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.