Abstract
Traumatic brain injury (TBI) often leads to impaired consciousness. Recent diffusion tensor imaging studies associated consciousness with imaging metrics including fractional anisotropy (FA) and apparent diffusion coefficient (ADC). We evaluated their correlations and determined the best index in candidate regions. Six databases were searched, including PubMed and Embase, and 16 studies with 701 participants were included. Data from region-of-interest and whole-brain analysis methods were meta-analysed separately. The FA-consciousness correlation was marginal in the whole-brain white matter (r = 0.63, 95% CI [0.47, 0.79], p = 0.000) and the corpus callosum (CC) (r = 0.60, 95% CI [0.48, 0.71], p = 0.000), and moderate in the internal capsule (r = 0.48, 95% CI [0.24, 0.72], p = 0.000). Correlations with ADC trended negative and lacked significance. Further subgroup analysis revealed that consciousness levels correlated strongly with FA in the CC body (r = 0.66, 95% CI [0.43, 0.89]), moderately in the splenium (r = 0.58, 95% CI [0.38, 0.78]), but insignificantly in the genu. In conclusion, FA correlates better with consciousness levels than ADC in TBI. The degree of correlation varies among brain regions. The CC (especially its splenium and body) is a reliable candidate region to quantitatively reflect consciousness levels.
Highlights
Traumatic brain injury (TBI) is a common and severe type of injury, responsible for about one-third of injury deaths[1]
10 records were identified through other sources (1 from reference lists and 9 from Clinicaltrials.gov searches)
We found that fractional anisotropy (FA) tended to correlate positively with levels of consciousness, while apparent diffusion coefficient (ADC) had a trend toward negative correlations
Summary
Traumatic brain injury (TBI) is a common and severe type of injury, responsible for about one-third of injury deaths[1]. The Glasgow Coma Scale (GCS), first introduced in 1974 by Teasdale G et al, was created to simplify assessment of the depth and duration of impaired consciousness and coma[3]. It provides a structured and objective grading system for bedside assessment[4]. The characteristics of DTI metrics in other subcortical regions such as the internal capsule (IC), centrum semiovale (CS), and thalamus have not been systematically summarised, and the subpopulation of moderate to severe TBI patients has not been investigated in a meta-analysis. Subgroup analyses and meta-regression are planned to confirm whether multiple factors including subregions, demographic features, and study characteristics influence heterogeneity of specific outcomes
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