Horner syndrome results from interruption of the sympathetic pathway. At which level does the preganglionic sympathetic neuron for the eye's dilator pupillae originate?

• A Edinger-Westphal nucleus in the midbrain
• B Superior cervical ganglion — postganglionic only
• C Dorsal nucleus of vagus — T6 to T10
• D Ciliospinal center of Budge — C8 to T2 lateral horn ✓

Explanation

The sympathetic supply to the eye follows a three-neuron arc: (1) first-order neuron from hypothalamus to the ciliospinal center of Budge (C8–T2 intermediolateral column), (2) second-order preganglionic neuron exits, travels over the lung apex and subclavian artery to the superior cervical ganglion, (3) postganglionic fibers follow the internal carotid artery to the dilator pupillae, superior tarsal muscle, and sweat glands. The Edinger-Westphal nucleus is parasympathetic (constrictor pupillae). Horner syndrome (ptosis, miosis, anhidrosis) results from interruption at any level.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.