The geniculate ganglion is a collection of sensory neurons in theNervo facial, what is heseventh cranial nerve(CN VII). The ganglion is located in a bony structure called the facial canal. It receives fibers from various components of the facial nerve and then sends fibers to various muscles, glands, tongue and other structures. It is involved in taste, the secretion of tears and saliva, facial expression, and a number of other functions.
A nerve ganglion is a group of nerves surrounded by a connective tissue capsule. Normally, all the nerves in a ganglion will have similar or related functions. It may be helpful to think of a ganglion as a relay station or intermediary connection between different structures in the nervous system. The plural of "ganglion" is "ganglion".
You have 12 cranial nerve ganglia on each side of your brain. Like nerves, they are usually referred to in the singular, although they exist in generally symmetrical pairs.
cranial nervesthey originate at the back of the head and progress towards the face, supplying nerve function as they go. Some deal with motor function (movement), some deal with sensory information (touch, taste, smell, sight, hearing, temperature) and some deal with both. These are called mixed nerves.
Four of your cranial nerve ganglia are parasympathetic and eight are sensory. The geniculate ganglion is one of the sensory ganglia, which means it helps collect information from your senses and relay it to and from your brain. It is also connected to the secretomotor fibers, which help the glands to secrete their fluids.
You may have heard of "ganglion cysts”, not to be confused with neural ganglia. Ganglion cysts are fluid-filled lumps that can develop in tendons or joints, most commonly in the hands and feet.
structure and location
The geniculate ganglion is part of the facial nerve, which is one of the longest cranial nerves and has a complex anatomy. It has two roots that arise from the brainstem (the structure that connects the brain and spinal cord) at the back of the head. One root is motor and the other is sensory. Inside the skull, the two roots move forward and pass close to the inner ear. There, they enter a Z-shaped structure called the facial canal.
In the facial canal, the two roots merge. At the first curve of the Z, they form the geniculate ganglion.
The ganglion then sends nerve fibers to various nerve branches, including:
- Tympanic (ear) segment of the facial nerve
- Greater superficial petrosal nerve
- lesser petrosal nerve
- external petrosal nerve
Fibers from the geniculate ganglion also innervate (provide nerve function for):
- glands: Lacrimal (tear), submandibular and sublingual (salivary)
- Muscles:Posterior belly of the diagastric (deals with the anchoring structure of the tongue), stylohyoid (elevates the tongue), numerous muscles related to facial expression
- Other structures: Language, palate (roof of the mouth), pharynx (throat area immediately behind the nose and mouth), external acoustic meatus (ear canal)
The knot itself is shaped like a pyramid and is between 1 and 2 millimeters long.
Anatomy discussions often focus on what is typical, but not everyone's anatomy is exactly the same. There are variations in nerve structures and pathways, and it is important for clinicians to be aware of these when it comes to diagnosis and treatment, especially when that treatment is surgical.
Studies have revealed some abnormalities that affect the geniculate ganglion:
- In 10-20% of people, the bone that forms the facial canal is not completely closed, leaving the ganglion and some of its surrounding nerve structures exposed during surgery on the area around the ganglion and therefore vulnerable to injury.
- The angle of the facial canal containing the geniculate ganglion varies significantly from person to person, between 19 and 107 degrees.
- The distance from the geniculate ganglion to an opening in the canal calledfallopian hiatuscan vary up to 7.75 millimeters.
The size and shape of the node itself is pretty consistent.
All of this information can help a surgeon determine the best approach to take during a procedure to minimize the risk of accidentally damaging the lump, as well as the nerves and other structures around it.
The word "geniculate" comes from the Latin word for knee, which is genu. In modern usage it means "having knee-like folds or joints". It is used for the geniculate ganglion because it resides within the bony canal which is loosely Z-shaped, so it has a curve similar to that of a knee.
The geniculate ganglion contains special sensory cells for the sense of taste that receive information from:
- The anterior two-thirds of the tongue through thechorda tympani nerve
- Two areas of the palate via the greater petrosal nerve.
In addition, it receives sensory information from the sensory branch of the facial nerve, sometimes called the intermediate nerve or intermediate nerve. This information comes from:
- The skin in a small area behind the ear.
- The outer surface of the tympanic membrane (eardrum)
Once these sensory signals enter the ganglion, it transmits them to the appropriate structures in the brainstem for processing.
