- An inflammatory demyelinating
- Presents as a solitary large (> 2 cm) focus of demyelination within a cerebral hemisphere with associated edema that may simulate neoplasm or abscess.
- Presentation is acute (≤ 3 weeks) with headache, seizures, and focal neurologic deficits.
- Often it may be a monophasic episode of disease without recurrence,
- Some may evolve into relapsing-remitting MS.
- Imaging features in 50% have contrast enhancement in the form of an incomplete ring, without enhancement at junctions with gray matter (or basal ganglia depending on orientation), and there is usually minimal mass effect.
- Advanced MR imaging techniques may be useful, and the rCBV values are significantly lower than for high-grade glial neoplasms.
- Management
- High-dose corticosteroid therapy.
- Radiation or surgical excision of lesions misdiagnosed as tumour will cause additional irreversible neurologic deficits.
- Differential diagnosis
- Ring-enhancing lesions
- Neoplasia
- Abscess
- MS
Differentiating | MRI | MRS | MR perfusion |
Tumefactive demyelination | - 50% show enhancement, usually an open ring with in complete portion facing grey matter - Mildy increased diffusion (unlike abscess) | - Elevation glutamate/glutamine peaks - Reduced NAA - Inc cho, lipis, lactate | - No elevation in rCBV |
High grade glioma | - Peripheral, heterogenous enhancement with nodules and necrosis - Can be ring enhancing Solid parts diffusion restriction | - Reduce NAA, Myoinositol - Inc. Lipid, choline and lactate | - Marked elevation rCBV |
Primary CNS lymphoma | - Homogenous enhancement common - Ring enhancing in HIV/immunocompromise - Restricted diffusion (lower ADC then metastasis or HGG) | - Large Choline peak - Reversed Cho/Cr Ratio - Markedly reduced NAA - Lactate peak possible | - Modest elevation rCBV |
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