Loss of arousal state in coma patients is clinically manifested by the disappearance of the patient’s arousal-sleep cycle and the patient is in a persistent deep sleep, unable to wake up. The patient’s perception, attention, thinking, emotion, orientation, judgment, memory and many other mental activities are all lost. There is no understanding of oneself and the external environment, and no response to external stimuli. Inability to carry out simple commands. Given strong painful stimuli, there is a complete lack of conscious response, except sometimes for a pained expression or moan. The complete diagnostic and differential points of coma should include: 1. Localization and diagnosis: coma signifies acute cerebral failure, which has the pattern of cascading deterioration along the neuraxis. Generally, only through the monitoring of bedside brain function, it is possible to determine the plane of impaired brain function and the plane of residual function in comatose patients. 2.Qualitative diagnosis: It is mainly seen in extracranial systemic diseases, including most metabolic encephalopathies and toxic encephalopathies, but it is also seen in a few intracranial diffuse diseases, such as diffuse axonal injuries, epileptic status quo, hypertensive encephalopathies and certain encephalitis. In the differential diagnosis, emphasis should be placed on past medical history, systemic examination, and blood biochemistry and organ function.