studies, a fourth study using machine learning found the battery could differentiate between healthy, mTBI, and PPCS participants with an ROC of 0.95. The four studies in this thesis show the CEA battery could become an effective detection and monitoring system for people with mTBI, helping with diagnosis, monitoring recovery, and assessing treatment efficacy. The results also add evidentiary weight to the argument that mTBI symptoms have some spinal or proprioceptive basis, as altering proprioceptive input appears to impact visual outcomes.