Though memory dysfunction may be the a sign of closed head injury, it commonly occurs together with a reduction in general intellectual capacity, disorders of language and visual perception, impairment of attention, and personality change. These multiple disorders are consistent with the variable and widespread pattern of cerebral damage that can result from severe head injury.

Closed head injuries are distinguished from open injuries in which the skull is breached.

There is evidence relatively trivial injuries to the head resulting in unconsciousness cause some structural brain damage,evidence of both intellectual and disturbed neurological function i.e. vision, hearing and balance. The time to recover full consciousness is a measure of the quality of brain tissue destroyed.

• 1 hour mild injury
• 24 hours, moderate injury
• One to seven days, severe injury
• Seven days plus, very severe injury

In a review of neuropsychological evaluation of mental deficits after brain damage injury, some are critical of the use of intelligence tests stating they are "flagrantly inadequate as measures of intellectual handicaps following brain injury." They do not dismiss its use of some tests as long as patients are given time to solve the problems irrespective of the time normally allowed as well as other factors. Thus, because the major part of handicap due to head injury is not in intelligence but in attention, memory and a broad range of information-processing skills, it is essential that psychological examination not be based solely on IQ measures.

Of all possible defects patients have, a disturbance of memory is the one that they and their relatives report most often. There is general agreement patients have marked difficulties in learning new material. There is also evidence material stored before injury is more readily recalled. Changes in personality and behavior...thinking disturbance, conceptual disorganization, unusual thought content and hallucinations. hostile suspiciousness; hostility, suspiciousness and uncooperativeness withdrawal/retardation; emotional withdrawal, motor retardation and blunted affect. anxiety/depression, anxiety, guilt feelings and depression.

Most behavioral disturbances are more common in both moderate and severely disabled.

• Emotional change; characterized by apathy, silliness, lability of mood, irritability and increased, or more often reduced or absent libido.
• Imparied social perceptiveness; characterized by selfishness in which feelings for others, self-criticicsm and an ability to reflect are greatly diminished or absent.
• Impaired self control; characterized by impulsivity, random restlessness and impatience.
• Increased dependency; characterized by lack of initiative despite talk of action and by impaired judgment and planning ability.
• Behavioral rigidity; characterized by inability to learn from experience even when the ability to learn new information is retained.