Special Report A Pain in the Ear: The Radiology of Otalgia Jane L. Weissman, Departments of Radiology and Otolaryngology, University of Pittsburgh (Pa) Medical Center Otalgia is ear pain. Ear disease causes pri- glands, and thyroid gland (2, 4, 5) (Fig 1C). mary otalgia. Secondary (referred) otalgia is Synalgia and telalgia are rarely used synonyms referred to the ear from disease in structures for referred pain (6). remote from the ear. Otalgia, especially referred otalgia, can be a diagnostic challenge. The radiologic approach to a patient with Pathways Mediating Primary Otalgia otalgia relies on the physical examination. If the The skin of the ear is an interface between otoscopic findings are abnormal, the computed branchial and postbranchial innervation. There- tomographic (CT) or magnetic resonance (MR) fore, sensory innervation of the external ear is study focuses on the temporal bone. (The ap- mediated by both cutaneous and cranial nerves propriate radiologic study depends on the dis- (5). However, innervation is variable, and the ease.) The physical examination for ear pain map of the sensory innervation of the ear re- includes the ear (auricle and temporal bone) mains imprecise (5). and structures that are potential sources of re- Trigeminal Nerve.—The mandibular division ferred pain. Imaging studies can show clinically of the trigeminal nerve (V3) gives off the auri- occult temporal bone disease as well as sources culotemporal nerve (1, 2, 7), which runs with of referred pain in the nasopharynx, retrophar- the superficial temporal artery and vein (7). The ynx, paranasal sinuses and nasal cavity, tem- auriculotemporal nerve receives sensory input poromandibular joint (TMJ), parotid gland, oro- from the anterior portions of the outer ear: the pharynx and oral cavity (including teeth), anterior auricle (pinna), the tragus, the anterior hypopharynx and larynx, thyroid gland, esoph- and superior walls of the external auditory canal agus, and trachea. Tailoring a CT or MR study to (EAC), and the lateral (EAC) surface of the evaluate primary or referred otalgia requires an tympanic membrane (TM) (1, 2, 4, 5, 7). understanding of the (admittedly complex) Facial Nerve.—The facial nerve is primarily a anatomy of ear pain. motor nerve. Its small sensory branches include the nervus intermedius of Wrisberg, the poste- rior auricular nerve, and the greater superficial Sensory Innervation petrosal nerve (GSPN). The nervus intermedius Briefly, sensation from the ear and adjacent carries sensation from a small part of the medial structures travels along four cranial nerves (V, EAC (8); its branches include the posterior au- VII, IX, and X), the upper cervical plexus, and ricular and greater superficial petrosal nerves. (possibly) cervical sympathetic fibers (1–5). The posterior auricular branch carries sensation These nerves mediate primary otalgia (Fig 1A from the posterior wall of the EAC, the posterior and B). TM, and the skin behind the pinna (1, 2, 5, 7). Referred pain is the subjective experience of The GSPN mediates referred otalgia, and is dis- pain in a structure remote from the disease. Pain cussed below. is referred along routes of shared innervation. In Glossopharyngeal Nerve.—The tympanic other words, referred pain (secondary otalgia) is branch of the glossopharyngeal nerve (Jacob- referred to the ear from distant structures that son’s nerve) carries sensation from the medial receive sensory innervation from the same four (middle ear) surface of the TM (7), the middle cranial nerves as the ear itself: the upper and ear mucosa, and the upper eustachian tube (4). lower aerodigestive tracts, TMJs, teeth, salivary Jacobson’s nerve anastomoses in the tympanic Address reprint requests to Jane L. Weissman, MD, Department of Radiology, Room D-132 PUH, University of Pittsburgh Medical Center, 200 Lothrop St, Pittsburgh, PA 15213. Index terms: Ear, diseases; Special reports AJNR 18:1641–1651, Oct 1997 0195-6108/97/1808–1641 © American Society of Neuroradiology 1641 1642 WEISSMAN AJNR: 18, October 1997 Fig 1. Sensory innervation of the ear and surrounding structures: primary and secondary otalgia. A, Primary otalgia: sensory innervation by location. B, Primary otalgia: sensory innervation by nerve. C, Secondary (referred) otalgia: the structures that refer pain to the ear, and the pathways of referred pain. plexus of the middle ear. The tympanic plexus Cervical Nerves.—The cervical plexus re- also contains sympathetic and parasympathetic ceives cutaneous innervation from the neck (1). fibers (5, 9). C2 and C3 contribute to the greater auricular Vagus Nerve.—Sensory input from the poste- and lesser occipital nerves. The greater auricu- rior-inferior ear travels along the auricular lar nerve runs with the external jugular vein to branch of the vagus nerve (Arnold’s nerve). Ar- supply the skin over the parotid gland (4), the nold’s nerve arises from the superior (jugular) lower (1, 9) and superior-medial pinna (5), and ganglion of the vagus (5), and can receive fibers the mastoid (2, 5). The lesser occipital nerve from the facial and glossopharyngeal nerves as innervates the skin over the mastoid (7) and well as the vagus (1, 5). Arnold’s nerve receives behind the ear (1, 4). input from the auricle and from the inferior and Sympathetic Nerves.