FIG 4. Axial T2-weighted (T2W), T1-weighted Gd-enhanced (T1W Gd), hemodynamic (rCBV), diffusion (ADC) MR images and selected proton MR spectra (MRSI) from a multivoxel MR spectroscopic data set in a 16-year-old male adolescent with an enlarging inoperable brainstem lesion that was identified after the acute onset of left-sided nerve palsy. The lesion with high signal intensity on the T2-weighted image appears hyperintense on the T1-weighted Gd-enhanced and ADC images, and it is hypointense on the rCBV image. Multivoxel proton MR spectra (TE, 65 milliseconds) show a large lipid peak, in addition to Cho and tCr peaks, within the central portion of the mass; in the anterior voxel, the same peak was absent. These findings suggest that the lesion has a high neoplastic potential because increased lipid levels represent necrosis. Findings on both rCBV and ADC images are not consistent with the MR spectroscopic findings.