Brain-derived neurotrophic factor in blood serum and lacrimal fluid of patients with focal epilepsy.

Objective: To evaluate brain-derived neurotrophic factor (BDNF) level in blood serum (BS) and lacrimal fluid (LF) of people with epilepsy (PWE).
Methods: It was a case-control study of 72 consecutive patients with focal epilepsy (cases, Epilepsy group) and 60 age- and gender-matched healthy volunteers (controls). Based on comorbid depression, two subgroups of PWE were formed. BDNF level was measured by enzyme-linked immunosorbent assay (ELISA) in BS and LF.
Results: Compared to controls, BDNF level (pg/mL) in PWE was lower both in BS (22,520 ± 3810 vs. 26,360 ± 3090, P < 0.000) and in LF (100.8 ± 23.3 vs. 113.4 ± 19.3, P = 0.001). However, no significant correlation was found between BDNF level in BS and LF either in the Epilepsy group or in controls. No impact of comorbid depression on BDNF level was found either in BS or LF of PWE. We revealed a higher BDNF level in LF of men as compared to women in controls and a similar non-significant trend in PWE. Higher BDNF level in BS of PWE receiving valproates versus other AEDs was found, however, a relatively small number of observations and use of polytherapy in most cases should be taken into account.
Significance: In patients with focal epilepsy, BDNF level is decreased both in BS and LF, though with no correlation between them. No association of BDNF levels with age and epilepsy characteristics, as well as the occurrence of depression, was found. Low BDNF level in LF could be considered as a non-invasive biomarker of focal epilepsy.
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