The group of patients with syringomyelia (group A) was further divided in three subgroups to exclude an influence of comorbidities on IL-31 levels in these patients: Patients with syringomyelia and no structural brain lesion (subgroup A.1, n = 27), patients with syringomyelia and otitis media and/or interna (subgroup A.2, n = 8; including primary secretory otitis [n = 4] and infectious otitis media and interna [n = 4]) and patients with syringomyelia and concomitant neurological disease (subgroup A.3, n = 13). Here, IL31 is linked to otitis media.