BDNF is a growth factor required for the survival of various neuronal populations in the CNS and is downregulated in the caudate and putamen of post-mortem HD brains compared with age-matched controls.62 Levels of BDNF in the CSF were previously reported to be unchanged across HD stages using an immunoassay.63 We observed a strong trend towards a reduction of BDNF in late HD compared with controls (P = 0.053) and moderate correlations with TFC (ρ = 0.45) and SDMT (ρ = 0.48). Here, BDNF is linked to Huntington disease.