Brain death
- Radiopaedia Australia Pty Ltd and Radiopaedia Events Pty Ltd, Director, Founder and CEO (Radiopaedia) (ongoing)
- Biogen Australia Pty Ltd, Investigator-Initiated Research Grant for CAD software in multiple sclerosis: finished Oct 2021 (past)
Updates to Article Attributes
Brain death refers to the irreversible end of all brain activity and is usually assessed clinically. Radiographic testing may be used as additional support for a clinical diagnosis of brain death, such as when clinical tests are impossible to perform, e.g. facial or ocular trauma, precluding brainstem function assessment.
As the diagnosis of brain death is considered equivalent withto cardiac death in many jurisdictions 4 and it allows organ donation for transplantation or withdrawal of life support, most countries have specific and varied related legal standards and practice guidelines 2,10.
It should be noted that brain death imaging is not synonymous with identifying extensive global hypoxic-ischaemic injury.
Radiographic features
Most imaging tests for brain death rely on the absence of cerebral blood flow as a surrogate for brain death. This can be assessed by a number of modalities including CT, MRI, ultrasoundcatheter angiography, nuclear medicine examinations, and catheterto a lesser degree CT angiography, MRI angiography and ultrasound.
It is important to note that not all modalities and examinations are approved for the legal determination of brain death and that this will vary from country to country.
Ultrasound
WhileFurthermore, it is essential to realise that the absence of brain perfusion implies brain death, but the converse is ultimately a clinical diagnosisnot true. In situations where intracranial pressure is not sufficiently elevated, transcranial Doppler sonography (TCD)used as an ancillary modalityprofound global brain infarction. This is, for example, encountered in patients who have large skull defects (traumatic or iatrogenic e.g. craniectomy for decompression) leading to provide further clinical support by detecting the presence of cerebral circulatory arrest, features of which include:
-
reverberant or oscillating flow in theMCAvessels has been reported812 -
loss or reversal of diastolic flow in the MCA/ICA low acceleration time in the MCA
CT
-
diffusecerebral oedemawith effacement of the grey-white matter borders-
reversal sign(density of cerebellum is greater than cerebral hemispheres) -
pseudosubarachnoid haemorrhagedue to venous congestion in effaced sulci swollen gyri, effaced/narrowed sulci, compressed ventricles/cisterns
-
-
CT angiography:non-opacification of the cortical middle cerebral arteries andinternal cerebral veinsare the most sensitive and specific markers on CTA3
Angiography (DSA)
considered the gold standard imaging test, with near 100% sensitivity and specificity 4,13
no forward flow above the terminal internal carotid arteries
MRI
-
T1: hypointense, with lost grey-white matter differentiation -
T2-
swollen gyri with hyperintense cortexcontrast should be seen in the external carotid artery branches
-
expectednote: flow
may bevoidabsent in vessels
-
-
DWI: hemispheric high signal, severe ADC drop -
MR angiography: may be interpreted similarlyseen up toCT angiography, with non-visualization ofthe supraclinioid internal carotid artery as the ophthalmic artery will continue to flow even if intracranialvessels5,6 -
BOLD: absence of long-range functional connectivity11pressure is very high
Nuclear medicine
Both radionuclide perfusion scintigraphy-SPECT and radionuclide angiography can be employed and have high sensitivity 13.
-
flow images are obtained in the anterior projection; delayed images follow 5 to 10 minutes after the injection
empty light bulb sign: absent intracranial uptake
hot nose sign: increased external carotid artery perfusion to the nasal region (an interesting sign, but of no real diagnostic value) 1
CT
Although CT may demonstrate extensive ischaemic damage (e.g. reversal sign, pseudosubarachnoid haemorrhage, cerebral oedema and herniation) as these are more or less subjective only CT angiography is recognised as a potential alternative to angiography and nuclear medicine studies in some jurisdictions 13-15.
CT angiography relies upon non-opacification intracranial vessels and which vessels are chosen can affect the sensitivity and specificity of the test 15.
It is also cruical to note that the timing of the study is different to a normal diagnostic study where the aim is to image as early as possible during the arterial phase to avoid excessive venous opacification. When intracranial perfusion is abnormal, such a routine study may result in false-positivies 15. Thus it is recommended that CT angiography in this setting is delayed to 60 seconds post injection to allow even the slowest perfusion to be detected 15.
