Coverage Policy Manual
Policy #: 2004010
Category: Radiology
Initiated: February 2004
Last Review: October 2018
  Magnetoencephalography/Magnetic Source Imaging

Description:
Magnetoencephalography (MEG) is a noninvasive functional imaging technique in which the weak magnetic forces associated with the electrical activity of the brain are recorded externally on the scalp. Using mathematical modeling, the recorded data are then analyzed to provide an estimated location of the 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 MSI. The primary advantage of MSI is that while the conductivity and thus measurement of electrical activity as recorded by the electro-encephalogram (EEG) is altered by surrounding brain structures, the magnetic fields are not. Therefore, MSI permits a high resolution image.
 
The technique itself is extremely sophisticated. Detection of the weak magnetic fields depends on gradiometer detection coils coupled to a superconducting quantum interference device (SQUID), which in turn 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 coordinate with the MRI. However, more recently the technique has evolved to multiple detection coils arranged in an array that can provide data more efficiently over a wide extracranial region.
 
The most thoroughly studied clinical application is localization of the pre- and postcentral gyri as a guide to surgical planning in those patients scheduled to undergo neurosurgery for epilepsy, brain neoplasms, arteriovenous malformations, or other brain disorders. 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 is variable, even among healthy patients. 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 electrocorticography (ECoG). While 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, sometimes these techniques can be limited by the small surgical field.
 
Another related 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 malformations, 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 are considered the gold standards for localizing epileptogenic foci. MSI has principally been investigated as an alternative to invasive monitoring.
 
Regulatory Status
 
FDA-cleared magnetoencephalograph devices include the 700 Series Biomagnetometer (Biomagnetic
Technologies; San Diego, CA) cleared in 1990 and subsequent devices (K901215, K941553, K962317,
K993708); the CTF Whole-Cortex MEG System (CTF Systems; British Columbia, Canada) cleared in
1997 and subsequent devices (K971329, K030737); and the Elekta Oy (Elekta Neuromag; Helsinki,
Finland) cleared in 2004 and subsequent devices (K041264, K050035, K081430, K091393).
 
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 enhances the diagnostic capability by providing useful information about the location relative to brain anatomy of active nerve tissue responsible for critical brain functions” (FDA, 2014a). 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 non-invasively 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” (FDA, 2014b).
 

Policy/
Coverage:
Effective July 2011
 
Meets Primary Coverage Criteria Or Is Covered For Contracts Without Primary Coverage Criteria
Magnetoencephalography/magnetic source imaging meets member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes when used to determine the laterality of language function, as a substitute for the Wada test, in patients prepared for surgery for epilepsy, brain tumors and other indications for brain resection.
 
Magnetoencephalography/magnetic source imaging as part of the preoperative evaluation of patients with intractable epilepsy (seizures refractory to medical therapy) meets member benefit certificate primary coverage criteria that there be scientific evidence of effectiveness in improving health outcomes when standard techniques, such as MRI, are inconclusive.
 
Does Not Meet Primary Coverage Criteria Or Is Investigational For Contracts Without Primary Coverage Criteria
  
Magnetoencephalography/magnetic source imaging for any indication not specified above does not meet member benefit certificate primary coverage criteria; magnetoencephalography is being studied in a randomized controlled trial comparing it to IC/EEG.  
 
For contracts without primary coverage criteria, magnetoencephalography/magnetic source imaging is considered investigational for any indication except as a substitute for the Wada test in the preoperative evaluation of patients being evaluated for brain resection.  Investigational services are an exclusion in the member certificate of coverage.
 
Effective May 2009 through June 2011
Magnetoencephalography/magnetic source imaging meets Primary Coverage Criteria when used to determine the laterality of language function, as a substitute for the Wada test, in patients prepared for surgery for epilepsy, brain tumors and other indications for brain resection.
 
Magnetoencephalography/magnetic source imaging for any indication not specified above does not meet certificate primary coverage criteria; magnetoencephalography is being studied in a randomized controlled trial comparing it to IC/EEG.  
 
For contracts without primary coverage criteria, magnetoencephalography/magnetic source imaging is considered investigational for any indication except as a substitute for the Wada test in the preoperative evaluation of patients being evaluated for brain resection.  Investigational services are an exclusion in the member certificate of coverage.
 
