The greater petrosal nerve branches off of the facial nerve in the skull. Along with a chain of other nerves, it innervates (provides nerve function to) thelacrimalgland, which produces tears.
Also referred to as the greater superficial petrosal nerve, it’s related to structures called thepterygopalatine ganglion, thegeniculate ganglion, and theforamen lacerum. The primary functions of this nerve are taste andsecretomotor(dealing with secretions from glands).
Enid Hajderi / Stocktrek Images / Getty Images
Anatomy
The nerves of the head and face—the cranial nerves—are unique in that they originate in the brain, while the rest of the body’s nerves come from the spinal cord.
Each person has12 cranial nerves, which exist as symmetrical pairs. (However, they’re typically referred to as a single nerve.) They arise from the back of the brain and wrap forward throughout your skull, exiting the skull through small holes called foramina so they can reach the muscles, skin, and other structures of the face.
Behind the ear, the facial nerve enters a bony structure called the facial canal. There, its roots are fused together and form a type of nerve relay station called thegeniculate ganglion. The ganglion then distributes nerve fibers to several branches of the facial nerve that provide nerve function to glands, muscles, and structures of the mouth and ear.
These branches include:
A lot of nerve signaling, called synapsing, happens inside ganglia (the plural of ganglion). However, the greater petrosal nerve doesn’t synapse inside the geniculate ganglion; it merely passes through.
Nerve GanglionA nerve ganglion is a capsule of connective tissue surrounding a group of nerves with similar or related functions. 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.
Nerve Ganglion
A nerve ganglion is a capsule of connective tissue surrounding a group of nerves with similar or related functions. 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 passes through an opening running through the hiatus of the facial canal, then along a narrow passage called the middle cranial fossa. It then exits the skull through the foramen lacerum.
From there, the greater petrosal nerve runs alongside the petrosal branch of themiddle meningeal artery. The nerve then enters the pterygoid canal and joins the deep petrosal nerve, which is a sympathetic nerve (it deals with heart rate, blood pressure, and blood vessel constriction). This is technically where the greater petrosal nerve ends, but its fibers continue on through various nerves and branches.
The combination of the greater petrosal and deep petrosal nerves is called the nerve of the pterygoid canal or the Vidian nerve. After the Vidian nerve leaves the pterygoid canal, it arrives at the pterygopalatine ganglion. This is where the greater petrosal nerve synapses with other nerves as they relay information back and forth from the brain to other body structures.
Structure
The parasympathetic fibers of the greater petrosal nerve leave the ganglion through several important branches:
Anatomical Variation
With nerves, it’s imperative for surgeons to know about possible variations so they can avoid accidental injuries during procedures.
The greater petrosal nerve has some known variations:
Function
What does the greater petrosal nerve do? Most nerves are either sensory (providing information through your five senses), motor (providing movement), or mixed, meaning they serve both functions. Some nerves also carry specialized nerve fibers called sympathetic and parasympathetic nerve fibers.
The greater petrosal nerve is a mixed nerve that carries sensory fibers and parasympathetic fibers, which are part of the parasympathetic nervous system.
The parasympathetic nervous system regulates activities that occur when your body is at rest, such as digestion, salivation, and tear production (which keeps your eyes moist at all times, not just when you cry).
The primary function of the greater petrosal nerve is to supply parasympathetic fibers to the nerves that travel from the pterygopalatine ganglion to structures of the mouth, throat, nasal passages, and eyes.
The fibers from the greater petrosal nerve contribute to the function of numerous glands and tissues through the five branches that carry them. In order to do this, they join fibers from themaxillary divisionof thetrigeminal nerve(CN5).
Greater and Lesser Palatine Nerves
The greater palatine nerve and two or three lesser palatine nerves carry specialized sensory fibers from the greater petrosal nerve.
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.
The greater palatine nerve also provides sensory fibers to the gums and a portion of your sinuses, and the lesser palatine nerves supply motor function to muscles of the uvula and tonsils.
Nasopalatine and Posterior Nasal Branches
The nasopalatine nerve and posterior nasal branches travel to the nasal cavity. The nasopalatine nerve supplies the nasal septum and the forward region of the hard palate and communicates with the greater palatine nerve.
The posterior nasal branches innervate the mucous membranes in the nasal passages.
