Also called the Wernicke-Korsakoff syndrome, this uncommon disorder is characterised by mental confusion or DELIRIUM that occurs in combination with an unsteady GAIT, nystagmus (see under EYE, DISORDERS OF), paralysis of the eye muscles and eventually PSYCHOSIS. It is caused by a deficiency of vitamin B1 (THIAMINE – see APPENDIX 5: VITAMINS) which affects the brain and nervous system. It occurs in people with alcohol dependence and in some patients with persistent vomiting. As soon as the condition is diagnosed, it must be treated with large doses of thiamine. Unless the patient has developed symptoms of psychosis, the condition is usually reversible with treatment.