Diseases Of The Nose Throat And Ear

CHAPTER 55

INFLAMMATION OF THE EXTERNAL
ACOUSTIC MEATUS

OTITIS EXTERNA

The origin of disorders of the skin involving the external ear may not be
immediately recognized, particularly those involving the meatus, and even
manifest disease of the auricle and adjacent skin areas may arise in the
meatus or middle ear. Otitis externa has been classified as localized or
generalized. When it is confined within the external meatus two clinical
forms are recognized: (i) circumscribed otitis externa or furuncle, (ii) diffuse
otitis externa.

The generalized form affecting meatus, auricle and adjoining areas of
skin may be primarily otological or primarily dermatological. In addition,
the condition may be classified as infective, due to bacterial, fungal or viral
agents; and reactive, from contact with numerous external sensitizing agents
or resulting from constitutional allergies. In many cases the disease is of
mixed origin, a primary infective lesion developing an eczematous reaction
and vice versa.

INCIDENCE. The incidence of otitis externa is highest in tropical countries
with a high humidity where the symptoms are often severe and recurrences
are frequent.

AETIOLOGY. Many factors can be implicated in the onset of otitis externa.
Scratching the ears with dirty fingers or with contaminate!! objects such as
a matchstick or a hair grip, or the use of dirty instruments may introduce
pathogenic organisms to the meatus. If the skin is traumatized infection may
penetrate the barrier of the stratum corneum. Syringeing the ear for the
removal of hard wax or badly fitting and infrequently cleaned hearing-aid
ear-pieces may also cause minor injury and subsequent infection. In other
cases allergy is the primary factor. The development of skin allergy may
be due to a large variety of antigens many of which are contained in topical
applications such as cosmetics and antibiotic preparations. Intense itching
is an early symptom of sensitization and scratching often leads to secondary
infection. A sensitivity reaction may result from psychological factors such
as prolonged mental stress.

BACTERIOLOGY. The normal external meatus is sterile, or contains Staphy-
lococcus albus alone or in combination with other non-pathogenic organisms.
Less often Staph. aureus or non-haemolytic streptococci are found. In cases
of otitis externa ^the bacteriological flora is often mixed, and Staph. aureus
and Gram-negative organisms such as Pseudomonas pyocyanea and Proteus
are present Escherichia coti occurs also in mixed infections. The

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