Case of the Week

Background:

• Tumefactive demyelinating lesions (TDLs) are demyelinating brain lesions, which are most commonly larger than 2 cm and often indistinguishable from brain tumors.
• The proportion of male and female patients are basically the same. All ages can develop the disease, but young people are more commonly affected.
• Most of the lesions are located in the supratentorial brain parenchyma, and rarely occur in the cerebellum, brainstem, and spinal cord.

Clinical Presentation:

• TDLs may alter the motor, sensory, cognitive, and cerebellar function, which depends on the different sizes and locations of the lesions. The most common presenting atypical symptoms include: headache, cognitive abnormalities, motor weakness, mental confusion, aphasia, apraxia, and/or seizures.

Key Diagnostic Features:

• The imaging findings include T1WI hypointensity, T2WI hyperintensity, open ring or incomplete rim enhancement.
• DWI shows peripheral restriction around lesion.
• ¹H-MR spectroscopy is also helpful when the Cho/NAA ratio is <2.

Differential Diagnoses:

• When they appear as a single mass lesion, the conventional MRI of TDLs may also mimic glial tumors, CNS lymphomas, and brain abscesses.
• Glial tumors usually have a higher relative cerebral blood volume than TDLs on perfusion imaging. High-grade gliomas have significantly lower FA and higher MD values in the peripheral enhancing portions of the lesions compared with those of TDLs.
• Higher Cho/Cr ratios, Cho/NAA ratios, and lipid and/or lactate peak grades are found in primary CNS lymphomas when compared with TDLs.
• Brain abscesses on diffusion-weighted imaging show obviously restricted diffusion and circular enhanced lesions on T1-weighted images postcontrast.

Treatment:

• Most patients with TDLs show an excellent response to corticosteroid treatment. Accurate diagnosis of TDLs is clinically important to avoid unnecessary invasive biopsy or operative treatment.