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

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.

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

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.

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.