Long-term effects of brain injuries can include cognitive impairments, and other psychological symptoms. When someone suffers from even a mild brain injury, they might be unable to focus, and have trouble remembering things. Although these short-term symptoms might be easily detectable immediately after an injury occurs, some long-term symptoms might take weeks or months to appear.
However, just because symptoms might not be apparent, doesn't mean the damage hasn't been done. Damage that causes long-term effects of brain injuries is often attributed to damage of the brain's white matter. Until recently, this damage has been difficult to detect using traditional magnetic resonance imaging (MRI).