30-year-old female who presented with a three-week history of vertigo, episodic dysarthria, left lower-extremity weakness.
Imaging demonstrates peripherally isointense and internally hypointense T1 signal of the deep and subcortical white matter. They do not restrict diffusion. SWI demonstrates no suggestion of hemorrhage or calcification. The lesions are T2/FLAIR hyperintense with perilesional vasogenic edema and smooth peripheral enhancement.
Answer: B. Tumifactive Multiple Sclerosis
(A) The colloidal vescicular phase of neurocystercosis often shows perilesional edema and peripheral enhancement, but cystic fluid on T1 weighted images are usually hyperintense to CSF, and the scolex may be found within the cysts as an internal focus of eccentric enhancement. (3)
(C) Tuberculous Granulomas often exhibit perilesional vasogenic edema; however, the cystic lesions are isointense to gray matter. They do not restrict diffusion, but do show peripheral enhancement. (4)
(D) Abscesses demonstrate T2 hyperintensity in along the periphery of the lesion and ring enhancement with surrounding vasogenic edema and ring enhancement; however, they restrict diffusion which is not present in this case and typically exhibit symptoms typical of infection not compatible with this patient presentation. (5)
Discussion: Tumefactive Multiple Sclerosis
The typical appearance of multiple sclerosis, with preferential involvement of major white matter tracts in a periventricular distribution, affords a relatively straight forward diagnosis; however, the differential may be expanded when a demyelinating lesions manifests as a single, or occasionally multiple, large or tumefactive demyelinating lesion, and sometimes the diagnosis is only clinched after brain biopsy. Tumefactive demyelinating lesions are usually larger than 2 cm, usually single, and their imaging characteristics mimic neoplasms and infection.
The disease most commonly afflicts women, with an average age of 37 years. These lesions almost are only rarely associated with a recent infection or vaccination. These lesions are indistinguishable from multiple sclerosis plaques on pathology, demonstrating reactive astrocytes with infiltrated by foamy macrophages. Myelin breakdown occurs, with resultant lipid accumulation in significant quantities within the plaques. (1)
Tumefactive demyelinating lesions have been misinterpreted as gliomas on frozen section, with the correct diagnosis revealed only after an unnecessary resection or adjunct therapy. The following imaging characteristics of tumefactive demyelinating lesions may aid the radiologist in distinguishing this disease from other differential considerations:
- Tumefactive demyelinating lesisons tend to be circumscribed lesions with little mass effect.
- They are typically supratentorial and are centered in the white matter, although they may extend to the cortex.
- Approximately 50% of cases demonstrate ringlike or open-ring enhancement, with the incomplete portion of a ring on the gray matter aspect of the lesion. The enhancing portion of the ring is felt to represent the leading edge of demyelination in the white matter.
- They may demonstrate dilated veins that traverse the center of the lesion.
- They exhibit decreased rCBV on perfusion.
- They respond rapidly and well to corticosteroid therapy, and may even disappear.
- The following imaging features to not specific for or do not aid in the diagnosis of tumefactive demyelinating lesions:
- a. Corpus callosum involvement: Also included in the diagnosis for "butterfly lesions" for GBM and lymphoma.
- b. Increased diffusion: Seen in brain abscesses and aggressive neoplasms.
- c. MR Spectroscopy: Tumefactive demyelinating lesions demonstrate spectra identical to neoplastic processes. (1)
1. American Journal of Radiology 2004; 182: 195-199
2. American Journal of Radiology 2009; 251: 467-475
3. RadioGraphics 2010; 30:1705–1719
4. RadioGraphics 2007; 27:1255–1273
5. RadioGraphics 2015; 35:1555–1562