CPT 64642 - Chemodenervation, One Extremity (1-4 Muscles)
Quick Reference
Chemodenervation (e.g., onabotulinumtoxinA, abobotulinumtoxinA) of 1 extremity, 1-4 muscles. Base code — reported once per session regardless of how many muscles (1-4) are injected in that first extremity.
Description
Reports chemical denervation via toxin injection into skeletal muscle(s) of a single extremity, targeting 1 to 4 distinct muscles, most commonly for spasticity management (post-stroke, cerebral palsy, TBI) or focal dystonia.¹
Key Coding Rules
- Muscle count drives code family, not code choice within 64642 itself — 1, 2, 3, or 4 muscles in one extremity all report as a single unit of 64642. Do not report per muscle.
- 5+ muscles in that same extremity → use 64644 instead, not 64642 with extra units.
- Second extremity → add-on code 64643 (1-4 muscles) or 64645 (5+ muscles), never a second unit of 64642.
- Extremity-based code, not paired-structure — -RT/-LT modifiers are not required the way they would be for a paired organ code.
Guidance Codes (frequently reported together)
- 95873 — electrical stimulation guidance, add-on
- 95874 — needle EMG guidance, add-on (not used in this example encounter) Only one guidance method is typically billed per extremity per session; documentation must support which method was used.
Documentation Checklist
- Named muscles injected (must be countable/identifiable, not “multiple muscles” alone)
- Toxin agent and total units administered
- Guidance method (EMG, e-stim, ultrasound, or none)
- Medical necessity — underlying spasticity/dystonia diagnosis with functional impairment
- Extremity laterality documented in the note (even though no RT/LT modifier applies to this code)