Bunina body in frontal lobe dementia without clinical manifestations of motor neuron disease.

We report here an early autopsy case of a 60-year-old woman clinically diagnosed as having frontal lobe dementia without other neurological deficits. Postmortem examination revealed mild spongiosis in layers II and III of the frontal cortex, together with depletion of melanin-containing neurons in the substantia nigra. In addition to ubiquitin-positive neurites, ubiquitin-positive, tau-negative inclusions, which were previously considered to be a hallmark for motor neuron disease with or without dementia, were identified in neurons of the hippocampal dentate gyrus and of the temporal cortex. Although the patient lacked lower motor symptoms, the presence of Bunina bodies identified in the hypoglossal nuclei further supported the relationship of this case to motor neuron disease. Bunina bodies might be present in some cases of frontal lobe dementia. The presence or absence of Bunina bodies should be scrutinized even in cases without motor symptoms. In this case, creatine kinase of skeletal muscle origin was elevated, which might also be a potential indicator that suggests subclinical involvement of lower motor neurons.