Hello @mayopost and welcome to Mayo Clinic Connect. That is a great question.

You will notice that I have moved your post into the following discussion which you can find here:
- Perineural or Tarlov cysts: https://connect.mayoclinic.org/discussion/perineural-or-tarlov-cysts/

From what I was able to find, shock or trauma of the spine, or exertion, can cause spinal fluid in the cysts to build up.

Recent members in the discussion such as @francesmharris123 @sarsarson and @taml may have more information to share.

Do you believe yours developed after a spinal tap?