CPT® Code 95955

Quick Reference

• Code definition: CPT 95955 covers an electroencephalogram performed by a neurophysiologist during a nonintracranial operation, most commonly carotid endarterectomy, to detect real-time cerebral ischemia during periods of vascular clamping.
• Key billing rule: 95955 is a flat, non-time-based code billed once per date of service regardless of operative duration; MUE = 1 with MAI = 3 (clinical nature of service edit, not overridable by modifier).
• Modifier essentials: PCTC indicator = 1 supports split billing; use -26 when a physician provides interpretation and a written report only, and -TC when an entity provides equipment and recording technologist only. Bill global (no modifier) when a single group furnishes both components.
• Documentation must-have: A written interpretation report signed by the interpreting physician is required for every professional component claim; absence of this report is the leading cause of -26 denials and OIG audit findings.
• Top confusion point: CPT 95829 (electrocorticogram at surgery) is the intracranial counterpart; using 95829 for carotid or cardiac surgery is a miscoding error that constitutes upcoding, as 95829 carries a substantially higher work RVU than 95955.
• Payer alert: CPT 95941 (remote IONM, per hour) is not valid for Medicare purposes; do not substitute it for 95955 or 95940 on Medicare claims. This is among the most consequential distinctions in IONM compliance.
• APC packaging: In the hospital outpatient and ASC facility settings, 95955 is packaged into the surgical APC rate; the facility receives no separate payment [2]. The interpreting physician's -26 claim remains separately payable.

When to Use This Code

CPT 95955 applies when a neurologist or clinical neurophysiologist performs continuous EEG monitoring during a surgical procedure that does not directly involve the brain itself but places cerebral perfusion at risk. The canonical procedure is carotid endarterectomy (CEA), where cross-clamping of the carotid artery temporarily reduces blood flow to the ipsilateral hemisphere. EEG changes during clamping serve as a real-time signal for the surgical team to consider shunt placement.

Other nonintracranial surgical settings where 95955 applies include:

• Aortic arch repair requiring hypothermic circulatory arrest, where EEG confirms electrocerebral silence before arrest and documents return of brain activity during perfusion recovery
• Cardiac surgery with cardiopulmonary bypass and cerebral perfusion risk
• Procedures requiring clamping of major cerebral feeding vessels for aneurysm repair

The procedure uses 10 to 20 scalp electrodes placed per the International 10-20 system, recording from 8 to 32 channels. Recording, real-time interpretation, communication of findings to the surgical team, and a written final report are all bundled into this single code.

Provider and setting context: 95955 is a facility-based service; place of service 11 (office) is not appropriate. The global indicator = XXX means the code is never bundled into the surgeon's global surgical period, so the neurophysiologist bills independently regardless of whether the monitoring is performed during a procedure still within another provider's postoperative period.

Not time-based: Unlike 95940 (IONM in the OR, each 15 minutes), 95955 does not accrue units over time. The entire monitoring session, regardless of length, is one unit. MUE = 1 with MAI = 3 confirms that billing more than one unit per date of service will be denied and cannot be unlocked with a modifier [3].

Code Differentiation Table

The most critical differentiator is anatomical: "nonintracranial" in the 95955 descriptor defines the entire boundary separating it from 95829. Any surgery that accesses the cranium and places electrodes directly on cortical tissue belongs to 95829; scalp EEG during any surgery that does not open the skull belongs to 95955.

flowchart TD
    A[EEG monitoring during surgery] --> B{Is surgery intracranial?}
    B -- Yes --> C[Direct cortical electrodes?]
    C -- Yes --> D[95829\nElectrocorticogram at surgery]
    C -- No --> E[Consult CPT guidelines]
    B -- No --> F[Scalp electrodes\nnonintracranial surgery]
    F --> G[95955\nEEG during nonintracranial surgery]
    G --> H{Single group provides TC and 26?}
    H -- Yes --> I[Bill global: 95955]
    H -- No --> J[Split: 95955-26 plus 95955-TC]

Billing and Modifier Rules

Global vs. split billing (PCTC = 1):