The geniculate ganglion can be damaged by trauma or disease. Several medical conditions are associated with it, determined by the exact location and nature of the damage.
|geniculate ganglion damage|
|Results||Through Relationship with|
|excessive tears||tear glands|
|Impaired tear flow.||tear glands|
|Impaired saliva flow.||submandibular gland|
|Impaired saliva flow.||sublingual gland|
|impaired taste||Tongue, through the chorda tympani|
|facial paralysis||facial muscles|
Problems with the geniculate ganglion are associated with several forms of facial paralysis:
- Ramsay Hunt syndrome
- bell's palsy
- Schwannoma of the geniculate ganglion
Ramsay Hunt syndrome
Herpes zoster oticus, which is the virus that causeschickenpox, can arise later in life as a very painful condition calledherpes. When shingles strikes close to the geniculate ganglion, it causes Ramsay Hunt syndrome. This usually occurs on only one side of the face at a time.
primary symptomsRamsay Hunt syndrome, which occurs only on the affected side, can include any combination of:
- hearing loss
- A painful rash characterized by blisters around the ear or mouth.
- Facial weakness or paralysis that can cause the eyelid and side of the mouth to droop
other symptomsmay include:
- Difficulty closing the eye on the affected side
- dry mouth and eyes
- Changes or loss of taste
- nystagmus(involuntary and nervous eye movements)
- Buzz(ringing in ears)
- Vertigo(spinning sensation)
- nausea and vomit
Early treatment is crucial to avoiding long-term complications, so be sure to get medical help right away if you experience these symptoms.
- permanent hearing loss
- Permanent facial weakness and drooping
- Damage to the eye causing pain and blurred vision
- Postherpetic neuralgia (persistent nerve pain)
Treatmentit often involves antiviral drugs and corticosteroids.Depending on your specific symptoms, your doctor may also prescribe standard pain medications (analgesics), antiseizure medications to help with nerve pain, and medications for vertigo. When the eye is involved, artificial tears and/or other lubricating products may be used to prevent damage to the cornea.
chickenpox vaccinesyherpesthey are the best defense against Ramsay Hunt syndrome.
In Depth: Ramsay Hunt Syndrome
Bell's palsy and Ramsay Hunt syndrome are often indistinguishable based on symptoms alone; the suspected causes and treatments, however, are different.
Bell's palsy is due to an inflammation of unknown origin that affects the geniculate ganglion. This can compress the facial nerve within the fallopian tube.
Symptomsof Bell's palsy can vary. They only occur on one side of the face and can include:
- Weakness, mild to complete paralysis
- Drooping eyelid and corner of the mouth
- Dry eye or excessive tearing
- Dry mouth
- Impaired sense of taste
- Pain around the jaw and behind the ear.
- hypersensitivity to sound
- speech impairment
Bell's palsy usually takes 3 to 6 months to resolve with or without treatment.When treatment is needed, usually involvescorticosteroidsto reduce inflammation,antiviralsin case of herpes infection and common painkillers. The eye should be kept lubricated with drops or other lubricating products, and an eye patch is often recommended. Plastic surgery can be performed to correct facial deformities, such as a crooked smile or an eyelid that doesn't close properly.
In Depth: Bell's Palsy
Schwannoma of the geniculate ganglion
This nodule can develop into a rare tumor called a geniculate ganglion schwannoma. Schwannomas are tumors that affect Schwann cells, which help conduct impulses in the cranial nerves and peripheral nervous system.
- facial paralysis
- Impaired tear flow.
- hearing loss
Some cases of geniculate ganglion schwannoma do not requiretreatment. In those who do, microsurgery may be performed to repair the facial nerve. A procedure called stereotactic radiosurgery, a type of radiation therapy used on small brain tumors, may also be recommended.
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Aristegui M, Martin-Oviedo C, Aristegui I, Garcia-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
Farbman AI, Guagliardo N, Sollars SI, Hill DL.Each sensory nerve arising from the geniculate ganglion expresses a unique fingerprint of neurotrophin and neurotrophin receptor genes..J Neurosci Res. 2004;78(5):659–667. doi:10.1002/jnr.20297
Kanerva M, Jones S, Pittsburgh A.Ramsay Hunt syndrome: features and long-term outcomes of patient self-reported facial palsy.Eur Arch Otorrinolaringol. 2020;277(4):1235–1245. doi:10.1007/s00405-020-05817-y
National Organization for Rare Disorders, Inc. (NORD).Ramsay Hunt syndrome.
National Institutes of Health: National Institute of Neurological Disorders and Stroke.Bell's palsy fact sheet.
American Journal of Neuroradiology.Schwannoma of the geniculate ganglion.
Adrienne Dellwo is an experienced journalist who has been diagnosed with fibromyalgia and has written extensively on the subject.
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