Most people are JC virus positive (over 75% of the population). It only becomes an issue if you are on certain MS DMT's that are immunosuppressants and can increase the risk of PML, most notably Tysabri, but there are others. A lot of people continue taking these medications even while JC virus positive but it can become more risky when you have been on them longer or if your JCV antibody level is high.

It's pretty unusual for your doctor to order a spinal tap just because you became JCV positive and are on a specific MS therapy. My understanding is that a spinal tap can help identify if you have started to develop PML (which can get activated by the JC virus) but MRI's can do this as well. But usually from what I read they only do it if you are suspected of having PML, not simply by being JCV positive. Maybe your doctor is really conservative and wants to be 100% sure you haven't started to develop it. Have you noted any symptoms or concerns? A lot of people stay on Tysabri who are JCV positive so its not necessarily a reason to panic and start doing spinal taps.

Is your neurologist a regular neuro or an MS specialist? I would think that most MS specialists would only resort to a spinal tap if your JCV antibody level was really high, if you were displaying symptoms of PML, or maybe if you were trying to start Ocrevus and they wanted to be 100% sure you were free of PML prior to starting.

BTW I have had a spinal tap and it was fine. I had mine done under xray (fluoroscopy). They found the right spot right away. It was painless. Some headaches afterwards though but the procedure was easy.

I had a spinal tap during my diagnosis process. It was not fun, by any means, but also it was not that big of a deal in comparison to the many other medical procedures/issues that I have had. Having a root canal is much worse, in my opinion.

Had to have a single blood test JC virus and tested positive. Spinal test made me feel unwell for about a week after won’t get another one!

That is or sure. Never had them while in delivery!!

The spinal tap if done correctly is a breeze.More anxiety leading up to it.