Latest Review Date: March 2024

Category:  Radiology                                                          

POLICY:

Magnetoencephalography/magnetic source imaging for the purpose of determining the laterality of language function, as a substitute for the Wada test, in patients being prepared for surgery for epilepsy, brain tumors, and other indications requiring brain resection, may be considered medically necessary.

 Magnetoencephalography/magnetic source imaging as part of the preoperative evaluation of patients with drug-resistant epilepsy (seizures refractory to medical therapy) may be considered medically necessary when standard techniques, such as MRI, are inconclusive.

Magnetoencephalography/magnetic source imaging is considered not medically necessary and investigational for all other indications.

DESCRIPTION OF PROCEDURE OR SERVICE:

Magnetoencephalography (MEG) is a noninvasive functional imaging technique that records weak magnetic forces. When this information is superimposed on an anatomic image of the brain, typically a magnetic resonance imaging (MRI) scan, the image is referred to as magnetic source imaging (MSI). MSI has been used to localize epileptic foci and to identify “eloquent” areas of the brain for neurosurgical planning.

Magnetoencephalography

Magnetoencephalography (MEG) is a noninvasive functional imaging technique in which weak magnetic forces associated with brain electrical activity are recorded externally. Using mathematical modeling, recorded data are then analyzed to provide an estimated location of electrical activity. This information can be superimposed on an anatomic image of the brain, typically a magnetic resonance imaging (MRI) scan, to produce a functional/anatomic image of the brain, referred to as magnetic source imaging or magnetic source imaging (MSI). The primary advantage of MSI is that, while conductivity and thus measurement of electrical activity as recorded by electroencephalogram is altered by surrounding brain structures, magnetic fields are not. Therefore, MSI permits a high-resolution image.

Detection of weak magnetic fields requires gradiometer detection coils coupled to a superconducting quantum interference device (SQUID), which requires a specialized room shielded from other magnetic sources. Mathematical modeling programs based on idealized assumptions are then used to translate the detected signals into functional images. In its early evolution, clinical applications were limited by the use of only one detection coil requiring lengthy imaging times, which, because of body movement, were also difficult to match with the MRI. However, more recently the technique has evolved to multiple detection coils in an array that can provide data more efficiently over a wide extracranial region.

Applications

One clinical application is localization of epileptic foci, particularly for screening of surgical candidates and surgical planning. Alternative techniques include MRI, positron emission tomography (PET), or single photon emission computed tomography (SPECT) scanning. Anatomic imaging (i.e., MRI) is effective when epilepsy is associated with a mass lesion, such as a tumor, vascular malformation, or hippocampal atrophy. If an anatomic abnormality is not detected, patients may undergo a PET scan. In a small subset of patients, extended electrocorticography (EcoG) or stereotactic electroencephalography EEG (SEEG) with implanted electrodes is considered the criterion standard for localizing epileptogenic foci. MEG/MSI has principally been investigated as a supplement to or an alternative to invasive monitoring.

Another clinical application is localization of the pre- and post-central gyri as a guide to surgical planning in patients scheduled to undergo neurosurgery for epilepsy, brain neoplasms, arteriovenous malformations, or other brain lesions. These gyri contain the "eloquent" sensorimotor areas of the brain, the preservation of which is considered critical during any type of brain surgery. In normal situations, these areas can be identified anatomically by MRI, but frequently the anatomy is distorted by underlying disease processes. In addition, the location of the eloquent functions varies, even among healthy people. Therefore, localization of the eloquent cortex often requires such intraoperative invasive functional techniques as cortical stimulation with the patient under local anesthesia or somatosensory-evoked responses on extended electrocorticography (ECoG). Although these techniques can be done at the same time as the planned resection, they are cumbersome and can add up to 45 minutes of anesthesia time. Furthermore, these techniques can be limited by the small surgical field. A preoperative test which is often used to localize the eloquent hemisphere is the Wada test. MEG/MSI has been proposed as a substitute for the Wada test.

KEY POINTS:

The most recent literature review was performed through March 4, 2024.

