Frontotemporal dementia with cerebral intraneuronal ubiquitin-positive inclusions but lacking lower motor neuron involvement.

A case of frontotemporal dementia with cerebral intraneuronal ubiquitin-positive, tau- and alpha-synuclein-negative inclusions is reported. A 50-year-old female patient exhibited mental changes; however, no clinical evidence of motor neuron disease was detected in her 11-year history. Neuronal loss and spongiform changes were mainly found in the frontotemporal cortices. Degeneration of the pyramidal tract was observed. Depletion of Betz cells was observed, whereas motor neurons of the hypoglossal nuclei and spinal anterior horn were well preserved. Immunohistochemically, intraneuronal ubiquitin-positive, tau and alpha-synuclein -negative inclusions were present in the small neurons of the dentate gyrus, frontal cortices and putamen. Neither Betz cells nor the anterior horn cells contained any inclusions. Fragmentation of the Golgi apparatus was visible only in 2.2% of anterior horn cells. A large number of tau-positive glial structures lacking argyrophilia were seen in the area of the frontopontine tract in the cerebral peduncle. The pyramidal tract lesions of the present case may be based on frontal lobe degeneration with spread of lesions to the motor cortex. Except for the pyramidal tract lesions, our case is similar to cases of motor neuron disease-inclusion dementia.