Transcranial Doppler for brain death after decompressive craniectomy: persistence of cerebral blood flow with flat EEG

Brain death (BD) diagnosis is made based upon clinical criteria—unresponsive coma with absence of brainstem reflexes and persistent apnea—and upon neurophysiologic observation of persistent “flat EEG.” Cerebral circulatory arrest (CCA) must also be assessed with “ancillary tests,” e.g. conventional angiography, transcranial Doppler (TCD), and other neuroimaging techniques, in infants younger than 12 months, when EEG flattening may be related to sedative treatment, and in BD of uncertain origin [1]. CCA may indeed happen both when intracranial pressure (ICP) overrides mean arterial blood pressure (MAP) as well as in diseases affecting cerebral tissue at a cellular level, with ICP not exceeding MAP. TCD is a sensitive, specific, and noninvasive technique to detect CCA in BD by identifying specific patterns [2]. However, it may lead to false-negative results in cases of skull defects (decompressive craniectomy, external drains, and in infants), because in these cases the increase in ICP may partially be compensated for. For these reasons, we recently described the TCD modifications of the CCA patterns in infants with BD, confirming that CCA detection for BD confirmation should be done cautiously in these cases [3]. Here we describe the different TCD findings observed in two adults with BD who were subjected to decompressive craniectomy.