CPT 64643 - Chemodenervation, Each Additional Extremity (1-4 Muscles) [Add-On]
Quick Reference
Add-on code. Reports chemodenervation of a second (or subsequent) extremity, 1-4 muscles, same session. Must always be billed with a primary chemodenervation code — never stands alone.
Description
Same mechanism as 64642, applied to each additional extremity beyond the first, still within the 1-4 muscle range for that extremity.¹
Key Coding Rules
- Always pairs with a primary code — typically 64642 (first extremity, 1-4 muscles) or 64644 (first extremity, 5+ muscles). 64643 itself is never the primary/first-listed procedure code.
- One unit per additional extremity treated, not per muscle. A 3rd extremity in the same session = a 2nd unit of 64643.
- If the additional extremity has 5 or more muscles injected, use 64645 instead of 64643 for that extremity.
- As an add-on code, 64643 is exempt from multiple-procedure payment reduction under standard CPT add-on code rules — do not append modifier -51.
Modifier Notes
- No -RT/-LT required (extremity-based code).
- If guidance (95873/95874) is separately reported for this second extremity, append modifier -59/-XS to the guidance code’s second unit to distinguish it from guidance already billed for the first extremity.
Documentation Checklist
- Confirms this is a distinct, separate extremity from the one billed under the primary code
- Named muscles (1-4) with individual doses
- Same-session timing with the primary chemodenervation procedure