Delirium: a disorder of consciousness?

Abstract

Delirium is recognised as a disorder of consciousness, however, no evidence has been previously generated to specifically address this premise. In order to evaluate this established notion, we have attempted to review consciousness, the components of consciousness and the emerging evidence for neuroanatomical correlates and then relate this to the recognized features of delirium. We have established that the level of awareness is modulated by alertness and arousal, focused by attention and has the ability to switch between the personal resonances of the experience to the precision of cognition. We have discussed consciousness's relationship with delirium and how the degree of integration of CNS function is mandatory for realisation of higher order function and this has implications for the conceptualisation and management of delirium. We have explored the understanding of downstream, components of consciousness as not giving rise to the full condition of delirium but as a subsyndromal state. We have argued that there is a need for future diagnostic criteria, such as DSM-V, to operationalize disturbance of consciousness together with non-cognitive manifestations of delirium. Intervention studies in delirium have focussed on drugs that improve memory (cholinesterase inhibitors). If memory is only one element of consciousness then we reason instead on evaluating the determinants of consciousness that may be modifiable, such as awareness. Reinforcement of environmental awareness by managing a patient within a low stimulus or familiar surrounding may therefore offer a therapeutic intervention. Overall there seemed support for, or no evidence against, the belief that delirium is a disorder of consciousness. From Descartes 'I think therefore I am' we can say 'I am aware not therefore delirious I am'.