IL31 and nervous system disorder: Since pain can occur due to otitis and other neurological disease like intervertebral disc protrusion or extrusion [23] or neoplasia [24], difference between IL-31 levels in serum and CSF of dogs with and without signs of pain were compared separately in dogs with syringomyelia only (group A.1), with syringomyelia and otitis (group A.2), and dogs with syringomyelia and concomitant neurological disease (A.3) (Table 3).