• Head injury

Categorising the severity of head injury is important clinically, in research, and for medicolegal purposes. Two commonly used measures are depth of coma when first assessed and duration of amnesia following the injury. Nakase-Richardson and colleagues1 have analysed data from 3846 of 4615 people registered on a National Database in the USA and have validated an improved classification of severity, as judged by returning to productive employment (see page 494). This classification is based on the length of post-traumatic amnesia (PTA), with four categories: 0–14 days, 15–28 days, 29–70 days and longer than 10 weeks.

Duration of post-traumatic amnesia has long been known to …