'Former World Player of the Year, Brodie Retallick has returned to the New Zealand squad as the specialist lock replacement, after he missed last week's match in Chicago, USA with concussion.'
The BMJ journal provides an article on Concussion in Sport, taken from their issue of 25th September 2013 -
Players with symptoms and signs of concussion, should not continue or return to play, until these resolve.
Definitions of concussion vary and include mechanistic, pathophysiological, and clinical features. These complex definitions are necessary for research but have little practical use for most clinicians, including those “pitch or track side.” A more pragmatic definition of a “traumatically induced, usually transient, disturbance of brain function that involves complex pathophysiological processes” is a diagnosis made in retrospect and provides little help with early clinical decision making.