Effective Feb 2004- April 2009:
Magnetoencephalography and magnetic source imaging are not covered by Group Contracts or Individual Contracts furnished on or after July 1, 2004, based on benefit certificate primary coverage criteria because magnetoencephalography is being studied in a randomized controlled trial comparing it to IC/EEG.  
 
For members with Individual Contracts issued prior to July 1, 2004 (contracts without primary coverage criteria), magnetoencephalography and magnetic source imaging is considered investigational.  Investigational services are an exclusion in the member certificate of coverage.

Rationale:
This policy originated from an Arkansas Blue Cross Blue Shield Technology Assessment in January 2004.
 
The diagnostic performance of MSI compared to either invasive (intraoperative monitoring) or noninvasive techniques (EEG, PET, or MRI scans) can be evaluated in a variety of ways. Initially, one might like to know how closely the localization of a lesion or identification of the “eloquent” cortex using MSI agrees with the alternative techniques, particularly intraoperative ECoG.  Statistical techniques may include correlation coefficients or Kappa statistics.
 
Alternatively, one could investigate the positive and negative predictive values in determining whether a patient is a surgical candidate or not. For example, a positive MSI result may be defined as one that suggests that the patient is a surgical candidate by localizing the lesion to a noneloquent portion of the brain. A negative test is one that suggests that the patient is not a surgical candidate.  Using these definitions, a positive predictive value would indicate how often the results of the test appropriately indicated that the patient was a surgical candidate, and a negative predictive value would indicate how often the test appropriately indicated that the patient was not a surgical candidate. For a positive predictive value, the false positive rate is the key determinant. A high false positive rate lowers the positive predictive value and suggests that an increasing number of patients would undergo unnecessary surgery.  In contrast, for the negative predictive value, the key determinant is the false negative rate. A high false negative rate suggests that in an increasing number of patients, potentially effective surgery is inappropriately withheld. Typically, in the lifesaving situations associated with neurosurgery, one is more apt to accept a certain incidence of unnecessary surgery compared to the consequences of withholding potentially effective surgery.  Therefore, the false negative rate of MSI compared to intraoperative monitoring may emerge as the critical measure. The final health outcomes differ for the two principal indications; for determining resectability, functional neurologic complications are a critical final health outcome. For localizing epileptogenic foci, elimination of seizures is the final health outcome.
 
Aside from the final health outcomes associated with surgery, one could look at how the use of MSI could alter the preoperative workup, or alter the surgery itself. For example, it is frequently suggested that MSI may simplify neurosurgery by enhancing preoperative surgical planning; i.e., presurgical MSI could simplify intraoperative EEG monitoring and thus shorten the overall operative time, or could possibly eliminate the need for intraoperative EEG.  For patients with epilepsy in which the epileptogenic focus cannot be localized with noninvasive EEG or PET scans, MSI may provide an alternative to long-term EEG monitoring with implanted electrodes. Although elimination or shortening of invasive procedures is always welcome, ultimately, one would like to ensure that the final health outcomes associated with the various techniques were at least equivalent.
 
Therefore, validation of this application of MSI requires estimates of sensitivity, specificity, and positive and negative predictive value compared to invasive monitoring. Again, avoidance of an invasive procedure is a valued health outcome, but the risk-benefit ratio cannot be evaluated until the comparative diagnostic capabilities of the technologies are known.
 
Clinical Studies
MSI is an evolving technique, both in terms of the number and configuration of detection coils used, but also in the mathematical models used to evaluate the recorded data.  While there is extensive literature on MSI, the bulk of it is devoted to its technical capability and small anecdotal case series. There are no studies that provide a statistical analysis of its diagnostic performance compared to other techniques. In addition, there are no studies that provide estimates of the sensitivity, specificity, and positive and negative predictive values of MSI compared to the standard diagnostic techniques used. Studies may report that invasive procedures were eliminated, such as intraoperative EEG monitoring, but without final health outcomes, one cannot be certain that such monitoring was appropriately withheld.
 
Gallen and colleagues’ 1993 article is representative; this study reported on the preoperative use of MSI in 5 patients who were scheduled to undergo neurosurgical excision of epileptic or neoplastic tissue. Somatosensory stimuli to the face/hand area were used to produce the MSI localization.  MSI localizations of the central sulcus and precentral gyrus were compared with corresponding intraoperative localizations via ECoG. In all cases, complete agreement was found between MSI and the intraoperative mapping. The authors conclude that the results of this study are encouraging, but that larger scale trials are needed to validate the precision and utility of MSI, particularly in comparison to the competing intraoperative methods.
 
