In the stridor subgroup, MSA patients with early stridor onset (n = 15) showed higher CSF NfL levels than those with late stridor onset (n = 30), but without reaching statistical significance [3825 (2420–4903) vs. 3169.5 (2399–4448), p = 0.0980] (Table 2). Here, NEFL is linked to multiple system atrophy.