Brain-derived neurotrophic factor (BDNF) is a well-studied neurotrophin with roles in neuronal survival and differentiation.66,67 Two studies tested BDNF as adjunctive treatment by delivering it through a cannula implanted into the cerebral ventricles.68,69 The first study started with adjunctive BDNF treatment at 24 hpi in eight infant rats and compared them to eight placebo-treated controls.68 Seven days after infection, hearing thresholds were significantly decreased in the treated group, indicating reduced hearing loss. This evidence concerns the gene BDNF and infection.