Summary of Evidence

For individuals who have drug-resistant epilepsy and are being evaluated for possible resective surgery, the evidence for MEG/MSI as an adjunct to standard clinical workup includes various types of case series. Relevant outcomes are test accuracy and functional outcomes. Published evidence on MEG is suboptimal, with no clinical trials demonstrating clinical utility. Literature on diagnostic accuracy has methodologic limitations, primarily selection and ascertainment bias. Studies of functional outcomes do not fully account for the effects of MEG, because subjects who received MEG were not fully accounted for in the studies. The evidence is insufficient to determine the effects of the technology on health outcomes.

For individuals who have brain lesions and a planned brain resection, the evidence for MEG/MSI for localization of eloquent function areas includes comparative studies. Relevant outcomes include test accuracy and functional outcomes. Available studies have reported that this test has high concordance with the Wada test, which is currently the main alternative for localizing eloquent functions. Management is changed in some patients based on MEG testing, but it has not been demonstrated that these changes lead to improved outcomes. The evidence is insufficient to determine the effects of the technology on health outcomes.

Practice Guidelines and Position Statements

The American Clinical Magnetoencephalography Society (ACMEGS)

The American Clinical Magnetoencephalography Society (ACMEGS) released a position statement that supported routine clinical use of MEG plus magnetic source imaging (MSI) for pre-surgical evaluation of patients with medically intractable seizures.

In 2011, ACMEGS issued a series of clinical practice guidelines on magnetic evoked fields (MEFs) addressing different aspects of this technology (recording and analysis of spontaneous cerebral activity, presurgical functional brain mapping using MEFs, MEG-EEG reporting, and qualifications of MEG-EEG personnel). Method of guideline development was not described.

Guideline 2 on presurgical functional brain mapping indicates that:

“Magnetoencephalography shares with EEG high temporal resolution, but its chief advantage in pre-surgical functional brain mapping is in its high spatial resolution. Magnetic evoked fields are therefore done for localization; unlike electrical evoked potentials (EPs), MEF latencies and latency asymmetries are not typically used to detect abnormalities.”

Proposed indications for MEG include localization of somatosensory, auditory, language, and motor evoked fields.

In 2017, ACMEGS issued another position statement supporting routine use of MEG/MSI for obtaining noninvasive localizing or lateralizing information regarding eloquent cortices (somatosensory, motor, visual, auditory, and language) in the presurgical evaluation of patients with operable lesions preparing for surgery.

U.S. Preventative Service Task Force Recommendations

Not applicable.

KEY WORDS:

Magnetoencephalography, MEG (Magnetoencephalography), Magnetic Source Imaging, MSI (Magnetic Source Imaging), superconducting quantum interference device (SQUID)

APPROVED BY GOVERNING BODIES:

The Food and Drug Administration (FDA) regulates MEG devices as Class II devices cleared for marketing through the 510(k) process. The FDA product codes OLX and OXY are used to identify the different components of the devices. OLX coded devices are source localization software for electroencephalograph or magnetoencephalography; the software correlates electrical activity of the brain using various neuroimaging modalities. This code does not include electrodes, amplitude-integrated electroencephalograph, automatic event-detection software used as the only or final electroencephalograph analysis step, electroencephalograph software with comparative databases (normal or otherwise) or electroencephalography software that outputs an index, diagnosis, or classification.

The OLY coded devices are magnetoencephalographs that acquire, display, store, and archive biomagnetic signals produced by electrically active nerve tissue in the brain to provide information about the location of active nerve tissue responsible for certain brain functions relative to brain anatomy. This includes the magnetoencephalography recording device (hardware, basic software).

Intended use of these devices is to “non-invasively detect and display biomagnetic signals produced by electrically active nerve tissue in the brain. When interpreted by a trained clinician, the data enhance the diagnostic capability by providing useful information about the location relative to brain anatomy of active nerve tissue responsible for critical brain functions.” More recent approval summaries add, “MEG is routinely used to identify the locations of visual, auditory, somatosensory, and motor cortex in the brain when used in conjunction with evoked response averaging devices. MEG is also used to noninvasively locate regions of epileptic activity within the brain. The localization information provided by MEG may be used, in conjunction with other diagnostic data, in neurosurgical planning.”