The most operationally complex aspect of 95955 is the professional/technical split, which mirrors the model used for diagnostic radiology codes. Three billing configurations exist:

1. Single group provides both equipment/technologist (TC) and physician interpretation (26): bill 95955 global (no modifier)
2. Independent physician interprets EEG recorded by another entity: bill 95955-26 only
3. Monitoring company provides equipment and technologist; independent physician interprets: monitoring company bills 95955-TC, physician bills 95955-26

The TC requires direct physician supervision (CMS supervision indicator = 02). A monitoring company cannot bill 95955-TC without a qualified physician available to supervise the recording in real time. OIG Report OEI-02-17-00540 [1] identified this supervision requirement as the primary source of IONM overpayment.

Modifier -26 usage:

• 2026 work RVU: 0.98; estimated Medicare payment approximately $53.11 using the 2026 conversion factor of $33.4009 [2]
• Requires a written interpretation report; the report is the deliverable, not physical presence during recording

Modifier -TC usage:

• 2026 non-facility total RVU: 4.33; estimated Medicare payment approximately $144.62 [2]
• No work RVU; practice expense RVU only
• Direct physician supervision required; cannot bill TC in remote-only arrangements without an appropriately available supervising physician

MUE and unit rules:

• MUE = 1, MAI = 3 [3]. Regardless of bilateral procedures or extended operative time, 95955 is billed once per date of service. The bilateral surgery indicator = 0 confirms the 150% bilateral adjustment does not apply.

Modifier -51 (Multiple Procedures):

• The multiple procedures indicator = 0; do not append -51 to 95955 when billing alongside surgical codes.

Add-on code interaction:

• 95940 (continuous IONM in OR, each 15 minutes) is an add-on code reported in addition to 95955 when a neurophysiologist provides continuous in-room IONM as a separately documented service. These codes serve different functions: 95955 captures the EEG-specific monitoring session; 95940 captures continuous time-based in-room attendance.
• G0453 (continuous IONM from outside the OR, per patient, each 15 minutes) is the HCPCS add-on used by some payers for remote monitoring scenarios where 95941 is not recognized.

Global surgery interaction:

• Global days = XXX; 95955 never falls within a surgeon's global surgical period. The neurophysiologist bills without regard to whether the surgery is still within another provider's 0, 10, or 90-day global period.

Documentation Essentials

Required elements for every 95955 claim:

1. Identification of the surgical procedure performed and the clinical basis for cerebral perfusion monitoring (diagnosis documenting the nonintracranial surgery with ischemic brain risk)
2. Electrode placement documentation: number of channels, electrode configuration, and recording system
3. Baseline EEG: pre-clamping or pre-procedure baseline pattern with interpretation
4. Intraoperative monitoring record: timestamps of EEG findings throughout the procedure, notation of any changes correlated with surgical events (e.g., carotid clamp applied at time X, EEG change noted at time Y)
5. Evidence of real-time interpretation: documentation that the interpreting physician was actively monitoring throughout the procedure, not reviewing a stored recording after the fact
6. Written final report signed by the interpreting physician: baseline findings, any intraoperative changes, clinical significance, interventions prompted, and correlation with operative events
7. Physician credentials establishing qualifications for EEG interpretation (neurologist, clinical neurophysiologist, or equivalent)

Audit red flags specific to 95955:

• Professional component claims without a physician-signed written report in the medical record
• TC claims without documentation of supervising physician availability (name, contact method, and confirmation of real-time oversight)
• POS 11 (office) on a claim for intraoperative EEG monitoring
• Billing units greater than 1 per date of service, particularly for bilateral same-session cases
• Monitoring records showing only pre- and post-operative EEG snapshots rather than a continuous intraoperative record
• Claims where the operative report and EEG monitoring record are internally inconsistent in dates or surgical event timing

Medicare and Commercial Payer Rules

Medicare:

No National Coverage Determination governs CPT 95955 or IONM broadly. Coverage is determined entirely by MAC-level Local Coverage Determinations. Noridian Healthcare Solutions (Jurisdictions E and F) has published LCD L34834, "Intraoperative Neurophysiology." Novitas Solutions, CGS Administrators, Palmetto GBA, and WPS each maintain jurisdiction-specific IONM coverage policies [4][5]. Verify current effective dates and covered diagnosis codes directly at each MAC's LCD directory, as these policies are subject to revision.

