Given that you will only get a couple of weeks relief and that you have already experienced a spread it is a lot to weigh. Have you considered a course of tDCS to see if you can get your pain under control? It is non-invasive, painless, low risk and quite effective if you are a responder.

If you are not totally comfortable with the plan for infusion maybe postponing it would be helpful for you to do your own research, ask more questions of your doctor, maybe get a second opinion and explore non-invasive treatments. You can always reschedule your treatment if you decide you are comfortable with it.