The MagView Biomagnetometer System (Tristan Technologies) has the unique intended use for patient populations who are neonates and infants and those children with head circumferences of 50 cm or less. A sampling of MEG devices (hardware, software) are summarized in Table 1.

Table 1. Magnetoencephalography Devices Cleared by FDA (Product Codes OLX and OLY)

EEG: electroencephalogram; FDA: Food and Drug Administration

In January 2000, Biomagnetic Technologies acquired Neuromag, a Finnish MEG company, and began doing business as 4-D Neuro-Imaging. The latter company ceased operations in 2009.

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:

HCPCS:

REFERENCES:

1. Albert GW, Ibrahim GM, Otsubo H, et al. Magnetoencephalography-guided resection of epileptogenic foci in children. J Neurosurg Pediatr. Nov 2014; 14(5):532-537.
2. Bagic A, Funke Me, Ebersole J. American Clinical Meg Society (acmegs) Position Statement: The Value of Magnetoencephalography (meg)/magnetic Source Imaging (msi) In Noninvasive Presurgical Evaluation Of Patients With Medically Intractable Localization-related Epilepsy. J Clin Neurophysiol 2009; 26(4):290-293.
3. Bagic Ai, Barkley Gl, Rose Df, Et Al. American Clinical Magnetoencephalography Society Clinical Practice Guideline 4: Qualifications of Meg-eeg Personnel. J Clin Neurophysiol. Aug 2011; 28(4):364-365.
4. Bagic AI, Bowyer SM, Kirsch HE, et al. American Clinical MEG Society (ACMEGS) Position Statement #2: The value of magnetoencephalography (MEG)/magnetic source imaging (MSI) in noninvasive presurgical mapping of eloquent cortices of patients preparing for surgical interventions. J Clin Neurophysiol. May 2017; 34(3):189-195.
5. Bagic Ai, Knowlton Rc, Rose Df, Et Al. American Clinical Magnetoencephalography Society Clinical Practice Guideline 1: Recording and Analysis of Spontaneous Cerebral Activity. J Clin Neurophysiol. Aug 2011; 28(4):348-354.
6. Bagic Ai, Knowlton Rc, Rose Df, Et Al. American Clinical Magnetoencephalography Society Clinical Practice Guideline 3: Meg-eeg Reporting. J Clin Neurophysiol. Aug 2011; 28(4):362-363.
7. Blue Cross Blue Shield Association Technology Evaluation Center (TEC). Special Report: Magnetoencephalography and magnetic source imaging for the purpose of presurgical localization of epileptic lesions—a challenge for technology evaluation. TEC Assessments 2008; Volume 23, Tab 8.
8. Burgess RC, Funke ME, Bowyer SM, et al. American Clinical Magnetoencephalography Society Clinical Practice Guideline 2: presurgical functional brain mapping using magnetic evoked fields. J Clin Neurophysiol. Aug 2011; 28(4):355-361.
9. De Tiege X, Carrette E, Legros B et al. Clinical added value of magnetic source imaging in the presurgical evaluation of refractory focal epilepsy. J Neurol Neurosurg Psychiatry 2012; 83(4): 417-423.
10. Food and Drug Administration (FDA). Devices @ FDA: CTF Systems, Inc. Whole-Cortex MEG system (with optional EEG subsystem) (K971329). 1997; www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K971329. 
11. Food and Drug Administration. Section 510(k) Premarket Notification K152184 MagView Biomagnetometer. 2016; https://www.accessdata.fda.gov/cdrh_docs/pdf15/k152184.pdf. 
12. IOM (Institute of Medicine). 2011. Clinical Practice Guidelines We Can Trust. Washington, DC: The National Academies Press.
13. Kim H, Kankirawatana P, Killen J, et al. Magnetic source imaging (MSI) in children with neocortical epilepsy: surgical outcome association with 3D post-resection analysis. Epilepsy Res. Sep 2013; 106(1-2):164-172.
14. Koptelova AM, Arkhipova NA, Golovteev AL, et al. [Magnetoencephalography in the presurgical evaluation of patients with drug-resistant epilepsy]. Zh Vopr Neirokhir Im N Burdenko. 2013; 77(6):14-21.
15. Mouthaan, BB, Rados, MM, Boon, PP. Diagnostic accuracy of interictal source imaging in presurgical epilepsy evaluation: A systematic review from the E-PILEPSY consortium. Clin Neurophysiol, 2019 Mar 3; 130(5). 
16. Niranjan A, Laing EJ, Laghari FJ et al. Preoperative magnetoencephalographic sensory cortex mapping. Stereotact Funct Neurosurg 2013; 91(5):314-22.
17. Ontario Ministry of Health, Medical Advisory Secretariat (MAS). Functional Brain Imaging. Health Technology Policy Assessment. Toronto, ON: MAS; December 2006. www.health.gov.on.ca/english/providers/program/ohtac/tech/reviews/pdf/rev_fbi_012507.pdf. 
18. Schneider F, Irene Wang Z, Alexopoulos AV et al. Magnetic source imaging and ictal SPECT in MRI-negative neocortical epilepsies: additional value and comparison with intracranial EEG. Epilepsia 2013; 54(2):359-369.
19. 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); 354-362.
20. U.S. Food and Drug Administration (FDA). Devices@FDA: CTF Systems, Inc. Whole-Cortex MEG system (with optional EEG subsystem), K971329; decision date 11/20/1997. www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K971329. 
21. U.S. Food and Drug Administration (FDA). Devices@FDA: Elekta Neuromag with MaxFilter, K091393; decision date 10/26/2010. www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K091393. 
22. Wang Y, Liu B, Fu L, et al. Use of interictal (18)F-fluorodeoxyglucose (FDG)-PET and magnetoencephalography (MEG) to localize epileptogenic foci in non-lesional epilepsy in a cohort of 16 patients. J Neurol Sci. Aug 15 2015; 355(1-2):120-124.
23. Widjaja E, Shammas A, Vali r et al. FDG-PET and magnetoencephalography in presurgical workup of children with localization-related nonlesional epilepsy. Epilepsia 2013; 54(4):691-699.