Carotid endarterectomy for significant carotid stenosis is broadly covered across MAC jurisdictions. Cardiac surgery indications vary; confirm coverage criteria with the applicable MAC before providing monitoring for aortic or cardiac procedures. Site-of-service payment: the non-facility total RVU for 95955 (global) is 5.92 in 2026 [2], consistent with the inherently non-facility professional service model. In hospital outpatient settings, APC packaging means the facility claim bundles 95955 into the surgical procedure APC; the interpreting physician's -26 claim is paid separately under the PFS [2].

CPT 95941 is not valid for Medicare (status "Not Valid," MUE = 0 [3]). IONM organizations using remote monitoring models must bill 95940 (in-room, time-based) or the modality-specific code 95955 for EEG as appropriate; 95941 will deny on every Medicare claim. CPT 99360 (standby service) is a statutory exclusion from the Medicare Physician Fee Schedule and cannot be used as a substitute billing vehicle for intraoperative EEG monitoring.

OIG compliance context:

OIG Report OEI-02-17-00540 (2019) [1] found IONM services were a significant source of Medicare overpayment due to services billed without required physician supervision, remote monitoring arrangements without contemporaneous documentation of physician availability, and monitoring furnished for procedures without established clinical utility. Providers billing 95955 should maintain compliance programs specifically addressing real-time supervision documentation and coverage eligibility verification before service.

Commercial payers:

CPT 95941 may be recognized by commercial payers that have not adopted the Medicare exclusion. Verify each commercial payer's policy before billing. Some commercial payers have adopted policies mirroring Medicare's supervision requirements for TC services; others apply prior authorization requirements for IONM services broadly. Medicare Advantage plans may require prior authorization; verify with the individual plan before service.

Common Denials and Prevention

Missing written interpretation report Audit programs and prepayment review target -26 claims without a physician-signed written report. The report is the deliverable for the professional component; without it, the claim lacks the documentation required to support the work RVU. Prevention: Require a signed final report before claim submission. Report templates should include baseline EEG description, intraoperative changes with timestamps, clinical significance, and correlation with surgical events.

Supervision violation for TC claims CMS and OIG auditors look for evidence that a qualified physician was available in real time during recording. Claims where the supervising physician cannot be identified or where monitoring was provided without documented physician oversight will not withstand audit [1]. Prevention: Maintain contemporaneous logs identifying the supervising physician by name, their location during the service, and the method of real-time communication with the recording technologist.

CPT 95941 billed to Medicare 95941 has Medicare status "Not Valid for Medicare Purposes" with MUE = 0 [3]; every unit will deny. Prevention: Implement a payer-specific billing rule in the practice management system that blocks 95941 on all Medicare and Medicare Advantage claims. Use 95940 for in-room time-based monitoring or 95955 for EEG-specific services.

Units greater than 1 per date of service MUE = 1 with MAI = 3 is a clinical nature edit and is not overridable with modifier -59 or similar distinction modifiers [3]. Even bilateral same-session procedures constitute a single unit. Prevention: Hard-stop any claim for 95955 with units greater than 1 in the billing system.

Medical necessity not supported by diagnosis Claims where the attached ICD-10-CM diagnosis does not reflect a condition requiring cerebral perfusion monitoring during surgery will fail MAC LCD medical necessity review. Prevention: Map covered diagnosis codes per the applicable MAC LCD and verify coverage before service. For carotid procedures, codes such as I65.21, I65.22, and I65.23 (occlusion and stenosis of carotid arteries) support medical necessity. For non-CEA indications, confirm covered diagnoses with the relevant MAC policy.

Coding Scenarios

Scenario 1: CEA with independent neurophysiologist group (split billing)

A 67-year-old patient with right internal carotid stenosis undergoes right carotid endarterectomy. An independent IONM monitoring company provides a technologist who applies scalp electrodes and records throughout the procedure. A neurophysiologist affiliated with the monitoring company monitors the EEG from an adjacent room and provides real-time interpretation. No significant EEG changes occur during carotid cross-clamping.

