1. Minimally Conscious State: This is a form of severe consciousness disorder where the content of consciousness is significantly impaired, and clarity of consciousness is markedly reduced. However, behavior indicates weak but definite awareness of self and environmental stimuli, with spontaneous eye-opening and arousal-sleep cycles. Although conscious behaviors are intermittent and discontinuous, they are repeatable or can be sustained long enough to distinguish them from primitive reflexive activities.

   Determining the patient's limited yet definite self or environmental awareness activities is the fundamental basis for diagnosing a minimally conscious state. This is specifically demonstrated by one or several repeatable or sustained behaviors: ① following simple commands; ② using postures or speech to express yes or no (regardless of correctness); ③ expressing understandable speech; ④ purposeful behaviors, including occasional non-reflexive movements or emotional activities corresponding to environmental stimuli.

2. Decorticate State: Extensive damage to the cerebral cortex results in loss of cortical function, while the functions of subcortical structures remain intact. The patient displays a fixed gaze or purposeless activity, with no spontaneous speech, unresponsive to calling, appearing awake but truly unconscious. There is an arousal-sleep cycle, but it is disrupted. The patient lacks voluntary movement, but primitive reflex activities are preserved. Emotional responses are absent, with occasional unconscious crying or spontaneous laughter. Tendon reflexes are hyperactive, and pathological reflexes are positive. There is incontinence, and glandular secretion is hyperactive. Sympathetic nervous system activity is heightened during wakefulness, while parasympathetic dominance occurs during sleep. The patient displays peculiar body postures, with both forearms flexed and adducted, wrists and fingers flexed, both lower limbs extended, and toes flexed.

3. Vegetative State: The patient exhibits a complete loss of cognitive functions regarding self and the external world, unresponsive to stimuli, unable to communicate with the outside world, and may demonstrate spontaneous or reflexive eye-opening, occasional visual tracking, spontaneous meaningless crying or laughing, and avoidance movements to painful stimuli. There are primitive reflexes such as sucking, chewing, and swallowing, with incontinence. An arousal-sleep cycle is present, but may lack a normal rhythm of daytime wakefulness and nighttime sleep, resulting in unpredictable durations of wakefulness and sleep periods. A persistent vegetative state refers to a vegetative state lasting more than 12 months following traumatic brain injury or more than 3 months due to non-traumatic causes.