Summary & Overview
CPT 61799: Add-On Procedure for Additional Complex Cranial Lesion Radiation
CPT code 61799 designates an add-on procedure for destruction of each additional complex cranial target using externally generated ionizing radiation performed in the same session after treatment of a first complex lesion. It applies to stereotactic radiosurgery or focused radiation procedures where the treated lesions are typically larger than 3.5 cm, and it captures incremental work and resources required when multiple complex intracranial targets are addressed in one encounter. Nationally, accurate use of this code affects billing specificity for high-complexity neuro-oncology and functional neurosurgical cases and supports appropriate resource measurement for payers and providers.
Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will learn clinical context for when the add-on applies, typical sites of service for these procedures, and the implications for coding and reimbursement workflows. The publication provides benchmarks and policy context relevant to payers and providers, clarifies clinical scenarios that align with the code definition, and highlights common billing considerations and documentation elements needed to support use of the add-on code. Data not available in the input for specific associated taxonomies, ICD-10 diagnoses, related codes, and payer-specific policy language will be noted where relevant.
Billing Code Overview
CPT code 61799 is an add-on procedure describing the use of externally generated ionizing radiation to destroy each additional complex target area in the brain during the same session after destruction of a first complex cranial lesion. The term complex typically denotes a lesion larger than 3.5 cm.
Service Type: Stereotactic radiosurgery/radiation ablation — add-on for additional complex cranial lesion(s)
Typical Site of Service: Hospital outpatient department or specialized radiation oncology center (ambulatory surgical center when equipped for stereotactic radiosurgery)
Data not available in the input for associated taxonomies, specific ICD-10 diagnoses, related codes, and service line.
Clinical & Coding Specifications
Clinical Context
A 62-year-old patient with a known history of a primary brain metastasis previously treated or a newly discovered large intracranial lesion greater than 3.5 cm is brought to the stereotactic radiosurgery (SRS) suite. The neurosurgeon/radiosurgeon and radiation oncology team perform a single-session complex cranial lesion ablation using focused, externally generated ionizing radiation (for example, Gamma Knife or linear accelerator-based SRS). During the same session the team identifies and treats an additional separate complex target in the brain that also exceeds the typical size threshold for complexity (>3.5 cm). Billing for the additional complex target uses the add-on procedure 61799 in conjunction with the primary destruction code for the first complex cranial lesion.
The clinical workflow includes pre-procedure neuroimaging (contrast MRI and planning CT), multidisciplinary treatment planning with stereotactic localization, delivery of focused ionizing radiation to the first complex lesion, immediate target localization for the additional lesion, and delivery of the add-on treatment during the same anesthetic/immobilization session. Post-procedure monitoring in the PACU or inpatient neurosurgical unit follows with follow-up imaging planned per institutional protocols.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component |