1. EP- 41 - Discordance of CTA and Digital Subtraction Angiography in Diagnosing Vasospasm Following Subarachnoid Hemorrhage ASNR 53 rd Annual Meeting – April 25-30, 2015 Thomas R. Williams, MD Jason W. Allen, MD, PhD Ryan P. Beck, MD Frank C. Tong, MD Seena Dehkharghani, MD Department of Radiology and Imaging Sciences Division of Neuroradiology

2. Disclosures The authors have no relevant disclosures.

3. Background  Vasospasm is a leading cause of morbidity and mortality in patients surviving aneurysmal subarachnoid hemorrhage (aSAH).  Prevalence of vasospasm approaches 70% in the first two weeks following aSAH.

4. Background  Digital subtraction angiography (DSA) is the gold standard for the diagnosis of vasospasm.  DSA is invasive, time-intensive, and not widely available.  CT Angiography (CTA) is an attractive alternative to DSA given non-invasive nature, speed of the exam, and ubiquitous availability.

5. Purpose  The purpose of this study is to analyze the degree of concordance between CTA and DSA in the diagnosis of vasospasm in patients with aSAH.

6. Materials and Methods  Two board-certified neuroradiologists reviewed the head CTAs of 15 patients with aSAH and a clinical concern for vasospasm.  Arteries were scored for vasospasm on a four point scale.  0 = none1 = mild  2 = moderate3 = severe

7. Materials and Methods  Each vasospasm score was also assigned a degree of confidence in the diagnosis.  Low or high confidence  The following arteries were scored in each case:  Bilateral supraclinoid ICAs, bilateral A1 ACA segments, bilateral distal ACAs, bilateral M1 MCA segments, bilateral distal MCAs, bilateral PCAs, and basilar artery.

8. Materials and Methods  Neurointerventionalist subsequently and independently analyzed the DSAs on this same set of patients.  DSAs were obtained within 8 hours of the respective CTA.  The same scoring system and confidence ratings were used.  Statistical analysis of the concordance between the interpretations of the CTAs and DSAs was then calculated.

9. Results  Agreement in the score of vasospasm on CTA and DSA was seen in 45% (88 of 195) of the vessels scored.  Scores on CTA and DSA were discordant by one point in 27% (53 of 195) of the vessels scored, and by two or more points in 28% (54 of 195) of the vessels scored.

10. Results  99% of scores on DSA given a score of high confidence.  By contrast, 75% of scores on CTA given a score of high confidence.  No trend towards overestimation or underestimation of vasospasm on CTA identified.

11. Results DSA and CTA images of one patient following aSAH. Vasospasm in the basilar artery was scored as mild on the DSA, while it was scored having focal severe vasospasm on the CTA. Both scores were given a high degree of confidence.

12. Results DSA and CTA images of another patient. Vasospasm in the basilar artery was scored as moderate on the DSA and severe on the CTA. Both scores were given a high degree of confidence.

13. Results DSA and CTA images of a third patient showing concordance between DSA and CTA with both showing focal severe vasospasm of the left A1 segment. Both scores were again given a high degree of confidence.

14. Conclusions  CTA has high reported rate of concordance with DSA, 93%, in the detection of cerebral aneurysms.  In this study, the concordance between CTA and DSA in the evaluation of vasospasm is much lower.

15. Conclusions  The lower concordance between CTA and DSA in vasospasm is believed to be secondary to multiple patient and modality-specific factors, which are more easily controlled with DSA, including:  Poor contrast bolus  Patient motion/compliance  Venous contamination  Artifact from coil/clip material  Artifact from adjacent blood products

16. References  Chappell ET, Moure FC, Good MC. Comparison of computed tomographic angiography with digital subtraction angiography in the diagnosis of cerebral aneurysms: a meta-analysis. Neurosurgery 2003:52:631-641.  Diringer MN. Management of aneurysmal subarachnoid hemorrhage. Crit Care Med 2009:37:432-440.  Wintermark, M, Ko NU, Smith WS, et al. Vasospasm after subarachnoid hemorrhage: utility of perfusion CT and CT angiography on diagnosis and management. Am J Neuroradiol 2006:27:26-34.