brain activity in deep coma

Researchers observe never-before-detected brain activity in deep coma

September 25, 2013

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Flat line and Nu-complex signals (credit: Daniel Kroeger et al./PLoS ONE)

University of Montreal researchers have found brain activity that kicks in after a patient’s EEG shows an isoelectric (“flat line”) EEG, according to their paper in PLoS ONE (open access).

The flatline EEG (brainwave) pattern is usually recorded during very deep coma and is considered to be one of the limit points in establishing brain death. In particular clinical conditions, it is accepted as the only criterion.

Beyond flatline

But is it? The new research challenged this conventional wisdom after Dr. Bogdan Florea from Romania observed a human patient in an extreme deep hypoxic (deprived of oxygen) coma under powerful anti-epileptic medication (required to control his seizures) and observed some unusual EEG (brain-wave) signals instead of just a flatline, and then contacted the University of Montreal team.

After looking at the EEG and other data, the team “realized that there was cerebral activity, unknown until now, in the patient’s brain,” said Dr. Florin Amzica, director of the study and professor at the University of Montreal’s School of Dentistry.

Amzica’s team then decided to recreate the patient’s state in cats, the standard animal model for neurological studies. Using a higher amount isoflurane anesthetic than normal, they placed the cats in an extremely deep coma (beyond what is. The cat EEG showed the expected flat (isoelectric) EEG line./.../