Developmental anomalies of the external ear: types, causes, diagnosis and treatment

Developmental anomalies of the external ear are congenital malformations of the auricle or the external auditory canal. This group of abnormalities causes functional and aesthetic impairments that result in delayed speech development and/or dissatisfaction with one’s appearance.

Determination

Complete atresia of the ear canal – absence of the external ear canal.

Auditory canal stenosis – narrowing of the lumen of the external auditory canal less than 4 mm in diameter.

Microtia – hypoplasia of the auricle. Macrotia is an increase in the size of the auricle.

Anotia (grade 4 microtia) is the complete absence of the ear drum.

A lop-earedness is an increase in the angle between the auricle and scalp of more than 30°.

Darwin ‘s tubercle is a rudimentary tubercle of the auricle.

Periaryngeal fistulas are blindly terminating passages whose exit holes are located in front of or on the auricle.

Periauricular cutaneous appendages (extra auricles) are tubercles located anterior to the auricle, representing skin growths, in some cases with cartilaginous contents inside.

Classification of developmental anomalies of the external ear

Partial (stenosis) and complete ear canal atresia

Changes in the size, shape and location of the auricle:

• Microtia 1-4
• Macrotia
• Lopopoulosity
• Darwin’s knoll

Parotid masses:

• Periauricular fistulas
• Periauricular skin appendages (auricular appendages)

Embryology

Formation of the auricle begins in the fifth week of gestation from 1 and 2 gill arches, from which 3 tubercles of Gis are formed intrauterine. Subsequently, these tubercles merge and by the 22nd week form a complete auricle with characteristic elements: the cochlea, anticochlea, curl pedicle, curl, navicular fossa, and anticuspid. By the age of 5-6 years, the auricle has almost completely reached its final size.

The external auditory canal develops from 12 to 28 weeks of gestation. The ectodermal epithelium of the first gill slit, located between gill arches 1 and 2, invaginates and forms the ear canal.

Epidemiology

Congenital anomalies of the ear structure occur in 1 out of 7000-15,000 newborns, of which 85% are unilateral, and in 60% the right ear is altered. In boys, the pathology is 2-2.5 times more common than in girls. There are ethnic differences, according to which the developmental abnormalities of the auricles are more common in Hispanics, Asians and Navajo Indians.

Microtia occurs in 1 in 7,000 live births. Grade 3 microtia is the most common (75%).

The incidence of atresia of the external auditory canal is 1 in 10,000-20,000 newborns and is also twice as common in males. Atresia and microtia can be combined.

The incidence ranges from 0.5% to 15%, with about 5% in Europeans. In 66% of cases it is inherited by autosomal dominant trait with incomplete penetrance.

Periauricular fistulae occur with an incidence of 15-43 cases per 100,000 people and are inherited in 27% of cases in an autosomal recessive pattern. Periauricular appendages are the most frequent anomaly of the external ear and occur in 5-10 cases per 1000 newborns.

Most congenital ear malformations are manifestations of genetic syndromes such as Konigsmark, Mebius, Treacher-Collins, Down syndromes, and so on.

Etiopathogenesis

Developmental anomalies of the external ear occur as a result of genetic mutations (about 15%), teratogenic factors, but in most cases are idiopathic. Teratogens affecting the development of the auricle include isotretinoin, thalidomide, and ethanol.

Due to various etiologic factors, invagination of the ectoderm epithelium of the first gill slit is disturbed, resulting in atresia. Bony atresia of the ear canal is always secondary and is associated with malformations of the temporal bone. Microtia occurs due to a violation of the fusion of the tuberosities of Gis and the formation of the auricle. Parotid fistulas are formed due to delayed migration of epithelium and cartilaginous tissue, or excessive tissue overgrowth. Auricular appendages are formed as a result of impaired migration of one of the 3 tubercles of the first gill arch. They may be found on the skin in the triangle formed by the corner of the mouth and the base of the auricle (between the cusp and the lobe).

Clinical picture

Developmental anomalies of the external ear are manifested by aesthetic dissatisfaction and/or hearing loss. With changes in the size and location of the auricles, as well as periauricular masses, patients may develop complexes because of their appearance. This especially often begins at the age of 5-6 years, when peers mock the distinctive features. This can lead to problems with self-esteem and social adaptation. With microtia of the 3-4 degree and atresia of the auditory canal, there is a decrease in hearing of varying degrees on the side of the lesion. However, with unilateral pathology, the disease can be masked for a long time, due to overhearing by the healthy ear. With unilateral stenosis of the auditory canal, the hearing function can be preserved, external changes are also not noticeable. Such patients more often turn to otorhinolaryngologists due to the formation of wax plugs. This is due to impaired self-cleaning of the ear canal due to anatomical narrowness.

