A mental disturbance in which the individual is unable to perceive, understand, and think clearly.When a patient’s consciousness becomes clouded he appears to be in a “mental fog” and it is hard to “get through” to him. Every perceptual function—the entire “sensorium”—is impaired. Sights and sounds fail to register, and events that occur around him pass unnoticed. It may be necessary to shout, shake him or repeat questions several times in order to capture attention and get a response. Clouding may be relatively mild, or may occur in extreme degree as in states of somnolence, stupor or coma.Clouding of consciousness may result from physical disturbances, such as infectious diseases or toxic conditions which affect brain functions. In epilepsy, clouded states may precede or follow a convulsive attack; in such cases the dazed reaction is accompanied by deep confusion or excitement, anxiety, and bewilderment. The symptom may also occur in psychogenic disorders. Patients suffering from acute anxiety and tension may become so preoccupied with inner turmoil that external reality cannot impress itself clearly upon them. In dissociative reactions, clouding may serve the unconscious purpose of self-defense against distressing or threatening events. It is a way of excluding these events from awareness and may be followed by complete amnesia for the clouded period.