CT angiography as a confirmatory test in diagnosis of brain death: comparison between three scoring systems

PURPOSE

Computed tomography (CT) angiography emerges as a viable alternative technique for confirmation of brain death. However, evaluation criteria are not well established for demonstration of cerebral circulatory arrest. This retrospective study aimed to evaluate CT angiography scoring systems in diagnosis of brain death, review the literature, and compare interobserver agreement between different scales for the diagnosis of brain death.

METHODS

CT angiography examinations of 25 patients with a clinical diagnosis of brain death were reevaluated according to 10-, 7-, and 4-point scales. Exams were performed with a 64-slice CT scanner including unenhanced, arterial (20 s) and venous phase (60 s) scans. Subtraction images of both phases were obtained. Interobserver agreement was evaluated for the assessment of vessel opacification and diagnosis of brain death.

RESULTS

According to 10-, 7-, and 4-point scales; 13, 16, and 22 of 25 patients had full score, respectively. Using the clinical exam as the reference standard, sensitivities obtained for 10-, 7-, and 4-point scales were 52%, 64%, and 88%, respectively. Percent agreement between readers was 100% for 10- and 7-point scales and 88% for 4-point scale. Percent agreement for opacification of scale vessels was equally high for all three scales (93.6%, 93.7%, 91% for 10-, 7-, and 4-point scales, respectively).

CONCLUSION

The 4-point scale appears to be more sensitive than the 10-and 7-point scales in CT angiography evaluation for brain death. Interobserver agreement is high for all three scales when subtraction images are used.Clinical diagnosis of brain death is established by national guidelines and laws in many countries. Deep unresponsive coma, absence of brain stem functions and spontaneous ventilation are principal requisites for diagnosis (1). Guidelines are revised by New York Task Forces in 2011 for determining brain death and represent a broad consensus on clinical evaluation (2). Although clinical criteria are well established, considerable practice variations are found between countries or leading hospitals of the countries such as the number of staff responsible from diagnosis, number of required examinations, observation period between examinations, application of apnea test, and confirmatory tests (3).Confirmatory tests are required in the presence of confounding factors that could influence the exam (e.g., sedative medications, electrolyte disturbances, acid-base disorders) or make the examination severely difficult to test (e.g., severe facial or orbital trauma) (4). In neonates and children, diagnosis of brain death is more complicated and ancillary tests are usually advocated (5–7). On the other hand, a confirmatory test demonstrating lack of cerebral function or circulation is obligatory after clinical evaluation in some countries. Among the ancillary tests demonstrating absence of cerebral blood flow, multidetector computed tomography (CT) angiography emerges as a viable alternative to other tests due to its noninvasiveness, ease of access, lower operator dependence, and greater rapidity (8). However, an international consensus about application and parameters of this technique is currently not established.The CT angiography protocols for diagnosis of brain death differ between studies in the literature. Scanning time of arterial or venous phase is the major difference in applied protocols. Beside this, disparities in scoring systems, evaluation of blood flow phases, specific vessels, and number of vessels may constitute confusing points for radiologists. Also, CT angiography findings in patients with open skull or anoxia following cardiac arrest may cause false negative interpretation (9). In the context of those diversities, diagnosis of brain death by CT angiography may become quite complicated.In the present study, we aimed to retrospectively evaluate CT angiograms of patients with a clinical diagnosis of brain death according to 10-, 7- and 4-point score systems, review the literature, and emphasize the difficulties and confusing points of the diagnosis by previous methods. Interobserver agreement was evaluated for the diagnosis of brain death and opacification of scale vessels by CT angiography.