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Navigated Transcranial Magnetic Stimulation (nTMS)

Policy Number: MP-556

Latest Review Date: June 2024

Category: Medicine                                                              

POLICY:

Navigated transcranial magnetic stimulation is considered investigational for all indications, including but not limited to, the preoperative evaluation of individuals being considered for brain surgery.

DESCRIPTION OF PROCEDURE OR SERVICE:

Navigated transcranial magnetic stimulation (nTMS) is a noninvasive imaging method for the evaluatiing of eloquent brain areas (e.g., controlling motor or language function). Navigated TMS is being evaluated as an alternative to other noninvasive cortical mapping techniques for pre-surgical identification of eloquent areas.

Management of Brain Tumors

Surgical management of brain tumors involves resecting the brain tumor and preserving essential brain function. “Mapping” of brain functions, such as body movement and language, is most accurately achieved with direct cortical stimulation (DCS), an intraoperative procedure that lengthens operating times and requires a wide surgical opening. Even if not completely accurate compared with DCS, preoperative techniques that map brain functions may aid in planning the extent of resection and the surgical approach. Although DCS is still usually performed to confirm the brain locations associated with specific functions, preoperative mapping techniques may provide useful information that improves individual outcomes.

Noninvasive Mapping Techniques

The most commonly used tool for the noninvasive localization of brain functions is functional magnetic resonance imaging (fMRI). Functional MRI identifies regions of the brain where there are changes in localized cortical blood oxygenation, which correlates with the neuronal activity associated with a specific motor or speech task being performed as the image is obtained. The accuracy and precision of fMRI depend on the individual's ability to perform the isolated motor task, such as moving the single assigned muscle without moving others. This may be difficult for individuals in whom brain tumors have caused partial or complete paresis. The reliability of fMRI in mapping language areas has been questioned. Guissani et al (2010) reviewed several studies comparing fMRI with DCS of language areas and found large variability in sensitivity and specificity rates of fMRI. Reviewers also pointed out a major conceptual point in how fMRI and DCS “map” language areas: fMRI identifies regional oxygenation changes, which show that a particular region of the brain is involved in the capacity of interest, whereas DCS locates specific areas in which the activity of interest is disrupted. Regions of the brain involved in a certain activity may not necessarily be required for that activity and could theoretically be safely resected.

Magnetoencephalography (MEG) is also is used to map brain activity. In this procedure, electromagnetic recorders are attached to the scalp. Unlike to electroencephalography, MEG records magnetic fields generated by electric currents in the brain, rather than the electric currents themselves. Magnetic fields tend to be less distorted by the skull and scalp than electric currents, yielding improved spatial resolution. MEG is conducted in a magnetically shielded room to screen out environmental electric or magnetic noises that could interfere with the MEG recording.

Navigated transcranial magnetic stimulation (nTMS) is a noninvasive imaging method for the evaluating eloquent brain areas. Transcranial magnetic pulses are delivered to the individual as a navigation system calculates the strength, location, and direction of the stimulating magnetic field. The locations of these pulses are registered to a magnetic resonance imaging (MRI) image of the inidividual’s brain. Surface electromyography (EMG) electrodes are attached to various limb muscles of the individual. Moving the magnetic stimulation source to various parts of the brain causes EMG electrodes to respond; indicating the part of the cortex involved in particular muscle movements. For evaluation of language areas, magnetic stimulation areas that disrupt specific speech tasks are thought to identify parts of the brain involved in speech function. Navigated TMS can be considered a noninvasive alternative to DCS, in which electrodes are directly applied to the surface of the cortex during craniotomy. Navigated TMS is being evaluated as an alternative to other noninvasive cortical mapping techniques, (e.g., fMRI and MEG), for pre-surgical identification of cortical areas involved in motor and language functions. Navigated TMS, used for cortical language area mapping, is also being investigated in combination with diffusion tensor imaging tractography for subcortical white matter tract mapping.

KEY POINTS:

The most recent literature review has been updated regularly with searches of the PubMed database. The most recent literature update was performed through April 25, 2024.

