In the Netherlands it is normal routine to have an LP in the diagnostic process.
It is not useless.

A LP can confirm the McDonald criteria, but also can help to exclude other disease.

Severe sleep deprivation and other confitions can also lead to ms like leasions

Or infection with brucelia (lime) and others.

In case of any doubt it ads relevant information.

At least we unfortunately have to convince sometimes the insurance. More information can help.

It’s more accurate. There are 26 other conditions that look like MS on the MRI

some states might require the additional test of lumbar puncture to confirm diagnosis of MS

My lumber puncture did not show the rings consistent with MS, (I am the one who finally requested the lumbar puncture, hoping it would be negative!) But, my brain lesion and symptoms are consistent with MS diagnoses, so here I am. I know a few people who have had long term aggressive MS that were also negative on their lumbar puncture. :/ Go figure. Diagnosing MS is apparently not an exact science.

Sdly it all makes them money which is what is wrong with the uSA medical system!!!

Some Drs order it and people don't feel comfortable questioning their Dr. Makes the system more money and then the Dr. might have something to confirm the MRI