MRI of demyelinating pseudotumor of the central nervous system

Objective: To describe the MR manifestations of demyelinating pseudotumor of the central nervous system (CNS), and to discuss the pathologic features and MR diagnostic value and limit in this disease entity. Methods: Seven pathologically proved and one clinically proved cases of demyelinating pseudotumor of CNS were studied with MR imaging, and the MR imaging features were retrospectively analyzed. Results: MR imaging demonstrated localized mass without adjacent multiple accompanying lesions in all 8 cases. On T1WI, the lesions showed homogenous low signal in 5 cases, inhomogeneous low signal in 2 cases, and mixed high and low signal in 1 case. On T2WI, the lesions presented as homogenous high signal in 5 cases and inhomogeneous high signal in 3 cases. Of the 7 cases with Gd-DTPA administration, marked enhancement was seen in each case. The enhancement pattern of vertical distribution of the lateral ventricle was demonstrated in left frontoparietal lobe in one case, and predominant dorsal white matter enhancement of the cervical spinal cord was revealed in another case. Follow-up MR imaging showed no lesion recurrence, and gradual shrinkage of the lesion after steroid therapy was demonstrated in one case. Conclusion: It is a difficult task to make the correct diagnosis of CNS demyelinating pseudotumor based on the clinical information and imaging findings, and this disease entity is often misdiagnosed as tumor by MR imaging. Thorough analysis of the clinical history and careful observation of MR manifestations (especially contrast enhanced MR findings) would be helpful in diagnosing the demyelinating pseudotumor and, in such circumstances, providing test steroid therapy, thus avoiding the devastating injury caused by surgery or radiation therapy