C h a p t e r 3 8
Disorders of Special Sensory Function: Vision, Hearing, and Vestibular Function
977
of the craniofacial base also render the tensor muscle
less efficient for opening the eustachian tube in this age
group. In addition, craniofacial disorders, such as a
cleft palate, alter the attachment of the tensor muscle,
producing functional obstruction of the eustachian tube.
Mechanical obstruction
results from internal
obstruction or external compression of the eustachian
tube (see Fig. 38-18C). Ethnic differences in the structure
of the palate may increase the likelihood of obstruction.
The most common internal obstruction is caused by
swelling and secretions resulting from allergy and viral
respiratory infections. With obstruction, air in the middle
ear is absorbed, causing a negative pressure and the
transudation of serous capillary fluid into the middle ear.
Otitis Media
O
titis media
(OM) refers to inflammation of the mid-
dle ear without reference to etiology or pathogenesis
(Fig. 38-19A). Inflammation of the middle ear may
present as acute otitis media or otitis media with
effusion.
50–52
Acute otitis media (AOM) refers to the
rapid onset of signs and symptoms of a middle ear
infection. Otitis media with effusion (OME) refers to
inflammation of the middle ear with the presence of fluid
in the middle ear without signs and symptoms of an acute
ear infection.
53
It is important to differentiate OME from
AOM to avoid unnecessary use of antimicrobial agents.
Risk Factors.
Otitis media may occur in any age
group, but is seen most frequently in infants and young
children between the ages of 3 months and 3 years, with
the peak incidence between 6 and 11 months.
51
There
is a second peak incidence at about 5 years of age that
is believed to be associated with entrance into school.
50
Risk factors include premature birth, male gender,
ethnicity (Native American, Inuit), family history of
recurrent OM, presence of siblings in the household,
genetic syndromes, and low socioeconomic status.
51
It is
more frequent in children with orofacial abnormalities
such as cleft lip and palate.
The most important factor that contributes to OM is
believed to be a dysfunction of the eustachian tube that
allows reflux of fluid and bacteria into the middle ear from
the nasopharynx. There are two reasons for the increased
risk of OM in infants and young children: the eustachian
tube is shorter, more horizontal, and wider in this age
group than in older children and adults; and infection
can spread more easily through the eustachian canal of
infants who spend most of their day in the supine posi-
tion.
51
Bottle-fed infants have a higher incidence of OM
than breast-fed infants, probably because they are held in
a more horizontal position during feeding, and swallow-
ing while in the horizontal position facilitates the reflux of
milk into the middle ear. Breast-feeding also provides for
the transfer of protective maternal antibodies to the infant.
Measures to reduce the risk for development of OM
during the first 6 months of life include breast-feed-
ing, avoidance or elimination of bottle propping, and
reduction or elimination of pacifier use.
51
Other ways
FIGURE 38-19.
Disorders of the middle ear.
(A)
Otitis
media. Otitis involves inflammation of the tympanic cavity.
Infection often enters through the eustachian tube.
(B)
Cholesteatoma, a cystlike mass of the middle ear that often
extends to involve the temporal bone.
(C)
Otosclerosis
involving formation of new, spongy bone around the stapes
and oval window.
Incus
Base (footplate) of
stapes occupying
oval window
Stapes
Tympanic
cavity
Eustachian
tube
Malleus
External acoustic
meatus
Tympanic
membrane
Petrous portion of
the temporal bone
A
Cholesteatoma
B
Otosclerosis
C
