Consciousness is a person’s ability to recognize and perceive their surroundings and their own state. If the brain and serious diseases damage the brain, there will be different degrees of consciousness disorder. There are five types: 1. drowsiness: the lightest disorder of consciousness, can wake up and answer questions correctly. 2. fuzzy consciousness: simple mental activity, but poor orientation. 3. lethargy: not easy to wake up, can not answer questions correctly. 4. coma: mild: no response to the call, there is a response to strong stimuli, corneal and pupil light reflexes exist. Moderate: defense reaction to severe pain, pupil to light reflex is sluggish. Severe: no response to all kinds of stimuli. 5. Delirium: blurred consciousness, babbling.