The three major disorders of consciousness are coma vegetative state, and minimally conscious state. In coma, which typically is present for the first one to two weeks after brain injury, patients are not awake or aware, meaning that they do not open their eyes, have only reflex responses and are unaware of those around them.
If a coma lasts more than two or three weeks, it evolves into the vegetative state. In this state, unlike coma, wakefulness is present, which means that patients' eyes open either spontaneously or in response to stimulus. However, as in coma, awareness is not present. If the vegetative state persists for more than three to six months, the term persistent vegetative state is applied.