Summary & Overview

CPT 64646: Chemodenervation of 1‑5 Trunk Muscles

CPT code 64646 represents chemodenervation of 1‑5 trunk muscles, a procedure frequently used to manage spasticity and dystonia in patients with neurological and musculoskeletal disorders. This intervention is performed by specialists in Physical Medicine & Rehabilitation, Neurology, and Pain Medicine, and is typically delivered in outpatient hospital or physician office settings. The code is recognized by major national payers, including Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare, ensuring broad coverage for eligible patients.

This publication provides a comprehensive overview of CPT 64646, including its clinical indications, payer coverage, and relevant policy updates. Readers will gain insight into the procedure’s role in treating conditions such as multiple sclerosis, cerebral palsy, and various forms of dystonia, as reflected in associated ICD-10 diagnoses. The article also highlights related CPT codes for chemodenervation procedures, common billing modifiers, and the specialties most frequently involved in delivering this service. Benchmarks and policy considerations are discussed to inform stakeholders about current trends and requirements for reimbursement and compliance. The summary is designed for a national audience, offering clarity on the clinical and administrative aspects of CPT 64646.

AetnaBlue Cross Blue ShieldCigna HealthMedicareUnitedHealthcareCPT 64646chemodenervationphysical medicinerehabilitationneurologyoutpatienttrunk musclesspasticitydystoniamedical billing

CPT Code Overview

CPT 64646 is used to report chemodenervation of trunk muscle(s); 1‑5 muscle(s). This procedure involves the injection of agents such as botulinum toxin to reduce abnormal muscle activity in the trunk, commonly performed for conditions resulting in spasticity or dystonia. The service is typically provided by specialists in Physical Medicine & Rehabilitation, Physical Therapy, or Neurology. The most common sites of service for this procedure are the outpatient hospital or physician office settings, corresponding to place of service codes 22 and 11.

Clinical & Coding Specifications

Clinical Context

A typical patient scenario involves an adult with spasticity or dystonia affecting the trunk muscles, such as a patient with multiple sclerosis, cerebral palsy, or paraplegia. The patient is referred to a neurologist, physical medicine & rehabilitation physician, or pain medicine physician for management of muscle overactivity. After clinical assessment, the provider determines that chemodenervation (e.g., botulinum toxin injection) of 1-5 trunk muscles is indicated to reduce spasticity, improve mobility, or decrease pain. The procedure is performed in an outpatient hospital or physician office setting. Documentation includes the number of muscles treated, the indication for chemodenervation, and the response to prior therapies.

Coding Specifications

Modifier 50 (Bilateral Procedure): Used when chemodenervation is performed on trunk muscles bilaterally.
Modifier 59 (Distinct Procedural Service): Used when chemodenervation is performed as a distinct service from other procedures, such as injections in different anatomical regions.

Provider Taxonomy Code	Specialty
`2084N0400X`	Neurologist
`2081P2900X`	Physical Medicine & Rehabilitation Physician
`2084P0800X`	Pain Medicine Physician

