Vasospasm after subarachnoid hemorrhage: utility of perfusion CT and CT angiography on diagnosis and management.

PURPOSE: To evaluate the utility of perfusion CT (PCT) combined with CT angiography (CTA) for the diagnosis and management of vasospasm, by using conventional digital subtraction angiography (DSA) as the gold standard.
METHODS: We retrospectively identified 27 patients with acute subarachnoid hemorrhage who had undergone CTA/PCT, DSA, and transcranial Doppler (TCD) ultrasonography within a time interval of 12 hours of one another. The patients' charts were reviewed for treatment of vasospasm. CTA, PCT, TCD, and DSA examinations were independently reviewed and quantified for vasospasm. PCT thresholds, CTA findings, noncontrast CT (NCT) hypodensities, and TCD thresholds were evaluated for accuracy, sensitivity, and specificity, as well as for negative (NPV) and positive predictive values (PPV) in the prediction of angiographic vasospasm and endovascular treatment, considering DSA as the gold standard.
RESULTS: Thirty-five CTA/PCT, TCD, and DSA examinations were performed on these 27 patients. A total of 123 arterial territories in 11 patients demonstrated angiographic vasospasm. Six patients underwent endovascular therapy. CTA qualitative assessment and PCT-derived mean transit time (MTT) with a threshold at 6.4 seconds represented the most accurate (93%) combination for the diagnosis of vasospasm, whereas MTT considered alone represented the most sensitive parameter (NPV, 98.7%). A cortical regional cerebral blood flow value </=39.3 (mL x 100 g(-1)x min(-1)) represented the most accurate (94.8%) indicator for endovascular therapy. PCT had significantly higher PPV (89.9%) than TCD (62.9%).
CONCLUSIONS: A CT survey combining CTA and PCT represents an accurate screening test in patients with suspected vasospasm. However promising, the value of PCT for selecting the best management strategy in such patients will need to be further investigated.