2006 Update
A Pubmed search was performed for the period of April 2005 through November 2006. A number of studies were identified on the use of magnetoencephalography in patients with epilepsy. However, evidence remains insufficient to change the policy statement.
 
One study compared MSI to intra-cortical EEG (ICEEG) and surgical outcomes in 49 patients who were candidates for surgery; sensitivity was 75% for both, specificity was 54% versus ICEEG and 70% versus surgical.  Concordance between the tests was at a semilobar level, and in 34% of cases no single site could be identified by MEG. Another study assessed the relative accuracy of ICEEG and MEG in 41 patients who had positive MEG recordings (interictal changes observed) prior to surgery.  There were no significant differences between the two methods in terms of their ability to predict the localization of the epileptic zone or seizure outcome in individual patients; ICEEG correctly identified the focus of the lesion in 54% of patients, while MEG identified the focus in 56% of the cases studied. However, an estimated 20% of cases were excluded from analysis since they did not show interictal changes during the 30- minute recording.  These results are consistent with and support prior research indicating that MSI, in conjunction with other non-invasive tests, could potentially take the place of ICEEG in some patients; which patients might benefit from this procedure is not currently known. In addition, methods for optimizing data collection and analysis remain in development.
 
2009 Update
Papanicolaou et al. (2004) reported on 100 surgical candidates who had whole-head MEG and then had Wada.  MEG laterality studies had an overall sensitivity of 98% but lower selectivity of 83%, due to MEG detection of more activity in the nondominant hemisphere than was predicted based on the Wada test.  Independent clinical judgment based on MEG and Wada data showed a high degree of concordance, 87%.   Hirata et al, (2004) reported on 20 patients who had MEG with synthetic aperture magnetometry (SAM).  In 19 patients language lateralization estimated by the laterality index was congruent with the result of the Wada test.  
 
In 2007 Pelletier et al. made many positive statements about the utility of MEG in the presurgical patient, emphasizing its safety.  They considered the disadvantages of MEG: cannot evaluate expressive language functions, limitation of source depth and the current inability to correct for head movement that might preclude its use in some patients.  
 
2011 Update
The literature search for this update did not identify major new studies. One study more specifically addresses the concept that MEG may improve the yield of IC-EEG, thus allowing more patients to ultimately receive surgery. In a study by Knowlton et al., out of 77 patients who were recommended to have IC-EEG, MEG results modified the placement of electrodes in 18 of the 77 cases (Knowlton, 2009). Seven cases out of the 18 had positive intracranial seizure recordings involving the additional electrodes placed because of the MEG results. It was concluded that 4 patients are presumed to have had surgery modified as a result of the effect of MEG on altering the placement of electrodes. In this type of study, it is difficult to know how the patients would have been treated in the absence of the MEG results. It is stated that there was no additional morbidity resulting from the additional electrode placement.
 
Based on review of the scientific literature and expert opinion, the coverage statement has been changed to indicate that MEG/MSI meets primary coverage criteria as part of the preoperative evaluation of patients with intractable epilepsy (seizures refractory to medical therapy) when standard techniques, such as MRI, are inconclusive.
 
2012 Update
A literature search was conducted using the MEDLINE database through August 2012.  There was no new information identified in the search that would prompt a change in the coverage statement.
 
2014 Update
 
A literature search conducted through September 2014 did not reveal any new information that would prompt a change in the coverage statement. The key identified literature is summarized below
 
In a retrospective review of 22 children with medically intractable focal epilepsy (median age at epilepsy surgery, 11 years), Kim et al (2013) used a cutoff of 70% or more for the number of MEG-identified spike dipole sources located within the resection margin to define a positive study (Kim, 2013). Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) for seizure-free status postoperatively was 67%, 14%, 63%, and 17%, respectively.
 
