Cranial nerves and autonomic innervation in the orbit

The orbit contains an extremely large and complex set of nerves to provide both motor control and sensory monitoring of the various tissues within the orbit. Within each bony orbit, there are branches of five cranial nerves (CNs) as well as autonomic innervation. The five cranial nerves are: (1) The optic nerve, or CNII, is part of the central nervous system. It is a special sensory nerve and relays information about the visual world to the brain. (2) The oculomotor nerve, or CNIII, innervates five muscles in the orbit: the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique. It also carries parasympathetic nerve fibers destined for the globe. (3) The trochlear nerve, or CNIV, innervates the superior oblique muscle. (4) The ophthalmic division of the trigeminal nerve, or CNV1, provides general sensory innervation for tissues within the orbit as well as the skin of the upper eyelid and scalp. The ophthalmic division forms several main branches: the frontal, lacrimal, and nasociliary nerves, all of which enter the orbit separately. In addition, a small branch from the maxillary division of the trigeminal nerve, or CNV2, runs in the orbital floor and provides general sensory innervation for the lower eyelid. (5) The abducens nerve, or CNVI, innervates the lateral rectus muscle. The classic description of the origins and nerve pathways taken by the parasympathetic and sympathetic innervation within the orbit is inaccurate. Current experimental data clarifying our current understanding of the anatomy of these pathways are reviewed in this article.