The CSF NfL level was the highest in the non-demyelinating diseases group (1169.64 [535.92−5120.11] pg/mL; p = 0.025), with subgroup values as follows: malignant brain tumors, 13099.84 ± 4507.57 pg/mL; benign brain tumors, 3033.50±3028.41 pg/mL; hydrocephalus, 3049.94±2937.34 pg/mL; differential diagnosis of headache, 3502.91 ± 4364.67 pg/mL; and other, 940.60±945.89 pg/mL. The gene discussed is NEFL; the disease is Headache.