A 62-year-old man is admitted to the hospital with dull, diffuse abdominal pain. A CT scan reveals a tumor at the head of the pancreas. The abdominal pain is mediated by afferent fibers that travel initially with which of the following nerves?

The afferent fibers mediating the pain from the head of the pancreas run initially with the greater thoracic splanchnic nerves. The greater splanchnic nerves arise from sympathetic ganglia at the levels of T5 to T9 and innervate structures of the foregut and thus the head of the pancreas. Running within these nerves are visceral afferent fibers that relay pain from foregut structures to the dorsal horn of the spinal cord. Also entering the dorsal horn are the somatic afferents from that vertebral level, which mediate pain from the body wall. Intercostal nerves T1 to T12 provide the terminal part of the pathway to the spinal cord of visceral afferents for pain from the thorax and much of the abdomen. Therefore, pain fibers from the pancreas pass by way of the splanchnic nerves to the sympathetic chains and then, by way of communicating rami, to ventral rami of intercostal nerves, finally entering the spinal cord by way of the dorsal roots. The phrenic nerve innervates the diaphragm and also carries visceral afferents from mediastinal pleura and the pericardium, but it does not carry with it any visceral afferent fibers from the pancreas. The vagus nerve innervates the pancreas with parasympathetic fibers and ascends all the way up to the medulla where it enters the brain. It has no visceral afferent fibers for pain. The subcostal nerve is from the level of T12 and innervates structures below the pancreas and carries no visceral afferents from the pancreas.