Summary of Evidence

For individuals who have brain lesion(s) undergoing preoperative evaluation for localization of eloquent areas of the brain who receive navigated transcranial magnetic stimulation (nTMS), the evidence includes systematic reviews, observational studies and case series. Relevant outcomes are overall survival (OS), test accuracy, morbid events, and functional outcomes. Several studies have evaluated the distance between nTMS hotspots and direct cortical stimulation (DCS) hotspots for the same muscle. Although the average distance in most studies is 10 mm or less, this does not take into account the error margin in this average distance or whether hotspots are missed. It is difficult to verify nTMS hotspots fully because only exposed cortical areas can be verified with direct cortical stimulation. Limited studies of nTMS evaluating language areas have shown high false-positive rates (low specificity) and sensitivity that may be insufficient for clinical use. Several controlled observational studies have compared outcomes in individuals undergoing nTMS with those (generally pre-TMS historical controls) who did not undergo nTMS. Findings of the studies were mixed. A meta-analysis of observational studies found improved outcomes with preoperative nTMS mapping in individuals with motor-eloquent brain tumors. However, in individual observational studies, outcomes were not consistently better in individuals who underwent pre-surgical nTMS. For example, overall survival did not differ significantly between groups in two studies. The controlled observational studies had various methodologic limitations and, being nonrandomized, might not have adequately controlled for differences in individual groups, which could have biased outcomes. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

Practice Guidelines and Position Statements

No guidelines or statements were identified.

U.S. Preventive Services Task Force Recommendations

Not applicable.

KEY WORDS:

Navigated transcranial magnetic stimulation, nTMS, Nexstim®, Nexstim NBS System 4, NexSpeech®, Navigated Brain Stimulation System (NBS), NexStim NBS 5 Motor Mapping System, NBS 5 Speech Mapping System

APPROVED BY GOVERNING BODIES:

The Nexstim Navigated Brain Stimulation (NBS) System 5 Motor Mapping System and NBS 5 Speech Mapping System with NexSpeech® were cleared for marketing by the U.S. Food and Drug Administration through the 510(k) process for noninvasive mapping of the primary motor cortex of the brain to its cortical gyrus and for localization of cortical areas that do not contain speech function for pre-procedural planning.

BENEFIT APPLICATION:

Coverage is subject to member’s specific benefits. Group-specific policy will supersede this policy when applicable.

ITS: Home Policy provisions apply.

FEP: Special benefit consideration may apply. Refer to member’s benefit plan.

CURRENT CODING:

CPT Codes:

As of 01/01/2018, there is no specific CPT code for this procedure. Use the following CPT code:

64999

Unlisted procedure, nervous system

REFERENCES:

  1. Baro V, Sartori L, Caliri SL, et al. Navigated Transcranial Magnetic Stimulation Motor Mapping and Diffusion Tensor Imaging Tractography for Diencephalic Tumor in Pediatric Patients. Brain Sci. Jan 30 2023; 13(2).

  2. Forster MT, Hattingen E, Senft C et al. Navigated transcranial magnetic stimulation and functional magnetic resonance imaging: advanced adjuncts in preoperative planning for central region tumors. Neurosurgery 2011; 68(5):1317-24; discussion 24-5.

  3. Forster MT, Limbart M, Seifert V, et al. Test-retest reliability of navigated transcranial magnetic stimulation of the motor cortex. Neurosurgery. Mar 2014; 10 Suppl 1: 51-5; discussion 55-6.

  4. Frey D, Schilt S, Strack V, et al. Navigated transcranial magnetic stimulation improves the treatment outcome in patients with brain tumors in motor eloquent locations. Neuro Oncol. Oct 2014; 16(10):1365-1372.

  5. Giussani C, Roux FE, Ojemann J et al. Is preoperative functional magnetic resonance imaging reliable for language areas mapping in brain tumor surgery? Review of language functional magnetic resonance imaging and direct cortical stimulation correlation studies. Neurosurgery 2010; 66(1):113-20.

  6. Hendrix P, Senger S, Simgen A, et al. Preoperative rTMS language mapping in speech- eloquent brain lesions resected under general anesthesia: a pair-matched cohort study. World Neurosurg. Apr 2017; 100:425-433.

  7. Ille S, Kelm A, Schroeder A, et al. Navigated repetitive transcranial magnetic stimulation improves the outcome of postsurgical paresis in glioma patients - A randomized, double-blinded trial. Brain Stimul. 2021; 14(4): 780-787.

  8. IOM (Institute of Medicine). 2011. Clinical Practice Guidelines We Can Trust. Washington, DC: The National Academies Press.

  9. Jeltema HR, Ohlerth AK, de Wit A, et al. Comparing navigated transcranial magnetic stimulation mapping and "gold standard" direct cortical stimulation mapping in neurosurgery: a systematic review. Neurosurg Rev. Aug 2021; 44(4):1903-1920.

