Sympathetic fibers to the head originate from which spinal levels?

• A. T1
• B. T2
• C. T3-T4
• D. T1 and T2

Answer: (D)

Sympathetic supply to the head comes from the upper thoracic spinal cord. The preganglionic neurons are located in the intermediolateral cell column at the upper thoracic levels, primarily at T1 and T2. These fibers exit with the ventral roots, enter the sympathetic chain, and ascend to the superior cervical ganglion, where they synapse. The postganglionic fibers then accompany the internal carotid artery and its branches to reach the head structures, producing effects like pupil dilation and sweat gland activation. This pathway centers on T1 and T2 as the spinal levels that give rise to head sympathetic fibers. (Lower thoracic levels contribute to other regions, and the superior cervical ganglion acts as the key relay to distribute fibers to the head.)