Pharyngeal Branch
The pharyngeal branch travels to the rear of the upper portion of thepharynx, which is the part of the throat behind the mouth and nose. It provides sensory function to the mucosal glands of the upper nasal pharynx.
Maxillary and Zygomatic Nerves
When the maxillary nerve leaves the ganglion, it carries secretomotor fibers from the greater petrosal nerve. The fibers then travel with the zygomatic nerve when it branches off from the maxillary.
Along with sensory nerves that provide feeling to some of the skin around the eye socket and cheek, the zygomatic nerve sends a communicating branch to the lacrimal nerve. Together, the zygomatic and lacrimal nerves provide secretomotor function to the lacrimal gland, meaning that they cause the gland to release tears.
Taste ReceptorsIn animal studies, the greater petrosal nerve has been found to influence the taste receptors for salt, bitterness, and sugar.
Taste Receptors
In animal studies, the greater petrosal nerve has been found to influence the taste receptors for salt, bitterness, and sugar.
Associated Conditions
Xerotic Keratitis
One rare but possible consequence of greater petrosal nerve damage is reduced tear secretion, calledxerotic keratitis, which can lead to extreme dryness of the eyes, ulceration of the cornea, and blindness.This condition is generally treated with eye drops or ointments to replace the moisture.
Crocodile Tears Syndrome
Lesions on the facial nerve (Bell’s palsy) can cause degeneration of the greater petrosal nerve. In some cases, the lesser petrosal nerve sometimes takes over the innervation of the lacrimal glands. Because the lesser petrosal nerve also innervates the salivary gland, when it takes on this extra function, salivation causes simultaneous eye watering.
Bell’s 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. One type of cluster headache related to this nerve can cause excessive eye watering, nasal congestion, and runny nose.
Treatment of cluster headaches can include triptan drugs or injections of octreotide, dihydroergotamine, or local anesthetics.
Summary
The greater petrosal nerve is a part of the facial nerve that helps control some important functions in the body, like tear production and saliva flow. It starts in the brainstem and travels through the skull to connect with glands that produce tears and mucus in the nose.
The nerve plays a big role in keeping your eyes moist and your nose working properly. If something goes wrong with the greater petrosal nerve, it can lead to problems like dry eyes, a dry mouth, or cluster headaches.
7 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.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-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553121/Arístegui M, Martín-Oviedo C, Aristegui I, García-Leal R, Ruiz-Juretschke F.Anatomical variations of the intrapetrous portion of the facial nerve.Anat Rec (Hoboken). 2019;302(4):588-598. doi:10.1002/ar.23923Paul Rea.Essential Clinically Applied Anatomy of the Peripheral Nervous System in the Head and Neck. 2016Sun C, Hummler E, Hill DL.Selective deletion of sodium salt taste during development leads to expanded terminal fields of gustatory nerves in the adult mouse nucleus of the solitary tract.J Neurosci. 2017;37(3):660-672. doi:10.1523/JNEUROSCI.2913-16.2016Prasad S, Lee TC, Chiocca EA, Klein JP.Superficial greater petrosal neuropathy.Neurol Clin Pract. 2014;4(6):505-507. doi:10.1212/CPJ.0000000000000066de Oliveira D, Gomes-Ferreira PH, Carrasco LC, de Deus CB, Garcia-Júnior IR, Faverani LP.The importance of correct diagnosis of crocodile tears syndrome.J Craniofac Surg. 2016;27(7):e661-e662. doi:10.1097/SCS.0000000000003006Khonsary SA, Ma Q, Villablanca P, Emerson J, Malkasian D.Clinical functional anatomy of the pterygopalatine ganglion, cephalgia and related dysautonomias: A review.Surg Neurol Int. 2013;4(Suppl 6):S422-S428. Published 2013 Nov 20. doi:10.4103/2152-7806.121628
