Brain-derived neurotrophic factor (Val66Met) polymorphism does not influence recovery from a post-traumatic vegetative state: a blinded retrospective multi-centric study

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that influences neuronal plasticity throughout life. Emergence from a vegetative state (VS) after a traumatic brain injury (TBI) implies that the brain undergoes plastic changes. A common polymorphism in the BDNF gene—BDNF Val66Met (referred to herein as BDNFMet)—impairs cognitive function in healthy subjects. The aim of this study was to determine whether the BDNFMet polymorphism plays a role in the recovery of consciousness and cognitive functions in patients in a VS after a TBI. Fifty-three patients in a VS 1 month after a TBI were included in the study and genotyped for the BDNFMet polymorphism. Scores of levels of cognitive functioning (LCF) at 1, 3, 6, and 12 months post-TBI were retrospectively compared in patients without (Val group), and with (Met group), the BDNFMet polymorphism. The BDNFMet polymorphism was detected in 20 out of the 53 patients. The mean LCF scores in the Val and Met groups were 1.6 – 0.5 and 1.4 – 0.5 at 1 month, 2.3 – 0.7 and 2.5 – 1.2 at 3 months, 3.3 – 1.7 and 3.5 – 1.7 at 6 months, and 4 – 1.9 and 3.9 – 1.8 at 12 months, respectively ( p > 0.05). The percentages of patients in the Val and Met groups who emerged from the VS were 36.4% and 30% at 3 months, 66.3% and 70% at 6 months, and 70% and 87.5% at 12 months ( p > 0.05), respectively. These findings provide evidence that the BDNFMet polymorphism is not involved in cognitive improvement in patients with a VS following TBI. Future studies should focus on the role of other BDNF polymorphisms in the recovery from a VS.