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MR Imaging in Brain Death: What a Radiologist need to know
SAMEER VYAS, PARAMJEET SINGH, NIRANJAN KHANDELWAL
DEPARTMENTS OF RADIODIAGNOSIS AND IMAGING
POSTGRADUATE INSTITUTE OF MEDICAL EDUCATION AND RESEARCH
CHANDIGARH, INDIA
Disclosures
Authors do not have any conflict of interest to disclose?
Or
None to disclose
PURPOSE
Brain death: Irreversible cessation of physiological
function of the brain and brainstem.
 Diagnostic criteria (Clinical) established by the
American Academy of Neurology include:
1.
Coma or unresponsiveness
2.
Absence of brainstem reflexes
3.
Apnea
Limitations:
1.
Considerable variability in adherence to published guidelines
and clinical practice for diagnosing brain death.
2.
The guidelines are opinion-based and alternative protocols
may be equally informative.
Wijdicks et al, Neurology 2010;74;1911-1918
PURPOSE
Ancillary tests currently used in clinical practice for
the diagnosis of brain death include:
1.
Electroencephalography (EEG)
2.
Cerebral angiography
3.
Nuclear medicine radionuclide scanning
4.
Trans Cranial Doppler ultrasonography
5.
CT Angiography
6.
MRI/MR Angiography.
Role of Ancillary tests:
1.
When clinical criteria cannot be applied
2.
To supplement the clinical examination in children.
PURPOSE
MRI:
1. Ancillary tool in the diagnosis of brain death but
imaging findings are not substitute for clinical
diagnosis of brain death.
2. No single MR imaging finding is specific for brain
death
Our purpose:
To delineate the common and important MRI findings
that provide an early diagnosis of brain death which
is particularly useful in preserving organ viability for
transplant and prognostication at the earliest.
Methods
 We reviewed MRI findings in five cases clinically
diagnosed as brain death who underwent Brain MRI
evaluation.
 We evaluated:
 Conventional brain sequences (T2- and T1weighted imaging, FLAIR)
 Advanced MRI sequences like susceptibility
weighted imaging (SWI), diffusion weighted
imaging (DWI) and MR angiography (MRA).
Common causes of Brain death
1. Brain trauma
2. Subarachnoid haemorrhage
3. Intra-cerebral haemorrhage
4. Hypoxic-ischemic encephalopathy
5. Ischemic stroke
IMAGING FINDINGS
MRI findings for brain death described in the
literature includes:
1. Tonsillar herniation
2. Absent intracranial vascular flow void in both
conventional MRI and MRA
3. Diffuse cortical high signal intensity and swelling of
the cerebral sulci on T2WI
4. Prominent superior ophthalmic veins
5. Diffuse hemispheric hyperintensities on DWI.
IMAGING FINDINGS
cont.
MRI findings for brain death described in the
literature includes:
6. Diffusion restriction of cortex due to cytotoxic edema
7. Hyperintensity of the substantia nigra
8. Subependymal diffusion restriction
9. Transcerebral vein and bilateral cortical vein sign
10. Basal ganglia hyperintensity and hemorrhage
1. Tonsillar herniation
 Increased intracranial
pressure and cortical
swelling → the
supratentorial structures
pushed down → tonsillar
herniation through
foramen magnum.
 One of the most
consistent finding
T1 weighted sagittal image shows tonsillar
herniation and sagging brainstem
2. Absent intracranial vascular flow void
 Diffuse brain edema →
Increased intracranial
pressure higher than
mean arterial pressure →
Non-filling phenomenon.
 One of the most
consistent finding.
