A large area of vasogenic oedema within the left occipital lobe surrounds an irregularly rounded lesion of intermediate signal intensity, measuring approximately 17 mm in diameter. T2-weighted scans indicate that the central lesion has a rim of reduced magnetic susceptibility within it, in the centre of which diffusion is markedly restricted. Contrast enhancement is vivid with some loculation and several "fingers" of enhancement extending into the adjacent tissue. Relative cerebral blood volume (CBV) is increased in the peripheral enhancing portion of the lesion. Spectroscopic imaging shows large lactate/lipid peaks indicative of necrosis. Choline peaks are not prominent. Elsewhere, scattered foci of white matter abnormal signal probably indicate chronic small vessel ischaemic disease. A small lateral occipital cortical signal abnormality may represent an old cortical infarct. Magnetic susceptibility effect from coils noted in relation to the terminal portion of the right internal carotid artery with the suggestion of residual aneurysmal cavity.
The vivid contrast enhancement, extensive oedema, restricted diffusion and slightly elevated relative cerebral blood volume (CBV) are most in keeping with a malignant tumour. Glioblastoma multiforme and metastasis could both produce such an appearance. The restricted diffusion and lack of prominent choline peaks means abscess cannot be entirely discarded as the diagnosis, despite the relative thickness of the enhancing walls, which can be a feature of atypical organisms in immunocompromised patients.