<prompt> True about delirium are all exceptPreserved attentionDisturbed sleepDisorientationHallucination  <response>: Delirium is characterized by an acute decline in both the level of consciousness and cognition with paicular impairment in attention. A life threatening, yet potentially reversible disorder of the central nervous system CNS, delirium often involves perceptual disturbances, abnormal psychomotor activity, and sleep cycle impairment. Reference: Kaplan Sadocks Synopsis of Psychiatry: Behavioral SciencesClinical Psychiatry, 11th Edition, page 697. 