T2 weighted axial image of shows absence
of b/l ICA vascular flow voids (yellow
arrows),
2. Absent intracranial vascular flow void cont.
Time of flight (TOF) MR Angiography
maximum intensity projection images
showing absence of flow related
enhancement in intracranial
circulation with opacification of both
external carotid artery branches
Contrast enhanced MR Angiography images
showing absence of flow related enhancement
in intracranial circulation with opacification of
both cervical internal carotid arteries and
external carotid artery branches
3. Swollen cortical gyri with diffuse
cortical high signal intensity
 Increased intracranial pressure and cortical swelling
T2-weighted and FLAIR axial image of shows cortical hyperintensity
with swelling and effacement of sulci
4. Absent intracranial venous flow and
Prominent superior ophthalmic veins
MR Venography shows absent flow in
superior sagittal sinus, left transverse
sinus, left sigmoid sinus, and internal
jugular veins.
T1W FS coronal postcontrast image
shows prominent superior ophthalmic
veins (blue arrows).
5. Diffuse hemispheric hyperintensities
on DWI
Diffusion weighted images (DWI, with b=1000) and apparent diffusion
coefficient (ADC) axial image of shows diffuse hyperintensity (arrows)
6. Diffusion restriction of cortex due to
cytotoxic edema
Diffusion weighted images (DWI, with b=1000) and apparent diffusion
coefficient (ADC) axial image of shows cortical hyperintensity (arrows)
7. Hyperintensity of the substantia nigra
Hyperintensity of the substantia nigra (arrows)
8. Subependymal diffusion restriction
Diffusion weighted images (DWI, with b=1000) and apparent diffusion
coefficient (ADC) axial image subependymal diffusion restriction (arrows),
9. Transcerebral and cortical vein sign
Susceptibility weighted imaging (SWI) shows bilateral transcerebral
(yellow arrows) and cortical vein ( red arrow) signs.
9. Transcerebral and cortical vein sign cont.
 Result of increase in deoxygenated blood and ischemia
induced vasodilator release.
 Transcerebral vein sign: Prominent deep medullary
veins and seen as multiple and branching structures
extending through the cerebral hemisphere parallel or
perpendicular to the outer wall of both lateral ventricles
 Cortical vein sign: Visualization of both cerebral
hemisphere cortical veins.
Similar imaging findings observed in acute stroke,
subarachnoid hemorrhage, cortical vein thrombosis,
vascular malformations and patients under general
anesthesia.
10. Hyerintensity of the basal ganglia
Hyperintensity of the basal ganglia.
Learning objectives
 No internationally accepted specific diagnostic criteria for
brain death despite having legal provision for it in most
countries.
 Role of Ancillary tests:
1. When clinical criteria cannot be applied
2. To supplement the clinical examination in children.
MRI
1. Very useful ancillary tool in the diagnosis of brain death
2. As a conjunct to the clinical criteria in equivocal cases.
3. Radiologist should aware of common and described
findings of brain death for early diagnosis.
CONCLUSION
The consistent and commonest findings in brain death
in MRI:
1. Tonsillar herniation.
2. Absence of cerebral flow voids
DWI findings:
1. Subependymal diffusion restriction
2. Diffuse hemispheric hyperintensities
SWI findings:
1. Transcerebral vein sign
2. Cortical vein signs
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2. Hermier M, Nighoghossian N, Derex L, Adeleine P, Wiart M,
Berthezène Y, et al. Hypointense transcerebral veins at T2*weighted MRI: a marker of hemorrhagic transformation risk in
patients treated with intravenous tissue plasminogen activator. J
Cereb Blood Flow Metab 2003;23:1362-70.
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imaging of hyperacute subarachnoid and intraventricular hemorrhage
at 3T: a preliminary report of gradient echo T2*- weighted sequences.
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Contribution of MRI and MR angiography in early diagnosis of brain
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cont.
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Sohn CH, Lee HP, Park JB, Chang HW, Kim E, Kim E, Park UJ, Kim
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Radiol. 2012; 13: 541-9.
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Wijdicks EFM, Varelas PN, Gronseth GS, Greer DM. Evidencebased guideline update: Determining brain death in adults: Report
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Neurology. Neurology 2010;74;1911-918