CPT® Code 95937

Quick Reference

• Code definition: CPT 95937 captures repetitive nerve stimulation (RNS) and paired-pulse testing of the neuromuscular junction (NMJ), billed once per peripheral nerve tested regardless of how many stimulation frequencies are applied to that nerve.
• Key billing rule: The code is billed per nerve with a Medicare MUE of 4 units per date of service. Each unit must correspond to a separately documented, distinct nerve. Testing the same nerve at multiple stimulation rates (3 Hz and 50 Hz) still constitutes one unit; the descriptor specifies "any 1 method" per nerve.
• Modifier essentials: Modifiers 26 (professional component) and TC (technical component) apply when the interpreting physician and the performing facility are separate entities. Modifier 51 does NOT apply (multiple procedure indicator = 0). Modifier 59 may be needed to counter an incorrect NCCI bundling edit on same-day NCS claims.
• Documentation must-have: The EDX report must identify each specific nerve tested per billed unit and document CMAP amplitude measurements across the stimulus train with the percent decrement or increment explicitly calculated.
• Top confusion point: Coders frequently interchange 95937 with 95872 (single-fiber EMG). These are distinct tests. CPT 95937 uses surface or percutaneous stimulation to record compound muscle action potentials; 95872 uses a specialized needle electrode to measure individual fiber jitter. Billing one when only the other was performed is upcoding.
• Payer alert: Medicare covers 95937 under the MPFS as a diagnostic test (Type of Service 5). The AChR antibody (86041) and MuSK antibody (86366) tests routinely ordered alongside 95937 are billed on the Clinical Laboratory Fee Schedule, not the MPFS. Do not include these on the same MPFS claim.

When to Use This Code

CPT 95937 applies when a neurologist or physiatrist performs repetitive nerve stimulation or paired-pulse testing to assess neuromuscular junction transmission. The test delivers trains of electrical stimuli to a peripheral nerve via a stimulating electrode while recording the compound muscle action potential (CMAP) from the innervated muscle. The critical measurement is whether successive CMAPs decrement (postsynaptic defect, as in myasthenia gravis) or increment (presynaptic defect, as in Lambert-Eaton myasthenic syndrome or botulism).

Clinical indications where 95937 is appropriate:

• Suspected or confirmed myasthenia gravis (MG) with fatigable proximal limb weakness, ptosis, diplopia, or bulbar symptoms
• Evaluation of Lambert-Eaton myasthenic syndrome (LEMS), particularly in patients with known or suspected small cell lung cancer
• Botulism (foodborne, wound, or infant forms) where presynaptic NMJ block is suspected
• Congenital myasthenic syndromes requiring electrophysiological characterization
• Post-treatment monitoring in established MG or LEMS where quantitative response data is needed

Scope boundaries: The code does not apply to standard nerve conduction studies, which measure nerve axon conduction velocity and CMAP amplitude in isolation without repetitive stimulus trains. It does not cover conventional needle EMG, which assesses muscle membrane stability and motor unit morphology. Single-fiber EMG (95872) is an entirely separate technique using a different electrode and recording individual fiber potentials rather than compound responses.

Provider and setting context: CPT 95937 carries PC/TC indicator = 1, allowing global billing (one entity performing both technical and professional components) or split billing between the interpreting physician (modifier 26) and the facility (modifier TC). The split-billing scenario is common in hospital outpatient neurology labs where hospital staff perform the test and an independent neurologist reads and signs the report.

Code Differentiation Table

The single most critical differentiator is 95937 versus 95872. The RNS study (95937) stimulates a nerve electrically and records a mass response from all innervated muscle fibers. The SFEMG study (95872) records firing of individual or paired muscle fiber action potentials using a specialized needle. Billing 95872 when the note documents only a repetitive stimulation protocol is upcoding; the reverse is also true.

Billing & Modifier Rules

Units: CPT 95937 is reported once per nerve tested. A comprehensive NMJ evaluation may test three to four nerves, for example the ulnar at the hypothenar eminence, the facial at the nasalis, and the spinal accessory at the trapezius, yielding three separate units. Testing the same nerve at multiple stimulation frequencies (3 Hz and 50 Hz) does not generate additional units; the CPT descriptor consolidates all stimulation rates applied to a single nerve into one unit.

MUE = 4: CMS limits 95937 to 4 units per date of service per provider. Billing 5 or more units triggers an automated edit. Units beyond the MUE require extraordinary clinical justification and will likely prompt medical review.

Modifier usage:

Add-on codes: CPT 95940 and 95941 are add-on codes for continuous intraoperative neurophysiological monitoring. Both CPT codebook guidelines list 95937 as an eligible companion study, meaning 95937 can serve as the primary procedure when intraoperative NMJ monitoring is performed alongside general IONM services.

