Cranial CT scan: Round or irregular shaped solitary mass in the brain. In acute or subacute cases, the mass is mostly hypodense, with uniform or heterogeneous density; the perifocal edema is mild to moderate, but may also be markedly edematous, with relatively mild occupying effects. The edematous zone of the lesion will decrease or disappear with the course of the disease. Those with chronic onset may show low, equal or high density, and the degree of edema and the occupying effect are not obvious. Cranial MRI manifestations: plain scan: if normal brain tissue is preserved in the lesion area or old and new lesions overlap, it may show mixed long T1 and T2 abnormal signals. Enhancement: The lesion may be diffusely, nodularly or circumferentially enhanced. The open ring sign is characteristic of this disease and is highly specific for the diagnosis of atypical demyelinating disease. The following metabolic features of MRS monosomal short echo technique are present: there can be a decrease in the NAA peak (neuronal destruction), an increase in Cho (cell membrane destruction), an increase in the Lac peak (macrophage activity in acute inflammation) and an increase in Lip (acute demyelination, due to myelin and cell membrane destruction and elevated free fat due to lipid release). Unlike gliomas the NAA /Cr ratio is lower in the necrotic or cystic portion of the lesion center than in other non-necrotic areas. There is an elevation of Lac, L ip peaks, β and γ-Glx peaks during the acute phase, and Lac and Lip peaks recover after the acute phase.