The sympathetic nerves of the parasellar region: pathways to the orbit and the brain.

Sympathetic nerves innervate targets in the orbit and the brain. They issue from the superior cervical ganglion and reach the parasellar region via the internal carotid nerve. Information on their further parasellar course and distribution is scant and contradictory. In this study the parasellar sympathetic pathways of 30 human infants and 6 human fetuses were investigated by microdissection and histologically. A common parasellar sympathetic trunk, which reunites all the nerve fibers emanating from the lateral and medial internal carotid plexus, is described as well as its further divisions. It was found that the posterior knee of the infant carotid siphon is free of large sympathetic nerve bundles. In addition a ganglion is described, which is situated in the parasellar adipose body. It is reached by nerve fibers coming from the parasellar sympathetic pathways. Fibers that issue from this ganglion join the periorbita and the orbital muscle of Müller. These anatomical facts are of immediate importance for preventing nerve damage during cavernous sinus surgery. Furthermore, the study improves the anatomical knowledge of the parasellar region and suggests a new concept for the innervation of the orbital muscle.