Bundling: CPT 95937 and the NCS family (95907 through 95913) are routinely performed together during a comprehensive electrodiagnostic study and are separately billable because they assess different physiological parameters. When an NCCI edit fires incorrectly, modifier 59 applied to 95937 documents that it represents a distinct service from the NCS study.

Documentation Essentials

The EDX report is the controlling document for 95937. Auditors reviewing these claims look for specificity confirming each billed unit represents a unique, medically necessary test of an identified nerve.

Required elements per billed unit:

• Name of the specific nerve tested (for example, "ulnar nerve" or "spinal accessory nerve"), not a generic reference to "NMJ testing performed"
• Stimulation frequency or protocol used (3 Hz, 20 Hz, 50 Hz trains, or paired-pulse protocol), including number of stimuli per train
• Baseline CMAP amplitude and the amplitude at each subsequent stimulus, with percent decrement or increment explicitly stated (for example, "10% decrement at 5th stimulus with 3 Hz repetitive stimulation")
• Results of any post-exercise or post-tetanic facilitation or exhaustion testing, when performed
• Clinical interpretation correlating electrophysiological findings to the patient's presentation and diagnosis
• Signature by the interpreting physician with credentials and date

Audit red flags specific to 95937:

• Reports listing only "repetitive nerve stimulation performed" without identifying the nerve or the CMAP amplitude measurements trigger probe review and downcoding
• Billing 4 units when the report documents only 1 or 2 nerves tested
• Reports describing single-fiber EMG techniques billed as 95937, or reports describing repetitive stimulation billed as 95872
• Same-provider, same-date claims for 95937 and 95872 without documentation explaining why both techniques were medically necessary (for example, equivocal RNS results prompting follow-up SFEMG)

Medical necessity: The clinical note or referral must document specific findings consistent with a NMJ disorder, such as fatigable weakness that worsens with exertion and improves with rest, ptosis, diplopia, bulbar symptoms, or a known associated condition (paraneoplastic, autoimmune, or toxic). Unspecified fatigue or weakness alone will not support medical necessity. ICD-10-CM code specificity also matters; G70.9 (myoneural disorder, unspecified) is appropriate only when a more specific diagnosis cannot be determined.

Medicare, Commercial & Medicaid Payer Rules

Medicare:

CPT 95937 is payable under the Medicare Physician Fee Schedule (MPFS). It carries global days of XXX (global concept does not apply) and Type of Service 5 (Diagnostic Laboratory). The APC status indicator "Procedure or Service, Not Discounted when Multiple" means that in the hospital outpatient setting, billing multiple units of 95937 on the same date does not trigger the standard 50% multiple-procedure APC discount.

CMS sets the MUE at 4 units per date of service. MAC-specific Local Coverage Determinations (LCDs) governing electrodiagnostic testing may impose additional frequency limits, for example restricting NMJ testing to a defined number of encounters per diagnosis within a rolling period. Providers should verify the applicable MAC LCD for their jurisdiction via the CMS Medicare Coverage Database.

Electrodiagnostic services, including 95937, have been identified in OIG work plans as areas of overutilization risk. High-volume EDX billers should ensure that each encounter includes a clinical note supporting the specific indication and that repeat testing is documented with a clinical reason such as change in medication, disease progression, or surgical planning.

Commercial payers:

Commercial coverage for 95937 generally follows Medicare criteria, but prior authorization requirements vary. Some plans require preauthorization when 95937 is billed with more than 2 units per date of service. Payer-specific policies on combined NCS and NMJ billing on the same date also differ; some commercial payers apply their own bundling edits that CMS does not. Verify coverage and bundling policies before the encounter for high-unit claims.

Note on lab serologies: CPT 86041 (AChR binding antibody) and 86366 (MuSK antibody), both added in 2024, are statutory exclusions from the MPFS and are billed on the Clinical Laboratory Fee Schedule. Do not include them on the same MPFS claim as 95937.

Common Denials & Prevention

Denial: Units exceed MUE

Units above the CMS MUE of 4 auto-adjudicate to zero. This occurs when the coder counts stimulation frequencies as separate units rather than nerves tested. Prevention: count nerves, not stimulation rates or train types. If a clinical situation genuinely requires more than 4 nerve tests, escalate to medical review with a supporting clinical statement before billing.

Denial: Medical necessity not established

The claim pays initially but is recouped on audit when the note lacks clinical findings consistent with a NMJ disorder. Prevention: ensure the clinical note documents specific symptoms and examination findings that prompted NMJ testing, not simply "ordered by referring physician." The diagnosis code on the claim must align with the documented clinical picture.

Denial: Incorrect code billed (95872 vs 95937)

Payers and auditors compare claim codes against the EDX report narrative. A report describing CMAP decrement on repetitive stimulation billed as 95872 generates a mismatch. Prevention: confirm the code selected matches the technique documented. If both RNS and SFEMG were performed on the same date, bill both with distinct documentation supporting each.

