Tmet-21. proton magnetic resonance spectroscopy (1h mrs) for the diagnosis of aggressive meningiomas with recurrence potential

In our previous study, we have observed elevated steady state levels of both alanine and glutamine in surgically resected tissue specimens from atypical meningioma (grade-II) patients compared to the benign (grade-I) meningioma patients. We have shown that meningioma cells utilize glutamine for the biosynthesis of alanine and other amino acids which may help in the cellular proliferation. While the role of elevated alanine in meningiomas is not well understood, this metabolite may serve as a metabolic marker for the diagnosis of aggressive meningiomas which may recur in the future. Here, we present a case of a large meningioma (7 cm x 4 cm x 8 cm) in a male patient (age: 68 years) who was diagnosed with an anterior cranial fossa, dural based extra-axial enhancing mass with the sinonasal extension compatible with a meningioma. The patient underwent multiple surgeries for the resection of the original tumor mass. Tumor tissue was collected from 2 regions: Nasal cavity and deeper tumor. Surgical pathology classified the tumor as a grade-I meningioma with MIB-1 index of ~10%. However, 1H MRS analysis of the tumor specimen showed elevated levels of alanine (Nasal cavity = 9.57 mM/g, tissue; Deep tumor = 5.50 mM/g, tissue), which are greater than the alanine levels reported for grade-II meningiomas (4.23 ± 1.92 mM). The elevated levels of alanine detected by 1H MRS suggested aggressive behavior of the tumor. After about 11 months, the repeat MRI examination showed tumor recurrence, and the patient underwent surgery again for the resection of the recurrent tumor. Surgical pathology of the recurrent tumor classified the tumor as a grade-I meningioma with increased proliferation rate (MIB-1 index of 10-12%). In conclusion, 1H MRS has potential to predict aggressive behavior of meningiomas and alanine can be used as a molecular marker for the differential diagnosis of meningiomas.