Indeed, CSF GAP-43 reflects pre-synaptic dysfunction, which is one of the earliest detectable changes in neurodegenerative diseases and is postulated to occur prior to other mechanisms such as neuronal loss.3,73 Taken together, these findings suggested that CSF GAP-43 may be a relatively important biomarker of episodic memory decline. Here, GAP43 is linked to neurodegenerative disease.