Multidedector CT Angiography in brain death diagnosis: How to perform and evaluate?

Transcription

1 Multidedector CT Angiography in brain death diagnosis: How to perform and evaluate? Poster No.: C-0102 Congress: ECR 2014 Type: Authors: Keywords: DOI: Educational Exhibit H. Sahin, Y. Pekcevik; Izmir/TR Hemodynamics / Flow dynamics, Computer Applications-3D, CT- Angiography, Neuroradiology brain /ecr2014/C-0102 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 24

2 Learning objectives Review the imaging protocols of multidedector CT angiography in diagnosis of the brain death Review the evaluation of the criteria and scoring systems in diagnosis by multidedector CT angiography according to the basis of literature findings Show the merits and discuss difficulties in interpretation. Background Deep coma and absence of brain stem reflexes are the major clinical criteria of brain death diagnosis. In specific situations ancillary tests are procured [1]. These are: Inability to complete the clinical examination Toxic drug levels Inconclusive apnea testing Normal neuroimaging Chronic CO 2 retention. Hemodynamic instability or hypoxia can make apnea testing challenging and potentially dangerous. Also, in the presence of confounding factors that could influence the exam (e.g. sedative medications, electrolyte disturbances, acid-base disorders) or that make the examination severely difficult to test (e.g., severe facial or orbital trauma), confirmatory tests are required [2]. On the other hand, in many countries, after clinical evaluation, a confirmatory test demonstrating lack of cerebral function or circulation is obligatory. Confirmatory ancillary testing is also required for infants less than one yearold [3]. In some countries, ancillary tests are used to reduce the observational period for optimization of transplant organ viability [4]. Confirmatory tests can be classified into two categories: Confirmation of loss of electrical activity (electroencephalography or somatosensory-evoked potentials) Demonstration of loss of cerebral blood flow (conventional four vesselcerebral angiography, multidedector CT angiography, CT perfusion, transcranial doppler ultrasonography or cerebral perfusion scintigraphy). Page 2 of 24

3 In general, absence of cerebral blood flow is accepted as a definite sign of brain death [4] ( Fig. 1 on page 3, Fig. 2 on page 4). When intracranial pressure exceeds the systemic arterial pressure of the patient, cerebral circulation arrest occurs leading to brain death. Among cerebral blood flow tests, CT angiography is noninvasive, easily accessible, operator-independent, highly specific and sensitive technique, so it emerges as a viable alternative to other tests. However, an international consensus about the use and the parameters of this technique is currently not established. In the literature, different imaging protocols and evaluation criteria are proposed in the reports. We review CT angiography imaging protocols, evaluation criteria in brain death diagnosis and the scoring systems in use on the basis of recent literature. Images for this section: Page 3 of 24

4 Fig. 1: Middle cerebral arteries are not filling although both external carotid arteries and superficial temporal arteries are opacified. This patient was diagnosed as brain death both clinically and radiologically. Page 4 of 24

5 Fig. 2: None of the intracranial arterial vessels are filling although external cerebral arteries and cervical segments of internal carotid arteries are filling. This patient was diagnosed as brain death both clinically and radiologically. Page 5 of 24

6 Findings and procedure details Preconditions: Clinical examination must confirm brain death at least 6 hour before referring the patient for CT angiography [5]. Mean arterial pressure should be hold above 60 mm Hg or systemic arterial pressure above 100 mm Hg during the entire examination in order to prevent false positive tests. In the presence of diseases that cause decreased right heart filling or severe carotid artery stenoses, patient experiences episodes of reduced mean arterial pressure. Afterwards, relatively elevated intracranial pressure could reduce or delay contrast arrival into the intracranial vasculature. Therefore, extra cerebral conditions reducing intracranial blood flow must be known for correct interpretation. Scanning protocol: A multislice CT scanner is preferred for better resolution, good quality reconstructions and to decrease pitfalls due to motion artifacts. Non-enhanced cranial CT scan: Axial images with mm thickness, coronal-sagittal reconstructions to evaluate intracranial pathology and as a reference scan for comparison of following contrast enhanced scans. Arterial phase CT angiography: After injection of ml nonionic contrast media with concentration of mg/ml from an antecubital vein or central venous catheter at a rate of ml/sec with power injector, spiral scan is taken from carotid bifurcation (preferentially from C6 vertebra) to vertex 20 sec. after start of contrast. Welschehold et al. performed arterial scan 5 sec. after opacification of the common carotid artery of more than 150 HU in their study [5]. Axial images with mm thickness reconstructed with a maximum of 2.0 mm increments. Venous phase CT angiography: At 60 sec. after contrast injection or 55 sec. after starting the second scan, spiral CT is taken using the same parameters in the second scan. Evaluation: Correct contrast application is demonstrated by intense opacification of CCA, ECA and superficial temporal artery in arterial phase series ( Fig. 1 on page 8, Fig. 2 on page 9). Page 6 of 24

