Fallibility of Ancillary Testing in Confirmation of Brain Death

Sir, Ancillary tests are necessary or corroborative in declaring brain death depending on the clinical situation and national laws.[1,2] When applying only clinical criteria, it is sometimes difficult to determine the time when testing should be done to ensure that neurologic functions have ceased irreversibly.[3] Ancillary bedside tests may be helpful in such scenario but may occasionally be misleading. We report a case where two ancillary tests confirmed cerebral circulatory arrest (CCA) and electrocerebral silence, while clinically brain stem reflexes persisted. A 30-year-old gentleman was admitted following trauma with a GCS (Glasgow Coma Scale) score of 3/15 and bilateral dilated and nonreacting pupils. He was found to have a left acute subdural hematoma with multiple infarcts in the left hemisphere and severe mass effect [Figure 1a and 1b]. In consultation with the family, no surgical intervention was attempted. He developed diabetes insipidus 8 hours after admission to the ICU (intensive care unit). A transcranial Doppler (TCD) done at this point showed a short systolic wave with reversal of diastolic flow in the middle cerebral arteries (MCA) and vertebral arteries (VA) [Figure 2] bilaterally. He continued to trigger breaths on the ventilator [Figure 3] and had a cough reflex on suction. The TCD blood flow pattern remained suggestive of brain death, and an EEG (electroencephalogram) [Figure 4] at that time also showed no electrical activity. The patient lost his residual brain stem function 20 hours later and was declared brain dead.Figure 1: (a) Uncal herniation. (b) Brain stem compressionFigure 2: Transcranial Doppler showing short systolic spikes with reversal of diastolic flowFigure 3: Persistent spontaneous respiratory effortFigure 4: Electroencephalogram showing elctrocerebral silenceThere is some confusion between the concepts of “whole brain death” as required in the United States and “brain stem death.” Although the process of declaration of whole brain death and brain stem death are identical, there are conceptual differences. Brain stem death is defined as the “irreversible loss of the capacity for consciousness combined with the irreversible loss of the capacity to breathe,” and the patient may continue to have electrocerebral activity and hypothalamic blood flow. Therefore, they are brain stem dead, but not whole brain dead.[4] Whole brain death or total brain failure requires the cessation of function of the entire brain, which in turn requires complicated reasoning to explain the fact that hypothalamic function can persist in a patient in whom whole brain death has been declared. By Indian law, a person is dead if he or she is clinically brain stem dead.[1] Ancillary tests are undertaken when clinical examination of brain stem function cannot be done or completed. Tests to demonstrate the complete cessation of cerebral flow are commonly performed for this purpose. TCD evaluation of the intracranial circulation is a noninvasive, bedside, and easily repeatable investigation that does not require transporting the patient out of the ICU. A meta-analysis by Chang et al.[5] showed a sensitivity of 89% and specificity of 99% for TCD as a tool to confirm brain death. The American Association of Neurology (AAN) has endorsed TCD as a useful adjunct to confirm cerebral circulatory arrest associated with brain death.[6] In accordance with these guidelines for TCD diagnosis of brain death, we found short systolic spikes with no forward but only reversed diastolic waves in the anterior and posterior circulation. Apart from the technical pitfalls of using TCD, in some cases the TCD might show a resumption of flow once the intracranial pressure has been reduced, and the TCD therefore needs to be repeated after at least 30 minutes to confirm the pattern of flow.[7] In our case, the flow pattern remained the same over 2 hours. We used an EEG as an additional ancillary test, and the electrocerebral inactivity was also suggestive of brain death in accordance with the technical guidelines established by AAN.[6] Dosemeci et al.[8] reported 18 patients who were clinically brain dead but did not have a TCD flow pattern confirming brain death. A case reported by Budohoski et al.[9] was similar to ours, where despite confirmation of brain death with multimodal monitoring (TCD, NIRS, EEG), the patient continued to have flexor motor posturing and spontaneous respiratory effort. Therefore, although TCD is an excellent tool to determine early signs of CCA, lack of activity on EEG is also suggestive of brain death, both may precede clinical signs of brain death. Clinical confirmation of the absence of brain stem reflexes should remain the primary method of declaring brain death, and ancillary tools must be used with full awareness of their limitations. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.