RÉSUMÉ
<p><b>OBJECTIVE</b>To study the clinicopathological characteristics diagnosis, differential diagnosis and etiology of demyelination pseudotumors of the brain.</p><p><b>METHODS</b>The clinical features, CT, MRI scan findings, corticosteroid therapeutic effects and follow-up data of 3 cases of demyelination pseudotumors of the brain were analysed, and pathological changes were observed by histologic (HE, Luxol fast blue and Bodian) and immunohistochemical (S-P method) techniques.</p><p><b>RESULTS</b>The acute onset of demyelination pseudotumors appeared to be more predominant in our data. Clinical manifestations included headache, vomiting, a depressed conscious level, dysphasia, and paresis. CT, MRI scans showed solitary or multiple lesions in cerebral hemisphere. All the patients presented excellent response to steroid treatment. Follow-up for a period of 6 to 31 months, revealed the absence of progression or recurrence. The pathological changes were mainly located in both cerebral hemispheres, in which there were relative axonal preservation in foci loss of myelin, reactive gliosis, profuse perivascular lymphocytic infiltration and mixtures of foamy macrophages.</p><p><b>CONCLUSION</b>Demyelination pseudotumor is a distinct clinicopathologic encephalitic entity. The findings of this study suggest that the cause of tumefactive demyelination may be related to an allergic reaction triggered by viral infection.</p>