The absence of a significant or identifiable period of loss consciousness does not mean that an injured person has not suffered a permanent brain injury. Likewise, permanent brain injury can occur without a person having hit his or her head. While seemingly not as dangerous as injuries involving coma, hematoma, and surgery, these injuries can be life altering, and in some cases as disabling as many coma injuries.

One ofthe most significant medical authorities pointing to the potential severity of brain injury without a significant period of unconsciousness is the definition which came out of meetings of the American Congress of Rehabilitation Medicine. While such definition still uses the term "mild" traumatic brain injury, it establishes clear cut authority for the premise that these non-coma type injuries can be serious and permanent. Such definition, establishes that a permanent brain injury can occur if any of the following four conditions occur as a result of trauma, or accident:

1. any period of loss of consciousness;

2. any loss of memory for events immediately before or after the accident (amnesia);

3. any alteration in mental state at the time of the accident (eg, feeling dazed, disoriented, or confused); or

4. focal neurological deficit(s).

[Source: Mild Traumatic Brain Injury Committee of the Head Injury Interdisciplinary Special Interest Group of the American Congress of Rehabilitation Medicine, published at J Head Trauma Rehabil 1993:8(3):86-87]