The thoracic spine is the exclusive outlet for the Sympathetic Nervous System. The cell bodies for the preganglionic sympathetic neurons are located in the intermediolateral cell column of the thoracic spinal cord (T1–L2).

T1–T11 supply limb muscles except T1 (hand).

Thoracic spine lesions can disrupt sympathetic outflow → Horner’s syndrome (T1), orthostatic hypotension (T5–T12), or impaired sweating.

These nerves run in the costal groove on the inferior border of each rib, situated between the internal intercostal muscle and the innermost intercostal muscle. They are accompanied by the intercostal artery and vein, forming the neurovascular bundle.