How should we use imaging in the determination of brainstem death?

Abstract

Brainstem death is defined as the “irreversible cessation of brainstem function”, either due to primary intracranial events or extracranial factors such as hypoxia. The importance of accurate and timely diagnosis of brainstem death in critical care should not be understated, as it allows the withdrawal of treatment when it is no longer deemed to beneficial. Additionally, it may facilitate the process of organ donation. Overall, the diagnosis of brainstem death has four common principles across the world: (1) neurological criteria based on clinical assessment; (2) evidence of irreversible brain damage from known aetiology; (3) demonstrating an absence of a reversible cause; and (4) the use of ancillary studies. The latter in particular has been a controversial issue, with much debate continuing on how imaging should be used. We discuss three key questions surrounding the role of imaging in the diagnosis of brainstem death as well as important issues the radiology community should consider.

Computed Tomography Angiography (CTA) in Selected Scenarios with Risk of Possible False-Positive or False-Negative Conclusions in Diagnosing Brain Death

“…In case of persistence of doubt the consultation of an experienced neurologist/neurosurgeon and/or confirmatory testing such as the examination of the cerebral circulation arrest [ 86 , 87 ] and/or the registration of cerebral bioelectrical signals (e.g., evoked potentials [ 88 ], electroencephalogram [ 89 ] are confirmatory options reported in the literature that can be in accordance with the respective national guidelines for BD-diagnosing.…”

The role of neuroimaging in the determination of brain death

“…Due to the regional variation in brain death criteria and the ancillary tests approved for its determination, the use of neuroimaging examinations in this context is controversial. In many countries, it is recommended only in specifi c circumstances, whereas in others it is legally required for the diagnosis ( 15 ) . In most European countries, although the diagnosis of brain death is based on clinical features, neuroimaging has been used prior to defi nitive clinical examination, as a prerequisite to determine whether the imaging alterations are consistent with brain death or the cause of coma ( 16 ) .…”

“…In Brazil, the diagnosis of the lesion responsible for coma must be established by clinical evaluation and confi rmed by neuroimaging or other diagnostic methods ( 17 ) . Standard neuroimaging is of great value in particular clinical scenarios, such as when the neurological evaluation is diffi cult or cannot be performed (e.g., because of multiple facial fractures), when intoxication of any origin cannot be excluded as the cause of coma, when cervical spinal cord injury has occurred or is suspected, and when the clinical picture leads to clinical uncertainty, due to spontaneous or refl ex movements ( 15 ) . Therefore, CT and MRI features associated with brain death can be important for identifying catastrophic brain injury consistent with cerebral circulatory arrest.…”

“…Unenhanced brain CT can provide evidence of irreversible brain damage and of the primary intracranial event that caused brain death ( 15 ) . Because CT is widely available, it is commonly used for the initial examination of comatose patients ( 9 ) .…”

“…Nuclear medicine tests have the advantage of measuring both brain metabolism and blood fl ow. However, scintigraphy and SPECT have some disadvantages, such as logistics problems, their time-consuming nature, and the need to use radiopharmaceuticals that can cross the blood–brain barrier, such as technetium-99m hexamethyl propylene amine oxime and technetium-99m ethyl cysteinate dimer, which may create issues at some facilities, because these radiopharmaceuticals may not be readily available ( 2 , 15 ) . In brain death, scintigraphy and SPECT typically demonstrate no uptake in the brain and cerebellum (the “hollow-skull” sign).…”