The vidian nerve is formed by post synaptic parasympathetic fibers and presynaptic sympathetic fibers. This is also known as the “Nerve of pterygoid canal”.
Nerves that gets involved in the formation of vidian nerve:
- Greater petrosal nerve (preganglionic parasympathetic fibers)
- Deep petrosal nerve (post ganglionic sympathetic fibers)
- Ascending sphenoidal branch from otic ganglion
Vidian nerve is formed at the junction of greater petrosal and deep petrosal nerves. This area is located in the cartilagenous substance which fills the foramen lacerum. From this area it passes forward through the pterygoid canal accompanied by artery of pterygoid canal. It is here the ascending branch from the otic ganglion joins this nerve.
The vidian nerve exits its bony canal in the pterygopalatine fossa where it joins the pterygopalatine ganglion.
It is through this canal the vidian nerve passes. This is a short bony tunnel seen close to the floor of sphenoid sinus. This canal transmits the vidian nerve and vidian vessels from the foramen lacerum to the pterygopalatine fossa.
According to CT scan findings the vidian canal is classified into:
Type I: The vidian canal lies completely within the floor of sphenoid sinus
Type II: In this type the vidian canal partially protrudes into the floor of sphenoid sinus
Type III: Here the vidian canal is competely embedded in the body of sphenoid bone
Study of these anatomical differences of vidian canal in relation to the floor of sphenoid sinus helps in deciding the surgical approach to the nerve.
CT images showing the anatomical types of vidian canal and their relationship to the floor of sphenoid sinus