These processes may lead to decreased responsiveness to visual, auditory, and tactile stimulation. They are NOT all or none phenomena. Altered levels of consciousness may be divided into four categories. This is a state of minimally decreased wakefulness where the primary deficit is attention. The patient is easily distracted and has faulty memory, but retains the ability to communicate by verbal or nonverbal means.
Drowsiness is prominent.
Communication is partially preserved. Stupor is clinically equivalent to deep physiologic sleep from which the patient can be partially or only temporarily aroused, and only by vigorous and repeated stimulation. Communication is minimal or nonexistent. Coma can be defined as a reduction in neuronal function resulting from disruption of cerebral cortical or brain stem integrity. This is a state of unarouseable unresponsiveness in which the patient lies without spontaneous movement with the eyes closed.