Neurochemical characterization of pterygopalatine ganglion branches in humans

Pterygopalatine ganglion (PPG) branches, seem to be involved in the pathophysiology of facial pain. The functions of these branches, including a recently discovered orbital branch, are not completely known but could be of clinical significance. This study was designed to characterize PPG branches through immunohistochemical stain and study their anatomy, specifically the orbital branches.

In a cadaver study of four specimens, the pterygopalatine fossa (PPF) was dissected out of its bony surroundings as a tissue block. Subsequently, cryostat sectioning of these blocks was performed. In one specimen the PPF was microscopically dissected. Recently discovered neural structures were identified, dissected out of the tissue block, and cryosectioned. All cryostat sectionings were immunohistochemically stained for protein gene product (PGP) 9.5, nitric oxide synthase (NOS), and tyrosine hydroxylase (TH).

A recently discovered neural connection between the PPG and the ophthalmic nerve could be confirmed and classified as an orbital PPG branch. The connection stained throughout for PGP 9.5 and partially stained for NOS. In other orbital branches, both NOS and TH(+) nerve fibers were found. The PPG contained NOS(+) cells. TH labeling was also found in nerve fibers running through the PPG and the vidian nerve.

The recently discovered orbital PPG branch is of a mixed parasympathetic and sensory nature. In the other orbital branches, sympathetic fibers were shown as well. This knowledge may add to understanding the symptomatology and therapies of headache syndromes such as nerve block.