Summary & Overview

CPT 64642: Chemical Neurolysis of One to Four Muscles in an Extremity

CPT code 64642 denotes chemical neurolysis (chemodenervation) involving injection of a neurolytic agent, such as botulinum toxin, into one to four muscles of a single extremity to relieve pain and reduce spasm. This code is used across specialties managing focal spasticity and dystonia and matters nationally due to its role in outpatient procedural management of movement disorders and chronic spasticity, impacting utilization, coverage policy, and outpatient procedural spend. Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare.

Readers will find a concise overview of clinical indications and service setting, payer coverage patterns and common reimbursement considerations, relevant ICD‑10 diagnosis mappings for appropriate use, and related CPT codes for additional or trunk-based procedures. The summary highlights benchmarks for single‑extremity chemical neurolysis, common billing pairings, and coding distinctions between the primary procedure and add‑on codes for additional extremities or muscle groups. The content provides clinicians, payers, and coding professionals with the clinical context and coding relationships needed to support accurate claims submission and policy assessment for outpatient chemodenervation services.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare64642CPTchemodenervationchemical neurolysisspasticity managementoutpatient procedurebotulinum toxinmovement disordersprocedure coding

Billing Code Overview

CPT code 64642 describes injection of a chemical neurolytic agent (for example, Botox®) into one to four muscles of a single extremity to relieve pain and reduce muscle spasm. This procedure is a targeted, minimally invasive intervention performed to chemically denervate or weaken specific muscles contributing to spasm, dystonia, or focal hypertonicity.

Service Type: Therapeutic chemical neurolysis / chemodenervation

Typical Site of Service: Outpatient clinic, ambulatory surgery center, or physician office procedure room

Clinical & Coding Specifications

Clinical Context

A 58-year-old patient with chronic, focal spasticity of the right upper extremity following a stroke presents to a pain medicine clinic for management of persistent painful muscle spasms and impaired function. The patient reports focal clonus and sustained muscle contractions in the wrist and forearm despite oral muscle relaxants and targeted physical therapy. After evaluation, the pain medicine physician discusses focal chemical neurolysis using botulinum toxin to paralyze one to four affected muscles of the right upper extremity to reduce spasm, improve comfort, and facilitate rehab. The clinical workflow includes pre-procedure assessment (history, review of prior treatments, medication reconciliation, and informed consent), identification and localization of target muscles (clinical exam, sometimes guided by EMG or ultrasound), sterile injection of the selected muscles with the neurolytic agent (documenting laterality, number of muscles injected, units/dose), immediate post-procedure observation for adverse effects, and scheduling follow-up to assess response and need for repeat injections. Typical documentation includes indication, targeted muscle(s), laterality, technique and guidance used, agent and dose, number of muscles treated (1–4 for one extremity), and any complications or patient instructions. Typical sites of service are outpatient ambulatory surgery centers, hospital outpatient departments, and office-based procedure suites. Payors involved in authorization and claims for this service commonly include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, BUCA, and Medicare.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	When reporting the physician’s professional service separate from technical components if applicable (rare for standalone injections but used if imaging or EMG interpretation billed separately).
`50`	Bilateral procedure	When injections are performed on both extremities during the same session and payer allows bilateral modifier application.
`51`	Multiple procedures	When multiple distinct procedures are reported on the same day in addition to the primary neurolytic injection.
`52`	Reduced services	When the planned service is partially reduced or not completed (eg, fewer muscles injected than planned).
`53`	Discontinued procedure	When the procedure is terminated due to extenuating circumstances or patient safety concerns before completion.
`59`	Distinct procedural service	When a separately identifiable injection or service is performed at a distinct anatomic site that is not normally reported together.
`62`	Two surgeons	When two surgeons work together as primary surgeons on the same procedure (rare for injections).
`76`	Duplicate procedure by same provider	When a procedure is repeated by the same provider subsequent to the original service on the same day (not in raw modifier list; not used).
`78`	Return to OR for related procedure during postoperative period	When an unplanned subsequent operative procedure related to the initial service occurs during the global period (unlikely for injections but included in provided list).
`79`	Unrelated procedure or service by same physician during postoperative period	When an unrelated procedure is performed during the global period.
`96`	Habilitative services	When the service is part of habilitation (use per payer guidance if applicable).
`97`	Rehabilitation services	When service is part of rehabilitation (use per payer guidance if applicable).
`LT`	Left side	When the left extremity is treated.
`RT`	Right side	When the right extremity is treated.

