The geniculate ganglion: taste, tears and facial expression (2023)

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.

Anatomy

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.

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.

anatomical variations

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.

Function

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.

Associated conditions

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.