Given that BDNF and its high affinity receptor tropomycin-related kinase B (TrkB) play a crucial role in axon guidance and growth as well as synapse formation and plasticity [76], [77], [78], [79] it is straightforward to think that polymorphisms at this gene would influence recovery of function after a brain injury, particularly in the close period of time when extensive synaptic remodeling might occur. The gene discussed is NTRK2; the disease is brain injury.