Over the last years, an increasing number of patients survive severe brain injury thanks to recent improvements in intensive care. Nevertheless, the recovery of brain capacities and motor skills is not always complete: it may happen that the patient maintains vital functions but does not show overt awareness of himself and the environment around them. From the diagnostic point of view, behavioral assessments can provide general and summary information on the patient’s state of consciousness, based on evidence found in attitudes and responses, voluntary or not. Despite this, such type of assessment can lead to a relevant number of misdiagnoses or inaccurate diagnoses, depending on the severity of brain injury, which may reveal incomplete or inconsistent behaviors.