According to Tim Graham of The Buffalo News, Kolb's latest concussion, which occurred on Saturday against the Washington Redskins, may threaten his career. It is at least the third documented concussion of his career—he suffered one apiece in 2010 and 2011.
Therein lies the problem.
Concussion knowledge continues to evolve at an ever-increasing pace, and doctors and researchers learn more each day. However, with that evolution comes uncertainty.
While the disease called chronic traumatic encephalopathy (CTE) frequently occupies the spotlight, acute complications of repeated concussions are very serious issues as well.
Many believe repeat concussions lead to more significant and longer-lasting symptoms with each successive injury. Those symptoms can include debilitating headache, confusion, nausea, vomiting and feeling in a fog, among others.
In a concussion-naive athlete, symptoms tend to fade within a week or two of physical and cognitive rest.
However, following Kolb's second documented injury, symptoms lingered for a total of six weeks. Perhaps he is particularly vulnerable to prolonged recoveries, or perhaps his history is catching up with him. So goes the uncertainty surrounding the injury.
In the worst-case scenario, following a concussion, the dreaded post-concussive syndrome (PCS) develops. It's a condition where symptoms persist for weeks or months, or even years.
Though rare, PCS garnered some attention when Sidney Crosby of the Pittsburgh Penguins was on and off the ice for over a year as he battled lingering effects.
Unfortunately, that's only the beginning of the problems that could face Kolb.
Depending on who is talking, successive concussions may actually lower the "concussion threshold" of an athlete—or the magnitude of head trauma required to cause another injury.
In other words, multiple concussions may not only make the next worse and last longer, they may also make it easier to suffer a future injury.
Talk about a vicious cycle.
Bear in mind that both of the above theories are controversial, and the relationship between repeat concussions and both short- and long-term consequences remains a bit of a mystery.
Timing of repeat injury, possible unknown genetic predispositions and countless other unclear factors may play a role. The science simply isn't there yet.
There is also no generally accepted standard number of concussions where concern reaches a critical threshold. Each athlete is unique.
For these reasons and more, for every medical or research professional on one side of a particular argument, it is likely possible to find another countering it.
For example, this older study out of the University of Pittsburgh suggests there is a cumulative effect of concussions in high school athletes. On the other hand, another more recent study out of the University of British Columbia inconclusively suggests lingering verbal memory deficits may result.
Finally, a third manuscript out of the University of Michigan states there actually is no cumulative impact of repeat injury on the concussion threshold.
Yet as concussions add up in a particular player, so does a physician's concern about medically clearing him or her to return to the field. The heartbreaking story of Jahvid Best is a recent example.
What does this all mean for Kolb?
Regrettably, it's too early to tell, and one can only hope his symptoms abate sooner rather than later. Every single concussion is unique in its constellation of symptoms, recovery time and lasting effects—or lack thereof.
In the end, the most important issue is Kolb's health. No one likes to see an athlete in pain nor an injury ending a career, and the thoughts of the NFL community are certainly with him as he starts down the road to recovery once again.
Dr. Dave is a resident physician at the University of Washington with plans to pursue fellowship training in Primary Care (non-operative) Sports Medicine. He has a particular interest in concussions and has evaluated dozens in the clinic, emergency room and training room settings.