Physicians refer to accumulations of nerve cell bodies in the area of ​​the peripheral nervous system as ganglions . The ganglia appear as nerve knots, which appear as knot-like thickenings during dissection. The basal ganglia are distinct 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, clusters of nerve cell bodies in the central nervous system are called nuclei. A nerve cell body accumulation of the peripheral nervous system is the otic ganglion, the so-called ear knot. This is a parasympathetically controlled ganglion located on the mandibular nerve within the base of the skull. The ganglion lies below the foramen ovale and is therefore located in the infratemporal fossa. Motor, sympathetic, and parasympathetic fibers pass through the otic ganglion. However, only parasympathetic fibers that are relevant for the parotid gland are connected in the ganglion area.

Anatomy & Structure

The otic ganglion is anatomically and topographically related to the auditory tube (pars cartilaginea), the tensor veli palatini muscle, the median meningeal artery and the mandibular nerve . Motor, sympathetic and parasympathetic fibers pass through the ganglia. For the motor and sympathetic nerve fibers, however, the ganglion is only a transit station.

The parasympathetic fibers of the ganglion arise from the glossopharyngeal nerve and have their nerve cell bodies in the inferior salivator nucleus, from where they reach the tympanic plexus together with the tympanic nerve and advance into the otic ganglion together with the minor petrosal nerve. The motor fibers of the nervus mandibularis or nervus pterygoidus medialis pass unconnected through the otic ganglion. The sympathetic fibers of the ganglion are postganglionic and enter the structure from the superior cervical ganglion, which they exit via the carotid plexus.

Function & Tasks

The otic ganglion carries parasympathetic nerves that are relevant to the function of the ears . These fibers are interconnected within the ganglion. In this context, the otic ganglion fulfills a mediating function and is therefore also referred to as the ear nerve node. The parasympathetic fibers are routed to the postganglionic neuron within the structure .

From there they use the auriculotemporal nerve as a pathway to advance to the parotid gland (glandula parotis) and the buccal salivary glands (glandulae buccales). The salivary glands are secretorily innervated by the parasympathetic nerve fibers of the otic ganglion. Due to the interconnection, the otic ganglion is involved in the secretory activity of the parotid and buccal salivary glands. The parotid gland continuously produces saliva, which is secreted through the duct system to solitary glands in the lining of the pharynx , oral cavity , and lips. Saliva cleans the pharynx and fulfills 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 . In particular, complex sugar molecules such as starch are dependent on being digested with saliva. Simple proteins are in turn cleaved by the proteases in the parotid saliva. The saliva also liquefies the solid food to make swallowing easier. The interconnection of parasympathetic fibers in the otic ganglion enables all these processes. In addition, the ganglion assumes distribution functions for its motor and sympathetic fibers.

Various motor and sensory parts 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 nervus tensoris tympani. 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 and parasympathetic nerve functions. Such a scenario can be caused, for example , by tumors that displace individual nerve structures near the otic ganglion and thus cause nerve compression. Disorders of saliva production in particular can indicate nerve damage in the area of ​​the otic ganglion.In addition to such damage, reduced or absent saliva production can also be related to a severe lack of fluids, the effects of medication, diseases such as Sjögren’s syndrome , radiation in the head area or age-physiological changes. Normally, damage to the otic ganglion does not manifest itself as an isolated disturbance in the production of saliva, but also leads to motor disturbances in the muscles of the palate and the middle ear . Restrictions of sensitivity can occur concomitantly.

Skull base fractures often lead to lesions in the area of ​​the otic ganglion. A fracture of the base of the skull usually occurs after extremely strong trauma in the head area. Most often, traumas are observed in the context of traffic accidents. The fracture is a potentially life-threatening injury that injures the bony structures of the middle, anterior, or posterior fossa. In this context, the fracture forms can correspond to a rhinobasal, frontobasal, laterobasal or otobasal fracture. In the case of the latter type of fracture in particular, the structure of the ears is injured in addition to the base of the skull. Typically, blood and brain fluid leak from the ears.

In addition to the neurological symptoms, disturbances of perception and consciousness usually occur. Shock symptoms can also often be observed in fractures of the base of the skull. Skull base fracture usually requires emergency surgery and subsequent monitoring in the intensive care unit.