Sorry to read of your impending lumbar picture. You wrote you have had them before so you know all to well what to expect. I do sincerely hope the puncture results shows NO reason to believe you're MS is now progressive.
I've only had one lumbar puncture that was performed in the ER, before I was officially diagnosed. I was given a mild sedative to help me relax and I was sitting up-right while it was done. This was back in '93, I imagine they have you lay on your side and bend your knees now?
I wouldn't look at the needle and my husband held my hand while it occurred. He said I squeezed his hand so hard, it nearly broke in two. :D
I hope you will have someone with you? I did have a headache afterward, but back then didn't know it was because of the puncture.
Please let me know how things turn out for you, OK? I'll join your fan club so you can contact me.
All the best to you, I'll be thinking about you.