Ring-enhancing brain lesion

NeuroMRI

A lesion with peripheral (rim) enhancement and a non-enhancing centre. Diffusion, wall morphology and number/location are decisive.

Differential

Pyogenic abscess

common

•Central restricted diffusion (bright DWI, low ADC)
•Smooth thin regular rim, thinner on ventricular side
•T2 hypointense rim; dual-rim sign on SWI

Glioblastoma

common

•Thick irregular/nodular enhancing wall
•Central necrosis WITHOUT central diffusion restriction
•Extensive infiltrative T2 oedema, crosses corpus callosum

Metastasis

common

•Grey–white junction location, often multiple
•Oedema disproportionate to lesion size
•Known primary malignancy

Subacute infarct / resolving haematoma

less-common

•Enhancement conforms to a vascular territory (infarct)
•Blood products on SWI/gradient echo (haematoma)

Demyelination (tumefactive MS)

rare

•Open (incomplete) ring enhancement, open toward cortex
•Little mass effect for size, younger patient

Toxoplasmosis

rare

•Basal ganglia lesions in AIDS (low CD4)
•Eccentric target sign; no central diffusion restriction
•Thallium-SPECT cold (vs hot lymphoma)

Key discriminators

•Central diffusion restriction (abscess) vs facilitated diffusion (tumour necrosis)
•Rim: smooth thin (abscess) vs thick irregular (GBM/met)
•Number and location (grey–white junction for mets)
•Open-ring sign (demyelination)
•Immune status / clinical history

Work-up / next steps

1.DWI/ADC and SWI as core problem-solving sequences
2.MR perfusion and spectroscopy to separate tumour from abscess/demyelination
3.Search for a systemic primary or infective source
4.Neurosurgical aspiration/biopsy for definitive diagnosis

References

Osborn AG. Osborn’s Brain, 2nd ed.
Radiopaedia: Ring-enhancing cerebral lesions.

Educational clinical decision support only. This differential does not make a diagnosis, is not a medical device, and must never substitute for interpretation by a qualified radiologist correlated with the full clinical picture and prior imaging.