Dr. Michael Farrell:

I am a brain pathologist at Beaumont Hospital where I have worked since the hospital opened. I have spent much of my life examining the consequences of head injury in patients who have been unfortunate enough to die.

At the far end of the spectrum is chronic traumatic encephalopathy. This condition has been around for over 100 years. It was recognised in the 1920s in boxers when its pathology was described. It has received enormous publicity recently because it has been recognised in a group of American professional football players. There have been other individual cases described in a rugby player and individuals from other sports. The pathology is one of progressive loss or death of nerve cells in the brain and the accumulation of a particular protein called tau. The filaments in the nerve cells are like fingers of asparagus tied in a bunch with string. They move down along the nerve cell over time. The string is known as tau. In patients with chronic traumatic encephalopathy the tau becomes abnormal. It changes shape, accumulates phosphate molecules and the process of supplying the far end of the nerve cell fails. The patient then develops a dementia which is progressive over time, characterised by behavioural changes, impulsivity, suicidality and so on. The diagnosis can be confirmed only at autopsy. The key question concerning all these sport-related concussions is whether repeated concussions over multiple periods of time result in chronic traumatic encephalopathy.

The scientific evidence is entirely anecdotal. There have been no prospective longitudinal studies conducted on players with established baselines before they become concussed and examined afterwards with a variety of different biomarkers and followed long enough to see whether they develop this condition. That is where we are at. Nobody has been able to come up with a study. We tried to design one ourselves involving the rugby football unions from a number of countries. The study would be enormously expensive but it is doable. It is doable because of the willingness of the rugby football unions and other sporting bodies to support the study. It requires new biomarkers of concussion to see how long an individual patient takes to return from concussion. We have all the return to play guidelines but we do not have really good biomarkers either in the blood, radiological or otherwise that would allow us to say one's brain has completely returned to normal and one is free to return.

We know there are individuals who are genetically or otherwise prone to concussion and that there are individuals who never get concussed. One hears people talk about boxers who have a glass chin, one blow and he is down. There are all these individual variations from person to person in one's susceptibility or resistance to concussion and that may or may not have a bearing on whether, in the long term, one gets chronic traumatic encephalopathy. From my point of view the condition exists, it is interesting, it is difficult to diagnose even pathologically with a brain in front of one, because one can never be sure that the patient did not have a gene that was disregulated, the code for tau, that perhaps this patient who got repeated blows was genetically predisposed to get a dementia related to tau, of which there are many. The science is dirty, the data is dirty, there is no data, there is no scientific data, all we have is anecdote and, unfortunately, that is the way it will continue.

The upside of all of this is that the publicity attended to chronic traumatic encephalopathy has resulted in all of the sporting bodies paying increased attention to concussion in its diagnosis and management. That can only be a good thing for players who now realise it is not natural to go back on the pitch having had a concussion, or to hide one's concussion symptoms. One is not doing one's team any favour, one must stay off the pitch and wait until one is better. That is filtered down to all levels to schools and so on. Yes, more can and will be done but in respect of the dramatic outcome in some footballers and some Rugby players there is no scientific evidence available and studies need to be done.