We report a patient with monophasic inflammatory demyelinizing disease whose initial symptoms and imaging studies led to the undertaking of a cerebral biopsy for suspicion of an expansive process. The evolution of the both the CT and MR imaging studies with contrast and overall the surprising size of the lesions in MR when the patient was clinically asymptomatic support the hypothesis of residual dysfunction in the hemato-encephalic barrier as a cause of the persistence of MR images. This explanation appears more acceptable than its attribution to a gliosis secondary to previous inflammation.