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CTA & Doppler both have low accuracy for predicting delayed ischemia after aneurysmal subarachnoid hemorrhage

Both CT angiography and transcranial Doppler have limited accuracy in detecting cerebral vasospasm and predicting delayed cerebral ischemia (DCI) in patients with subarachnoid hemorrhage (SAH) due to ruptured aneurysm, according to a study published in the inaugural edition of Critical Care Explorations (van der Harst JJ  et al. Transcranial Doppler Versus CT-Angiography for Detection of Cerebral Vasospasm in Relation to Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage Critical Care Explorations 2019; 1;1) “Cerebral vasospasm is frequently present on CT angiography and transcranial Doppler, lacking accurate prediction of DCI or unfavorable outcome after six months,” according to the report by Dr.  Joep van der Harst and colleagues of University of Groningen, The Netherlands.

The prospective study of sub-arachnoid haemorrhage (SAH) included 59 patients with aneurysmal SAH treated at the authors’ neurocritical care unit and neurosurgical ward between 2013 and 2016. At five and ten days, the patients underwent both CT angiography and transcranial Doppler.

The study is the first to directly compare the diagnostic performance of the two tests, which are commonly used for early detection of cerebrovascular spasm (CVS) to detect the “dreaded secondary complication” of DCI. “The optimal screening modality for detecting symptomatic CVS is a matter of debate,” according to the researchers.

On both days, CT angiography showed CVS in at least one vessel in nearly all patients. In contrast, transcranial Doppler showed CVS in less than half of patients. Agreement between the two tests was just 0.47. Sixteen patients had DCI, while 12 patients had unfavorable outcomes at six months. CT angiography was highly sensitive in predicting DCI for prediction of DCI, but it had “extremely low” specificity compared to transcranial Doppler. On day five, accuracy in predicting unfavorable outcomes was 61 percent with transcranial Doppler versus 27 percent with CT angiography.

The results suggest that CVS after aneurysmal SAH is a common finding, and that neither test is an accurate predictor of DCI or unfavorable outcome. “Our study does not support a prominent role of screening with TCD or CTA,” Dr. van der Harst and coauthors conclude. “Detection of CVS that does not become clinically manifest likely leads to overtreatment and prolonged hospital stay.”

Critical Care Explorations 2019;1:1