Following severe traumatic brain injury (sTBI),patients may remain in a coma,vegetative state (VS),or minimally conscious state (MCS),all of which are also clinically termed disorders of consciousness.Patients in a coma show complete disability in the arousal system and fail to achieve awareness spontaneously;yet true coma represents a transient state and rarely lasts longer than a month [1].The VS (also known as unresponsive wakefulness syndrome),characterized as a state with spontaneous or stimulus-induced eye-opening but the patient appears totally unaware of self and environment,may persist for months or years [2].In contrast,the MCS is evidenced by preserved and reproducible signs of awareness as well as sleep-wake cycles,suggesting better recovery than coma and VS.Considering that no signs of consciousness are detectable,patients in a VS suffer from a high rate of misdiagnosis [3].