Otalgia pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S [2]
Overview
Otalgia or ear pain is one of the most common complaints in the pediatric age group presenting to the primary care or emergency room. Otalgia can be primary or referred. Primary being caused by diseases of the ear per se and referred being caused by disease else where. The ear canal is heavily innervated, and the skin lining the canal lies directly against the bone without an intervening subcutaneous layer; therefore, even mild pressure, swelling, or inflammation in this area can cause immediate and severe pain.
Pathophysiology
The ear is supplied by a number of different sensory nerves, including cranial nerves V, VII, IX, and X, as well as the cervical plexus. Diseases affecting structures innervated by these nerves may result in referred (ie, secondary) Otalgia.
- The auriculotemporal branch of the mandibular division of cranial nerve V (ie, V3) innervates the skin of the tragus and part of the helix of the external ear, the anterior and superior walls of the external auditory canal, and the anterior portion of the tympanic membrane. Ear pain can also be referred via cranial nerve V from the teeth, gums, mouth, jaw, and face. Rarely, trigeminal neuralgia can cause otalgia.
- The facial nerve (VII) innervates the posterior tympanic membrane and part of the posterior wall of the external auditory canal. Disorders of teeth, Temporomandibular joint and Parotid glands can cause referred pain in ear.
- The glossopharyngeal nerve (IX) innervates the posterior portion of the external auditory canal and meatus, the posterior portion of the tympanic membrane, the mastoid, and the Eustachian tube. The tympanic branch of cranial nerve IX ascends into the middle ear and forms the tympanic plexus before proceeding as the lesser petrosal nerve to the otic ganglion. Ear pain can also be referred via cranial nerve IX from the posterior tongue, tonsils, and pharynx
- The auricular branch (Arnold's nerve) of the vagus nerve (X) innervates part of the cavum conchae (the vestibule to the external auditory canal), the posterior wall of the external auditory canal, and the posterior portion of the tympanic membrane. Ear pain can also be referred via cranial nerve X from the pharynx, Larynx, Trachea, diaphragm, Thyroid gland, and Esophagus, among other thoracic and abdominal structures.
- The upper cervical nerves (C2 and C3), particularly the posterior branch of the great auricular nerve, innervate the posterior surface of the external ear and some of the cavum conchae. Ear pain can also be referred via the cervical plexus from structures in neck and cervical spine.
- Somatic afferent fibers from cranial nerves V, VII, IX, and X as well as the cervical plexus (C2 and C3) all synapse in the spinal trigeminal nucleus in the caudal medulla and the upper Cervical spinal cord.
Hence any disease of the ear or in the areas innervated by the nerves which also supply ear can cause ear pain. Psychogenic otalgia is when no cause to the pain in ears can be found, suggesting a functional origin. The patient in such cases should be kept under observation with periodic re-evaluation.