Early Fetal Development of the Otic and Pterygopalatine Ganglia with Special Reference to the Topographical Relationship with the Developing Sphenoid Bone.

Abstract

The otic and pterygopalatine ganglia are located close to the greater wing (alisphenoid) of the sphenoid bone and many researchers have noted nerves connecting these ganglia in human embryos. The greater wing (alisphenoid) arises from the cartilaginous ala temporalis independently of the lesser wing, but no topographical changes between this cartilage and nerve elements have been demonstrated. We examined histological sections of 20 human embryos and fetuses from 6 to 15weeks of development (WD). At 6WD, the ala temporalis, the alar process and ganglia were all identified as a single, undifferentiated cell mass. Subsequently, the two ganglia became identifiable, but were continuous on the superior side of the initial ala temporalis. The temporal, superior spine of the ala temporalis was surrounded by the part that connected the ganglia. At 7WD, the superior spine of the ala temporalis was reduced in size and the continuity of these ganglia was lost. At this point, a secondarily-formed communicating branch between the ganglia, the nervus sphenoidalis was first identifiable. At 9WD, the ala temporalis and the alar process had clearly become cartilages, and the anterior end of the otic ganglion was separated from the ala temporalis. The nervus sphenoidalis became longer. At 15WD, the otic and pterygopalatine ganglia were clear separated from the alisphenoid, which consisted of the cartilaginous ala temporalis and membranous bone. Consequently, the separation between the otic and pterygopalatine ganglia seemed to be due to the developing ala temporalis. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.