64640 but if the medial branches are being treated while the third occipital nerve is being treated then TON RF would be inclusive to the medial branch facet level being treated. I know the medial branches are not being described in your question but I was just going to point that out, here a response I received in the past:
nquiry Question:
I believe the below procedure should be coded as such: 64626 (C2), 64640 (TON), 64627 (C3), 64627 (C4) 77003
Is it appropriate to report 64640 for destruction of third occipital nerve by radiofrequency ablation?
Radiofrequency neuolysis cervical medial branches(facets) RIGHT X 4 Levels C2,TON, C3, C4 Fluoroscopy for needle guidance
Above was part of my question Below is part of their response
"64626 Destruction by neurolytic agent, paravertebral facet joint nerve; cervical or thoracic, single level
64627 x2 Destruction by neurolytic agent, paravertebral facet joint nerve; cervical or thoracic, each additional level (List separately in addition to code for primary procedure)
77003 x1 Fluoroscopic guidance and localization of needle or catheter tip for spine or paraspinous diagnostic or therapeutic injection procedures (epidural, subarachnoid, or sacroiliac joint), including neurolytic agent destruction
"It would not be appropriate to report code 64640 Destruction by neurolytic agent, paravertebral facet joint nerve; other peripheral nerve or branch. The third occipital nerve is the medial branch of C-3 and its location is similar anatomically with performing a paravertebral facet joint injection. However, the difference is that the location of the third occipital nerve may
vary, so the physician may need to burn over a wider area to ensure capturing the third occipital nerve in the procedure."