In the practice of a neurologist, neurosurgeon, cases of acute loss of consciousness are often encountered, and of course, there is a question of finding out the cause of loss of consciousness (to differentiate it/and provide timely emergency (urgent) care). An important aspect of the problem is the diagnosis and emergency care of coma of unknown genesis. The purpose of the lecture is to clarify the etiopathogenetic factors that lead to acute disturbance of consciousness syndrome (syncopal and comatose states), differential diagnosis, clinic and emergency care at the pre- and early hospital stages. The lecture highlights the etiopathogenetic mechanisms of loss of consciousness, the development of comatose states, and individual symptoms that indicate damage to the relevant parts of the brain. The general provisions (principles) of providing emergency and urgent medical care at the early stages are presented, which in some cases will allow restoring the functioning of vital organs and systems and saving the patient’s life.