Female, 15 years old, with new seizures and a lesion in the temporal lobe. A lesion is present peripherally within the inferior temporal gyrus on the right measuring 12 mm TV, 11 mm AP and 10 mm CC. The lesion involves the cortex and underlying white matter and appears to be partially solid with interspersed areas of spongy or cystic tissue, some of which suppresses on FLAIR imaging. Mild T2 hyperintensity is evident within the surrounding white matter and cortical gray matter.Spectroscopic assessment of this lesion was challenging due to the proximity of calvarium and skull base. This necessitated the use of a small voxel which compromises the signal-to-noise ratio. Nevertheless, short TE spectra were obtained over the lesion and, for comparison, over the contralateral normal temporal lobe. Lesional tissue demonstrates reduced NAA and no significant choline elevation. Lipid and lactate are not present in significant quantities.Elsewhere, the morphology and signal characteristics of the brain are within normal limits. No diffusion restriction is seen. No additional areas of focal signal abnormality are detected. The mesial temporal lobe structures are symmetric. No evidence of intracranial hemorrhage or any abnormal extra-axial fluid collection is seen. Ventricular size and morphology are within normal limits.
A lesion is present peripherally within the inferior right temporal lobe involving the cortex and subcortical white matter. Signal characteristics suggest a mixture of solid and spongy or cystic tissue. The differential diagnosis would include a low-grade tumor such as a ganglioglioma, DNET, or PXA. Lack of significant choline elevation on spectroscopy would argue against a high-grade neoplastic process, and lack of lipid/lactate would argue against on-going cellular damage as might be seen with active inflammation. A nonneoplastic process, such as a cortical dysplasia, is considered less likely based on the morphology of the lesion.