Neurochemical biomarkers in the diagnosis of frontotemporal lobar degeneration: an update.

Frontotemporal lobar degeneration (FTLD) is a spectrum of rare neurodegenerative diseases with overlapping symptoms and neuropathology. It includes the behavioral variant of frontotemporal dementia (bvFTD), the semantic and non-fluent variant of primary progressive aphasia (svPPA and nfvPPA), FTD with motor neuron disease (FTD-MND), progressive supranuclear palsy, and corticobasal syndrome. The diagnosis of the FTLD spectrum of diseases is based on clinical symptoms which hampers the differentiation of the diseases among each other and with other disorders that show a similar clinical appearance resulting in a high rate of misdiagnoses. This highlights the need for objective and selective measures in the diagnostic criteria and there is extensive research on neurochemical biomarkers in FTLD as one option to address this unmet clinical need. Here, we review the advances in CSF biomarker research in FTLD in the last 2 years with regard to the validation of previously suggested and identification of new biomarker candidates for the differential diagnosis of FTLD. New biomarkers for frontotemporal lobar degeneration (FTLD) are urgently needed to support differential diagnosis within the disease spectrum and with related neurodegenerative diseases such as Alzheimer disease (AD). Here, we review the advances in cerebrospinal fluid biomarker research in FTLD and provide a list of promising candidate markers.