The otic ganglion is also known as the auricular nerve node and interconnects parasympathetic nerve fibers that subsequently innervate the parotid glands secretory. The nerve cluster is also a distribution station for motor and sympathetic nerve fibers of the head. In an otobasal skull base fracture, the otic ganglion can be damaged and cause secretory restrictions.
What is the otic ganglion?
A ganglion is the medical term for clusters of nerve cell bodies in the peripheral nervous system. The ganglia appear as nerve nodules, which appear as nodular thickenings when dissected. The basal ganglia must be distinguished from the ganglia of the peripheral nervous system because they are located beneath the cerebral cortex within the central nervous system. Unlike in the peripheral nervous system, nerve cell body accumulations in the central nervous system are called nuclei or nuclei. One nerve cell body cluster of the peripheral nervous system is the otic ganglion, or ear node. This is a parasympathetically controlled ganglion with localization at the mandibular nerve within the skull base. The ganglion lies below the foramen ovale and is thus located in the infratemporal fossa. Motor, sympathetic and parasympathetic fibers pass through the otic ganglion. However, only parasympathetic fibers relevant to the parotid gland are interconnected in the ganglion.
Anatomy and structure
The otic ganglion is anatomically topographically related to the auditory tuba (pars cartilaginea), the tensor veli palatini muscle, the media meningeal artery, and the mandibular nerve. Motor, sympathetic as well as parasympathetic fibers run through the ganglionic area. For the motor and sympathetic nerve fibers, however, the ganglion forms only a transit station. The parasympathetic fibers of the ganglion originate from the glossopharyngeal nerve and have their nerve cell bodies in the nucleus salivatorius inferior, from where they reach the tympanic plexus together with the tympanic nerve and, together with the petrosal minor nerve, advance into the otic ganglion. The motor fibers of the mandibular or medial pterygoid nerve pass through the otic ganglion unconnected. The sympathetic fibers of the ganglion are postganglionic and reach the structure from the cervical superior ganglion, which they exit via the carotid plexus.
Function and Tasks
The otic ganglion carries parasympathetic nerves relevant to ear function. These fibers are interconnected within the ganglion. In this context, the otic ganglion fulfills a mediating function and for this reason is also referred to as the auricular nerve node. The parasympathetic fibers are directed within the structure to the postganglionic neuron. From there, they use the auriculotemporal nerve as a conduction pathway to advance to the parotid gland (parotid glandula) as well as the buccal glands (buccal glandulae). The salivary glands are innervated secretorially by the parasympathetic nerve fibers of the otic ganglion. By circuitry, the otic ganglion is thus involved in the secretory activity of the parotid and buccal salivary glands. The parotid gland produces saliva continuously, which is delivered through the excretory duct system to solitary glands in the mucosa of the pharynx, oral cavity, and lips. Saliva cleanses the pharynx and performs protective and defensive functions within the oral cavity. In addition, the salivary secretion of the parotid gland carries salivary enzymes to initiate the digestive process. Complex sugar molecules in particular, such as starch, depend on digestion by saliva. Simple proteins, in turn, are broken down by the proteases of the parotid gland. To facilitate the act of swallowing, saliva also liquefies solid food. The interconnection of parasympathetic fibers in the otic ganglion makes all these processes possible. In addition, the ganglion performs distribution functions for its motor and sympathetic fibers. Various motor and sensory portions of the mandibular nerve use the otic ganglion as a distribution station without entering into a functional relationship with the structure. The motor fibers reach the tensor tympani muscle via the distribution station in the form of the tensor nerve. In the form of the ramus musculi tensoris veli palatini, they in turn run to the musculus tensor veli palatini.
Diseases
Damage to the otic ganglion affects motor, sympathetic, as well as parasympathetic nerve functions. Such a scenario may be caused, for example, by tumors that displace individual nerve structures near the otic ganglion, causing nerve compression. Above all, disorders of saliva production may refer to nerve damage in the area of the otic ganglion. However, reduced or absent saliva production can also be related to severe fluid deficiency, medication effects, diseases such as Sjögren’s syndrome, radiation in the head region or age-related physiological changes. Normally, damage to the otic ganglion does not manifest itself as isolated saliva production disorders, but also results in motor disorders of the palatal and middle ear muscles. Restrictions of sensibility may occur concomitantly. Skull base fractures often lead to lesions in the area of the otic ganglion. A skull base fracture usually presents after extremely severe force to the head. Most often, the trauma is observed in the context of traffic accidents. The fracture is a potentially life-threatening injury in which the bony structures of the middle, anterior or posterior cranial fossa are injured. In this context, the fracture forms may correspond to a rhinobasal, frontobasal, laterobasal or otobasal fracture. Especially in the latter type of fracture, the ear structure is injured in addition to the skull base. Typically, blood and cerebrospinal fluid leak from the ears. In addition to neurological deficits, disturbances of perception and consciousness usually occur. Shock symptomatology is also common in skull base fracture. Skull base fracture usually requires emergency surgery and subsequent monitoring in the intensive care unit.