The brain may live on after what's long been considered brain death. New research from the University of Montreal finds that there's a deeper state of coma beyond what doctors have been considering to be the final line. Traditionally, when an EEG recording — a measurement of electrical activity along the scalp — comes to a flatline, a brain's activity is considered to have ceased. But the Montreal research team found that it can actually return again through a medically induced coma. In a paper published Wednesday in PLOS ONE, the researchers write that this newly identified coma state is "the deepest form of coma obtained so far."

Establishing brain death isn't simple

The discovery could impact what doctors consider true brain death. "At the very least the current findings should serve clinicians in their assessment of patients’ depth of coma," the researchers write. It should also "draw attention to the difficulties in establishing clinical brain death." Though it remains unclear why brain activity returns in this deeper coma, the researchers suggest that as major brain functions relax, other functions may become free from prior constraints and begin to initiate new activities.

Over 20 cats were anesthetized into a medically induced coma as part of the researchers' experiments. From there, the researchers measured the cats' brain activities at different coma states. The team knew to look for this deeper, medically induced state due to a discovery in a previous patient whose brain activity returned after being given epilepsy medication while in a coma. While it's still necessary for neurons to continue functioning throughout the earlier coma states in order for this to happen, the researchers write that if they do remain intact, it now appears the brain could survive.