No significant differences in CSF BDNF levels were present between the three groups of patients (ALS: 1.35 ± 0.66 pg/mL; AD: 1.36 ± 1.13 pg/mL; ID: 0.53 ± 0.30 pg/mL) compared to healthy controls (0.32 ± 0.16 pg/mL pg/mL) and among patients’ groups (p > 0.05). This evidence concerns the gene BDNF and amyotrophic lateral sclerosis.