Ubiquitin-positive inclusions and progression of pathology in frontotemporal dementia and motor neurone disease identifies a group with mainly early pathology

Frontotemporal lobar degeneration (FTLD) with tau-negative, ubiquitin-positive inclusions has been a topic of major interest in recent years, with this group now accounting for the majority of tau-negative cases of frontotemporal degeneration. The severity of neurodegeneration in FTLD is dependent on the stage of disease and is substantial even in the earliest stages. Elucidating the pathogenesis of FTLD requires evaluation of changes during the earliest possible stage of disease. However, the long survival of most frontotemporal dementia cases means that cases with early neuropathology are not frequently encountered. Cases of FTLD with the shortest survival are those with coexisting motor neurone disease (FTLD + MND), making these the ideal group for studying early FTLD pathology. It is not clear, however, what the pathological contribution of MND is in these cases. This study evaluates the pathology of 20 cases of FTLD (11 with no clinical signs of MND and nine with FTLD + MND) as well as 10 cases of MND without dementia. Our findings indicate that the deposition of ubiquitin does not play a key role in the neurodegenerative process in FTLD, and that the severity of neurodegeneration in FTLD is similar in cases with and without clinical MND.