NEFL and COVID-19: Stratifying COVID-19 patients according to the occurrence of severe neurological symptoms into neuro-COVID and COVID groups, plasma NfL levels were significantly increased in neuro-COVID compared to COVID group (71.7 [27.9–95.1] and 21.8 [13.9–34.0] pg/mL, respectively, p = 0.0034) (Figure 2F).