ImPACT Version 4

Administration and Interpretation Manual

[Download PDF Version of the Manual]

What Is a Concussion?

A concussion is a disturbance in brain function following either a blow to the head or as a result of the violent movement of the head. Existing research suggests that concussion is more of a metabolic rather than anatomic injury to the brain. In other words, following concussion there is a temporary disruption of energy utilization in the brain that does not appear to produce permanent injury in the majority of cases. However, research also suggests repeated injury, particularly during the recovery period, may result in more severe and, in some rare cases, life-threatening injury. It is important to emphasize the underlying pathophysiology of concussion is still being investigated and the definition of the injury continues to develop and evolve.

Because a concussion is currently thought to be primarily a metabolic rather than structural injury, traditional neurodiagnostic techniques (e.g., CT scan, MRI) are often normal following concussive insult; however, these techniques can be invaluable in ruling out more serious difficulties (e.g., cerebral bleed, skull fracture) that also may occur with head trauma.

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