—The sympathetic posterior portions of the EAC and TM (5). plexus accompanies the internal carotid artery AJNR: 18, October 1997 PAIN IN THE EAR 1643 Fig 2. Malignant otitis externa. A, Axial CT scan (soft-tissue algorithm) shows infiltration of the fat around the right internal carotid artery and internal jugular vein and in the stylomandibular tunnel (wavy arrows). Compare to the normal left side. The pinna is edematous (straight arrows). This image was obtained at a level below the EAC. B, Axial CT image (bone algorithm) shows erosion of the mastoid cortex (arrows) along the posterior wall of the EAC. The mastoid air cells are opacified (curved arrow). C, Axial T1-weighted MR image (625/20/1 [repetition time/echo time/ excitations]) below the EAC shows infiltration of the fat beneath the skull base (open arrows), around the mandibular condyle (black arrow), and partially surrounding the internal carotid artery (curved arrow). This could be edema or granulation tissue. There is also a sympathetic mastoid effusion (straight white arrow). D, Axial contrast-enhanced T1-weighted MR image (625/20/1) with fat suppression at a slightly higher level than C shows hyperin- tense signal from the soft tissue (arrows). through the upper neck and skull base. Sympa- to the ear along the auriculotemporal branch of thetic fibers join Jacobson’s nerve in the tym- the trigeminal nerve. panic plexus of the middle ear (7). It is not clear Facial Nerve.—The GSPN arises from the whether and how these autonomic fibers trans- geniculate ganglion of the facial nerve. Sympa- mit pain (9). thetic fibers that accompany the internal carotid artery join the GSPN to form the vidian nerve (the nerve of the pterygoid canal). The vidian Pathways Mediating Referred Otalgia nerve enters the pterygopalatine fossa, where it Trigeminal Nerve.—Diseases of the mouth synapses in the sphenopalatine ganglion (5, 7). and face are the most frequent sources of re- The vidian nerve innervates the mucosa of the ferred otalgia, and the trigeminal nerve is the nasal cavity, the posterior ethmoidal sinus, and most frequent pathway for referred otalgia (2). the sphenoidal sinus (4), but the exact distribu- The central pathway involved is most likely the tion of sensory innervation by the GSPN is not spinal tract nucleus of the trigeminal nerve (3). known (5). The nervus intermedius, which con- The maxillary and mandibular divisions of the tributes fibers to the GSPN (1), is the presumed trigeminal nerve receive sensory innervation path along which pain from the nose and si- from the nasopharynx, paranasal sinuses, up- nuses can be referred to the ear. (The nervus per and lower teeth, and three pairs of major intermedius also carries sensation from the salivary glands, most notably (for referred otal- EAC and so is also a pathway of primary otal- gia) the parotid gland (5, 9). The mandibular gia.) division supplies both motor and sensory inner- Glossopharyngeal Nerve.—The glossopha- vation to the muscles of mastication and the ryngeal nerve receives sensory input from the tensor tympani and tensor veli palatini muscles nasopharynx down to the hypopharynx (4, 7). (2). Pain from all of these structures is referred Pain from the anterior eustachian tube, the soft 1644 WEISSMAN AJNR: 18, October 1997 Fig 3. CT images (bone algorithms) of EAC masses. A, Coronal image of a young patient with keratosis obturans shows soft tissue (k) filling both EACs. There is no erosion of the canal walls, but the right EAC ap- pears to be expanded. B, Axial image of a squamous cell car- cinoma (arrows) that has eroded the pos- terior wall of the EAC (open arrow). palate (4), the posterior third of the tongue or can cause excruciating ear pain, is unilateral or tongue base (1, 4, 7), the pharyngeal tonsils bilateral, and can be accompanied by a (“sym- (7), and the lateral wall of the pharynx (1, 4, 7) pathetic”) middle ear effusion (11). Bullous my- is referred to the ear along the tympanic branch ringitis is diagnosed and treated clinically. of the glossopharyngeal (Jacobson’s) nerve Malignant external otitis (MEO), or malignant (4). external otitis, is a virulent, necrotizing infec- Vagus Nerve.—The vagus nerve carries sen- tion, not (despite the name) a neoplasm (14, sory innervation from the lower aerodigestive 15) (Fig 2). This potentially fatal pseudomonas tract (1, 7). Sensation from the mucosa of the osteomyelitis of the skull base occurs in pa- valleculae, piriform sinuses, and larynx travels tients immunosuppressed by tumor, drugs along the internal branch of the superior laryn- (chemotherapy, steroids), and diabetes mellitus geal nerve (1, 10).