Proton MR spectroscopy of tumefactive demyelinating lesions

Abstract

Background and purpose: Tumefactive demyelinating lesions (TDLs) can simulate intracranial neoplasms in clinical presentation and MR imaging appearance, and surgical biopsy is often performed in suspected tumors. Proton MR spectroscopy has been applied in assessing various intracranial diseases and is increasingly used in diagnosis and clinical management. Our purpose was to determine if multivoxel proton MR spectroscopy can be used to differentiate TDLs and high-grade gliomas.

Methods: Conventional MR images, proton MR spectra, and medical records were retrospectively reviewed in six patients with TDLs diagnosed by means of biopsy or by documented clinical improvement, with or without supporting laboratory testing and follow-up imaging. Proton MR spectra of 10 high-grade gliomas with similar conventional MR imaging appearances were used for comparison. In contrast-enhancing, central, and perilesional areas of each lesion, peak heights of N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) were measured and the lactate peak noted. Cho/Cr and NAA/Cr ratios of corresponding regions in TDLs and gliomas were compared.

Results: No significant differences in mean Cho/Cr ratios were found in the corresponding contrast-enhancing, central, or perilesional areas of TDLs and gliomas. The mean central-region NAA/Cr ratio in gliomas was significantly lower than that of TDLs, but mean NAA/Cr ratios in other regions were not significantly different. A lactate peak was identified in four of six TDLs and three of 10 gliomas.

Conclusion: In the cases examined, the NAA/Cr ratio in the central region of TDLs and high-grade gliomas differed significantly. However, overall metabolite profiles of both lesions were similar; this finding emphasizes the need for the cautious interpretation of spectroscopic findings.

Fig 1.

Images in a 50-year-old woman with biopsy-proven tumefactive demyelinating lesion. A, Contrast-enhanced axial T1-weighted image (600/14/1) demonstrates an ill-defined enhancing mass (arrow) in the left frontoparietal periventricular white matter. B, Axial T2-weighted image (3400/119/1) shows increased signal intensity (arrow) around the lesion. C, Localizing image (600/14/1) for proton MR spectroscopy displays a voxel in the central portion of the lesion. D, Proton MR spectrum obtained by using PRESS (1500/144) demonstrates an elevated Cho value, a decreased NAA value, and a Lac doublet.

Fig 2.

Images in an 81-year-old man with a high-grade mixed glioma. A, Contrast-enhanced axial T1-weighted image (600/14/1) demonstrates an ill-defined enhancing mass (arrow) in the left temporal region. B, Axial T2-weighted image (3400/119/1) shows increased signal intensity (arrow) around the lesion. C, Localizing image (600/14/1) for proton MR spectroscopy displays a voxel in the central portion of the lesion. D, Proton MR spectrum obtained by using PRESS (1500/144) demonstrates an elevated Cho value and a decreased NAA value.

Fig 3.

Photomicrographs of a biopsy specimen from a tumefactive demyelinating lesion in a 50-year-old woman. Left, A Luxol fast blue stain demonstrates extensive myelin loss. The lower left corner (arrow) shows a relatively normal pattern of myelination. Right, Silver stain demonstrates relative preservation of axis cylinders.