harlequins and england full-back mike brown may not play again this season due to on-going concussion issues .
the 29-year-old has not played since returning from international duty last month after being knocked out in a six nations game against italy .
nine weeks later , brown is still suffering from headaches and nausea .
harlequins director of rugby conor o'shea has insisted that he does not blame the england set-up for brown 's injury .