A ring enhancing left cerebellar hemisphere lesion, which is favoured to be intra-axial is T1 hypointense, and T2 hypointense to grey matter. In addition to the rim of contrast enhancement, it contains 2 central enhancing nodules. Faint susceptibility artefact is present in its rim, but there is no diffuse susceptibility blooming to suggest internal haemorrhage. The lesion demonstrates diffusion restriction (ADC = 600 x 10^-6 mm2/s), corresponding to the non-enhancing central content rather than enhancing rim and nodules. MR spectroscopy demonstrates an elevated lactate peak, with reversal of the choline:creatine ratio.
It causes significant adjacent T2/FLAIR hyperintensity, consistent with vasogenic oedema. There is mass effect with compression of the fourth ventricle/cerebellar vermis and rightward deviation of the superior medullary velum. The lateral and third ventricles are slightly larger than expected for age, suggesting mild obstructive hydrocephalus.
Conclusion: Ring-enhancing 2cm left cerebellar mass with posterior fossa mass effect resulting in mild obstructive hydrocephalus, in the context of a right upper lobe and paratracheal nodal complex conglomerate mass. The presence of diffusion restriction in the non-enhancing or poorly enhancing internal portion of the mass raises suspicion for cerebral abscess (including tuberculous), the morphologic appearance is not entirely classic and occasionally the contents of a metastasis can demonstrate restricted diffusion.