Hi,
The costs of SCS are quite high and with the potential for complications I can't imagine they would insist on that first. They can't dictate that you try an invasive treatment.
I don't know anything about getting pre-auth for inpatient infusions or how long it would take. Often there does seem to be some skill involved on the part of pre-auth people. I too am concerned about where that leaves you in the interim.
Did they say the reason for going straight to inpatient? Though I get a low dose outpatient, CDwall is getting something really high like 500mg as an outpatient over 4 hours or so. Inpatient may very well be the best protocol for you. I just hope you don't have to wait to long...
You might try calling your insurance company to see if they can offer any history of how they have handled this in the past.
Hang in there and let us know what happens.
Sending hugs and healing love,