MR Imaging in Brain Death: What a Radiologist need to know eEdE#: eEdE-15 (Shared Display) 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: Coma or unresponsiveness Absence of brainstem reflexes Apnea Limitations: Considerable variability in adherence to published guidelines and clinical practice for diagnosing brain death. 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: Electroencephalography (EEG) Cerebral angiography Nuclear medicine radionuclide scanning Trans Cranial Doppler ultrasonography CT Angiography MRI/MR Angiography. Role of Ancillary tests: 1. When clinical criteria cannot be applied 2. To supplement the clinical examination in children.

PURPOSE MRI: Ancillary tool in the diagnosis of brain death but imaging findings are not substitute for clinical diagnosis of brain death. 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 T1- weighted imaging, FLAIR) Advanced MRI sequences like susceptibility weighted imaging (SWI), diffusion weighted imaging (DWI) and MR angiography (MRA).

Common causes of Brain death Brain trauma Subarachnoid haemorrhage Intra-cerebral haemorrhage Hypoxic-ischemic encephalopathy Ischemic stroke

IMAGING FINDINGS MRI findings for brain death described in the literature includes: Tonsillar herniation Absent intracranial vascular flow void in both conventional MRI and MRA Diffuse cortical high signal intensity and swelling of the cerebral sulci on T2WI Prominent superior ophthalmic veins Diffuse hemispheric hyperintensities on DWI.

IMAGING FINDINGS cont. MRI findings for brain death described in the literature includes: Diffusion restriction of cortex due to cytotoxic edema Hyperintensity of the substantia nigra Subependymal diffusion restriction Transcerebral vein and bilateral cortical vein sign 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 Very useful ancillary tool in the diagnosis of brain death As a conjunct to the clinical criteria in equivocal cases. 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: Tonsillar herniation. Absence of cerebral flow voids DWI findings: Subependymal diffusion restriction Diffuse hemispheric hyperintensities SWI findings: Transcerebral vein sign Cortical vein signs

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