A search of online site, ClinicalTrials.gov, identified several studies of MEG/MSI for various indications
 
  • NCT01735032 Partial Epilepsy. Multimodal Imaging in Pre-surgical Evaluation of Epilepsy (EPIMAGE) with 140 enrollees and an estimated completion date of May 2016.
  • NCT02077504 Cerebral Primitive Tu7mor. Glial Tumors Electromagnetic Signature Study by MagnetoEncephaloGraphy (MEG) /CONDUCTOME/ with 20 enrollees and an estimated completion date of August 2015.
  • NCT02159300 Fibromyalgia. Brain Rhythms in Fibromyalgia: A Magnetoencephalography (MEG) Study (FMP) with 80 enrollees and an estimated completion date of May 2015.
  • NCT01317121 Schizophrenia. Multi-site Communication Deficits in Schizophrenia with 144 enrollees and an estimated completion date of June 2015.
  • NCT02132052 Movement Disorders. Defining Phenotypes of Movement Disorders :Parkinson's Plus Disorders, PD, Essential Tremor, (ET),Cortical Basal Degeneration, (CBD),Multiple Systems Atrophy (MSA),  Magnetoencephalography (PHENO) with 18 enrollees and an estimated completion date of May 2014.
  • NCT02069613 Mild Traumatic Brain Injury. Multimodal Approach to Testing the Acute Effects of Mild Traumatic Brain Injury (mTBI) with 200 enrollees and an estimated completion date of February 2017.
  • NCT01974427 Cognition. Functional Brain Imaging in Healthy Volunteers to Study Cognitive Functions with 120 enrollees and an estimated completion date of April 2023.
 
None of the clinical trials identified are randomized. Additional ongoing studies with no completion date identified evaluate MEG/MSI in mood and anxiety disorders (NCT00024635, NCT00047853) and autism spectrum disorders (NCT01031407).
 
2017 Update
A literature search conducted using the MEDLINE database through September 2017 did not reveal any new information that would prompt a change in the coverage statement.
 
2018 Update
A literature search was conducted through September 2018.  There was no new information identified that would prompt a change in the coverage statement.  

CPT/HCPCS:
95965Magnetoencephalography (MEG), recording and analysis; for spontaneous brain magnetic activity (eg, epileptic cerebral cortex localization)
95966Magnetoencephalography (MEG), recording and analysis; for evoked magnetic fields, single modality (eg, sensory, motor, language, or visual cortex localization)
95967Magnetoencephalography (MEG), recording and analysis; for evoked magnetic fields, each additional modality (eg, sensory, motor, language, or visual cortex localization) (List separately in addition to code for primary procedure)
S8035Magnetic source imaging

References: Abou-Khalil B.(2007) An update on determination of language dominance in screening for epilepsy surgery: the Wada test and newer noninvasive alternatives. Epilepsia, 2007; 48(3):442-55.

Assaf BA, Karkar KM, et al.(2004) Magnetoencephalography source localization and surgical outcome in temporal lobe epilepsy. Clin Neurophysiol, 2004; 115:2066-76.

Bagic AI, Bowyer SM, Kirsch HE, et al.(2017) 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. PMID 28059855

Barkley GL, Baumgartner C.(2003) MEG and EEG in epilepsy. J Clin Neurophysiol, 2003; 20:163-78.

Barkley GL.(2004) Controversies in neurophysiology. MEG is superior to EEG in localization of interictal epileptiform activity: PRO. Clin Neurophysiol, 2004; 115:1001-9.

Baumgartner C.(2004) Controversies in clinical neurophysiology. MEG is superior to EEG in localization of interictal epileptiform activity: CON. Clin Neurophysiol, 2004; 115:1010-20.

Castillo EM, Simos PG, et al.(2004) Integrating sensory and motor mapping in a comprehensive MEG protocol: clinical validity and replicability. NeuroImage, 2004; 21:973-83.

Ebersole JS.(1997) Magnetoencephalography/magnetic source imaging in the assessment of patients with epilepsy. Epilepsia 1997; 38 (suppl 4):S1-5.

Gallen CC, Hirschkoff EC, Buchanan DS.(1995) Magnetoencephalography and magnetic source imaging. Capabilities and limitations. Neuroimaging Clin N Am 1995; 5:227-49.

Gallen CC, Sobel DF, Waltz T, et al.(1993) Noninvasive presurgical neuromagnetic mapping of somatosensory cortex. Neurosurgery 1993; 33:260-8.

Grondin R, Chuang S, et al.(2006) The role of magnetoencephalography in pediatric epilepsy surgery. Childs Nerv Syst, 2005; 22:779-85.

