Cognitive outcome following traumatic brain injury.

Objective: To determine whether an association exists between traumatic brain injury (TBI) sustained in adulthood and cognitive impairment 6 months or longer after injury.
Design: Systematic review of the published, peer-reviewed literature.
Results: From 430 articles, we identified 11 primary and 22 secondary studies that examined cognitive impairment by using performance measures for adults who were at least 6 months post-TBI. There was clear evidence of an association between penetrating brain injury and impaired cognitive function. Factors that modified this association included preinjury intelligence, volume of brain tissue lost, and brain region injured. There was also suggestive evidence that penetrating brain injury may exacerbate the cognitive effects of normal aging. We found clear evidence for long-term cognitive deficits associated with severe TBI. There was suggestive evidence that moderately severe brain injuries are associated with cognitive impairments. There was inadequate/insufficient evidence to determine whether an association exists between a single, mild TBI and cognitive deficits 6 months or longer postinjury.
Conclusion: In adults, penetrating, moderate, and severe TBIs are associated with cognitive deficits 6 months or longer postinjury. There is insufficient evidence to determine whether mild TBI is associated with cognitive deficits 6 months or longer postinjury.