@summerstar I am a spine surgery patient, and I have had MRI's with gadolinium. The people who tend to have problems from gadolinium are patients with kidneys that don't function well. You can search the internet and find complaints about gadolinium.

It gave me a headache. I also drank a lot of water afterward to try to flush it out and took antihistamines in case of allergy. I believe that gadolinium will always linger in your body after it is injected. It is a metal that is supposed to be safe. I really don't know, and I question that too. I have had a doctor test me for metals, and it did show the presence of a significant amount of gadolinium in my body years later, so now I always question why it is necessary to use contrast dyes in imaging. It may not be absolutely necessary. Upon asking the question, I have had doctors tell me that they wouldn't allow it in their bodies, and long term, maybe no one knows if it is really safe. There have been some reports of kidney damage which makes sense because the kidneys are filtering out everything from the blood.

Do you have a physical therapist you can ask about this? There can be other reasons for pain at the base of the skull and neck. That happens to me intermittently when my vertebrae spontaneously rotate because of neck muscle spasms. I have thoracic outlet syndrome which causes one side of my neck to be to tight creating an imbalance. It has also caused vertigo and loss of balance before I had cervical fusion surgery and had a collapsed disc in my neck that was causing spinal cord compression. TOS, (thoracic outlet syndrome) can also cause breathing issues, dizziness and fainting in some people.
https://mskneurology.com/how-truly-treat-thoracic-outlet-syndrome/
You may not have a spinal fluid leak, the neurologist is taking a guess and suggesting tests to confirm of deny it, and it is your choice to do the test or not. You can always seek a second opinion elsewhere. You could try physical therapy to see if it will help. My PT also does myofascial release which releases the tight tissue and fascial tightness allowing my body to move better and releasing the pressure.

MFR is Myofascial Release Therapy. There is a discussion on MFR that you might find helpful.

Myofascial Release Therapy (MFR) for treating compression and pain: https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/

I agree is is good to be cautious and understand everything completely before you decide. Have you had physical therapy since your spine surgery?