Objective To observe any effect of hyperbaric oxygen therapy on cognitive dysfunction caused by traumatic brain injury,and to explore possible neural mechanisms.Methods Sixty-four patients with cognitive impairment after a traumatic brain injury were randomly divided into a hyperbaric oxygen group (n =32) and a control group (n=32) using a random number table.Both groups accepted routine medical therapy and cognitive rehabilitation training,but the hyperbaric oxygen group additionally received hyperbaric oxygen treatment.Both groups' cognitive functioning was assessed using the Mini Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) before and after the treatment.Fifteen patients were randomly selected from both groups to receive T1WI and diffusion tensor imaging scans.The correlation between the two evaluation resuhs was analyzed.Results After the intervention,improvement was observed in the average MMSE and MoCA scores of both groups,with the improvement in both average scores in the hyperbaric oxygen group significantly greater than among the control group.There was no significant correlation between the fractional anisotropy (FA) values of damaged white matter and the average MMSE or MoCA score in the controi group,but in the hyperbaric oxygen group there were significant positive correlations between the FA values of the corpus callosum,the anterior limb of the internal capsule and the left superior longitudinal fasciculus and the average MMSE and MoCA scores.Conclusions Hyperbaric oxygen therapy combined with rehabilitation training can further improve cognition after a traumatic brain injury.This is probably due to its adjusting the structure and function of the corpus callosum,of the anterior limb of the internal capsule and of the left superior longitudinal fasciculus.