The greater petrosal nerve branches off of the facial nerve in the skull.
The primary functions of this nerve are taste andsecretomotor(dealing with secretions from glands).
Each person has12 cranial nerves, which exist as symmetrical pairs.
Enid Hajderi / Stocktrek Images / Getty Images
(However, theyre typically referred to as a single nerve.)
Thefacial nerveis the seventh cranial nerve (CN7) and one of the more complex ones.
Its formed by two roots that emerge from the brainstem at a spot called the pontomedullary junction.
CN7 and its branches control most of the facial muscles and glands that produce saliva and tears.
This nerve also plays a role in taste.
Behind the ear, the facial nerve enters a bony structure called the facial canal.
There, its roots are fused together and form a key in of nerve relay station called thegeniculate ganglion.
However, the greater petrosal nerve doesnt synapse inside the geniculate ganglion; it merely passes through.
Inside the ganglion, the nerves may communicate with each other or combine fibers to form new branches.
The human brain contains 12 nerve ganglia on either side.
Location
After leaving the geniculate ganglion, the greater petrosal nerve continues forward toward the cheek.
It then exits the skull through the foramen lacerum.
From there, the greater petrosal nerve runs alongside the petrosal branch of themiddle meningeal artery.
After the Vidian nerve leaves the pterygoid canal, it arrives at the pterygopalatine ganglion.
The greater petrosal nerve has some known variations:
Function
What does the greater petrosal nerve do?
Some nerves also carry specialized nerve fibers called sympathetic and parasympathetic nerve fibers.
to do this, they join fibers from themaxillary divisionof thetrigeminal nerve(CN5).
They travel together from the ganglion to the mouth.
There, the greater palatine nerve innervates the mucous membrane of the rear portion of the hard palate.
The lesser palatine nerves innervate the soft palate.
They both contribute to your sense of taste.
Nasopalatine and Posterior Nasal Branches
The nasopalatine nerve and posterior nasal branches travel to the nasal cavity.
The posterior nasal branches innervate the mucous membranes in the nasal passages.
It provides sensory function to the mucosal glands of the upper nasal pharynx.
The fibers then travel with the zygomatic nerve when it branches off from the maxillary.
So what happens if the greater petrosal nerve is damaged?
In some cases, the lesser petrosal nerve sometimes takes over the innervation of the lacrimal glands.
This rare complication of Bells palsy is called crocodile tears syndrome because it involves false tears.
In many cases, it doesnt need to be treated since it doesnt cause much distress.
More commonly, the eye affected by Bells palsy is chronically dry.
Bells palsy is sometimes treated with corticosteroids, antiviral medications, electrical nerve stimulation, and facial exercises.
Successful treatment of the condition may relieve crocodile tears syndrome as well.
Cluster Headaches
Parasympathetic dysfunction involving the greater petrosal nerve can causecluster headaches.
Treatment of cluster headaches can include triptan drugs or injections of octreotide, dihydroergotamine, or local anesthetics.
The nerve plays a big role in keeping your eyes moist and your nose working properly.
Nturibi E, Fakoya AO, Bordoni B.Anatomy, Head and Neck: Greater Petrosal Nerve.
[Updated 2024 May 25].
In: StatPearls [Internet].
Treasure Island (FL): StatPearls Publishing; 2024 Jan-.
2016;27(7):e661-e662.
2013;4(Suppl 6):S422-S428.
Published 2013 Nov 20. doi:10.4103/2152-7806.121628
