Pain arising from structures served by the phrenic nerve is often "referred" to other somatic regions served by spinal nerves C3-C5. For example, a subphrenic abscess beneath the right diaphragm might cause a patient to feel pain in the right shoulder (Kehr’s sign). Irritation of the phrenic nerve (or the tissues supplied by it) leads to the hiccough reflex. A hiccough is a spasmodic contraction of the diaphragm, which pulls air against the closed folds of the larynx.