Changes in the Default Mode Network and Recovery of Impaired Consciousness in Traumatic Brain Injury: A Case Series

Background and Clinical Significance: We report on three patients with traumatic brain injury (TBI) who showed improvement of impaired consciousness and changes in the default mode network (DMN), which was demonstrated on follow-up diffusion tensor tractographies (DTTs). Case Presentation: Three TBI patients underwent comprehensive rehabilitation during their first and second evaluations. Their Coma Recovery Scale-Revised (CRS-R) scores were obtained, and DTT was performed at 98.7 ± 22.0 days (first) and subsequently at 216.0 ± 78.1 (second) after onset. Compared with the first evaluation, the CRS-R scores increased by 12, 8, and 10 points on the second evaluation of the three patients. Although not reconstructed on the results of the first DTT, the second DTT results showed reconstruction of the medial prefrontal cortex (mPFC)–posterior cingulate cortex (PCC) DMN in patients 1 and 2. Regarding the continuously reconstructed DMNs (both mPFC-PCC and mPFC–precuneus), structural thickenings were generally observed in patients 1 and 3; however, narrowing was observed on the right mPFC-PCC DMN of patient 3. On the second DTT, all fractional anisotropy values of the reconstructed DMNs increased in patients 1 and 3, whereas all mean diffusivity values of the reconstructed DMNs decreased. Except for the right mPFC-PCC DMN in patient 3, all tract volume values of the reconstructed DMNs increased on the second DTT. Conclusions: DTT demonstrated changes in the mPFC-PCC/precuneus DMN concurrent with the improvement of impaired consciousness in three patients. In conclusion, recovery of the mPFC-PCC/precuneus DMN is closely associated with improvement of impaired consciousness in TBI patients.