7 There is not an international consensus or guideline about which arteries and veins should be evaluated in diagnosis of brain death. Mainly used evaluation criteria in reports in the literature are written below. 7- point scoring system: Absence of opacification of both MCA- M4 segments, both ACA-A3 segments, both internal cerebral veins and great cerebral vein of Galen [6]. One point is given for each non-opacified vessel. 4- point scoring system: Absence of opacification of both MCA- M4 segments and both internal cerebral veins [7]. One point is given for each non-opacified vessel. The absence of internal cerebral veins is the most sensitive and earliest sign according to Frampas et al [7]. But evaluating internal cerebral veins is not always easy ( Fig. 3 on page 10, Fig. 4 on page 11). According to Welcshehold et al: Absence of opacification of both MCA- M4 segments, both ACA-A3 segments, basilar artery and both PCA-P2 segments in arterial scanning series and absent venous blood return in both internal cerebral veins in venous scanning series is indicative for intracranial circulatory arrest [5]. They proposed that the use of CT angiography for determination of brain death without evaluation of the posterior circulation is incomplete and inconsistent with other established brain perfusion tests. So they added basilar artery and PCA-P2 segment in their evaluation criteria. For all criteria above, there must be lack of enhancement in all related vessels. If scores are less than the maximum point, than a complementary CT angiography or another confirmatory ancillary test is recommended. Debates: Apart from evaluation of specific vessels and scoring systems, debate occurs in interpretation of the scanning phases. Several authors assessed intracranial circulatory arrest in arterial [6, 8, 9, 10], others in venous phases [7, 11, 12]. Berenguer et al. proposed that there is no utility in obtaining a delayed venous phase CT angiography since delayed blood flow is from collaterals and is not significant [9]. According to Welschehold et al. analysis of arterial vasculature should be carried out in the arterial scanning phase and of deep venous system in the venous phase [5]. Evaluation of brain death in venous phase represents no improvement in diagnostic safety but results only in a severe reduction in sensitivity. Another problem with CT angiography is detection of cerebral blood flow in some brain death patients. This occurs in patients whose skull is open, because of multiple skull fractures, ventricular drainage or decompressive Page 7 of 24

8 craniectomy [8] ( Fig. 5 on page 12, Fig. 6 on page 13, Fig. 7 on page 14, Fig. 8 on page 15, Fig. 9 on page 16). It may also be seen in patients with anoxia following cardiac arrest causing false negative interpretation. The main reason for the presence of cerebral blood flow is that the intracranial perfusion pressure does not exceed the cerebral perfusion pressure. Slow propagation of contrast media from the arterial to the venous scanning (due to diffusion and heartbeat driven slow propagation of contrast agent in arterial system), opacification of MCA-M1 segment and proximal segments of ACA (due to stasis filling) ( Fig. 10 on page 17, Fig. 11 on page 18, Fig. 12 on page 19), opacification of superior sagittal sinus or transverse sinus (due to scalp blood flow of ECA via bridging veins or meningeal vessels into the sagittal sinus) ( Fig. 13 on page 20, Fig. 14 on page 21) does not indicate true cerebral blood flow and does not contradict the brain death diagnosis [5]. Images for this section: Page 8 of 24

9 Fig. 1: Middle cerebral arteries are not filling although both external carotid arteries and superficial temporal arteries are opacified. This patient was diagnosed as brain death both clinically and radiologically. Page 9 of 24

10 Fig. 2: None of the intracranial arterial vessels are filling although external cerebral arteries and cervical segments of internal carotid arteries are filling. This patient was diagnosed as brain death both clinically and radiologically. Page 10 of 24

11 Fig. 3: Non-enhanced CT scan of a patient with frontal bone fracture and cerebral herniation. Note the severe displacement of central structures. Page 11 of 24

12 Fig. 4: Venous phase CT scan of the patient in figure 3. Left internal cerebral vein and great cerebral vein of Galen are opacified but it is hard to evaluate right internal cerebral vein. Left MCA-M4 segments are also opacified. Although clinically evaluated as brain death, diagnosis was not confirmed by CT angiography in this patient. Page 12 of 24

13 Fig. 5: Non-enhanced CT scan of a patient with decompressive craniotomy. He was clinically evaluated as brain death. Page 13 of 24

14 Fig. 6: Arterial phase CT scan of the patient in figure 5. Cortical segments of left MCA show contrast enhancement but same segments of right MCA are not opacified. This finding was evaluated as a pitfall due to craniotomy and CT angiography was interpreted as brain death. Page 14 of 24

