Gunshot wounds are the commonest form of penetrating trauma that cause TBI.[13] Less commonly, knife wounds and shrapnel from motor vehicle accidents can also penetrate the airways.[6] Most injuries to the trachea occur in the neck,[3] because the airways within the chest are deep and therefore well protected; however, up to a quarter of TBI resulting from penetrating trauma occurs within the chest.[14] Injury to the cervical trachea usually affects the anterior (front) part of the trachea.[9]