Why would my doctor order a small nerve biopsy before a spinal tap?

Hi Christophrighter! This is a great question. I cannot provide medical diagnosis or advice for your safety. That said, have you asked your physician why he ordered this test? It sounds like he (or she) may be looking for another cause of your symptoms, especially since your imaging and bloodwork came back normal. Here are some conditions that physicians frequently like to rule out before diagnosing MS -- https://multiplesclerosis.net/diagnosis/ruling-out-other-health-conditions/. Could you possibly be dealing with any of the listed conditions? Again, if you have any questions, I hope your physician is open to answering those questions! Good luck and I hope your biopsy procedure goes smoothly. Best, Erin, MultipleSclerosis.net Team Member.