What happens in our brain moments before we die? As a team of neurologists at the Hospital Charité-Universitätsmedizin Berlin (Germany) has discovered, a wave of electrical activity in our brains called a “brain tsunami” seems to mark the beginning of the end.
The experts, who continuously examined brain activity in 9 dying patients, observed a burst of activity that appears to precede the fatal shutdown of our most vital organ.
The finding suggests that consciousness may still be present many minutes after the rest of the body has stopped showing signs of life, raising the possibility that for up to five minutes, the brain’s shutdown process may be reversed.
All study patients, who hailed from Berlin, Germany, and Cincinnati, Ohio, USA, had fatal brain injuries and had requested not to be resuscitated.
The experts hoped that, by implanting electrodes into the brains of their test subjects, they would be able to uncover both the timing and the mechanisms of events during the death process. To their surprise, they discovered that even five minutes after the heart stopped beating, brain cells, or neurons, could still function. Furthermore, a kind of ‘brain tsunami’ marked the moment when these neurons shut down before their final and irreversible death.
“After circulatory arrest, the diffusion of depolarization – the decrease in the potential of the neuron – marks the loss of electrochemical energy stored in brain cells and the appearance of toxic processes that eventually lead to death. Importantly, it is reversible , to a certain extent, when circulation is restored, “says Jens Dreier, leader of the work.
Neurons die when blood stops flowing, depriving them of the oxygen they need for fuel to function. When this happens, neurons draw on energy reserves for a few minutes before shutting down completely. This happens when the mechanisms neurons use to keep ions apart begin to fail. Ions are electrically charged particles formed when atoms lose or gain electrons.
Breaking down the barriers between these particles releases a massive amount of electrochemical energy into the brain as neurons frantically try to consume fuel.
This process, known as depolarization propagation, is characterized by hyperactivity in neurons, followed by sudden silence.
However, this silence only marks the final countdown to death and can be reversed for a period, the researchers found. Exactly how long, remains open to debate.
One last ‘wave’ appears to mark the point at which neurons last remain active, although the research team cautioned that it may still be an unreliable marker for ‘true death’.
For now, scientists do not have a clear method to diagnose brain death, and there is no way to be sure when all consciousness is lost, according to the authors.
While the study does not have a direct effect on patient care today, it may lead to better diagnostic and treatment procedures in the future. The findings may be helpful in developing strategies for treating cardiac arrest and stroke that complement efforts to restore circulation in the body. In fact, this discovery could save the lives of people who are at risk of brain damage, death from cerebral ischemia or any cardiovascular accident, although a lot of work will still be necessary for it to be applied medically.
Reference: Terminal spreading depolarization and electrical silence in death of human cerebral cortex. Jens P. Dreier et alia. Annals of Neurology. DOI: 10.1002 / ana.25147