15 Fig. 7: Non-enhanced CT scan of a patient with large craniectomy defect, cerebral herniation, subarachnoid hemorrhage and diffuse brain infarction. Page 15 of 24

16 Fig. 8: Arterial phase CT scan of the patient in figure 7. M1 and M2 segments of right MCA show contrast enhancement but same segments of left MCA are not intensely opacified. Page 16 of 24

17 Fig. 9: Venous phase CT scan of the patient in figure 7. Some of the cortical segments of the right and left MCA show contrast enhancement. Although clinically evaluated as brain death, diagnosis could not be confirmed by CT angiography in this patient. Page 17 of 24

18 Fig. 10: Non-enhanced CT scan of a patient with clinical diagnosis of brain death. There is hematoma in left frontal lobe. Page 18 of 24

19 Fig. 11: Arterial phase CT scan of the patient in figure 10. Intracranial vessels are not opacified. Both ECA and superficial temporal artery have intense opacification. Page 19 of 24

20 Fig. 12: Venous phase CT scan of the patient in figure 10. Left MCA-M1 segment and A1- A2 segments of ACA are opacified in late venous phase due to slow contrast propagation. This finding did not contradict brain death diagnosis. Note that cortical branches of both MCA are not opacified. CT angiography confirmed brain death in this patient. Page 20 of 24

21 Fig. 13: Non-enhanced CT scan of a patient with clinical diagnosis of brain death. There is small hemorrhage in anterior and posterior interhemispheric fissure and diffuse cerebral infarction. Page 21 of 24

22 Fig. 14: Venous phase CT scan of the patient in figure 13. Superior sagittal sinus is opacified although none of the intracranial arteries show opacification. This patient was evaluated as brain death both clinically and radiologically. Page 22 of 24

23 Conclusion CT angiography is a fast accessible confirmatory test in brain death diagnosis. Lower invasiveness, wider availability, lower operator dependence, greater rapidity and ability to evaluate patients in the presence of central nervous system depressants are the advantages of this test. But its evaluation is not easy and sometimes confusing. Standardized imaging protocols and new well established criteria are necessary for image analysis. Personal information Hilal Sahin, M.D. Department of Radiology, Tepecik Training and Research Hospital, Izmir, Turkey Yeliz Pekcevik, M.D. Department of Radiology, Tepecik Training and Research Hospital, Izmir, Turkey References 1. Greer DM, Varelas PN, Haque S, Wijdicks EFM. Variability of brain death determination guidelines in leading US neurologic institutions. Neurology 2008;70: Greer DM, Strozyk D, Schwamm LH. False positive CT angiography in brain death. Neurocrit Care 2009;11: Jan MM. Brain death criteria. Neurosciences 2008;13: Karantanas AH, Hadjigeorgiou GM, Paterakis K, Sfiras D, Komnos A. Contribution of MRI and MR angiography in early diagnosis of brain death. Eur Radiol 2002;12: Welschehold S, Kerz T, Boor S, Reuland K, Thömke F, Reuland A, Beyer C, Wagner W, Müller-Forell W, Giese A. Detection of intracranial circulatory arrest in brain death using cranial CT-angiography. Eur J Neurol. 2013;20: Page 23 of 24

24 6. Dupas B, Gayet-Delacroix M, Villers D, Antonioli D, Veccherini MF, Soulillou JP. Diagnosis of brain death using two-phase spiral CT. AJNR Am J Neuroradiol 1998;19: Frampas E, Videcoq M, de Kerviler E, Ricolfi F, Kuoch V, Mourey F, Tenaillon A, Dupas B. CT angiography for brain death diagnosis. AJNR Am J Neuroradiol. 2009;30: Escudero D, Otero J, Marqués L, Parra D, Gonzalo JA, Albaiceta GM, Cofiño L, Blanco A, Vega P, Murias E, Meilan A, Roger RL, Taboada F. Diagnosing brain death by CT perfusion and multislice CT angiography. Neurocrit Care 2009;11: Berenguer CM, Davis FE, Howington JU. Brain death confirmation: Comparison of computed tomographic angiography with nuclear medicine perfusion scan. J Trauma 2010:68; Qureshi AI, Kirmani JF, Xavier AR, Siddiqui AM. Computed tomographic angiography for diagnosis of brain death. Neurology 2004;62: Quesnel C, Fulgencio J-P, Adrie C, Marro B, Payen L, Lembert N, Metaoua SE, Bonnet F. Limitations of computed tomographic angiography in the diagnosis of brain death. Int Care Med 2007;33: Leclerc X, Taschner CA, Vidal A, Strecker G, Savage J, Gaurit JY, Pruvo JP. The role of spiral CT for the assessment of the intracranial circulation in suspected brain-death. J Neuroradiol 2006;33: Page 24 of 24