It depends on how it was “closed,” so to speak.  If you received any type of “settlement” to end your workers’ compensation case (i.e. a lump sum commutation or a denial and dismissal), then the answer is no, you cannot reopen your case, and indeed you would have had to have stated to a judge at the settlement hearing that you understand the case is over forever and all time and that you can never come back to reopen it.  

If on the other hand, you returned to work and began having problems again or you injury reappeared or worsened and you have to come out of work again, then yes, you may “reopen” your case in that sense.