Traumatic brain injury can have delayed symptoms.
A traumatic brain injury isn't always immediately apparent. In both children and adults, problems might not be seen until a few days, months or years after the injury. The reasons for this can be different for children and adults:
"Growing into" a brain injury is a common occurrence in children. A healthy brain can normally handle more and more difficult challenges as the child gets older. For a child with a TBI, however, the increasing demands on his or her brain cannot be accommodated. A child with a TBI might easily read the simple words in a first-grader's book, but as that child grows, his or her brain is not able to take in and understand the more complex words in a higher-grade book.
"Growing into" a brain injury often creates a real problem in identifying a TBI in an older child, because of the lapse in time between the injury itself and the onset of problems. Friends and teachers don't understand that the cause might be the playground accident or car crash of a few years ago, particularly since they might not even be aware that there had been a playground accident or a car crash involving this child. Cause and effect are not usually separated by long periods. But, for children with a brain injury, these "late" symptoms are common.
Adults can also experience a delay between the injury and the onset of problems. This can occur because often the demands on the brain immediately following injury are few and easily handled. The demands on the brain increase greatly when the injured adult returns to his or her normal life, such as returning to work or to being responsible for parenting and household tasks.
For example, consider the case of an adult who works as an accountant and falls from a ladder while making repairs at home, breaking several ribs. He is dazed from the fall, but remains conscious. Because of his physical injuries, he must stay home from work for two weeks. During that time, the only problem he notices is the pain from his broken ribs. However, when he returns to work, he discovers that parts of his job which used to be easy he can still handle, but more slowly than before the accident. Mistakes he would not have made before his fall are now common occurrences for other parts of his job. It is likely that the fall didn't just injure his ribs but also resulted in an injury to an area of the brain that controls the complex skills he needs at work. Most likely, he does not make the connection between the injury and these new cognitive difficulties, which delays the diagnosis of TBI.