The exact number of Purple Hearts awarded is not tracked by The Pentagon, nor is the type of injury a soldier has suffered. Thus, it is not clear how many soldiers have received the Purple Heart for mild traumatic brain injuries, or how many applied but were denied. Soldiers who receive a denial must first appeal through their chain of command. Beyond that, a soldier can appeal through the Army Human Resources Command, and depending on the time of the injury, different boards may review an appeal before making a final decision. This process can take months, even years.