Correct coding: 95955-TC (monitoring company claim) + 95955-26 (neurophysiologist professional claim), both with diagnosis I65.21.

Why: Two separate entities furnish the TC and the professional component; the global code cannot be billed on a single claim. The supervising physician's availability must be contemporaneously documented to support the TC claim.

Scenario 2: University neurology department provides global service

A university medical center neurology service provides both the EEG equipment and technologist and a staff neurologist who monitors the case and provides a written interpretation report. The neurologist is present in the adjacent monitoring suite throughout the operative period.

Correct coding: 95955 global (no modifier) with the appropriate surgical indication diagnosis code.

Why: A single group provides both TC and professional components; splitting the claim between 95955-TC and 95955-26 would constitute double-counting of a single service.

Scenario 3: Attempted billing of 95955 twice for bilateral same-session carotid procedures

A patient undergoes repair of bilateral carotid stenosis in a single operative session. The IONM team submits a claim for 95955 with two units.

Correct coding: 95955 with one unit only.

Why: MUE = 1 with MAI = 3 [3]; the bilateral surgery indicator = 0 confirms no bilateral payment adjustment applies. Both carotids in the same session constitute a single monitoring service on one date of service; the second unit will deny and cannot be appealed on clinical grounds.

Scenario 4: Routine diagnostic EEG performed same day as carotid surgery monitoring

A patient with a documented seizure disorder has a baseline diagnostic EEG (95819) performed in the neurology clinic in the morning before their afternoon carotid endarterectomy. Intraoperative EEG monitoring (95955) is performed during the CEA.

Correct coding: 95955 (intraoperative monitoring) + 95819-59 (morning diagnostic EEG, distinct service). Both claims require separate signed interpretation reports.

Why: The two EEG services are clinically distinct, performed in different settings at different times for different purposes. Modifier -59 documents the distinct service relationship. Verify the current NCCI PTP table for the 95955/95819 column 1/2 relationship before billing; without the modifier, the routine EEG may be denied as bundled into the intraoperative service.

Related Codes

• 95940: Continuous IONM in OR, each 15 minutes; add-on; in-room, one-on-one; active for Medicare; may be billed alongside 95955 for continuous time-based in-room attendance
• 95941: Continuous IONM remote or nearby, per hour; NOT valid for Medicare; commercial payers only
• 95829: Electrocorticogram at surgery; intracranial counterpart to 95955; direct cortical electrodes during brain surgery
• 95957: Digital analysis of EEG; may be separately reportable when digital reformatting and analysis is performed on the intraoperative EEG record
• 95819: EEG awake and asleep; routine diagnostic; requires -59 if billed same day as 95955 for a genuinely separate study
• 95816: EEG awake and drowsy; routine diagnostic; same bundling risk as 95819 when billed same day as 95955
• G0453: Continuous IONM from outside OR, per patient, each 15 minutes; HCPCS add-on used for remote monitoring scenarios by payers that do not recognize 95941
• 99360: Standby service; statutory exclusion from Medicare PFS; do not substitute for 95955 on Medicare claims

Sources

1. HHS OIG Report OEI-02-17-00540: Intraoperative Neurophysiological Monitoring: Questionable Billing Practices (2019) — OIG findings on IONM supervision violations and Medicare overpayments
2. CMS 2026 Physician Fee Schedule RVU File — released 12/29/2025 — source for 2026 RVU values, APC status indicator, PCTC indicator, and conversion factor ($33.4009) for 95955
3. CMS NCCI MUE Practitioner Services, effective 04-01-2026 — MUE = 1, MAI = 3 confirmed for 95955
4. Noridian LCD L34834, Intraoperative Neurophysiology — MAC LCD for IONM, Jurisdictions E and F; verify current effective date
5. CMS Medicare Coverage Database, LCD Search — search for active IONM LCDs across all MAC jurisdictions
6. Federal Register CY2026 MPFS Final Rule — 2026 PFS final rule with 95955 RVU finalization