A mental condition in which a patient experiences neurological symptoms or deficits that occur unconsciously and involuntarily, without an injury or other physical condition as an underlying cause.  Some researchers think it develops as a way for a person’s brain to deal with emotional strife by converting emotional and psychological stress into a physical response.  Symptoms usually develop suddenly and are almost always triggered by emotional distress or other mental disorders.  A person may experience symptoms such as temporary blindness, tunnel vision, paralysis, loss of voice, loss of sense of smell or touch, tingling sensations, coordination disturbances, impaired or jerky movements, or other symptoms affecting the nervous system.