  10. Kato N, Schilt S, Schneider H, et al. Functional brain mapping of patients with arteriovenous malformations using navigated transcranial magnetic stimulation: first experience in ten patients. Acta Neurochir (Wien). May 2014; 156(5):885-895.

  11. Krieg SM, Sollmann N, Obermueller T, et al. Changing the clinical course of glioma patients by preoperative motor mapping with navigated transcranial magnetic brain stimulation. BMC Cancer. Apr 08 2015; 15: 231.

  12. Krieg SM, Shiban E, Buchmann N et al. Utility of presurgical navigated transcranial magnetic brain stimulation for the resection of tumors in eloquent motor areas. J Neurosurg 2012; 116(5):994-1001.

  13. Krieg SM, Sollmann N, Obermueller T, et al. Changing the clinical course of glioma patients by preoperative motor mapping with navigated transcranial magnetic brain stimulation. BMC Cancer. 2015; 15:231.

  14. Mangraviti A, Casali C, Cordella R et al. Practical assessment of preoperative functional mapping techniques: navigated transcranial magnetic stimulation and functional magnetic resonance imaging. Neurol Sci 2013; 34(9):1551-1557.

  15. Nexstim. Healthcare providers: clinical evidence. www.nexstim.com/healthcare- providers/navigated-brain stimulation/clinical-evidence/.

  16. Opitz A, Zafar N, Bockermann V, et al. Validating computationally predicted TMS stimulation areas using direct electrical stimulation in patients with brain tumors near precentral regions. Neuroimage Clin. 2014; 4:500-507.

  17. Picht T, Schmidt S, Brandt S, et al. Preoperative functional mapping for rolandic brain tumor surgery: comparison of navigated transcranial magnetic stimulation to direct cortical stimulation. Neurosurgery. Sep 2011; 69(3):581-588; discussion 588.

  18. Picht T, Schulz J, Hanna M et al. Assessment of the influence of navigated transcranial magnetic stimulation on surgical planning for tumors in or near the motor cortex. Neurosurgery 2012; 70(5):1248-56; discussion 1256-1247.

  19. Raffa G, Scibilia A, Conti A, et al. The role of navigated transcranial magnetic stimulation for surgery of motor-eloquent brain tumors: a systematic review and meta-analysis. Clin Neurol Neurosurg. May 2019; 180: 7-17.

  20. Rizzo V, Terranova C, Conti A, et al. Preoperative functional mapping for rolandic brain tumor surgery. Neurosci Lett. Sep 16 2014; 583C:136-141.

  21. Schiller K, Choudhri AF, Jones T, et al. Concordance Between Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging (MRI) Derived Localization of Language in a Clinical Cohort. J Child Neurol. May 2020; 35(6): 363-379.

  22. Schmidt S, Bathe-Peters R, Fleischmann R, et al. Nonphysiological factors in navigated TMS studies; confounding covariates and valid intracortical estimates. Hum Brain Mapp. Jan 2015; 36(1): 40-9.

  23. Schramm S, Albers L, Ille S, et al. Navigated transcranial magnetic stimulation of the supplementary motor cortex disrupts fine motor skills in healthy adults. Sci Rep. Nov 28 2019; 9(1): 17744.

  24. Sollmann N, Ille S, Boeckh-Behrens T, et al. Mapping of cortical language function by functional magnetic resonance imaging and repetitive navigated transcranial magnetic stimulation in 40 healthy subjects. Acta Neurochir (Wien). Jul 2016; 158(7): 1303-16.

  25. Sollmann N, Tanigawa N, Tussis L, et al. Cortical regions involved in semantic processing investigated by repetitive navigated transcranial magnetic stimulation and object naming. Neuropsychologia. Apr 2015; 70:185-195.

  26. Tarapore PE, Picht T, Bulubas L, et al. Safety and tolerability of navigated TMS for preoperative mapping in neurosurgical patients. Clin Neurophysiol. Mar 2016; 127(3):1895-1900.

  27. Tarapore PE, Tate MC, Findlay AM et al. Preoperative multimodal motor mapping: a comparison of magnetoencephalography imaging, navigated transcranial magnetic stimulation, and direct cortical stimulation. J Neurosurg 2012; 117(2):354-62.

  28. Weiss C, Nettekoven C, Rehme AK et al. Mapping the hand, foot, and face representations in the primary motor cortex-- retest reliability of neuronavigated TMS versus functional MRI. Neuroimage 2013; 66:531-542.

