Reader Response: Practice Current: When do you order ancillary tests to determine brain death?

We recently reported a case (case 3 in our article)¹ contributing to the discussion of using ancillary tests in brain death.² This case showed brain death clinical features leading to a death certification. We studied the case 9 months later.¹ We found preservation of intracranial structures, with a huge lesion at the brainstem.¹ Conceptually, brain death is characterized by absence of cerebral blood flow.³ Conservancy of brain structures rejects brain death diagnosis.^1,3 EEG signal was found in this case. EEG signal may persist in posterior fossa catastrophes.² Using heart rate variability (HRV) methodology, we found preservation of all HRV bands, contrary to reports in brain death.⁴ This case also showed autonomic reactivity to “mother talks” stimulation. This is a demonstration of autonomic CNS activity preservation.¹ Our patient showed brain death clinical features, but the use of ancillary tests denied this diagnosis. We claimed that this is a new state, not previously classified, of a disorder of consciousness.¹ Is there a diagnosis of any disease in which a confirmatory test (blood test, imaging) is not used, considering that pitfalls in clinical examination can occur? Brain death determination is the most challenging diagnosis for a physician. Why not use a confirmatory test?^1,5