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L.2.01.442
Navigated transcranial magnetic stimulation (nTMS) is a noninvasive imaging method for evaluating eloquent brain areas (eg, those controlling motor or language function). Navigated TMS is being evaluated as an alternative to other noninvasive cortical mapping techniques for presurgical 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 patient outcomes.
Noninvasive Mapping TechniquesThe 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 correlate with 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 patient’s ability to perform the isolated motor task, such as moving the single assigned muscle without moving others. This may be difficult in patients in whom brain tumors have caused partial or complete paresis. The reliability of fMRI in mapping language areas has been questioned. Guissani and colleagues reviewed several studies comparing fMRI with DCS of language areas and found large variability in the 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 used to map brain activity. In this procedure, electromagnetic recorders are attached to the scalp. Unlike 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 an 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. See Magnetoencephalography (MEG)/Magnetic Source Imaging medical policy for additional information about magnetoencephalography and magnetic resonance imaging.
Navigated TMS is a noninvasive imaging method for evaluating eloquent brain areas. Transcranial magnetic pulses are delivered to the patient 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 image of the patient’s brain. Surface electromyography electrodes are attached to various limb muscles of the patient. Moving the magnetic stimulation source to various parts of the brain causes electromyography 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 direct cortical stimulation (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 (eg, fMRI, MEG) for presurgical 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.
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 FDA 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 preprocedural planning.
Navigated transcranial magnetic stimulation is considered investigational for all purposes, including but not limited to the preoperative evaluation of individuals being considered for brain surgery when localization of eloquent areas of the brain (eg, controlling verbal or motor function) is an important consideration in surgical planning.
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.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
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.
04/01/2014: Approved by Medical Policy Advisory Committee.
01/20/2015: Policy title updated to remove "(nTMS)." Policy description updated regarding magnetoencephalography. Policy statement unchanged.
07/31/2015: Code Reference section updated for ICD-10.
06/01/2016: Policy number A.2.01.90 added. Investigative definition updated in Policy Guidelines section.
08/17/2016: Policy description updated. Policy statements unchanged.
07/11/2017: Policy description updated. Policy statement unchanged.
12/22/2017: Code Reference section updated to add CPT code 64999.
06/28/2018: Policy description updated. Policy statement unchanged.
07/08/2019: Policy reviewed; no changes. Code Reference section updated to remove deleted CPT code 0310T.
08/14/2020: Policy reviewed; no changes.
08/25/2021: Policy reviewed; no changes.
07/12/2022: Policy reviewed. Policy statement updated to change "patients" to "individuals."
07/31/2023: Policy description updated regarding devices. Policy statement unchanged.
10/15/2024: Policy description updated. Policy statement unchanged. Medical policy number changed from "A.2.01.90" to "L.2.01.442."
Blue Cross and Blue Shield Association Policy # 2.01.90
This may not be a comprehensive list of procedure codes applicable to this policy.
Code Number | Description |
CPT-4 | |
64999 | Unlisted procedure, nervous system |
HCPCS | |
ICD-10 Procedure | |
ICD-10 Diagnosis |
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