This chapter discusses common nontraumatic conditions affecting
the external, middle, and inner ear. Selected traumatic conditions
include auricular hematoma, burns, and frostbite. Management of
lacerations to the ear is described in detail in Chapter 46, Lacerations to the Face and Scalp. Removal of foreign bodies
in the ear is discussed in detail in Chapter 143A, Pediatric Procedures: Nasal and Otic Foreign Bodies in the
Pediatrics section. Barotrauma to the middle ear, also called barotitis media,
is discussed in Chapter 208, Dysbarism and Complications of Diving.
The auricle, or pinna, is the visible external portion of the
ear, whose trumpet shape enables it to collect air vibrations. It
consists of a thin plate of elastic cartilage with a tightly adherent
covering of skin. The external auditory canal is an S-shaped skin-lined
tube that extends from the auricle to the tympanic membrane (TM).
The outer one third of the external auditory canal is composed of
an incomplete cartilaginous tube. Its thick skin supports hair follicles
plus apocrine and sebaceous glands. The inner two thirds of the
canal is composed of bone covered by a thin layer of tightly adherent
skin, which is easily torn by minimal trauma.
The blood supply to the external ear is derived from the posterior
auricular, superficial temporal, and deep auricular arteries. Venous
drainage of the external ear is into the superficial temporal and
posterior auricular veins, which then drain into the external jugular
vein. The posterior auricular vein frequently connects to the sigmoid
sinus, providing a route for extension of infected material into
the intracranial cavity.
The middle ear is an air-containing cavity in the petrous temporal
bone. It contains the auditory ossicles, which transmit vibrations
of the TM to the perilymph of the internal ear. It communicates
with the nasopharynx anteriorly via the eustachian tube and with
the mastoid air spaces posteriorly via the aditus ad antrum (Figure 237-1).
Sagittal section of the middle ear and related structures.
The TM is a thin, pearly gray, fibrous membrane, that produces
a cone-shaped light reflex anteroinferiorly when illuminated.
Superiorly, the pars flaccida is the relatively slack portion of the
membrane between the malleolar folds; the remainder of the membrane
is tense and is called the pars tensa. The auditory
ossicles are the malleus, incus, and stapes. Both the incus and
the handle and lateral processes of the malleus are typically visible
through the TM (Figure 237-2). Figure
237-1 shows the relationships of the facial nerve, sigmoid
sinus, and internal carotid artery to the middle ear.
Right tympanic membrane as seen through the otoscope.
The inner ear consists of the cochlea, which contains the auditory
sensory receptors, and the vestibular labyrinth, which contains
balance receptors. Cristae in the semicircular canals detect angular
acceleration and macules detect linear acceleration. Afferent nerves
from the vestibular labyrinth connect to brainstem nuclei to maintain
smooth movement of the eyes during head movement and to the cerebellum
to control oculomotor and postural functions. Blood supply is from
the vertebrobasilar system (Figure 237-3).
The otolithic organs (utricle and saccule) lie in the vestibule.
The internal auditory artery divides into the common cochlear artery
and the anterior vestibular artery. The anterior vestibular artery
provides the blood supply to the anterior and horizontal semicircular
canals but not to the cochlea. Isolated occlusion of the anterior
vestibular artery may therefore cause acute vestibular syndrome
without hearing loss.
Schematic of the bony labyrinth containing the vestibular
and auditory sensory organs.
Primary otalgia is caused by auricular and periauricular disease,
whereas referred otalgia is caused by disease originating from remote
structures. Referred otalgia is common because of the multiple cranial
nerves and branches of the cervical plexus that supply sensory innervation
to both the ear and other structures of the head and neck. The sensory
innervation of the ear is mediated by the fifth, seventh, ninth,
and 10th cranial nerves, as well as by the cervical plexus, with
much overlapping and variability. Table 237-1 lists
common causes of primary and
237-1 Causes of Otalgia
| Save Table
237-1 Causes of Otalgia
|Trauma||Dental||Trigeminal (tic douloureux)|
|Infection||Temporomandibular joint disease||Herpetic geniculate (Ramsay Hunt syndrome)|
|Otitis media||Abscessed teeth/dental
|Cholesteatoma||Retro- and oropharyngeal|
|Throat and neck|
The mandibular division of the trigeminal nerve mediates sensation
for the anterior outer ear: the auricle, tragus, external auditory
canal, and external surface of the TM. The facial nerve carries
sensory innervation from the external auditory canal and the skin
behind the auricle. The glossopharyngeal nerve and the auricular
branch of the vagus nerve (the Arnold nerve) carry sensory input
from the medial ear structures. Branches of the second and third
cervical nerves form the greater auricular and lesser occipital
nerves, which receive input from the skin over the parotid gland
and behind the ear, respectively.
Disease from any portion of the ear or its surrounding skin and
structures may result in primary otalgia. A history and physical
examination of the external ear, external auditory canal, and TM
will usually identify the cause of primary otalgia, with specific
therapy as appropriate.