Periauricular fistulas may become inflamed in addition to a cosmetic defect. In this case, a pathologic discharge is released from the fistula, local pain and hyperemia may occur.

Dermal appendages can be located in the cheek area or in front of the ear and have different shapes (spherical, lobular, nodular, ovoid). They do not cause any functional problems, but only aesthetic defects.

Diagnosis of developmental anomalies of the external ear

Physical and instrumental examination methods are used to establish the diagnosis. They allow determining the localization of abnormalities and the extent of tissue damage, the nature and degree of hearing loss, as well as the involvement of middle and inner ear structures.

Inspection

The size and shape of the auricles, their position relative to the skull, and the presence of additional parotid masses (fistulas, appendages) are evaluated. The ear components of the ear should be examined and compared with the opposite side. In microtia of the 1st degree, the auricle is reduced in size, anatomical landmarks are preserved.

Grade 2 microtia is characterized by a reduction in size and deformation of the auricle, some anatomical elements are preserved

In grade 3 microtia, the auricles are represented by rudimentary outgrowths of cartilage and skin of small size in the form of “peanuts”. In grade 4 microtia, the auricle is not defined together with the ear canal, in rare cases it may be preserved. Lopopoulosity is characterized by an increase in the auriculocephalic angle of more than 30 °. In macrotia, the vertical size of the auricles is increased more than 6 cm.

Darwin’s tubercle is a rudimentary enlargement of cartilage at the top of the curl.

Otoscopy

The presence or absence of the external ear canal is determined. Absence is an indication of complete atresia of the ear canal. If it is preserved, its size, shape and visibility of the tympanic membrane are noted. If the diameter in the widest part of the canal is less than 4 mm, the diagnosis of stenosis is made. The identifying contours, color and transparency of the tympanic membrane are also evaluated. In microtia of 2-4 degrees, the ear canal may be atresized.

Audiologic examinations

Tone audiometry, acoustometry, short-latency auditory evoked potentials and otoacoustic emission (CSEP, OAE). The results of the study determine the type and degree of hearing loss. In case of isolated atresia of the auditory canal, conductive hearing loss from mild to severe is determined. Both ears must be examined.

A CT scan of the temporal bones

The study is performed to determine the degree of atresia of the auditory canal, the state of the middle and inner ear structures, the course of the facial nerve, and the presence of additional anomalies. Based on the results of computed tomography, the possibilities of surgical correction are determined (Jarsdorfer criteria, see treatment). In case of unilateral pathology, this examination is not recommended for children under 6 years of age due to high radiation exposure and delayed surgical treatment.

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Treatment of developmental anomalies of the external ear

In the case of anomalies of the outer ear, ectoprosthetics, hearing aids or surgical treatment is performed, depending on the severity of the process.

Atresia of the external auditory canal

Hearing aid

Hearing canal stenosis with conductive hearing loss can be compensated with behind-the-ear or in-the-ear hearing aids. The principle of operation is to amplify the sound signal and transmit it to the structures of the middle ear. In the case of complete atresia of the ear canals and conductive hearing loss, implantable bone conduction hearing aids are used. This type of hearing aid consists of two parts. The first part is a titanium implant that is implanted into the temporal bone. Over a long period of time, the implant sprouts bone tissue – osseointegrates. The second component is a removable sound processor that is fixed to the implant and picks up sounds. With the help of this device, sound from the external environment is transmitted directly to the cochlea through the bones of the skull (bone conduction). In children, the apparatus is secured with an elastic bandage on the head. In the case of complete bilateral atresia, early (in the first 3-4 months of life) hearing aids are mandatory for proper speech development and prevention of developmental disorders.

Surgical treatment for atresia of the external auditory canal is aimed at restoring the anatomy. It is performed meatoplasty (canaloplasty)if necessary in combination with tympanoplastyin one or several stages. In combination with malformations of the middle ear, the treating physician determines the treatment tactics (ossiculoplasty).
Indications: Bilateral atresia of the external auditory canal (complete or partial). Preserved cochlear function (conductive hearing loss). Jahrsdoerfer scale – at least 7 points (most favorable outcome in the postoperative period, 6 – borderline). This scale is the sum of scores (10 points maximum), which the patient receives according to the results of CT scan of temporal bones on the side of the lesion.