Grover KM, Bowyer SM, et al.(2006) Retrospective review of MEG visual evoked hemifield responses prior to resection fo temporo-parieto-occipital lesions. J Neurooncol, 2006; 77:161-6.

Hirat M, Kato A, et al.(2004) Determination of language dominance with synthetic aperture magnetometry: comparison with the Wada test. Neuroimage, 2004; 23(1):46-53.

Kamada K, Sawamura Y, et al.(2007) Expressive and receptive language areas determined by a non-invasive reliable method using functional magnetic resonance imaging and magnetoencephalography. Neurosurgery, 2007; 60(2):296-306.

Knowlton RC, Elgavish R, et al.(2006) Magnetic source imaging versus intracranial electroencephalogram in epilepsy surgery: a prospective study. Ann Neurol, 2006; 59:835-42.

Knowlton RC, Elgavish RA, Limdi N et al.(2008) Functional imaging: I. Relative predictive value of intracranial electroencephalography. Ann Neurol 2008; 64(1):25-34.

Knowlton RC, Shih J.(2004) Magnetoencephalography in epilepsy. Epilepsia, 2004:45 Suppl 4:61-71.

Lau M, Yam D, Burneo JG.(2008) A systematic review on MEG and its use in the presurgical evaluation of localization-related epilepsy. Epilepsy Res, 2008; 79(2-3):97-104.

Magnetic source imaging for neurologic applications. Hayes Technology Assessment 1998.

Magnetoencephalography and magnetic source imaging of the brain. Hayes Directory, Feb 2005.

Magnetoencephalography and magnetic source imaging of the brain. Hayes Directory, Sep 2008.

Magnetoencephalography and magnetic source imaging: presurgical localization of epileptic lesions and presurgical functional mapping. Blue Cross Blue Shield Association Technology Evaluation Center Assessment; 2003.

Papanicolaou AC, Simos PG, et al.(2004) Magnetoencephalography: a noninvasive alternative to the Wada procedure. J Neurosurg, 2004; 100(5):867-76.

Papanicolaou AC, Pataraia E, et al.(2005) Toward the substitution of invasive electroencephalography in epilepsy surgery. J Clin Neurophysiol, 2005; 22:231-7.

Pelletier I, Sauerwein HC, et al.(2007) Non-invasive alternatives to the Wada test in the presurgical evaluation of language and memory functions in epilepsy patients. Epileptic Disord, 2007; 9(2):111-26.

Roberts TP, Ferrari P, Perry D, et al.(2000) Presurgical mapping with magnetic source imaging: comparisons with intraoperative findings. Brain Tumor Pathol 2000; 17:57-64.

Rosenow F, Luders H.(2001) Presurgical evaluation of epilepsy. Brain 2001; 124:1683-700.

Rowley HA, Roberts TP.(1995) Functional localization by magnetoencephalography. Neuroimaging Clin N Am 1995; 5:695-710.

Schiffbauer H, Berger MS, et al.(2002) Preoperative magnetic source imaging for brain tumor surgery: a quantitative comparison with intraoperative sensory and motor mapping. J Neurosurg, 2002; 97:1333-42.

Shih JJ, Weisent MP, et al.(2004) Areas of interictal spiking are associated with metabolic dysfunction in MRI-negative temporal lobe epilepsy. Epilepsia, 2004; 45:223-9.

Snead OC.(2001) Surgical treatment of medically refractory epilepsy in childhood. Brain Dev 2001; 25:199-207.

U.S. Food and Drug Administration (FDA).(1997) Devices@FDA: CTF Systems, Inc. Whole-Cortex MEG system (with optional EEG subsystem), K971329; decision date 11/20/1997 http://www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K9 71329. Accessed September 18, 2014a.

U.S. Food and Drug Administration (FDA).(2010) Devices@FDA: Elekta Neuromag with MaxFilter, K091393; decision date 10/26/2010. http://www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm?db=pmn&id=K0 91393. Accessed September 18, 2014b.

Wheless JW, Castillo E, et al.(2004) Magnetoencephalography (MEG) and magnetic source imaging (MSI). Neurologist, 2004; 10:138-53.


Group specific policy will supersede this policy when applicable. This policy does not apply to the Wal-Mart Associates Group Health Plan participants or to the Tyson Group Health Plan participants.
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