[The first 24 hours - the unconscious patient from the neurologist's viewpoint]

About 50 % of non-traumatic impairments of consciousness are caused by primary cerebral diseases such as epilepsy, intracerebral hemorrhage or meningoencephalitis. In addition to primary cerebral conditions, internal diseases can also lead to focal neurological symptoms or neuroimaging abnormalities. Anamnestic informations, body inspection, clinical neurological examination as well as laboratory and imaging findings have to be added and categorized by a multilevel composition to establish a conclusive diagnosis. Simultaneously therapeutic measures for suspected primary cerebral diseases must be initiated, for example a rapid antibiotic treatment in case of a possible bacterial meningitis. A fast and structured diagnostic approach is crucial for ensuring a good prognosis and helps to miss relevant diagnostic steps. Potential diagnostic and therapeutic pitfalls must be kept in mind.