My first thought was also possible error in the needle placement. Although ESI's and nerve blocks can always end up being hit or miss...whether they work or not. Did you ever have surgery? If so, do you have any scar tissue? I ask because that can be a cause, if the needle isn't placed in the correct area, the meds might not even reach the problem spot. And maybe it's even possible that when you felt better, you might have overdone things and now the problem is worsened...And of course, sometimes there is no explanation.