After a severe injury to the brain, individuals may present difficulties to maintain awareness of themselves and of the environment, and to respond to environmental stimuli. Recovery of consciousness usually moves from the comatose phase to an unresponsive wakefulness syndrome, where wakefulness is preserved but there are no signs of awareness, to a minimally conscious state, where subjects can present certain level of awareness although not consistent enough to enable communication, or to a locked-in syndrome, where awareness is present but no motor response.
Disorders of consciousness represent a neurologic challenge from a diagnostic, prognostic, and therapeutic point of view. Misdiagnosis reaches up to 15% to 43% of the cases, prognosis is uncertain, and no treatment has been empirically shown to be effective. During the last two decades, the increased survival and the prolonged life expectancy of these individuals have generated an increase in case incidence and prevalence, and consequently a renewed clinical and scientific concern. However, more efforts are still needed to improve current clinical knowledge about these states.