Unfortunately, no generally agreed upon CTA criteria for brain death are available with a variety of point systems and criteria being proposed. Vessles that can be assessed, looking for failure of opacification include 3, 15:
internal carotid artery above the level of the anterior clinoid processes
vertebral arteries after they have entered the dura and basilar artery
cortical branches (M4) of the middle cerebral artery3
Ultrasound
Transcranial Doppler sonography (TCD) has been used as an ancillary modality to provide further clinical support by detecting the presence of cerebral circulatory arrest, although it is not uniformly recognised as a valid alternative. Features include:
reverberant or oscillating flow in the MCA vessels has been reported 8
loss or reversal of diastolic flow in the MCA/ICA
low acceleration time in the MCA
MRI
Altough MRI can demonstrate extensive ischaemic change more accurately than CT, only MR angiography has been proposed as a potential ancillary test for the diagnosis of brain death, using similar criteria to CT angiography 5,6,13,14. Generally, however, MRI is not recommended 14.
-<p><strong>Brain death</strong> refers to the irreversible end of all brain activity and is usually assessed clinically. Radiographic testing may be used as additional support for a clinical diagnosis of brain death, such as when clinical tests are impossible to perform, e.g. <a href="/articles/ocular-trauma">ocular trauma</a>, precluding brainstem function assessment. </p><p>As the diagnosis of brain death is considered equivalent with cardiac death in many jurisdictions <sup>4</sup> and it allows organ donation for transplantation or withdrawal of life support, most countries have specific and varied related legal standards and practice guidelines <sup>2,10</sup>. </p><h4>Radiographic features</h4><p>Most imaging tests for brain death rely on the absence of <a href="/articles/cerebral-blood-flow">cerebral blood flow</a> as a surrogate for brain death. This can be assessed by a number of modalities including CT, MRI, ultrasound, nuclear medicine examinations, and catheter angiography. </p><p>It is important to note that not all modalities and examinations are approved for the legal determination of brain death and that this will vary from country to country. </p><h5>Ultrasound</h5><p>While brain death is ultimately a clinical diagnosis, <a href="/articles/transcranial-doppler-sonography-ultrasound-1">transcranial Doppler sonography (TCD)</a> may be used as an ancillary modality to provide further clinical support by detecting the presence of cerebral circulatory arrest, features of which include:</p><ul>-<li>reverberant or oscillating flow in the <a href="/articles/middle-cerebral-artery">MCA</a> vessels has been reported <sup>8</sup>-</li>-<li>loss or reversal of diastolic flow in the MCA/<a href="/articles/internal-carotid-artery-1">ICA</a>-</li>-<li>low acceleration time in the MCA</li>-</ul><h5>CT</h5><ul><li>diffuse <a href="/articles/cerebral-oedema-1">cerebral oedema</a> with effacement of the grey-white matter borders<ul>-<li>-<a href="/articles/white-cerebellum-sign">reversal sign</a> (density of cerebellum is greater than cerebral hemispheres)</li>-<li>-<a href="/articles/pseudosubarachnoid-haemorrhage">pseudosubarachnoid haemorrhage</a> due to venous congestion in effaced sulci</li>-<li>swollen gyri, effaced/narrowed sulci, compressed ventricles/cisterns</li>- +<p><strong>Brain death</strong> refers to the irreversible end of all brain activity and is usually assessed clinically. Radiographic testing may be used as additional support for a clinical diagnosis of brain death, such as when clinical tests are impossible to perform, e.g. facial or ocular trauma, precluding brainstem function assessment. </p><p>As the diagnosis of brain death is considered equivalent to cardiac death in many jurisdictions <sup>4</sup> and it allows organ donation for transplantation or withdrawal of life support, most countries have specific and varied related legal standards and practice guidelines <sup>2,10</sup>. </p><p>It should be noted that brain death imaging is not synonymous with identifying extensive <a href="/articles/hypoxic-ischaemic-encephalopathy-adults-and-children" title="Global hypoxic-ischaemic injury">global hypoxic-ischaemic injury</a>. </p><h4>Radiographic features</h4><p>Most imaging tests for brain death rely on the absence of <a href="/articles/cerebral-blood-flow-cbf" title="Cerebral blood flow (CBF)">cerebral blood flow</a> as a surrogate for brain death. This can be assessed by a number of modalities including catheter angiography, nuclear medicine examinations, and to a lesser degree CT angiography, MRI angiography and ultrasound.