Many years ago I was d iagnosed with Tarlov cysts, which are thought to be congenital .M ine are VERY large and may be symptoms of lower back pains.... or not. There is erosion if L3 (1/4 of L3) ,with about 1/3 of my sacrum. Some nerve fibers go through the cysts. I have U. Colitis in remission, and I have been hospitalized many times for rest ^& blood transfusions. The steroids have caused cataracts, glaucoma & severe osteoporosis. When is surgery necessary? ?