Denial: PC/TC mismatch resulting in duplicate claim

When services are split, the interpreting physician bills with modifier 26 and the facility bills with modifier TC. If either party bills globally (without a modifier), the other party's claim denies as a duplicate. Prevention: establish a standing arrangement between the physician and facility regarding which component each bills, and audit claims quarterly to catch modifier omissions.

Denial: ICD-10-CM sequencing error on manifestation codes

G73.1 (LEMS in neoplastic disease) and G70.81 (Lambert-Eaton in disease classified elsewhere) are etiology or manifestation codes requiring the underlying condition to be listed first. Claims sequencing G73.1 before the neoplasm code generate a sequencing edit. Prevention: train coders to recognize manifestation codes identified in ICD-10-CM by the "code first" instruction, and sequence them after the etiology.

Coding Scenarios

Scenario 1: Initial MG workup, outpatient neurology office

A neurologist evaluates a 52-year-old woman with three months of fatigable ptosis, diplopia, and proximal arm weakness. RNS is performed on the ulnar nerve at the hypothenar eminence and the spinal accessory nerve at the trapezius, each tested at 3 Hz and at high frequency post-exercise.

Correct coding: 95937 x 2; diagnosis: G70.00 if MG is confirmed at this encounter, or applicable sign or symptom codes if the diagnosis remains suspected (outpatient ICD-10-CM convention requires confirmed diagnoses; code symptoms when MG is not yet established).

Why: Two distinct nerves = 2 units. Testing each nerve at both 3 Hz and high frequency does not add units; "any 1 method" per nerve consolidates all stimulation rates into one unit.

Scenario 2: Paraneoplastic LEMS in a known SCLC patient

A 67-year-old man with known small cell lung cancer develops proximal leg weakness and areflexia. RNS is performed on the ulnar, peroneal, and tibial nerves, demonstrating incremental CMAP responses on high-frequency stimulation consistent with LEMS.

Correct coding: 95937 x 3; G73.1 sequenced first, followed by the neoplasm code.

Why: Three nerves = 3 units. G73.1 is a manifestation code; the neoplasm must be listed before the manifestation per ICD-10-CM convention. Testing at both 3 Hz and 50 Hz on the same nerve does not generate an additional unit.

Scenario 3: Split billing in a hospital outpatient neurology lab

A hospital outpatient lab performs RNS on two nerves using hospital-owned equipment and hospital-employed technicians. A neurologist from an independent practice group interprets the tracings and signs the report.

Correct coding: Hospital bills 95937 x 2 with modifier TC. Neurologist bills 95937 x 2 with modifier 26.

Why: PC/TC indicator = 1 permits split billing. Neither party bills globally. Both claims must reflect the same unit count or one will deny as a duplicate.

Scenario 4: Combined EDX study, NCS and RNS on same date

A comprehensive EDX evaluation for suspected MG includes 4 conventional nerve conduction studies (ulnar motor, median motor, ulnar sensory, and median sensory) and RNS of the ulnar nerve.

Correct coding: 95908 (3-4 NCS studies, one unit) + 95937 x 1; G70.00 or applicable symptom codes.

Why: NCS and RNS assess different physiological parameters and are separately reportable. 95908 captures the 4 NCS studies (the 3-4 study tier). 95937 captures the RNS. No NCCI prohibition applies to this combination.

Related Codes

• 95872: Single-fiber EMG, jitter, blocking, and fiber density; alternative NMJ test more sensitive than RNS for MG, uses a specialized needle electrode, billed per muscle
• 95857: Cholinesterase inhibitor challenge test for MG; pharmacological alternative to electrophysiological NMJ testing, MUE = 1
• 95907: Nerve conduction studies, 1-2 studies; commonly performed alongside 95937 in a comprehensive EDX workup
• 95908: Nerve conduction studies, 3-4 studies; same as above, selected by NCS count
• 95905: Automated NCS using preconfigured electrode array, each limb; alternative NCS approach billed per limb
• 95940: Continuous intraoperative neurophysiology monitoring, in-person attendance, each 15 minutes; add-on reportable in conjunction with 95937 when IONM is concurrent
• 86041: AChR binding antibody (added 2024); MG serology ordered alongside NMJ testing, billed on the CLFS not the MPFS
• 86366: MuSK antibody (added 2024); seronegative MG serology, same CLFS billing distinction as 86041

Sources

1. CPT 95937 code record: official descriptor, MUE, PC/TC indicator, global days, multiple procedure indicator, and code history. Local CPT database.
2. CPT 95872, 95857, 95905, 95907, 95908, 95940, 95941 code records. Local CPT database.
3. CPT 86041 and 86366 code records (added 2024). Local CPT database.
4. ICD-10-CM code records: G70.00, G70.01, G70.80, G70.81, G70.1, G70.2, G70.89, G70.9, G73.1, G73.3, P94.0, A05.1, A48.51, A48.52. Local ICD-10-CM database.