POLICY HISTORY:

Medical Policy Group, January 2009 (4)

Medical Policy Administration Committee, February 2009

Available for comment February 6-March 23, 2009

Medical Policy Panel, May 2011

Medical Policy Group, May 2011 (2)

Medical Policy Administration Committee, June 2011

Available for comment June 8 – July 25, 2011

Medical Policy Group, October 2012 (2): 2012 Updates to Description, Key Points and References

Medical Policy Panel, October 2013

Medical Policy Group, December 2013 (2): Policy statement unchanged.  Key Points and References updated with literature review through September 2013.

Medical Policy Panel, October 2014

Medical Policy Group, October 2014 (3): 2014 Updates to Key Points, Key Words, Governing Bodies & References; removal of policy statements for DOS prior to July 26, 2011; no change in policy statement

Medical Policy Panel, December 2015

Medical Policy Group, January 2016 (3): 2016 Updates to Key Points, Approved Governing Bodies and References.  No change to policy statement.

Medical Policy Panel, September 2017

Medical Policy Group, October 2017 (3): 2017 Updates to Description, Key Points, Approved by Governing Bodies & References; clarification made to Policy statement but no change to policy intent.

Medical Policy Panel, September 2018

Medical Policy Group, October 2018 (3): Updates to Key Points, References, and Key Words: added: superconducting quantum interference device. No changes to policy statement or intent.

Medical Policy Panel, September 2019

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

Medical Policy Panel, October 2020

Medical Policy Group, November 2020 (3): 2020 Updates to Key Points and Approved by Governing Bodies. No changes to policy statement or intent.

Medical Policy Group, March 2022 (3) 2022 Updates to Key Points. Reviewed by consensus. No new published peer-reviewed literature available that would alter the coverage statement in this policy.

Medical Policy Group, March 2023 (3) Updates to Key Points, Benefit Application, and References. Reviewed by consensus. No new published peer-reviewed literature available that would alter the coverage statement in this policy.

Medical Policy Group, March 2024 (11) Updates to Key Points, Benefit Application, and References. Reviewed by consensus. No new published peer-reviewed literature available that would alter the coverage statement in this policy.

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.