• Defined as neurological deterioration related to ischaemia (unrelated to treatment of the aneurysm) that persists for one hour and has no other cause
  • The clinical syndrome is of focal neurologic deficits
  • Approximately 25% of patients develop clinical evidence of delayed ischaemia/infarction; of these 25% die as a result. About 10% of the survivors remain permanently disabled
  • Despite a general belief that vasospasm causes delayed cerebral ischemia, there is significant evidence to suggest other factors contributes to pathogenesis:
    • Less than half of patients with proven vasospasm develop DCI
    • DCI does not consistently occur in the territory supplied by vessels undergoing vasospasm and has been reported in its absence
  • Despite this many strategies aimed at treating DCI are developed with the view that vasospasm is the main cause