Where is the abnormality?
There is altered signal in the subcortical left temporal lobe (middle gyrus).
What is the likely diagnosis?
In this age group with this presentation, a focal cortical dysplasia is most likely. However a low grade tumour, such as DNET, should also be considered with similar imaging findings.
If this were to be classified, which system is favoured?
Currently the Blumcke system is used for classification of FCDs, with this meeting some criteria for Blumcke type I. However, this system is actually based on histopathological findings, and there are many other classification systems in use. A good accurate description (as always in radiology) is more important!
Focal swelling of left temporal lobe. Gyriform low T1w/high T2w signal, predominantly in the subcortical white matter with blurring of GM/WM junction. Remainder of parenchyma normal, with normal mesial temporal lobe appearances. Normal CSF configuration. No abnormal restricted diffusion. No contrast enhancement or SWI abnormality.