POLICY HISTORY:

Medical Policy Panel, December 2013

Medical Policy Group, December 2013 (3): New policy; does not meet medical criteria for coverage and therefore considered investigational

Medical Policy Administration Committee, February 2014 Available for comment February 5 through March 21, 2014 Medical Policy Panel, December 2014

Medical Policy Group, February 2015 (6): Updated Key Points, Key Words, Approved by Governing Bodies and References; no change in policy statement.

Medical Policy Panel, June 2016

Medical Policy Group, July 2016 (6): Updated Description of Procedure, Key Points, Key Words, Summary of Evidence, Approved by Governing Bodies and References; no change in policy statement.

Medical Policy Panel June 2017

Medical Policy Group, June 2017 (6): Updates to Description, Key Points and References. No change to policy statement.

Medical Policy Group, December 2017: Annual Coding Update 2018. Created Previous Coding section and moved deleted code 0310T to this section. Added existing CPT code 64999 to current coding.

Medical Policy Panel, June 2018

Medical Policy Group, June 2018 (6): Updates to Key Points.

Medical Policy Group, December 2018 (6): Edit to policy statement verbiage. No change to policy intent.

Medical Policy Panel, June 2019

Medical Policy Group, July 2019 (3): 2019 Updates to Key Points and References. No changes to policy statement or intent.

Medical Policy Panel, July 2020

Medical Policy Group, July 2020 (3): 2020 Updates to Key Points. No changes to policy statement or intent.

Medical Policy Panel, June 2021

Medical Policy Group, July 2021 (3): 2021 Updates to Key Points and References. Policy statement    updated to remove “not medically necessary.” No other changes to policy statement or intent.

Medical Policy Panel, June 2022

Medical Policy Group, June 2022 (3): 2022 Updates to Key Points. Policy statement terminology changed from "patients" to "individuals"; policy statement and intent unchanged.

Medical Policy Panel, June 2023

Medical Policy Group, July 2023 (3): 2023 Updates to Key Points, Approved By Governing Bodies, Benefit Applications, and References. Removed Previous Coding section. Key Words added: NexStim NBS 5 Motor Mapping System and NBS 5 Speech Mapping System. No changes to policy statement or intent.

Medical Policy Panel, June 2024

Medical Policy Group, June 2024 (3): Updates to Description, Key Points, and References. No change to the policy statement or intent.

This medical policy is not an authorization, certification, explanation of benefits, or a contract. Eligibility and benefits are determined on a case-by-case basis according to the terms of the member’s plan in effect as of the date services are rendered. All medical policies are based on (i) research of current medical literature and (ii) review of common medical practices in the treatment and diagnosis of disease as of the date hereof. Physicians and other providers are solely responsible for all aspects of medical care and treatment, including the type, quality, and levels of care and treatment.

This policy is intended to be used for adjudication of claims (including pre-admission certification, pre-determinations, and pre-procedure review) in Blue Cross and Blue Shield’s administration of plan contracts.

The plan does not approve or deny procedures, services, testing, or equipment for our members. Our decisions concern coverage only. The decision of whether or not to have a certain test, treatment or procedure is one made between the physician and his/her patient. The plan administers benefits based on the member’s contract and corporate medical policies. Physicians should always exercise their best medical judgment in providing the care they feel is most appropriate for their patients. Needed care should not be delayed or refused because of a coverage determination.

As a general rule, benefits are payable under health plans only in cases of medical necessity and only if services or supplies are not investigational, provided the customer group contracts have such coverage.

The following Association Technology Evaluation Criteria must be met for a service/supply to be considered for coverage:

1. The technology must have final approval from the appropriate government regulatory bodies;

2. The scientific evidence must permit conclusions concerning the effect of the technology on health outcomes;

3. The technology must improve the net health outcome;

4. The technology must be as beneficial as any established alternatives;

5. The improvement must be attainable outside the investigational setting.

Medical Necessity means that health care services (e.g., procedures, treatments, supplies, devices, equipment, facilities or drugs) that a physician, exercising prudent clinical judgment, would provide to a patient for the purpose of preventing, evaluating, diagnosing or treating an illness, injury or disease or its symptoms, and that are:

1. In accordance with generally accepted standards of medical practice; and

2. Clinically appropriate in terms of type, frequency, extent, site and duration and considered effective for the patient’s illness, injury or disease; and

3. Not primarily for the convenience of the patient, physician or other health care provider; and

4. Not more costly than an alternative service or sequence of services at least as likely to produce equivalent therapeutic or diagnostic results as to the diagnosis or treatment of that patient’s illness, injury or disease.