A previously healthy 69-year-old man developed a progressive neurological illness with bulbar signs and ataxic paraparesis. Repeated MRI examinations revealed a large space occupying lesion in the lower brain stem with patchy contrast enhancement. MRI angiography was unremarkable and CSF had normal cell count but raised protein content. A brainstem tumor was suspected and a course of intravenous glucocorticosteroids was started. No improvement occurred and the patient died of pneumonia 11 weeks after onset. Neuropathology revealed confluent areas of complete or incomplete necrosis with marked edema in the lower brainstem. Predominantly venous meningeal vessels of the brainstem showed extensive fibromuscular thickening of all layers with luminal narrowing. In addition, intramural mononuclear infiltration was found. With the exception of localisation, this case exhibits all pathologic features of subacute diencephalic angioencephalopathy (SDAE), a rare fatal disease of unknown aetiology. In addition, the clinical features of typical age, male sex, disease duration and raised CSF proteins are shared. A common disease entity is suggested and the pathogenetic relevance of inflammation and venous outflow obstruction is discussed.