Following relay in the superior cervical ganglion, how do postganglionic sympathetic fibres destined for the dilator pupillae, sweat glands of the forehead, and cerebral vessels reach these structures?

• A They rejoin spinal nerves C1 to C4 via grey rami and travel peripherally
• B They ascend as the internal carotid nerve and form a plexus around the internal carotid artery ✓
• C They hitchhike with the ophthalmic division of the trigeminal nerve through the superior orbital fissure exclusively
• D They descend along the vertebral artery into the posterior cranial fossa

Explanation

From the superior cervical ganglion, postganglionic fibres form the internal carotid nerve, which ascends into the carotid canal and breaks up as the internal carotid plexus surrounding the artery. These fibres distribute to the ophthalmic artery branches, dilator pupillae, and intracranial vessels. Some fibres do later join branches of the trigeminal nerve, but the primary highway is periarterial, which rules out option C as the defining route.

Reference: Gray's Anatomy for Students, 4th ed.

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