Is lumber puncture necessary before MRI result?


I’ve got an appointment for a full spine and brain mri with contrast on 2nd Feb, and have just received an appointment for my lumber puncture for the 27th Jan. I’m really nervous about the LP, and wondered if its really necessary, if say the mri was clear, wouldn’t that be conclusion enough, and/or, if something did show up on the mri, then is it actually necessary to confirm a diagnosis?

I’m concerned because I’ve had back problems on and off for years, suffer terrible migraines, and (apart from being a wuss), worry that it could antagonise them.

I need to let the hospital know if the appointment is convenient, I thought perhaps I could try and postpone it for a week or two when hopefully someone will have looked at the mri results? Or can I refuse? would that annoy the neuro?!

Any advice greatly appreciated!