GENERAL INFORMATION

• It is an expectation that all patients receive care/services from a licensed clinician. All appropriate supporting documentation, including recent pertinent office visit notes, laboratory data, and results of any special testing must be provided. If applicable: All prior relevant imaging results and the reason that alternative imaging cannot be performed must be included in the documentation submitted. 
• Where a specific clinical indication is not directly addressed in this guideline, medical necessity determination will be made based on widely accepted standard of care criteria. These criteria are supported by evidence-based or peer-reviewed sources such as medical literature, societal guidelines and state/national recommendations.
• The guideline criteria in the following sections were developed utilizing evidence-based and peer-reviewed resources from medical publications and societal organization guidelines as well as from widely accepted standard of care, best practice recommendations.

Policy
INDICATIONS FOR FUNCTIONAL BRAIN MRI^1,2
Pre-Operative/Procedural Evaluation¹
fMRI may have a significant role in the mapping of a lesion in relation to eloquent cortex (i.e., language, motor, sensory and visual centers) to determine the appropriateness of surgical intervention in the following:

• Focal brain lesion (i.e., tumor or vascular malformation) for presurgical planning ^(3–6)
• Pre-operative evaluation for epilepsy surgery ^(7,8)
• Brain tumor for radiation treatment planning ^(9,10)

Therapeutic follow-up: A documented medical reason must clearly explain the medical necessity for follow up (i.e., evaluation of post-treatment eloquent cortex).

Background

During resting-state fMRI (rs-fMRI), unlike task-based functional MRI, the individual is not required to perform any specific task ^(12–14) . This is beneficial for patients who have difficulty performing tasks, such as pediatric and certain neurologic or psychiatric patients. This technique has been well-utilized in research, and its clinical use is increasing considerably, especially in presurgical planning (e.g., mapping epileptic foci) and neuropsychiatric diseases. For the above indications, non-tasked based fMRI such as resting state fMRI can also be performed.

fMRI is often used before surgery in the evaluation of patients with brain tumors. fMRI may have a significant role in mapping lesions that are located in close proximity to vital areas of brain function (language, sensorimotor, and visual). It can determine the precise spatial relationship between the lesion and adjacent functionally essential parenchyma, allowing removal of as much pathological tissue as possible during resection of brain tumors without compromising essential brain functions. fMRI provides an alternative to other invasive tests, such as the Wada test and direct electrical stimulation. ⁽¹⁵⁾

Brain surgery is often the treatment for patients with refractory epilepsy, especially patients with a single seizure focus. fMRI can be used to image and localize abnormal brain function in patients with seizures and help determine brain functions (language, sensorimotor, and visual) of areas bordering the lesion, resulting in better outcomes with less neurologic deficit. ⁽¹⁶⁾ fMRI is increasingly being used to evaluate candidates for surgical treatment of intractable epilepsy (Phase 1 evaluation) to see If they are an appropriate candidate.

• Contraindications and reasons why a CT/CTA cannot be performed may include: impaired renal function, significant allergy to IV contrast, pregnancy (depending on trimester).
• Contraindications and reasons why an MRI/MRA cannot be performed may include: impaired renal function, claustrophobia, non-MRI compatible devices (such as non-compatible defibrillator or pacemaker), metallic fragments in a high-risk location, patient exceeds wight limit/dimensions of MRI machine.

Current State of Functional MRI in the Presurgical Planning of Brain Tumors ⁽⁵⁾

• Study Design: This review article discusses the current state of functional MRI (fMRI) for preoperative assessment in patients undergoing brain tumor resection.
• Target Population: The study focuses on patients with malignant primary brain tumors, particularly astrocytomas, which commonly occur in the frontal, temporal, and parietal lobes.
• Key Factors: The article highlights the use of fMRI for noninvasive preoperative mapping of brain function, emphasizing its advantages over direct cortical stimulation (DCS). It discusses task-based fMRI (tb-fMRI) and resting-state fMRI (rs-fMRI), noting the challenges and limitations of each technique. The review also addresses the impact of fMRI on surgical planning, extent of resection, and functional outcomes, while acknowledging the limited evidence supporting its impact on survival and functional outcomes.

Integration of BOLD-fMRI and DTI into radiation treatment planning for high-grade gliomas located near the primary motor cortexes and corticospinal tracts ⁽¹⁰⁾

• Study Design: This research article evaluates the efficacy of integrating blood oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI) and diffusion tensor imaging (DTI) data into radiation treatment planning for high-grade gliomas located near the primary motor cortexes (PMCs) and corticospinal tracts (CSTs).
• Target Population: The study includes 20 patients with high-grade gliomas adjacent to PMCs and CSTs, recruited between 2012 and 2014.
• Key Factors: The article discusses the integration of BOLD-fMRI and DTI into radiation treatment planning, comparing different treatment plans (3DCRT, IMRT, and IMRT_PMC&CST). The findings indicate that integrating BOLD-fMRI and DTI is feasible and beneficial, as it helps to spare critical brain structures during treatment without compromising target volume coverage.

Neurological update: structural and functional imaging in epilepsy surgery ⁽⁸⁾

• Study Design: This neurological update reviews the role of structural and functional imaging in epilepsy surgery, focusing on techniques such as computed tomography (CT), magnetic resonance imaging (MRI), functional MRI (fMRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET).
• Target Population: The review targets patients with medically refractory epilepsy who are potential candidates for resective surgery.
• Key Factors: The article highlights the importance of fMRI in localizing eloquent brain areas, such as language and motor cortices, to minimize postoperative deficits. It discusses the advantages of fMRI over invasive techniques like direct cortical stimulation (DCS) and the Wada test. The review also addresses the use of PET and SPECT in identifying the epileptogenic zone and guiding surgical planning.

Shared Conclusions ^(5,8,10) :

• All three studies emphasize the importance of advanced imaging techniques, such as fMRI, in preoperative assessment and treatment planning for brain conditions.
• They highlight the noninvasive nature of fMRI and its role in improving surgical planning and minimizing functional deficits.
• The studies underscore the need for accurate and timely diagnosis to facilitate appropriate treatment and improve patient outcomes.

Summary ^(5,8,10) :

In summary, these articles collectively provide valuable insights into the use of fMRI for preoperative assessment and treatment planning in patients with brain tumors and epilepsy. They highlight both the shared importance of advanced imaging techniques and the unique contributions of each study to the understanding of functional brain MRI. 

References

Coding Section

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community,  and other nonaffiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

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