Dead or alive? New confirmatory test using quantitative analysis of computed tomographic angiography.

BACKGROUND

When clinical examination is not reliable for brain death (BD) diagnosis, the preferred confirmatory test at our institution is nuclear medicine perfusion test (NMPT). Computed tomographic angiography (CTA) has been described as an alternative for BD confirmation. This study was designed to quantitatively analyze CTA, assess its accuracy compared with NMPT, and define set parameters for BD confirmation.

METHODS

This is a prospective clinical study, from 2007 to 2014, evaluating a consecutive series of clinically BD patients (n = 60) and randomly selected control group with normal CTA findings (n = 20). NMPT, used as the reference standard, was performed on all study patients followed immediately by CTA. Assessment of NMPT and quantitative CTA Hounsfield units of the horizontal segment of middle cerebral artery (M1), precommunicating segment of anterior cerebral artery (A1), and basilar artery (BA) was performed.

RESULTS

In the study cohort, 88% demonstrated absence of cerebral blood flow (CBF) on NMPT; however, only 50% demonstrated absence on CTA. Together, 50% had no CBF on NMPT and CTA (Group 1), 38% had no CBF on NMPT but persistent CBF on CTA (Group 2), 12% had persistent CBF on both NMPT and CTA (Group 3). Analysis of variance demonstrated that all groups varied significantly for M1, A1, and BA (p < 0.001). We were able to establish criteria that differentiate persistent CBF on CTA as either preserved cerebral perfusion or stasis filling.

CONCLUSION

We propose that a CTA Hounsfield units less than 80 in M1, A1, and BA is concordant with no CBF on NMPT, therefore indicative of a lack of physiologic cerebral perfusion, and thus allows the confirmation of BD with 97% sensitivity and 100% specificity.

LEVEL OF EVIDENCE: Diagnostic study, level II.