Related Diagnoses

G04.1 Tropical spastic paraplegia: Relevant for patients with spasticity affecting trunk muscles due to this condition.
G11.4 Hereditary spastic paraplegia: Indicates hereditary causes of spasticity, often requiring chemodenervation.
G24.02 Drug induced acute dystonia: Acute dystonic reactions may involve trunk muscles, treated with chemodenervation.
G24.09 Other drug induced dystonia: Other dystonic movements from drugs, possibly affecting trunk muscles.
G24.2 Idiopathic nonfamilial dystonia: Nonfamilial dystonia can cause abnormal trunk muscle contractions.
G24.8 Other dystonia: Includes dystonic disorders affecting trunk muscles.
G35.A Relapsing‑remitting multiple sclerosis: MS patients may develop trunk spasticity requiring chemodenervation.
G35.B0 Primary progressive multiple sclerosis, unspecified: Progressive MS can cause trunk muscle spasticity.
G35.B1 Active primary progressive multiple sclerosis: Active disease may increase spasticity in trunk muscles.
G35.B2 Non‑active primary progressive multiple sclerosis: Even in non-active MS, spasticity may persist.
G35.C0 Secondary progressive multiple sclerosis, unspecified: Secondary progressive MS often leads to muscle overactivity.
G35.C1 Active secondary progressive multiple sclerosis: Active phase may worsen trunk spasticity.
G35.C2 Non‑active secondary progressive multiple sclerosis: Spasticity may remain despite non-active disease.
G35.D Multiple sclerosis, unspecified: General MS diagnosis, relevant for trunk muscle involvement.
G36.0 Neuromyelitis optica [Devic]: May cause trunk muscle dysfunction requiring chemodenervation.
G36.1 Acute and subacute hemorrhagic leukoencephalitis [Hurst]: Can result in spasticity or dystonia of trunk muscles.
G36.8 Other specified acute disseminated demyelination: Demyelinating diseases may affect trunk muscle tone.
G36.9 Acute disseminated demyelination, unspecified: Similar clinical relevance for trunk muscle involvement.
G37.0 Diffuse sclerosis of central nervous system: May cause trunk muscle spasticity.
G37.1 Central demyelination of corpus callosum: Demyelination can affect trunk muscle control.
G37.2 Central pontine myelinolysis: May result in spasticity or dystonia of trunk muscles.
G37.3 Acute transverse myelitis in demyelinating disease of central nervous system: Trunk muscle involvement is common.
G37.4 Subacute necrotizing myelitis of central nervous system: May cause trunk muscle dysfunction.
G37.5 Concentric sclerosis [Balo] of central nervous system: Trunk muscle spasticity may occur.
G37.9 Demyelinating disease of central nervous system, unspecified: General demyelinating conditions affecting trunk muscles.
G80.0 Spastic quadriplegic cerebral palsy: Trunk muscle spasticity is a key feature.
G80.1 Spastic diplegic cerebral palsy: Trunk involvement may require chemodenervation.
G80.2 Spastic hemiplegic cerebral palsy: Trunk muscles may be affected.
G80.3 Athetoid cerebral palsy: Abnormal trunk movements may benefit from chemodenervation.
G80.4 Ataxic cerebral palsy: Trunk muscle tone abnormalities may be present.
G80.8 Other cerebral palsy: Includes cases with trunk muscle involvement.
G80.9 Cerebral palsy, unspecified: Trunk muscle spasticity may be present.
G81.11 Spastic hemiplegia affecting right dominant side: Trunk muscles may be involved in hemiplegia.
G81.12 Spastic hemiplegia affecting left dominant side: Trunk involvement possible.
G81.13 Spastic hemiplegia affecting right nondominant side: Trunk muscle spasticity may occur.
G81.14 Spastic hemiplegia affecting left nondominant side: Trunk involvement possible.
G82.21 Paraplegia, complete: Trunk muscle spasticity is common.
G82.22 Paraplegia, incomplete: Trunk muscle involvement may require chemodenervation.
G82.51 Quadriplegia, C1‑C4 complete: Trunk muscle spasticity is a feature.
G82.52 Quadriplegia, C1‑C4 incomplete: Trunk involvement may be present.
G82.53 Quadriplegia, C5‑C7 complete: Trunk muscle spasticity may occur.
G82.54 Quadriplegia, C5‑C7 incomplete: Trunk involvement possible.
G83.0 Diplegia of upper limbs: Trunk muscle dysfunction may coexist.
G83.11 Monoplegia of lower limb affecting right dominant side: Trunk muscle involvement may be present.
G83.12 Monoplegia of lower limb affecting left dominant side: Trunk muscle dysfunction may occur.

Related CPT Codes

CPT Code	Description	Clinical Relationship
`64642`	Chemodenervation of one extremity; 1‑4 muscle(s)	Used for extremity muscles, not trunk; may be performed in conjunction with trunk chemodenervation if both regions are treated.
`64643`	Chemodenervation of one extremity; each additional extremity, 1‑4 muscle(s) (List separately in addition to code for primary procedure)	Add-on code for additional extremities; not used for trunk muscles.
`64644`	Chemodenervation of one extremity; 5 or more muscles	Used for extremity muscles when more than 5 are treated; may be an alternative if extremity involvement is greater.
`64645`	Chemodenervation of one extremity; each additional extremity, 5 or more muscles (List separately in addition to code for primary procedure)	Add-on code for additional extremities with 5 or more muscles; not used for trunk.
`64647`	Chemodenervation of trunk muscle(s); 6 or more muscles	Used when chemodenervation is performed on 6 or more trunk muscles; alternative to `64646` when more muscles are treated.

National Reimbursement Benchmarks

For CPT code 64646, the national mean rate for Medicare is $174.28, while the BUCA (average commercial) mean rate is $198.62. Commercial payers such as UnitedHealth Group and Cigna report higher mean rates, with UnitedHealth Group at $257.21 and Cigna at $242.99, compared to Medicare.

Rate dispersion, measured by the difference between the 75th and 25th percentiles, varies significantly across payers. Medicare exhibits the tightest range at $17.00, indicating relatively consistent reimbursement rates. In contrast, UnitedHealth Group shows the widest dispersion at $145.00, reflecting greater variability in commercial rates. Cigna also demonstrates a wide range of $131.25, while Aetna and Blue Cross Blue Shield have moderate dispersions of $65.50 and $89.33, respectively.

The table and chart below present the full breakdown of national benchmarks for CPT code 64646 across major payers.

National Mean Rates for CPT 64646 by Payer

Related Codes

95971

CPT 95971: Electronic Analysis of Implanted Neurostimulator Pulse Generator

64645

CPT 64645: Chemodenervation of Additional Extremity, 5 or More Muscles

64642

CPT 64642: Neurolytic Destruction of Somatic Nerves in One Extremity

95970

CPT 95970: Electronic Analysis of Implanted Neurostimulator Pulse Generator

99205

CPT 99205: Office Visit for New Patients, High Complexity

99215

CPT 99215: Office Visit for Established Patients, High Complexity

95972

CPT 95972: Complex Programming of Implanted Neurostimulator Pulse Generator

64643

CPT 64643: Neurolytic Destruction of Somatic Nerves

95816

CPT 95816: Electroencephalogram, Awake and Drowsy

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