Diagnostic Performance of Computed Tomography Angiography and Computed Tomography Perfusion Tissue Time-to-Maximum in Vasospasm Following Aneurysmal Subarachnoid Hemorrhage

Abstract

Background Vasospasm is a treatable cause of deterioration following aneurysmal subarachnoid hemorrhage. Cerebral computed tomography perfusion mean transit times have been proposed as a predictor of vasospasm but suffer from well-known technical limitations. We evaluated fully automated, thresholded time-to-maxima of the tissue residue function (T_max) for determination of vasospasm following aneurysmal subarachnoid hemorrhage. Methods and Results Retrospective analysis of 540 arterial segments from 36 encounters in 31 consecutive patients with aneurysmal subarachnoid hemorrhage undergoing computed tomography angiography (CTA), computed tomography perfusion, and digital subtraction angiography (DSA) within 24 hours. T_max at 4, 6, 8, and 10 s was generated using RAPID (iSchemaView Inc., Menlo Park, CA). Dual-reader CTA and computed tomography perfusion interpretations were compared for patients with and without vasospasm on DSA (DSA+ and DSA-). Logistic regression models were developed using CTA and T_max as input predictors and DSA vasospasm as outcome in adjusted and unadjusted models. Imaging studies from all 31 subjects (mean age 47.3±11.1, 77% female, 65% with single aneurysm with mean size of 6.0±2.9 mm) were included. Vasospasm was identified in 42 segments on DSA and 59 segments on CTA, with significant associations across individual vessel segments (P<0.001). In adjusted analyses, DSA vasospasm was associated with CTA (odds ratio [OR], 2.43; 95% CI, 0.94-6.32; P=0.068) as well as territory-specific T_max>6 seconds delays (OR, 3.57; 95% CI, 1.36-9.35; P=0.009). Sensitivity/specificity for DSA vasospasm was 31%/91% for CTA, 26%/89% for T_max>6 seconds, and 12%/99% for CTA+T_max>6 seconds. Conclusions CTA and T_max offer high specificity for presence of vasospasm; their utility, even in combination, as screening tests is, however, limited by poor sensitivity.

Keywords: angiography; computed tomography angiography; digital subtraction; logistic models; retrospective studies; subarachnoid hemorrhage.

Figure 1. 40‐year‐old woman with coiled ruptured right internal carotid artery (ICA) aneurysm and concordant computed tomography perfusion (CTP), computed tomography angiography (CTA), and digital subtraction angiography (DSA) on posthemorrhage day #9.

Patient was symptomatic at the time of the studies. CTP processed with RAPID demonstrates region of prolonged tissue time‐to‐maximum (T _max)>6 seconds within the right middle cerebral artery (MCA) territory (A). Severe vasospasm involving the right M1 MCA segment (white arrow) on simultaneously obtained CTA (B). Additional moderate‐to‐severe right supraclinoid ICA vasospasm seen on CTA not shown. Moderate‐to‐severe vasospasm of the right supraclinoid ICA and M1 MCA segment (black arrows) on DSA performed 5 hours after CTA (C). Aneurysm coil mass is visible both on CTA and DSA. CBF indicates cerebral blood flow.