Ciliary ganglion afferents and efferents variations: a possible explanation of postganglionic mydriasis.

Purpose: Ciliary ganglion is a pre-visceral vegetative ganglion, relay of ocular bulb vegetative pathways, concerning three types of fibers: parasympathetic, sympathetic and somatosensory. The objective of this study was to describe the different patterns of distribution of those fibers around the ciliary ganglion to explain rare post-traumatic or postoperative ocular symptoms.

Methods: Dissection of 20 orbits, from cavernous sinus to ocular bulb, after intravascular injection of colored latex.

Results: Concerning afferents, or roots, three dispositions have to be described: all of them were identified (55 %); parasympathetic root was absent and ciliary ganglion was attached directly to the inferior branch of the oculomotor nerve (25 %); sympathetic root was absent (20 %). Somatosensory root, coming from nasociliary nerve, was constant. Efferents (short ciliary nerves), including these three types of fibers, were variable in number but always constituted two bundles.

Conclusion: The absence of identifiable parasympathetic root, resulting in a close relationship between ciliary ganglion and the inferior branch of the oculomotor nerve, could be a possible explanation of postganglionic mydriasis following blow-out orbital floor fracture or surgical repair of this type of fracture. The absence of sympathetic root is due to a forward retro-orbital connection between internal carotid plexus and ophthalmic nerve within cavernous sinus, corresponding to gray rami communicans.