The normal and variant clinical anatomy of the sensory supply of the orbit.

Orbital and retro-orbital pain are relatively common clinical conditions that are associated with such disorders as trigeminal, lacrimal, and ciliary neuralgia, cluster headaches, paroxysmal hemicrania, inflammatory orbital pseudotumor, trochleitis, and herpetic neuralgia ophthalmicus, thus making the nerves supplying the orbit of great clinical importance. Surprisingly, how pain from this region reaches conscious levels is enigmatic. Classically, it has been assumed that pain reaches the ophthalmic division of the trigeminal nerve (V1 ) and travels to the descending spinal trigeminal nucleus. However, exactly where the receptors for orbital pain are located and how impulses reach V1 is speculative. In this project, we reviewed all of the reported connections between the orbital nerves and V1 in order to understand how pain from this region is transmitted to the brain. We found reported neural connections to exist between cranial nerve (CN) V1 and CNs III, IV, and VI within the orbit, as well as direct neural branches to extra-ocular muscles from the nasociliary, frontal, and supraorbital nerves. We also found reported neural connections to exist between the presumed carotid plexus and CN VI and CN V1 , CN VI and CN V1 and V2 , and between CN V1 and CN III, all within the cavernous sinus. Whether or not these connections are sympathetic or sensory or some combination of both connections remains unclear. An understanding of the variability and frequency of these neural connections could lead to safer surgical procedures of the orbit and effective treatments for patients with orbital pain.