Recently, there have been a number of articles addressing efficacy of bike helmets and their ability or inability to prevent concussions and more serious traumatic brain injuries.  Bicycling Magazine featured an article entitled “Senseless” stating “bicycling helmets do an outstanding job of keeping our skulls intact in a major crash. When they do almost nothing to prevent concussions and other significant brain injuries – and the very government agency created to protect us is part of the problem.  The time has come to demand something safer.”  The article was written by Bruce Barcott. 

More recently, CBC News, July 3, 2013, posted an article entitled “Bike Helmets Should Address Concussion Risk, Scientists Say”. 
Picking up on the Bicycling Magazine article, the article quotes neurosurgeon Charles Tator, who was quoted as saying “the evidence from science is that concussion is more related to rotational acceleration, which in layman’s terms is really a giggle of the brain.  It is like the movement of Jell‑o in a bowl when you giggle it.  It is time that our standards include measures of angular acceleration.” 
Doctor Tator goes on to state “current bike helmets are pretty well useless in attenuating rotational acceleration.”