Otalgia

Excerpt

Otalgia or ear pain is divided into 2 broad categories based on etiology: primary and secondary otalgia. Primary otalgia is ear pain arising directly from inner, middle, or external ear pathology. Secondary or referred otalgia is ear pain from extraotic conditions. The ear receives sensory innervation from an intricate neural network due to the organ's complex embryologic development. The ear shares this neural network with other regional and distant organs, leading to numerous potential causes of referred ear pain (see Image. Ear Anatomy).

The trigeminal (cranial nerve V or CN V), facial (CN VII), glossopharyngeal (CN IX), and vagus (CN X) nerves and cervical plexus branches C2 and C3 all innervate the ear (see Images. Cranial Nerves & Cervical Plexus).

1. The auricle is innervated by cranial nerves V, VII, and X, and C2 and C3.

2. The ear canal is innervated by cranial nerves V, VII, and X.

3. The tympanic membrane is innervated by cranial nerves VII, IX, and X.

4. The middle ear is innervated by cranial nerves V, VII, and IX.

Cranial nerves V, VII, IX, X, and C2 and C3 also supply organs outside the ear, resulting in multiple sources of referred ear pain.

1. CN V is composed of the ophthalmic (V1), maxillary (V2), and mandibular (V3) divisions. The trigeminal nerve provides sensory innervation to the face, sinuses, palate, and teeth and controls the tensor tympani, tensor veil palatini, and mastication muscles. CN V's auriculotemporal branch innervates the temporomandibular joint (TMJ). This branch is most commonly implicated in TMJ dysfunction. Dental and TMJ pathology commonly cause secondary otalgia.

2. CN VII provides taste sensation to the tongue's anterior two-thirds via the chorda tympani nerve and innervates the sublingual and submandibular salivary glands. The facial nerve also controls the stapedius, digastric posterior belly, stylohyoid, and facial expression muscles. The nervus intermedius is CN VII's sensory portion, innervating a part of the external auditory canal's skin and the nasal and nasopharyngeal mucosa. These fibers also carry taste sensations from the chorda tympani. Inflammatory nervus intermedius pain is known as geniculate neuralgia due to the nerve's synapse at the geniculate ganglion.

3. CN IX provides taste and somatic sensation to the tongue's posterior third and afferents to the carotid body and oropharynx. The glossopharyngeal nerve also controls the stylopharyngeus muscle.

4. CN X innervates the sinuses, thyroid gland, pharynx, and larynx. The vagus nerve's superior laryngeal branch innervates the vocal cords. The vagus nerve also innervates distant organs such as the heart, lungs, and parts of the gastrointestinal tract.

5. C2 and C3 are cervical plexus branches innervating the auricular lobule, cervical paraspinal muscles, and posterior head.

Understanding the innervation patterns of these nerves helps in the differential diagnosis of otalgia and determining whether the pain originates from the ear itself or is referred from nearby structures. Accurate diagnosis based on the underlying etiology is essential for appropriate management and ear pain resolution.