7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.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-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553121/Arístegui M, Martín-Oviedo C, Aristegui I, García-Leal R, Ruiz-Juretschke F.Anatomical variations of the intrapetrous portion of the facial nerve.Anat Rec (Hoboken). 2019;302(4):588-598. doi:10.1002/ar.23923Paul Rea.Essential Clinically Applied Anatomy of the Peripheral Nervous System in the Head and Neck. 2016Sun C, Hummler E, Hill DL.Selective deletion of sodium salt taste during development leads to expanded terminal fields of gustatory nerves in the adult mouse nucleus of the solitary tract.J Neurosci. 2017;37(3):660-672. doi:10.1523/JNEUROSCI.2913-16.2016Prasad S, Lee TC, Chiocca EA, Klein JP.Superficial greater petrosal neuropathy.Neurol Clin Pract. 2014;4(6):505-507. doi:10.1212/CPJ.0000000000000066de Oliveira D, Gomes-Ferreira PH, Carrasco LC, de Deus CB, Garcia-Júnior IR, Faverani LP.The importance of correct diagnosis of crocodile tears syndrome.J Craniofac Surg. 2016;27(7):e661-e662. doi:10.1097/SCS.0000000000003006Khonsary SA, Ma Q, Villablanca P, Emerson J, Malkasian D.Clinical functional anatomy of the pterygopalatine ganglion, cephalgia and related dysautonomias: A review.Surg Neurol Int. 2013;4(Suppl 6):S422-S428. Published 2013 Nov 20. doi:10.4103/2152-7806.121628
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553121/Arístegui M, Martín-Oviedo C, Aristegui I, García-Leal R, Ruiz-Juretschke F.Anatomical variations of the intrapetrous portion of the facial nerve.Anat Rec (Hoboken). 2019;302(4):588-598. doi:10.1002/ar.23923Paul Rea.Essential Clinically Applied Anatomy of the Peripheral Nervous System in the Head and Neck. 2016Sun C, Hummler E, Hill DL.Selective deletion of sodium salt taste during development leads to expanded terminal fields of gustatory nerves in the adult mouse nucleus of the solitary tract.J Neurosci. 2017;37(3):660-672. doi:10.1523/JNEUROSCI.2913-16.2016Prasad S, Lee TC, Chiocca EA, Klein JP.Superficial greater petrosal neuropathy.Neurol Clin Pract. 2014;4(6):505-507. doi:10.1212/CPJ.0000000000000066de Oliveira D, Gomes-Ferreira PH, Carrasco LC, de Deus CB, Garcia-Júnior IR, Faverani LP.The importance of correct diagnosis of crocodile tears syndrome.J Craniofac Surg. 2016;27(7):e661-e662. doi:10.1097/SCS.0000000000003006Khonsary SA, Ma Q, Villablanca P, Emerson J, Malkasian D.Clinical functional anatomy of the pterygopalatine ganglion, cephalgia and related dysautonomias: A review.Surg Neurol Int. 2013;4(Suppl 6):S422-S428. Published 2013 Nov 20. doi:10.4103/2152-7806.121628
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-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553121/
Arístegui M, Martín-Oviedo C, Aristegui I, García-Leal R, Ruiz-Juretschke F.Anatomical variations of the intrapetrous portion of the facial nerve.Anat Rec (Hoboken). 2019;302(4):588-598. doi:10.1002/ar.23923
Paul Rea.Essential Clinically Applied Anatomy of the Peripheral Nervous System in the Head and Neck. 2016
Sun C, Hummler E, Hill DL.Selective deletion of sodium salt taste during development leads to expanded terminal fields of gustatory nerves in the adult mouse nucleus of the solitary tract.J Neurosci. 2017;37(3):660-672. doi:10.1523/JNEUROSCI.2913-16.2016
Prasad S, Lee TC, Chiocca EA, Klein JP.Superficial greater petrosal neuropathy.Neurol Clin Pract. 2014;4(6):505-507. doi:10.1212/CPJ.0000000000000066
de Oliveira D, Gomes-Ferreira PH, Carrasco LC, de Deus CB, Garcia-Júnior IR, Faverani LP.The importance of correct diagnosis of crocodile tears syndrome.J Craniofac Surg. 2016;27(7):e661-e662. doi:10.1097/SCS.0000000000003006
Khonsary SA, Ma Q, Villablanca P, Emerson J, Malkasian D.Clinical functional anatomy of the pterygopalatine ganglion, cephalgia and related dysautonomias: A review.Surg Neurol Int. 2013;4(Suppl 6):S422-S428. Published 2013 Nov 20. doi:10.4103/2152-7806.121628
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