Otic ganglion

The otic ganglion is a small (2–3 mm), oval shaped, flattened parasympathetic ganglion of a reddish-grey color, located immediately below the foramen ovale in the infratemporal fossa and on the medial surface of the mandibular nerve.

It is in relation, laterally, with the trunk of the mandibular nerve at the point where the motor and sensory roots join; medially, with the cartilaginous part of the auditory tube, and the origin of the tensor veli palatini; posteriorly, with the middle meningeal artery. It surrounds the origin of the nerve to the medial pterygoid.

The preganglionic parasympathetic fibres originate in the inferior salivatory nucleus of the glossopharyngeal nerve. They leave the glossopharyngeal nerve by its tympanic branch and then pass via the tympanic plexus and the lesser petrosal nerve to the otic ganglion. Here, the fibers synapse and the postganglionic fibers pass by communicating branches to the auriculotemporal nerve, which conveys them to the parotid gland. They produce vasodilator and secretomotor effects.

Its sympathetic root is derived from the plexus on the middle meningeal artery. It contains post-ganglionic fibers arising in the superior cervical ganglion. The fibers pass through the ganglion without relay and reach the parotid gland via the auriculotemporal nerve. They are vasomotor in function.

The sensory root comes from the auriculotemporal nerve and is sensory to the parotid gland.

The motor fibers supplying the medial pterygoid and the tensor veli palatini and the tensor tympani pass through the ganglion without relay.

The ganglion is connected to the chorda tympani nerve and also to the nerve of the pterygoid canal. These pathways provide an alternate pathway of taste from the anterior two-thirds of the tongue. These fibers do not pass through the middle ear.

Frey's syndrome is caused by re-routing of parasympathetic and sympathetic fibres of the auriculotemporal nerve (V3) within the otic ganglion. It is a complication of surgery involving the parotid gland whereby injury to these branches, which innervate the parotid gland and sweat glands of the face respectively, form abnormal connections. Salivation leads to perspiration and flushing of the pre-auricular region and is called 'gustatory sweating'.

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  Plan of the facial and intermediate nerves and their communication with other nerves.
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  Diagram of efferent sympathetic nervous system.

This article incorporates text in the public domain from page 897 of the 20th edition of Gray's Anatomy (1918)

• Shimizu T (1994). "Distribution and pathway of the cerebrovascular nerve fibers from the otic ganglion in the rat: anterograde tracing study". J. Auton. Nerv. Syst. 49 (1): 47–54. doi:10.1016/0165-1838(94)90019-1. PMID 7525688.

• cranialnerves at The Anatomy Lesson by Wesley Norman (Georgetown University) (V, IX)