</p><p>It is important to note that not all modalities and examinations are approved for the legal determination of brain death and that this will vary from country to country. </p><p>Furthermore, it is essential to realise that the absence of brain perfusion implies brain death, but the converse is not true. In situations where intracranial pressure is not sufficiently elevated, perfusion can continue to occur even though there may be profound global brain infarction. This is, for example, encountered in patients who have large skull defects (traumatic or iatrogenic e.g. craniectomy for decompression) leading to false negatives <sup>12</sup>.</p><h5>Angiography (DSA)</h5><ul>
- +<li><p>considered the gold standard imaging test, with near 100% sensitivity and specificity <sup>4,13</sup></p></li>
- +<li><p>no forward flow above the terminal <a href="/articles/internal-carotid-artery-1">internal carotid arteries</a></p></li>
- +<li><p>contrast should be seen in the external carotid artery branches</p></li>
- +<li><p>note: flow may be seen up to the supraclinioid internal carotid artery as the ophthalmic artery will continue to flow even if intracranial pressure is very high</p></li>
- +</ul><h5>Nuclear medicine</h5><p>Both radionuclide perfusion scintigraphy-SPECT and radionuclide angiography can be employed and have high sensitivity <sup>13</sup>.</p><ul><li>
- +<p><a href="/articles/cerebral-perfusion">cerebral perfusion</a> <sup>4</sup></p>
- +<ul>
- +<li><p>flow images are obtained in the anterior projection; delayed images follow 5 to 10 minutes after the injection</p></li>
- +<li><p><a href="/articles/empty-light-bulb-sign-brain-death">empty light bulb sign</a>: absent intracranial uptake</p></li>
- +<li><p><a href="/articles/hot-nose-sign">hot nose sign</a>: increased external carotid artery perfusion to the nasal region (an interesting sign, but of no real diagnostic value) <sup>1</sup></p></li>
-</li></ul><ul><li>-<strong>CT angiography:</strong> non-opacification of the cortical middle cerebral arteries and <a href="/articles/internal-cerebral-vein">internal cerebral veins</a> are the most sensitive and specific markers on CTA <sup>3</sup>-</li></ul><h5>Angiography (DSA)</h5><ul>-<li>considered the gold standard imaging test <sup>4</sup>-</li>-<li>no forward flow above the terminal <a href="/articles/internal-carotid-artery-1">internal carotid arteries</a>-</li>-</ul><h5>MRI</h5><ul>-<li>-<strong>T1</strong>: hypointense, with lost grey-white matter differentiation</li>-<li>-<strong>T2</strong><ul>-<li>swollen gyri with hyperintense cortex</li>-<li>expected <a href="/articles/flow-void">flow void</a> may be absent in vessels</li>-</ul>-</li>-<li>-<strong>DWI</strong>: hemispheric high signal, severe ADC drop</li>-<li>-<strong>MR angiography</strong>: may be interpreted similarly to CT angiography, with non-visualization of the intracranial vessels <sup>5,6</sup>-</li>-<li>-<strong>BOLD</strong>: absence of long-range functional connectivity <sup>11</sup>-</li>-</ul><h5>Nuclear medicine</h5><ul><li>-<a href="/articles/cerebral-perfusion">cerebral perfusion</a> <sup>4,7</sup><ul>-<li>flow images are obtained in the anterior projection; delayed images follow 5 to 10 minutes after the injection</li>-<li>-<a href="/articles/empty-light-bulb-sign-brain-death">empty light bulb sign</a>: absent intracranial uptake</li>-<li>-<a href="/articles/hot-nose-sign">hot nose sign</a>: increased external carotid artery perfusion to the nasal region (an interesting sign, but of no real diagnostic value) <sup>1</sup>-</li>-</ul>-</li></ul>- +</li></ul><h5>CT</h5><p>Although CT may demonstrate extensive ischaemic damage (e.g. <a href="/articles/white-cerebellum-sign">reversal sign</a>, <a href="/articles/pseudosubarachnoid-haemorrhage">pseudosubarachnoid haemorrhage</a>, <a href="/articles/cerebral-oedema-1">cerebral oedema</a> and herniation) as these are more or less subjective only CT angiography is recognised as a potential alternative to angiography and nuclear medicine studies in some jurisdictions<sup> 13-15</sup>.