The superior ganglion is a collection of nerve cell bodies in the cranial cavity and is a switching point for fibers from the 9th and 10th cranial nerves. It lies above the inferior ganglion and processes temperature, touch, and pain signals from innervated regions. Ganglion blockers can inhibit the ganglion’s ability to function.
What is the superior ganglion?
The superior ganglion is a dense cluster of nerve cell bodies (somata) in the skull capsule or zygomatic vein hole (foramen jugulare). The 9th, 10th, and 11th cranial nerves pass through this bottleneck, as do three important blood vessels: inferior petrosal sinus, posterior meningeal artery, and internal jugular vein. Despite its spatial proximity to the brain, the superior ganglion does not belong to the central nervous system, but to the peripheral one. After its discoverer Johann Ehrenritter, the superciliary ganglion is more rarely referred to as the Ehrenritter ganglion; this term is found mainly in the English-language literature. Strictly speaking, the superciliary ganglion is not a single ganglion but two functionally distinct nerve nodes; they are associated with different cranial nerves and are named after them ganglion superius nervi glossopharyngeus (“superior ganglion of the glossopharyngeal nerve”) and ganglion superius nervi vagi (“superior ganglion of the vagus nerve“).
Anatomy and structure
The superior ganglion represents a cluster of nerve cell bodies (somata) that are not surrounded by a solid nucleus. Nevertheless, the ganglion forms a simple processing center for nerve signals that enter the superior ganglion in the form of electrical impulses (action potentials) via one of the cranial nerves. The superius nervi glossopharyngei ganglion is associated with the 9th cranial nerve. From it, nerve fibers lead to the inferior nervi glossopharyngei ganglion, also called the petrosal ganglion. The inferior ganglion is generally larger than the superior ganglion and again switches neurons. Subsequently, the glossopharyngeal nerve leads inside the head to the lower facial region and innervates the nasopharynx and the posterior third of the tongue. The actual cell bodies are located in the superciliary ganglion, while the connection to the supplied area is made by the axons of the cells. The superius nervi vagi ganglion is the superior nerve node of the 10th cranial nerve and is also known as the jugular ganglion. The vagus nerve also runs through a second – usually larger – ganglion inferius nervi vagi; other branches of the neuronal pathway extend beyond the head and lead to deeper parts of the body. The neuronal bodies responsible for these, however, are not located in the superior ganglion.
Function and tasks
The function of the superior nervous ganglion is to switch nerves. The glossopharyngeal superciliary ganglion receives viscerosensitive signals from the nasopharynx and the posterior part of the tongue. Its cells are sensitive to temperature, pain, and touch. This type of information is used, among other things, for coordination during swallowing and for a number of protective stimuli. Temperature perception in the nose, mouth and throat protects people from eating food that is too hot or too cold. Sensitive mucous membranes are very susceptible to damage from temperature and other influences. The perception of pain can result from the activation of special pain receptors or nociceptors. The majority of these are free nerve endings located in the tissue. The cells of the superius nervi vagi ganglion also receive information about temperature, pain and touch. They innervate the larynx, the auditory canal and the outermost meninges (dura mater). Sensory nerve signals travel from the dura mater not only via the vagi nerve, but also via the ophthalmic nerve, the anterior ethmoidal nerve, the maxillary nerve and the mandibular nerve. In each case, specific branches of the corresponding nerves are responsible for supplying the dura mater. Both the glossopharyngeal nerve and the vagus nerve run extensively through the human body and cover a much larger area than described here; however, the nerve cell bodies responsible for the respective areas are located in other ganglia rather than in the superior ganglion.
Diseases
Its location in the skull capsule or zygomatic vein hole protects the superciliary ganglion to the greatest extent possible against injury from external agents.However, like all ganglia, it is susceptible to the effects of nonspecific ganglion blockers. Today, medicine rarely uses ganglion blockers or ganglioplegics; in the past, many sleeping pills and sedatives belonged to this group of drugs. Because of their nonspecific effects, they are highly susceptible to side effects. As with all forms of treatment, physicians must therefore consider the individual risk-benefit ratio. Hydroxyzine is intended as an agent against severe allergic reactions. Indications include severe hives (urticaria), neurodermatitis, hyperarousal, anxiety, sleep disturbances, and tension states. In studies, hydroxyzine has also been shown to relieve psychosis, thought disorder, and obsessive-compulsive disorder, but the substance is not regularly approved for this use. Another ganglion blocker is phenobarbital, which is considered for the drug treatment of epilepsy. This ganglion blocker was originally popular as a sleep aid. However, the inhibitory effect can also cause fatigue, headache, drowsiness, dizziness, ataxia, coordination difficulties, and psychological side effects, which is why, for example, patients’ ability to drive is limited under phenobarbital. Tetraethylammonium ion also acts as a ganglion blocker, but has greater importance in laboratory research, where it is used in experimental studies to prevent the normal function of potassium channels in cells. In medical practice, this process is maximally relevant in the context of disease as poisoning.