Activation of TrkB.FL by BDNF is neuroprotective, promoting cell survival and synaptic plasticity in experimental SCI and traumatic brain injury (TBI) [49,52,53,54], while mutations in TrkB.FL are associated with neurological disorders, such as schizophrenia, posttraumatic stress disorder, Parkinson’s disease, Alzheimer disease, and Huntington’s disease [55,56,57,58,59,60]. The gene discussed is NTRK2; the disease is juvenile Huntington disease.