There is a large 4.3 x 5.0 CM (axial x CC) hypodensity involving the left anterior frontal lobe on medial aspect, affecting both cortex and white matter.
There is marked mass effect leading to subfalcine herniation and displacement of the distal ACAs, and effacement of the frontal horns.
No enhancement can be appreciated.
There is opacification of the left frontal sinus with possible hyperdense fluid on the dependent portion.
The posterior table appears intact.
No extra axial lesion can be appreciated.
Comment: Differentials is between a primarily intra-axial lesion (and neoplasm will be one consideration), in which case left frontal sinus fluid would be incidental; or infection spreading from the frontal sinus resulting in marked oedema and cerebritis.
MRI is recommended, and should include diffusion imaging and possibly MRS.