</p><p>CT angiography relies upon non-opacification intracranial vessels and which vessels are chosen can affect the sensitivity and specificity of the test <sup>15</sup>.</p><p>It is also cruical to note that the timing of the study is different to a normal diagnostic study where the aim is to image as early as possible during the arterial phase to avoid excessive venous opacification. When intracranial perfusion is abnormal, such a routine study may result in false-positivies <sup>15</sup>. Thus it is recommended that CT angiography in this setting is delayed to 60 seconds post injection to allow even the slowest perfusion to be detected <sup>15</sup>.</p><p>Unfortunately, no generally agreed upon CTA criteria for brain death are available with a variety of point systems and criteria being proposed. Vessles that can be assessed, looking for failure of opacification include <sup>3, 15</sup>:</p><ul>
- +<li><p><a href="/articles/internal-cerebral-vein" title="Internal cerebral veins">internal cerebral veins</a>, <a href="/articles/great-cerebral-vein-1" title="Vein of Galen">vein of Galen</a> and <a href="/articles/straight-sinus" title="Straight sinus">straight sinus</a></p></li>
- +<li><p><a href="/articles/internal-carotid-artery-1" title="Internal carotid artery">internal carotid artery</a> above the level of the anterior clinoid processes</p></li>
- +<li><p><a href="/articles/vertebral-artery" title="Vertebral arteries">vertebral arteries</a> after they have entered the dura and <a href="/articles/basilar-artery" title="Basilar artery">basilar artery</a></p></li>
- +<li><p>cortical branches (M4) of the <a href="/articles/middle-cerebral-artery" title="Middle cerebral artery">middle cerebral artery</a> <sup>3</sup></p></li>
- +</ul><h5>Ultrasound</h5><p><a href="/articles/transcranial-doppler-sonography-ultrasound-1">Transcranial Doppler sonography (TCD)</a> has been used as an ancillary modality to provide further clinical support by detecting the presence of cerebral circulatory arrest, although it is not uniformly recognised as a valid alternative. Features include:</p><ul>
- +<li><p>reverberant or oscillating flow in the <a href="/articles/middle-cerebral-artery">MCA</a> vessels has been reported <sup>8</sup></p></li>
- +<li><p>loss or reversal of diastolic flow in the MCA/<a href="/articles/internal-carotid-artery-1">ICA</a></p></li>
- +<li><p>low acceleration time in the MCA</p></li>
- +</ul><h5>MRI</h5><p>Altough MRI can demonstrate extensive ischaemic change more accurately than CT, only MR angiography has been proposed as a potential ancillary test for the diagnosis of brain death, using similar criteria to CT angiography <sup>5,6,13,14</sup>. Generally, however, MRI is not recommended <sup>14</sup>.</p>
References changed:
- 12. Zampakis P, Panagiotopoulos V, Kalogeropoulou C et al. Computed Tomography Angiography Scoring Systems and the Role of Skull Defects in the Confirmation of Brain Death. Sci Rep. 2021;11(1):15081. <a href="https://doi.org/10.1038/s41598-021-94763-8">doi:10.1038/s41598-021-94763-8</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/34302043">Pubmed</a>
- 13. Drake M, Bernard A, Hessel E. Brain Death. Surg Clin North Am. 2017;97(6):1255-73. <a href="https://doi.org/10.1016/j.suc.2017.07.001">doi:10.1016/j.suc.2017.07.001</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/29132508">Pubmed</a>
- 14. Greer D, Shemie S, Lewis A et al. Determination of Brain Death/Death by Neurologic Criteria. JAMA. 2020;324(11):1078. <a href="https://doi.org/10.1001/jama.2020.11586">doi:10.1001/jama.2020.11586</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/32761206">Pubmed</a>
- 15. Sawicki M, Bohatyrewicz R, Walecka A, Sołek-Pastuszka J, Rowiński O, Walecki J. CT Angiography in the Diagnosis of Brain Death. Pol J Radiol. 2014;79:417-21. <a href="https://doi.org/10.12659/PJR.891114">doi:10.12659/PJR.891114</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/25419255">Pubmed</a>
- 7. Kazerooni EA, JH Austin, WC Black, et-al. ACR-STR Practice Parameter for the Performance and Reporting of Lung Cancer Screening Thoracic Computed Tomography (CT): 2014 (Resolution 4). (2014) Journal of thoracic imaging. <a href="https://doi.org/10.1097/RTI.0000000000000097">doi:10.1097/RTI.0000000000000097</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/24992501">Pubmed</a> <span class="ref_v4"></span>
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