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Official Description

Central motor evoked potential study (transcranial motor stimulation); lower limbs

© Copyright 2026 American Medical Association. All rights reserved.

Common Language Description

A central motor evoked potential (MEP) study is a diagnostic procedure that assesses the functionality of the motor pathways in the body. Specifically, CPT® Code 95929 pertains to the evaluation of the lower limbs through transcranial motor stimulation. This study involves the application of electrical stimulation to the motor area of the cerebral cortex, which is the region of the brain responsible for voluntary movement. The stimulation is followed by the recording of electrical activity from peripheral muscles located in the lower extremities, such as those in the legs. The primary goal of this procedure is to evaluate the integrity and functionality of the motor pathways that connect the brain to the muscles, thereby providing valuable insights into any potential neurological disorders affecting motor control. Prior to conducting the MEP study, baseline nerve conduction studies are typically performed to establish a reference point for comparison. The procedure is meticulously designed to ensure accurate measurements of motor response, including the amplitude and latency of the evoked potentials, which are critical for diagnosing conditions that may impair motor function.

© Copyright 2026 Coding Ahead. All rights reserved.

1. Indications

The central motor evoked potential study (CPT® Code 95929) is indicated for the evaluation of motor pathway function in the lower extremities. This procedure is typically performed in patients presenting with symptoms or conditions that may affect motor control, including but not limited to:

  • Neurological Disorders Conditions such as multiple sclerosis, amyotrophic lateral sclerosis (ALS), or other demyelinating diseases that may impair motor function.
  • Peripheral Nerve Injuries Assessment of motor pathway integrity in cases of trauma or injury to the peripheral nerves affecting the lower limbs.
  • Stroke Evaluation of motor function post-stroke to determine the extent of motor pathway involvement and recovery potential.
  • Spinal Cord Injuries Assessment of motor function in patients with spinal cord injuries that may impact lower limb movement.

2. Procedure

The procedure for conducting a central motor evoked potential study for the lower limbs involves several detailed steps to ensure accurate assessment of motor pathway function:

  • Baseline Nerve Conduction Studies Prior to the MEP recording, baseline nerve conduction studies are performed on the lower extremities to establish reference values for comparison during the MEP assessment.
  • Electrode Placement Electrodes are strategically placed on the skin over selected muscles in the legs, which may include muscles such as the quadriceps, hamstrings, and gastrocnemius, to capture the electrical activity during stimulation.
  • Impedance Check The impedances of the electrodes are checked to ensure proper contact with the skin. Adjustments are made as necessary to optimize the quality of the recordings.
  • Optimal Scalp Location Identification The optimal scalp location for electrical stimulation is identified, beginning with the muscle that is first tested. This involves determining the precise area on the scalp that corresponds to the motor cortex controlling the lower limbs.
  • MEP Threshold Determination The motor evoked potential (MEP) threshold is established by gradually increasing the stimulation intensity until a consistent response is recorded from the targeted muscles.
  • Cortex Stimulation and Recording The motor area of the cerebral cortex is stimulated, and the MEPs are recorded. The amplitude and latency of the responses are measured and compared to the baseline nerve conduction study results.
  • Compound Muscle Action Potential (CMAP) Testing The compound muscle action potential (CMAP) is tested by stimulating the relevant peripheral nerve, such as the tibial nerve, to assess the strength of the muscle response in relation to the MEP.
  • Central Motor Conduction Time (CMCT) Calculation The central motor conduction time (CMCT) is calculated to evaluate the speed of conduction along the motor pathways.
  • Dissociation Measurement The stimulator output is reduced in 5% increments to measure the dissociation between the MEP threshold and the cortical stimulation silent period (CSSP), identifying any inhibitory effects.
  • Data Replication and Storage The data collected during the procedure is replicated to ensure accuracy, and the signals are stored for further analysis.
  • Contralateral Testing The procedure is repeated on 3-4 muscles in the ipsilateral lower extremity, followed by testing of the contralateral lower extremity in the same manner to provide a comprehensive evaluation.
  • Physician Review Finally, the physician reviews the recordings and compiles a written report detailing the findings of the study, which will assist in diagnosing any underlying conditions affecting motor function.

