Miliary brain metastases presenting as rapidly progressive dementia

We report the case of a 79‐year‐old woman who developed a rapidly progressive dementia (RPD) with severe memory impairment, early visual hallucinations and extrapyramidal signs. Symptoms started suddenly after hip replacement surgery following an accidental fall. Motor epileptic seizures appeared at the end of the illness. Dementia worsened gradually leading to akinetic mutism. She died five and a half months after the onset of symptoms. MRI showed cerebral atrophy but failed to detect any other lesion. Results of all laboratory tests performed were negative. After the most frequent treatable diseases were excluded, the diagnosis of dementia with Lewy bodies was initially considered. CJD was also suggested based on the rapid evolution of the disease and the positivity of 14‐3‐3 protein in CSF. Neuropathological examination revealed an extensive miliary metastatic dissemination from an unknown primary adenocarcinoma. Pulmonary origin was suggested according to the immunohistochemical profile. Histopathological changes of Alzheimer's disease were also observed in the cerebral cortex and hippocampus. Neither Lewy bodies nor PrP deposits were found. The sudden onset of the dementia just after the hip replacement surgery raises the possibility of a pathological fracture with secondary tumoral microembolic dissemination. Despite its rarity, this entity should be included in the differential diagnosis of RPD. This case illustrates the definite importance of neuropathological post‐mortem examination in order to elucidate the different types of dementia.