Researchers at Boston University's Center for the Study of Traumatic Encephalopathy, where Cantu is a co-director, performed a December 2012 study of 85 braindonors who had played football.
Stefan Duma, a Virginia Tech professor who is studying the issue, said it would be "incorrect" to rely too much on small pools of braindonors whose families may have suspected there was something amiss.
"The problem is that the standard (or brain death) donors seem to be decreasing over the last few years, and the number of (cardiac death) donors is increasing, " said Orman.
Even some of the sharpest critics of the brain-death criteria argue that there is no possibility that donors will be in pain during the harvesting of their organs.