Tumefactive Demyelination – Open Ring Sign — SCE Neurology MCQ

Instant feedback + full explanation. One question, done properly.

HardMultiple Sclerosis & CNS InflammationTumefactive Demyelination – Open Ring SignSCE Neurology

A 50-year-old man with RRMS develops new-onset seizures. MRI brain shows a large, solitary, ring-enhancing white matter lesion with surrounding oedema crossing the corpus callosum. There is incomplete ring enhancement with the open ring facing the cortex. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Tumefactive demyelinating lesion

Tumefactive demyelination (tumefactive MS) presents with a large (>2 cm) solitary demyelinating lesion that can mimic a brain tumour or abscess. Key MRI features that favour demyelination over neoplasia include: incomplete ring enhancement ('open ring sign' with the open edge facing the cortex/grey matter), minimal mass effect relative to lesion size, and location in white matter. The open ring sign has high specificity (~85%) for demyelination. Biopsy may be needed if the diagnosis is uncertain. A: GBM has complete ring enhancement with central necrosis. B: Abscess has complete ring with restricted diffusion centrally. D: PCNSL has homogeneous enhancement. E: Toxoplasmosis occurs in immunocompromised patients.

Reference: ABN MS Guidelines (2022); NICE NG100; Lucchinetti et al. Brain (2008)