Summary & Overview

CPT 61737: Laser Interstitial Thermal Therapy for Multiple or Complex Brain Lesions

CPT code 61737 designates laser interstitial thermal therapy (LITT) for multiple brain lesions or for one or more complex lesions that require multiple trajectories. LITT is a minimally invasive, image-guided neurosurgical technique that uses laser energy to ablate intracranial lesion tissue and is increasingly used for select metastatic tumors, radiation necrosis, and other focal brain pathologies. Nationally, recognition of this code matters because it defines billing and reporting for a specialized procedure with distinct resource use, imaging needs, and facility requirements.

Key payers in this overview include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The discussion highlights how payers approach coverage and reimbursement for LITT, operational considerations for site of service, and common billing modifiers used with complex neurosurgical procedures.

Readers will find a concise clinical context for CPT code 61737, typical settings where the service is delivered, and the elements that affect billing and utilization. The publication provides benchmarks and policy-relevant context where available, clarifies common billing practices, and notes when input data are not provided. This summary is intended for billing professionals, surgical program managers, and policy analysts seeking a national-level briefing on the code and its clinical use.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare61737CPTlaser interstitial thermal therapyLITTneurosurgeryimage-guided ablationambulatory surgeryhospital services

Billing Code Overview

CPT code 61737 describes laser interstitial thermal therapy (LITT) performed for multiple brain lesions or for one or more complex brain lesions that require multiple trajectories. The procedure uses a laser to thermally ablate and damage target lesion tissue within the brain. Magnetic resonance imaging (MRI) guidance may be used to plan and monitor catheter placement and thermal effects during the procedure.

Service type: Image-guided minimally invasive neurosurgical ablation
Typical site of service: Inpatient or outpatient hospital setting or ambulatory surgery center where MRI guidance and neurosurgical facilities are available.

Clinical & Coding Specifications

Clinical Context

A patient in their 50s with a symptomatic brain metastasis or recurrent primary brain tumor presents with progressive focal neurologic deficits and imaging-confirmed enhancing lesions. After multidisciplinary review by neurosurgery, neuro-oncology, and neuroradiology, the patient is selected for laser interstitial thermal therapy (LITT) because lesions are deep-seated, surgically inaccessible, or prior surgery/radiation makes open resection high risk. Pre-procedure workflow includes history and physical, medication reconciliation (anticoagulation management), informed consent, preoperative MRI for trajectory planning, and anesthesia evaluation. On the day of service the patient is brought to an intraoperative MRI suite or hybrid operating room. Under general anesthesia, stereotactic frame or frameless navigation is used to place one or more laser fiber catheters along planned trajectories. Continuous MRI thermography or other intraoperative imaging monitors ablation zone as the laser delivers thermal energy to target tissue. For multiple lesions or a single complex lesion requiring several trajectories, the operator repositions or places additional fibers and repeats ablation cycles. Post-ablation MRI assesses treatment extent. The patient is monitored in PACU then admitted to neurosurgical observation or inpatient service for neurologic checks, pain control, and imaging follow-up. Typical sites of service are an operating room, intraoperative MRI suite, or ambulatory surgical center with appropriate imaging capability.

Coding Specifications

Modifier	Description	When to Use
`11`	Normal, pre-existing physician work	Use when the service is the usual, expected performance without unusual circumstances.
`22`	Increased procedural services	Use when the LITT required substantially greater work (eg, unusually complex trajectories, prolonged operative time) and documentation supports increased work.
`23`	Unusual anesthesia	Use when medically necessary anesthesia is provided for a procedure that normally may be performed with local or no anesthesia.
`50`	Bilateral procedure	Use if bilateral intracranial ablations are performed and payor accepts bilateral modifier for the code.
`51`	Multiple procedures	Use when LITT is one of multiple distinct procedures performed during the same session; append per payor rules.
`52`	Reduced services	Use when the LITT was partially reduced or not completed as planned.
`53`	Discontinued procedure	Use when the procedure is started but terminated due to extenuating circumstances documented in the record.
`62`	Two surgeons	Use when two surgeons work together as primary surgeons on separate tasks during the same operative session.
`63`	Procedure performed on infants less than 4 kg	Use when applicable for neonatal patients meeting weight criteria.
`66`	Surgical team approach	Use if a documented surgical team approach was used for complex combined procedures.
`78`	Unplanned return to OR for related procedure during global period	Use when the patient returns to the OR for a related procedure during the global period and this LITT is that return.
`79`	Unrelated procedure or service by the same physician during the postoperative period	Use when a separate unrelated procedure is performed during the global period.
`80`	Assistant surgeon	Use when an assistant surgeon performs part of the operation and payer accepts assistant surgeon billing.
`62`	Two surgeons	Use when two surgeons perform distinct parts of the procedure (duplicate entry reflects clinical relevance).

Taxonomy Code	Specialty	Notes
207XS0101X	Neurosurgery	Primary specialty performing intracranial LITT procedures.
2084P0200X	Interventional Neuroradiology	Performs image-guided catheter placement and intraoperative MRI guidance.
207L00000X	Neurology	Neurology involvement for peri-procedural management and follow-up.
163W00000X	Anesthesiology	Provides general anesthesia and neuro-anesthesia monitoring during LITT.
363L00000X	Radiation Oncology	May be involved in multidisciplinary planning when prior or adjuvant radiation is relevant.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`C71.9`	Malignant neoplasm of brain, unspecified	Primary brain tumors that may be treated with LITT when deep or in eloquent locations.
`C79.31`	Secondary malignant neoplasm of brain	Brain metastases commonly treated with LITT for symptomatic, limited intracranial metastatic disease.
`D33.3`	Benign neoplasm of brain, supratentorial	Selected benign tumors (eg, low-grade gliomas, cavernous malformations) in challenging locations may be candidates for LITT.
`G93.1`	Anoxic brain damage, not elsewhere classified	Not a direct indication for LITT; included for completeness when post-injury lesions are considered — clinical relevance limited.
`I63.9`	Cerebral infarction, unspecified	Cerebral infarcts are generally not treated with LITT; included for differential considerations when necrotic tissue is evaluated.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`61737`	Laser interstitial thermal therapy (LITT) of multiple lesions or complex lesion requiring multiple trajectories	Primary procedure code describing thermal ablation of multiple intracranial targets or complex single lesions requiring multiple trajectories.
`61796`	Stereotactic computer-assisted procedure for lesion localization and biopsy, intracranial	Used when stereotactic systems or registration for catheter placement and targeting are performed prior to LITT.
`62195`	Stereotactic computer-assisted ablation including image guidance, percutaneous, intracranial	Related stereotactic guidance and percutaneous access procedures that may be performed in conjunction with LITT planning and access.
`70554`	Magnetic resonance (MRI) brain; without and with contrast	Pre- and post-procedure MRI to plan trajectories and assess ablation extent; intraoperative MRI sequences also billed per facility rules.
`77021`	Magnetic resonance guidance for interventional procedure; per procedure	Supports MRI thermography or MR guidance used during LITT when separately reportable under payer policy.