3. Post-Procedure

After the completion of the central motor evoked potential study, patients may be monitored briefly to ensure there are no immediate adverse effects from the electrical stimulation. Typically, there are no significant post-procedure complications, and patients can resume normal activities shortly after the study. The physician will provide a detailed report of the findings, which may include recommendations for further evaluation or treatment based on the results of the MEP study. Follow-up appointments may be scheduled to discuss the findings and any necessary interventions.

Short Descr C MOTOR EVOKED LWR LIMBS
Medium Descr CTR MOTOR EP STD TRANSCRNL MOTOR STIMJ LWR LIMBS
Long Descr Central motor evoked potential study (transcranial motor stimulation); lower limbs
Status Code Active Code
Global Days XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC) 1 - Diagnostic Tests for Radiology Services
Multiple Procedures (51) 0 - No payment adjustment rules for multiple procedures apply.
Bilateral Surgery (50) 2 - 150% payment adjustment does NOT apply.
Physician Supervisions 09 - Concept does not apply.
Assistant Surgeon (80, 82) 0 - Payment restriction for assistants at surgery applies to this procedure...
Co-Surgeons (62) 0 - Co-surgeons not permitted for this procedure.
Team Surgery (66) 0 - Team surgeons not permitted for this procedure.
Diagnostic Imaging Family 99 - Concept Does Not Apply
APC Status Indicator Procedure or Service, Not Discounted when Multiple
Type of Service (TOS) 1 - Medical Care
Berenson-Eggers TOS (BETOS) T2D - Other tests - other
MUE 1
CCS Clinical Classification 7 - Other diagnostic nervous system procedures

This is a primary code that can be used with these additional add-on codes.

95940 Addon Code Resequenced Code MPFS Status: Active Code APC N Continuous intraoperative neurophysiology monitoring in the operating room, one on one monitoring requiring personal attendance, each 15 minutes (List separately in addition to code for primary procedure)
95941 Addon Code Resequenced Code MPFS Status: Not valid for Medicare purposes APC N Continuous intraoperative neurophysiology monitoring, from outside the operating room (remote or nearby) or for monitoring of more than one case while in the operating room, per hour (List separately in addition to code for primary procedure)
G0453 Add-on Code Medicare Coverage: Carrier Priced MPFS Status: Active Code APC N Continuous intraoperative neurophysiology monitoring, from outside the operating room (remote or nearby), per patient, (attention directed exclusively to one patient) each 15 minutes (list in addition to primary procedure)
26 Professional component: certain procedures are a combination of a physician or other qualified health care professional component and a technical component. when the physician or other qualified health care professional component is reported separately, the service may be identified by adding modifier 26 to the usual procedure number.
52 Reduced services: under certain circumstances a service or procedure is partially reduced or eliminated at the discretion of the physician or other qualified health care professional. under these circumstances the service provided can be identified by its usual procedure number and the addition of modifier 52, signifying that the service is reduced. this provides a means of reporting reduced services without disturbing the identification of the basic service. note: for hospital outpatient reporting of a previously scheduled procedure/service that is partially reduced or cancelled as a result of extenuating circumstances or those that threaten the well-being of the patient prior to or after administration of anesthesia, see modifiers 73 and 74 (see modifiers approved for asc hospital outpatient use).
59 Distinct procedural service: under certain circumstances, it may be necessary to indicate that a procedure or service was distinct or independent from other non-e/m services performed on the same day. modifier 59 is used to identify procedures/services, other than e/m services, that are not normally reported together, but are appropriate under the circumstances. documentation must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual. however, when another already established modifier is appropriate it should be used rather than modifier 59. only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used. note: modifier 59 should not be appended to an e/m service. to report a separate and distinct e/m service with a non-e/m service performed on the same date, see modifier 25.
GC This service has been performed in part by a resident under the direction of a teaching physician
GZ Item or service expected to be denied as not reasonable and necessary
TC Technical component; under certain circumstances, a charge may be made for the technical component alone; under those circumstances the technical component charge is identified by adding modifier 'tc' to the usual procedure number; technical component charges are institutional charges and not billed separately by physicians; however, portable x-ray suppliers only bill for technical component and should utilize modifier tc; the charge data from portable x-ray suppliers will then be used to build customary and prevailing profiles
XP Separate practitioner, a service that is distinct because it was performed by a different practitioner
XU Unusual non-overlapping service, the use of a service that is distinct because it does not overlap usual components of the main service
Date
Action
Notes
2011-01-01 Changed Short description changed.
2005-01-01 Added First appearance in code book in 2005.
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