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Radiofrequency ablation of the S1, S2, and S3 lateral branches of the sacral dorsal rami.: "A 3.5 inch 22g spinal needle was then used as a marker to gauge depth and was inserted into the S1 foramen. This was repeated at the S2 and S3 foramen with separate needle... Each level was pretreated with 1 ml Bupivacaine 0.25%. Radiofrequency lesioning was performed, at 80 degrees C for 90s." We reported code 64625. Can you please explain the difference between codes 64625 and 64635? Code 64635 has sacral in its description as well as 64625. Also, codes 64625 and 64635 cannot be billed together, even with modifier-59? Is that correct?