Introduction: The study aims to determine if there is a relationship between cerebrovascular reactivity (CVR) measured with BOLD MRI and post concussion symptoms (PCS) following mild traumatic brain injury (mTBI).
Methods: Twenty-five patients with mTBI (mean = 43 years; 72% male) and 18 matched control participants underwent CVR testing using BOLD imaging and RespirActTM controlled CO2 manipulation in 2 occasions (two and six months after TBI). PCS were assessed using the SCAT2 questionnaire at each time point. Whole brain, grey matter (GM), white matter (WM) CVR and volumes were calculated at each visit. Correlations between imaging metrics and PCS symptoms were investigated in each tissue type.
Results: Whole Brain CVR and SCAT2 scores showed a significant correlation (r=0.4, p=0.05); patients with lower CVR were more likely to have higher PCS reporting. A significant correlation was also found between GM CVR and SCAT2 scores at early testing (r= 0.4, p=0.04), and these GM findings persisted at 6-month follow-up (r=0.4; p=0.02). CVR values were lower, and variance higher in mTBI patients than in controls, though statistical significance was not reached. Cerebral volumes - WM (WMv) and GM (GMv) - were similar in between TBI and healthy control participants (WM p=0.71; GM p=0.36) at two months. At 6 months GMv decrease was seen in mTBI patients (p=0.005). WMv did not change over time, nor did WM CVR appear correlated with PCS in this sample.
Conclusions: Persistent PCS severity appears correlated with CVR impairment when measured with BOLD MRI. Whether a state of vasoparalysis in response to CO2 may be occurring after mTBI and is part of the pathophysiology of PCS remains to be determined. A larger sample size and more detailed neurocognitive assessments will be required to confirm the role of CVR as a biomarker for concussion and PCS resolution.
Patient Care: The longitudinal evolution of PCS shows correlation with CVR change. This may hold clinical value in determining readiness to resume sport and regular activity following mild head injury- an area where clear guidelines are not established.
Learning Objectives: By the conclusion of the presentation, participants should be able to: 1) describe how CVR is associated with PCS, and 2) describe the measurement technique for CVR and 3) discuss feasibility of CVR measurement in the recovery of concussion.