Toxoplasmosis

There are four peripherally enhancing masses in the supratentorial brain at the grey-white matter junction. Additional non-enhancing foci of vasogenic edema in the right frontal region. There is marked surrounding vasogenic edema surrounding the peripherally enhancing masses, with marked mass effect and convexity sulcal effacement.

Conclusion: Multiple enhancing masses at the supratentorial grey-white matter junction is concerning for multiple abscesses or metastatic disease.

Innumerable, irregular, peripherally contrast-enhancing (T1 C+ not shown) lesions are seen in the supra and infratentorial brain, of varying sizes. These are mostly distributed in the basal ganglia and at the grey-white matter junction. Several of lesions have a mural nodule e.g. in the right basal ganglia, and the left frontal lobe lesion has a target-like pattern of enhancement. No convincing central diffusion restriction. Many are however T2 hypointense centrally, and with foci of susceptibility. Extensive surrounding vasogenic edema. No definite leptomeningeal or pachymeningeal thickening/hyperenhancement. No ventricular enlargement or ependymal enhancement to suggest ventriculitis. No subfalcine, uncal or tonsillar herniation. Paranasal sinuses are unremarkable

Conclusion: Innumerable intra-axial lesions. These most likely represent atypical infection (such as toxoplasmosis, fungal or tuberculosis), especially if the patient is immunosuppressed. The alternative diagnosis is multiple metastases.