When it comes to injury of any kind, including head injury, classification of severity is important. The first AIS (Abbreviated Injury Scale) was published in 1971, propelled by the American Medical Association, the Association for the Advancement of Automotive Medicine, and the Society of Automotive Engineers. It was originally created to assess impact injuries, but it has been revised a number of times since then.
The scale uses numbers to rank injuries by severity, based upon the anatomical injury. This means that any lingering consequences of the injury, like disabilities, are not noted. Each injury only receives one AIS score, and there is no single assessment for multiple injuries.
The system has a 6-point scale, with 1 meaning a minor injury and 6 being the worst possible injury. Later revisions included a six-digit code for each injury. The first number signified body region, the second anatomic structure, the third and fourth the specific nature of an injury if external, and the fifth and sixth related to the level of injury in an anatomic region. Later revisions included further categorization for brain injuries.
The AIS also provides a way to classify head injury based on the level of consciousness according to the Glasgow Coma Scale and studies done in Nassau and Suffolk. These are only used when there seems to be a more serious injury than the actual trauma suggests or when there is no visible sign using imaging or autopsy.