The intercostal nerves originate segmentally from the anterior rami of the thoracic spinal nerves T1 to T11. They run in the intercostal space between the adjacent ribs. The intercostal nerves are situated within or slightly below the subcostal grooves and go alongside the intercostal vessels. Within the subcostal groove, the intercostal nerve lies inferior to the intercostal vein and intercostal artery.