Coma is defined as the brutal loss, of which we do not know if it is definitive or temporary, of the functions of communication. It is the perception that the relatives of the coma, it is what they describe ... Whatever the cause, whatever is the duration, it is about a definitive or temporary abolition communication functions. Associated with this is the loss of functions of motor skills, comprehension ... But communication and its temporary or definitive abolition are the key elements that define coma.