The Association Between Loss of Consciousness and the Default Mode Network at the Chronic Stage of Diffuse Axonal Injury: A Diffusion Tensor Imaging Study

Objectives: We investigate the relationship between the loss of consciousness (LOC) and the state of default mode network (DMN) connectivity in diffuse axonal injury (DAI) patients, using diffusion tensor tractography (DTT).

Methods: Twenty-one consecutive patients with DAI were recruited in this study. The DMN connectivity [medial prefrontal cortex (mPFC)—posterior cingulate cortex (PCC)/precuneus and retrosplenial cortex (RSC)—medial temporal lobe (MTL)] was reconstructed using DTT. Fractional anisotropy (FA) value, mean diffusivity (MD) value, and tract volume (TV) of the DMN connectivity at the chronic stage were measured in this study.

Results: After adjusting for covariates, none of the DTT parameters reached definitive statistical significance at the p < 0.05 level. However, the LOC duration revealed a marginal trend toward a negative correlation with the TV of the mPFC-PCC/precuneus neural connectivity (partial r = −0.466, p = 0.060) and a marginal trend toward a positive correlation with the MD value of the MTL-RSC neural connectivity (partial r = 0.467, p = 0.059). The FA and MD of the mPFC-PCC/precuneus, and the FA and TV of the MTL-RSC, showed no significant associations (p > 0.05).

Conclusions: This exploratory study identified a marginal trend between the LOC duration and the state of DMN connectivity (mPFC-PCC/precuneus and MTL-RSC) at the chronic stage in DAI patients. Chronic-stage microstructural changes in the DMN are likely influenced by several factors, including the severity of the initial injury and the time since injury. Therefore, although the LOC duration provides useful clinical information, it should not be considered a direct predictor of chronic DMN deterioration in patients with DAI.