Motor neuron disease-frontotemporal dementia: a clinical continuum

Overlap between motor neuron disease (MND) and frontotemporal dementia (FTD) occurs at clinical, genetic and pathological levels, and has been recently strengthened through the discovery of the C9orf72 genetic expansion. MND is now considered to be a multisystem disorder in which cognitive involvement may be present and, in some cases, may evolve to frank FTD. Identifying cognitive features in MND can be challenging, while, similarly, motor dysfunction in FTD may be overlooked. As such, the present review aims to decipher the variety of overlapping clinical features across the MND-FTD continuum.