Congenital malformation of the auricle and congenital meatal atresia (Fig.
162) are due to maldevelopments of the first pharyngeal cleft and the first
and second visceral arches. The tympanum, malleus, incus and stapes are
also involved. Several varieties of auricular deformity are described, varying
from slight cases, such as pointed or Darwinian ears, to total absence of
the external ear (anotia). In marked cases of meatal atresia the tympanic
membrane is defective or even absent. As the otic vesicle, from which the
membranous labyrinth is formed, develops earlier than, and quite
independently of, the external and middle ears, the labyrinth is usually
normal in these cases. The condition is as a rule unilateral. Facial paresis,
maldevelopment of the mandible, hemiatrophy of the face, and other con-
genital deformities are sometimes associated with microtia and meatal atresia
(Treacher Collins syndrome). It has been found in association with a con-
genital abnormality of the urinary tract. Hearing tests usually show the
results obtained in lesions of the sound-conducting apparatus (p. 265), but
even in bilateral cases the human voice is, as a rule, heard well enough to
allow the patient's speech to develop.
TREATMENT. Operative treatment may be indicated in cases of bilateral
congenital atresia but should not be undertaken until a thorough assessment
has been made of the extent of the deformity and the degree of impairment
of cochlear function. The first step in the management of these children is
the early fitting of a bone-conduction hearing aid so that the natural stage
of 'readiness for listening' is employed. A close liaison between parents,
teacher and surgeon must be maintained. Surgery may be undertaken
between the ages of 18 months and 2 years although some authorities recom-
mend a delay for a further year depending upon the child's progress. Whilst
the anatomical deformity can be defined with some accuracy by radiographic
examination including tomography, the assessment of cochlear function may
be more difficult.
The operative technique varies with the circumstances in each case. Where
superficial landmarks are recognizable, an approach may be made to the
mastoid antrum and the middle ear explored as in a radical mastoid opera-
tion, the two-tunnel approach. When no landmarks are present, a one-
tunnel approach is made to the middle ear in the angle formed by the level
of the dura mater above and by the posterior wall of the mandibular joint
in front. When the necessary tympanoplastic procedure is completed, the
resulting cavity is lined by a sac formed from a split-thickness skin graft.
In the case of gross middle ear deformity a second-stage fenestration may
be undertaken when the ear is healed or an air-conduction hearing aid may
be worn in the reconstructed meatus.