Thus, the anatomical unit consisting of the varicosity of the peptidergic nerve terminal (from where CGRP is released) and the surrounding Schwann cell (probably of the unmyelinated Remak bundle, which expresses the CGRP-R) and another afferent PSN fiber that conveys the pain signal to the spinal cord may be necessary and sufficient to elicit migraine pain. The gene discussed is CALCRL; the disease is migraine disorder.