The ciliospinal reflex (pupillary-skin reflex) consists of dilation of the ipsilateral pupil in response to pain applied to the neck, face, and upper trunk.If the right side of the neck is subjected to a painful stimulus, the right pupil dilates (increases in size 1-2mm from baseline).This reflex is absent in Horner's syndrome and lesions involving the cervical sympathetic fibers.f the right side of the neck is subjected to a painful stimulus, the right pupil dilates (increases in size 1-2mm from baseline). This reflex is absent in Horner's syndrome and lesions involving the cervical sympathetic fibers.