Magnetoencephalography/Magnetic Source Imaging

POLICY NUMBER

L.6.01.419

DESCRIPTION

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 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 that records weak magnetic forces associated with brain electrical activity. 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 MRI scan, to produce a functional/anatomic image of the brain, referred to as 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 the surrounding brain structures, the 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, which requires a specialized room shielded from other magnetic sources. Mathematical modeling programs based on idealized assumptions are then used to translate 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 scanning. Anatomic imaging (ie, 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 or stereotactic electroencephalography 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 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. 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. Futhermore, these techniques can sometimes 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.

The Food and Drug Administration regulates MEG devices as class II devices cleared for marketing through the 510(k) process. The Food and Drug Administration product codes OLX and OXY are used to identify the different components of the devices. OLX-coded devices are source localization software for electroencephalography 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, electroencephalography software with comparative databases (normal or otherwise), or electroencephalography software that outputs an index, diagnosis, or classification.

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 magnetoencephalograph recording device (hardware, basic software).

The 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.

The table below summarizes a sampling of relevant MEG devices (hardware, software).

Magnetoencephalography Devices Cleared by the FDA (Product Codes OLX and OLY)

In 2000, Biomagnetic Technologies acquired Neuromag and began doing business as 4-D NeuroImaging. The latter company ceased operations in 2009.

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 at least two first-line anticonvulsants) may be considered medically necessary when standard techniques, such as MRI and EEG, do not provide satisfactory localization of epileptic lesion(s).

Magnetoencephalography/magnetic source imaging is considered investigational for all other indications.

POLICY EXCEPTIONS

Federal Employee Program (FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity.

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Medically Necessary is defined as those services, treatments, procedures, equipment, drugs, devices, items or supplies furnished by a covered Provider that are required to identify or treat a Member's illness, injury or Mental Health Disorders, and which Company determines are covered under this Benefit Plan based on the criteria as follows in A through D:

A.  consistent with the symptoms or diagnosis and treatment of the Member's condition, illness, or injury; and

B.  appropriate with regard to standards of good medical practice; and

C.  not solely for the convenience of the Member, his or her Provider; and

D.  the most appropriate supply or level of care which can safely be provided to Member. When applied to the care of an Inpatient, it further means that services for the Member's medical symptoms or conditions require that the services cannot be safely provided to the Member as an Outpatient.

For the definition of medical necessity, “standards of good medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. BCBSMS makes no payment for services, treatments, procedures, equipment, drugs, devices, items or supplies which are not documented to be Medically Necessary. The fact that a Physician or other Provider has prescribed, ordered, recommended, or approved a service or supply does not in itself, make it Medically Necessary.

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.

POLICY HISTORY

2/2000: Approved by Medical Policy Advisory Committee (MPAC).

2/11/2002: Investigational definition added.

2/21/2002: Code Reference section completed, CPT code 95965, 95966, 95967 added.

5/1/2002: Type of Service and Place of Service deleted.

8/15/2005: Code Reference section updated, CPT code 95965, 95966, 95967 description revised.

10/23/2006: Policy reviewed, no changes.

1/7/2009: Policy reviewed, medically necessary application listed.

2/4/2009: Policy statement updated to indications which are now medically necessary. Code section update.

04/22/2010: “Magnetic Source Imaging” added to the policy title. Policy description updated. Added language to the policy statements to clarify that they apply to MEG and MSI. HCPCS code S8035 was previously added to codes table. FEP verbiage added to the Policy Exceptions section. Deleted outdated references from the Sources section. 

04/20/2011: Policy reviewed; no changes.

11/30/2012: Policy statement revised to state that magnetoencephalography/magnetic source imaging as part of the preoperative evaluation of patients with intractable epilepsy (seizures refractory to at least two first-line anticonvulsants) may be considered medically necessary when standard techniques, such as MRI and EEG, do not provide satisfactory localization of epileptic lesion(s).

12/13/2013: Policy reviewed; no changes.

11/19/2014: Policy reviewed; description updated regarding devices. Policy statements unchanged.

08/26/2015: Medical policy revised to add ICD-10 codes.

01/18/2016: Policy reviewed. Policy statements unchanged. Policy guidelines updated to add medically necessary and investigative definitions.

05/31/2016: Policy number A.6.01.21 added.

10/16/2017: Policy description updated regarding devices. Second medically necessary policy statement updated to change "intractable" to "drug-resistant."

10/04/2018: Policy reviewed; no changes.

10/21/2019: Policy reviewed; no changes.

10/20/2020: Policy description updated regarding devices. Policy statements unchanged.

06/01/2023: Policy updated to change the medical policy number from "A.6.01.21" to "L.6.01.419." Policy reviewed. Policy statements unchanged. Policy Guidelines updated to change "Nervous/Mental Conditions" to "Mental Health Disorders" and "Medically Necessary" to "medical necessity."

09/29/2023: Code Reference section updated to add new ICD-10 diagnosis codes G40.C01, G40.C09, G40.C11, and G40.C19, effective 10/01/2023.

06/06/2024: Policy reviewed; no changes.

08/04/2025: Policy reviewed. Policy statements unchanged. Sources updated.

SOURCE(S)

1. Blue Cross Blue Shield Association policy #6.01.21

2. Wheless JW, Castillo E, Maggio V, Kim HL, Breier JI, Simos PG, Papanicolaou AC. Magnetoencephalography (MEG) and magnetic source imaging (MSI). Neurologist. 2004 May;10(3):138-53. doi: 10.1097/01.nrl.0000126589.21840.a1. PMID: 15140274. Accessed April 2025.

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.

The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.

Covered Codes

CPT copyright American Medical Association. All rights reserved. CPT is a registered trademark of the American Medical Association.