Taxonomy Code	Specialty	Notes
`208VP0000X`	Pain Medicine Physician	Common specialist performing neurolytic injections for focal spasticity and dystonia.
`207LP2900X`	Physical Medicine & Rehabilitation Physician	Frequently performs targeted botulinum toxin injections to manage spasticity and facilitate rehabilitation.
`207R00000X`	Internal Medicine Physician	May perform injections in outpatient settings, particularly for chronic spasticity management.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`M62.411`	Spasm of muscle	Focal muscle spasm targeted by neurolytic injection to reduce painful involuntary contractions.
`M62.838`	Spasm of other muscle	Additional spasm diagnosis applicable to atypical or multiple muscle groups in an extremity.
`G11.4`	Hereditary spastic paraplegia	Progressive spasticity affecting lower extremities that may be managed with focal injections for symptomatic relief.
`G24.1`	Genetic torsion dystonia	Dystonic muscle contractions that may be treated with targeted neurolytic agent injections.
`G24.2`	Idiopathic nonfamilial dystonia	Primary dystonia causing focal limb spasm addressed by botulinum toxin injections.
`G24.8`	Other dystonia	Other specified dystonias that present with focal muscle overactivity treatable with injections.
`G24.9`	Dystonia, unspecified	Unspecified dystonic conditions where focal chemical neurolysis may be appropriate.
`G25.89`	Other specified extrapyramidal and movement disorders	Miscellaneous movement disorders with focal spasm responsive to neurolytic injections.
`G35.A`	Relapsing‑remitting multiple sclerosis	MS-related spasticity in extremities that can be managed with targeted injections to improve function.
`G35.B0`	Primary progressive multiple sclerosis, unspecified	Progressive MS with spasticity potentially treated with focal neurolytic injections.
`G35.B1`	Active primary progressive multiple sclerosis	Active disease state with spasticity requiring symptomatic management via injections.
`G35.B2`	Non‑active primary progressive multiple sclerosis	Stable disease state where injections may be used for chronic spasticity control.
`G35.C0`	Secondary progressive multiple sclerosis, unspecified	Secondary progressive MS often causes disabling spasticity addressed with focal injections.
`G35.C1`	Active secondary progressive multiple sclerosis	Active secondary progressive disease with symptomatic spasticity treated with injections.
`G35.C2`	Non‑active secondary progressive multiple sclerosis	Non-active secondary progressive MS where injections are used for ongoing spasticity management.
`G35.D`	Multiple sclerosis, unspecified	General MS diagnosis applicable when spasticity is an indication for neurolytic injection.
`G36.0`	Neuromyelitis optica [Devic]	Demyelinating disorder with potential focal spasticity treatable with injections.
`G36.1`	Acute and subacute hemorrhagic leukoencephalitis [Hurst]	Rare demyelinating condition that may produce focal spasm amenable to symptomatic injection therapy.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`64643`	Destruction by neurolytic agent (eg, chemical, thermal, electrical or radiofrequency) procedures on the somatic nerves; each additional extremity	Used when neurolytic procedure is performed on an additional extremity beyond the primary extremity coded with `64642`.
`64644`	Destruction by neurolytic agent ... trunk; 1–5 muscles	Related code for neurolytic injections targeting trunk muscles rather than extremities; used in cases where trunk rather than limb muscles are treated.
`64645`	Destruction by neurolytic agent ... trunk; each additional 5 muscles (List separately in addition to code for primary procedure)	Add-on code when more trunk muscles are treated beyond the initial `64644` allowance.
`64646`	Destruction by neurolytic agent ... trunk muscle(s); 1–5 muscles	Alternate trunk-specific code for neurolytic injection procedures similar in scope to extremity codes.
`64647`	Destruction by neurolytic agent ... trunk muscle(s); each additional 5 muscles (List separately in addition to code for primary procedure)	Add-on for additional trunk muscles treated beyond the base trunk code.