Figure 6.

Pathophysiological mechanisms and phylogenetic aspects of spreading depolarizations (SD). Terminal SD involves impaired neurovascular coupling and is the biological hallmark of the dying neuron and brain death. Of note, terminal SD is a phylogenetically highly preserved mechanism and must also have occurred in the last common ancestor of humans and insects for over 500 million years ago. Figure inset shows intracranial recordings from a patient with subarachnoid hemorrhage at the time of brain death, reprinted with permission from (12) and courtesy of Jens P. Dreier and Coline L. Lemale, Berlin. Note that while arterial pressure remains stable (i.e., the heart is still functioning), terminal SD evolve into negative ultraslow potentials (NUP) and spreading depressions, marking the transformation to brain death. DC/AC ECoG, direct current/alternating current electrocorticography.