Delayed cerebral ischemia
Delayed cerebral ischemia (DCI) is a frequent complication of subarachnoid hemorrhage. It contributes substantially to the morbidity and mortality following subarachnoid hemorrhage. It is defined as symptomatic vasospasm related to subarachnoid hemorrhage or cerebral infarction demonstrated on imaging felt to be attributable to vasospasm .
DCI is demonstrated radiologically in up to 40-60% of patients .
Although vasospasm is thought of as the main cause of DCI, other etiologies have been proposed since areas of acute cerebral infarction have been identified following subarachnoid hemorrhage despite mild or absent vasospasm . Hypovolemia, especially in the settings of dysfunctional vascular autoregulation, and iatrogenic etiologies (damage to arteries following embolization or clipping) have been proposed as potential causes.
DCI presents clinically as new focal neurological deficits or altered consciousness felt to be attributable to ischemia in the setting of vasospasm .
Typical features of acute cerebral infarction are seen on CT-scan and/or MRI. Vasospasm is also often seen on CTA, MRA or DSA. The two most common patterns are single cortical infarct (40%) and multifocal infarcts (often bilateral) distal to the ruptured aneurysm (50%) .