Jahrsdoerfer scale (Jahrsdoerfer):

Contraindications: Unilateral atresia. Age below 5-6 years.
Method description: The temporal bone is exposed by a posterior or anterior access (the temporal fascia is detached and preserved). Neuromonitoring of the facial nerve is recommended throughout. In case of complete atresia of the auditory canal, a new canal is formed with a burr in the direction of the tympanic cavity. Drilling of the ear canal continues up to 12 mm in diameter. The preserved auditory ossicles are exposed. Thinned donor cartilage and temporal fascia are placed on top of the malleus. In parallel, a full-layer skin flap is taken from the anterior surface of the thigh. After the new ear canal is formed, the skin flap is placed around its circumference, covering the entire exposed bone and covering the neotympanal membrane (temporal fascia).
In the case of a stenotic ear canal, the ear canal is widened to the required diameter. The skin is preliminarily peeled off and then placed on the walls of the formed canal. Tight tamponade of the ear canal is performed for 10-14 days.
Results: Re-establishment of an anatomical sound-conducting pathway with improved hearing.
Complications, disadvantages: Restenosis. Lack of hearing gain.

Microtia

In microtia of 3-4 degrees, the use of ectoprostheses has become widespread. ectoprostheses (non-surgical method of treatment). In this method, a silicone prosthesis is made from impressions of a healthy ear and placed in place of the existing defect. The ectoprosthesis is selected as naturally as possible according to the skin color and structure, it is attached with adhesive, clips or magnets (the latter are implanted intraosseously). This method of treatment is suitable for people of any age, the only contraindication is intolerance to the material. The advantage is the simplicity and speed of execution.

In case of microtia, surgical correction is performed – auriculoplasty (reconstruction of the auricle). To restore the auricle, one’s own cartilage (autotransplantation) or a model of the ear made of artificial tissue is used.
Indications: 3-4 degree microtia.
Contraindications: The minimum age for surgery is 5-6 years. By this age, the healthy ear has almost reached its final size (85%) and a similar graft can be modeled. The rib cartilage is also sufficiently formed by this age.

Step-by-step description of the method: In autotransplantation, the first step is to make an impression of a healthy ear, on the basis of which the missing auricle will be modeled. A fragment of the 6th, 7th and 8th rib cartilage with suprachondral cartilage, measuring 7-9 cm, is extracted. The cartilaginous tissue is sutured in different directions to form the framework of the auricle with anatomical curves (curl, anti-curl, etc.). The skin in the temporal region at the place of the proposed auricle is thinly cut off from the underlying tissues. The modeled graft is immersed into the formed pocket for engraftment. After 3-4 months, a skin incision is made along the posterior edge of the curl, the auricle is detached along its medial surface together with the skin, the necessary position is set. A full-layer skin flap taken from the thigh area is placed to the posterior surface of the formed auricle and the defect of the temporal region. A pressure tampon is applied in the auricular region, regular dressings are performed until complete healing. If necessary, the next steps are to form the cochlea and external auditory canal.
When medical implants are used, they are placed at the site of the intended auricle and covered with a skin graft.
Results: Formed auricle, no visible cosmetic defect.
Complications, disadvantages: Hypertrophic scars may form, deformation of the graft. Cellulitis and chondritis are extremely rare. The disadvantages also include the difficulty of creating an ideal copy of a healthy ear.

Macrotia, lobosity. otoplasty..

Indications: Macrotia, crow’s feet.
Contraindications: concomitant somatic pathology, age less than 6 years.
Step-by-step description of the method: The skin is peeled away from the posterior surface of the auricle. Depending on the condition of the auricle, the cartilage is excised and/or stitched in various directions to create the desired curves and shape. The skin is sutured with cosmetic sutures. A pressure dressing is applied. If necessary, the intervention is repeated on the second ear.
Results: Auricle of desired shape, no visible cosmetic defect.
Complications, disadvantages: Hypertrophic scarring, deformation of the auricle may occur. Cellulitis and chondritis are extremely rare.

Parotid masses (fistulas, appendages) are surgically excised.
Indications: Aesthetic dissatisfaction. Recurrent inflammation of the fistula.
Contraindications: concomitant somatic pathology. Acute phase of inflammation of the fistula.
Step-by-step description of the method: If a fistula is present, a border incision is made around the fistula opening. The fistula is excised along its entire length within healthy tissue. In some cases, it is possible to inject a contrast agent (methylene blue) to clarify its location. The wound edges are sutured.
The appendages are removed with a scalpel or laser.
Results: Absence of anatomical defects.Complications, drawbacks: incomplete removal of the fistulous passage and its subsequent infection is possible.