What are possible differentials to be considered? What is the next step?
Appearances strongly favour a primary brain tumour, low-grade glioma (astrocytoma or less likely oligodendroglioma). The lack of enhancement essentially excludes metastases. Appearances are not those of a subacute or acute infarction. Further assessment with MRI is recommended.
In the left posterior part of the superior frontal gyrus, extending medially to involve the anterosuperior part of the paracentral lobule, there is a region of hypoattenuation with the involvement of the overlying cortex and positive mass effect. There is associated low attenuation in the white matter extending into the precentral gyrus (oedema/tumour spread). On postcontrast imaging, no abnormal enhancement is demonstrated. The remainder of the brain is unremarkable in appearance. Ventricles are within normal limits in size. No focal osseous lesion. Small subcutaneous nodule is demonstrated beneath the left parietal scalp, most likely representing a sebaceous cyst/epidermal cyst.