Neuropathological and neuroradiological aspects of acute disseminated Encephalomyelitides (ADEM)

Among non-neoplastic lesions of the central nervous system, demyelinating p seudotumors of the group of acute disseminated encephalomyelitis (ADEM) mos t frequently occasion neurosurgical intervention for purposes of definitive diagnosis and thus enter the domain of the surgical pathologist. Typically , ADEM presents with multifocal, bilateral lesions in an asymmetrical distr ibution. Especially monolocular manifestations may be diagnostically challe nging. Due to the acuteness of clinical symptoms and the expansive, space-o ccupying character of the lesions a diffuse glioma, a metastatic disease, a primary cerebral Non-Hodgkin's lymphoma, brain abscess, a parasitosis or a n ischemic brain tissue necrosis may be suspected. This impression is suppo rted by uptake of contrast medium most pronounced at the periphery of the l esion and the subcortical location. The histo morphologic feature of relati ve axonal preservation in areas with acute myelin breakdown and lymphocytic infiltrates make the diagnosis of an acute primary demyelinating disease p robable. A diagnosis of glioma may be prompted by the florid, cytologically atypical astrogliosis especially in intraoperative request. Based on a ser ies of 14 cases of radiologically and bioptically documented cases of ADEM typical examples will be demonstrated and discussed.