Study: CT perfusion, digital angio similar for detecting cerebral ischemia

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A retrospective study showed that CT perfusion (CTP) and digital subtraction angiography have similar testing characteristics for determining incidences of delayed cerebral ischemia in patients with aneurysmal subarachnoid hemorrhage. The study was published in the September issue of Academic Radiology.

“Cerebral vasospasm is a significant cause of morbidity in patients with aneurysmal subarachnoid hemorrhage (A-SAH), occurring in 20 percent to 50 percent of patients after successful surgical or endovascular treatment of the ruptured aneurysm,” Ronan P. Killeen, MB, of the New York-Presbyterian Hospital in New York City, and colleagues wrote. While the gold standard for vasospasm is arterial narrowing documented by digital subtraction angiography, recently CTP imaging has been used to detect hemodynamic changes that could indicate vasospasm or delayed cerebral ischemia.

Killeen and colleagues set out to compare test characteristics of CTP and DSA for determining delayed cerebral ischemia (DCI) in 57 patients with aneurysmal subarachnoid hemorrhage who were admitted to New York-Presbyterian between December 2004 and December 2008.

Of the 57 study participants, 79 percent were classified as being delayed cerebral ischemic and 21 percent were not. Eighty percent of DCI patients and 33 percent of non-DCI patients had CTP perfusion deficits and 63 percent of the patients had vasospasm detected by digital subtraction angiography.

Killeen and colleagues reported that CTP data showed a significant difference in cerebral blood flow for DCI patients (29.4 mL/100 g/minute) and non-DCI patients (40.5 mL/100 g/minute). The sensitivity, specificity and positive and negative predictive values for CTP were 0.80, 0.67, 0.90 and 0.47, respectively. These same numbers for DSA were 0.73, 0.75, 0.92 and 0.43, respectively.

“DCI is a devastating condition that occurs secondary to A-SAH and contributes to significant morbidity and mortality in this patient population,” the authors wrote. “A diagnosis of DCI is based on clinical criteria for the presence of clinical deterioration not explained by other causes or imaging criteria for new infarction not attributed to the initial hemorrhagic event or postoperative changes.”

Killeen et al noted that the results may be due partly to thresholds clinicians use to manage patients; therefore, they noted that treatment threshold decisions are variable, accounting for clinicians' practice patterns and patient populations.

While the two tests, CT perfusion and digital subtraction angiography, are similar, the authors noted that CTP could be an alternative for critically ill patients due to its availability, faster acquisition time and fewer contraindications. Additionally, CTP has been associated with less adverse events.