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.

Policy
INDICATIONS FOR BRAIN MRS²

• For the evaluation of a recurrent or residual brain tumor from post-treatment changes, e.g., radiation necrosis^2,3,4
• For further evaluation of a brain lesion to distinguish a brain tumor from other non- tumor diagnoses (e.g., abscess or other infectious or inflammatory process)^1,5
• Suspected inherited metabolic disorders such as Canavan disease and primary mitochondrial disorders;⁶ can be done in combination with Brain MRI when not previously performed^7,8

Rationale
Magnetic resonance spectroscopy (MRS) determines the concentration of brain metabolites, such as N-acetylaspartate, choline, creatine, and lactate, within the body tissue examined. Radiofrequency waves are translated into biochemical composition of the scanned tissue; the resulting metabolic profile is useful in identifying brain tumors, e.g., differentiating neoplastic and non-neoplastic brain lesions. This modality should be considered as an adjunct to conventional imaging rather than replacement for histopathological evaluation.⁹ In terms of brain tumor evaluation and classification, carefully designed multi-center trials complying with criteria of evidence-based medicine have not yet been completed.¹⁰

Tumor Recurrence vs. Radiation Necrosis⁴
Differentiation between recurrent brain tumors and treatment related injury, e.g., radiation necrosis, is difficult using conventional MRI. MRS is a quantitative approach, measuring various brain metabolic markers, to help in the differentiation of recurrent tumors vs. radiation necrosis.³ However, no consensus exists regarding the value of this in clinical decision making, and no approach has yet been validated to be sufficiently accurate.^2,4

Glioma^4,11
MRS has been proposed for pre-operative grading of gliomas and differentiating high-grade gliomas (HGGs) from low-grade gliomas. It has been found to have moderate diagnostic value and should be combined with other advanced imaging techniques to improve accuracy. Currently, the data is limited; more research is needed for a definite conclusion for the utility of MRS for this indication. Therefore, it remains experimental/investigational.(12,13)

Inherited Metabolic Conditions⁶
Although Brain MRS may show abnormalities in many inherited metabolic conditions, primary mitochondrial disease, storage diseases and other neurometabolic disorders (including leukodystrophies), it’s role in the diagnosis, prognosis, and management of most of these conditions is not well established by research and condition-specific guidelines. In a select few conditions MRS does have a more specific role in diagnosis and/or management (primary mitochondrial disorders and Canavan disease). For most of these conditions, Brain MRS is considered Experimental/Investigational. In all cases, basic work-up should first be completed including appropriate family history for inheritance and specific labs related to the suspected condition.

MRS in other Diseases
A role for MRS has been suggested in the management of neurodegenerative disease, epilepsy, and stroke. MRS can also be applied in conjunction with MRI in the evaluation traumatic brain injury and neonatal hypoxia-ischemia.^14,15 However, to better define these roles, it will be necessary to standardize the MRS methodology, as well as the collection, analysis, and interpretation of data so it can be consistently translated to the applicable clinical settings. Currently, these potential applications remain experimental/investigational.¹⁵

Contraindication and Preferred Studies

• 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 weight limit/dimensions of MRI machine.

References

1. Reddy V, Kummari S, Burra K, Das S. Accuracy of Proton Magnetic Resonance Spectroscopy in Distinguishing Neoplastic From Non-neoplastic Brain Lesions. Cureus. 2023; 15: e49824. 10.7759/cureus.49824.
2. American College of Radiology, American Society of Neuroradiology, Society for Pediatric Radiology. ACR–ASNR–SPR practice parameter for the performance and interpretation of magnetic resonance spectroscopy of the central nervous system. American College of Radiology. 2019; https://www.acr.org/-/media/ACR/Files/Practice-Parameters/MR-Spectroscopy.pdf.
3. Chuang M T, Liu Y S, Tsai Y S, Chen Y C, Wang C. Differentiating Radiation-Induced Necrosis from Recurrent Brain Tumor Using MR Perfusion and Spectroscopy: A Meta-Analysis. PLoS One. 2016; 11: e0141438. 10.1371/journal.pone.0141438.
4. Weinberg B, Kuruva M, Shim H, Mullins M. Clinical Applications of Magnetic Resonance Spectroscopy in Brain Tumors: From Diagnosis to Treatment. Radiologic clinics of North America. 2021; 59: 349-362. 10.1016/j.rcl.2021.01.004.
5. Alshammari Q, Salih M, Gameraddin M, Yousef M, Abdelmalik B. Accuracy of Magnetic Resonance Spectroscopy in Discrimination of Neoplastic and Non-Neoplastic Brain Lesions. Current medical imaging. 2021; 17: 904-910. 10.2174/1573405617666210224112808.
6. Chinnery P. Primary Mitochondrial Disorders Overview. 2000 Jun 8 [Updated 2021 Jul 29]. GeneReviews® [Internet]. 2021; Accessed May 2024:
7. Liserre R, Pinelli L, Gasparotti R. MR spectroscopy in pediatric neuroradiology. Translational pediatrics. 2021; 10: 1169-1200. 10.21037/tp-20-445.
8. Lunsing R, Strating K, de Koning T, Sijens P. Diagnostic value of MRS-quantified brain tissue lactate level in identifying children with mitochondrial disorders. European radiology. 2017; 27: 976- 984. 10.1007/s00330-016-4454-8.
9. Hellström J, Romanos Zapata R, Libard S, Wikström J, Ortiz-Nieto F et al. The value of magnetic resonance spectroscopy as a supplement to MRI of the brain in a clinical setting. PLoS One. 2018; 13: e0207336. 10.1371/journal.pone.0207336.
10. Horská A, Barker P. Imaging of brain tumors: MR spectroscopy and metabolic imaging. Neuroimaging Clin N Am. Aug 2010; 20: 293-310. 10.1016/j.nic.2010.04.003.
11. Galijasevic M, Steiger R, Mangesius S, Mangesius J, Kerschbaumer J et al. Magnetic Resonance Spectroscopy in Diagnosis and Follow-Up of Gliomas: State-of-the-Art. Cancers. 2022; 14: 3197. 10.3390/cancers14133197.
12. Abrigo J M, Fountain D M, Provenzale J M, Law E K, Kwong J S et al. Magnetic resonance perfusion for differentiating low-grade from high-grade gliomas at first presentation. Cochrane Database Syst Rev. 2018; 1: Cd011551. 10.1002/14651858.CD011551.pub2.
13. Wang Q, Zhang H, Zhang J, Wu C, Zhu W et al. The diagnostic performance of magnetic resonance spectroscopy in differentiating high-from low-grade gliomas: A systematic review and meta-analysis. Eur Radiol. 2016; 26: 2670-84. 10.1007/s00330-015-4046-z.
14. Blüml S, Saunders A, Tamrazi B. Proton MR Spectroscopy of Pediatric Brain Disorders. Diagnostics (Basel, Switzerland). 2022; 12: 10.3390/diagnostics12061462.
15. Oz G, Alger J R, Barker P B, Bartha R, Bizzi A et al. Clinical proton MR spectroscopy in central nervous system disorders. Radiology. 2014; 270: 658-79. 10.1148/radiol.13130531.

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.

"Current Procedural Terminology © American Medical Association. All Rights Reserved" 

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