- 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