Xe/CT cerebral blood flow evaluation of delayed symptomatic cerebral ischemia after subarachnoid hemorrhage.

PURPOSE We examined the xenon/CT method of measuring cerebral blood flow in assessing the location, pattern of onset, and severity of delayed cerebral ischemia. PATIENTS AND METHODS Fourteen patients with delayed neurologic deficits due to ischemia were selected from a group of 66 patients with subarachnoid hemorrhage. All blood flow studies were performed within 12 hours of deterioration and at regular intervals during medical management. RESULTS In 10 of the 14 patients, noncontrast CT did not identify a cause for deterioration, whereas the blood flow study revealed diminished flow values. Location of blood flow reduction was variable. In five of the 14 patients, blood flow reduction was closely related anatomically to the vessel of aneurysm origin. In another three, blood flow reduction was anatomically remote to the vessel of origin. The remaining six experienced local and remote cerebral blood flow reduction. Six of 14 patients suffered sudden, devastating deterioration, refractory to therapy and associated with blood flow of 15 cc/100 g.min or less, resulting in local or widespread infarction. The remaining eight had less severe blood flow reduction and did not infarct those territories. CONCLUSIONS Vasospasm can affect remote vessels as severely as local vessels and can affect remote vessels alone. Diminished cerebral blood flow correlated closely with clinical vasospasm in this group of patients. Xenon/CT cerebral blood flow studies can identify tissue at risk of infarction when CT is normal.