Aural Atresia and Microtia

Definition and epidemiology

Aural atresia (congenital aural atresia) is the failure of the external ear canal to develop, or its narrowing, from birth; it is usually accompanied by middle ear and ossicular anomalies. Microtia is a small, malformed pinna (auricle); complete absence of the pinna is called anotia. Because both involve structures that develop from the first and second pharyngeal (branchial) arches at the same embryological stage, they frequently occur together (Luquetti et al., 2012).

The prevalence of microtia varies considerably between populations and has been reported as 0.83 to 17.4 per 10,000 births (Luquetti et al., 2012). Most cases are unilateral, and the right ear is affected more often. Bilateral cases are less common; in these children early access to sound for speech and language, and a search for an associated syndrome, are particularly important.

One of the most widely used grading systems for microtia is the Marx classification (Luquetti et al., 2012). Canal anomalies are grouped as stenosis, partial atresia and complete atresia; in complete atresia a bony plate replaces the canal and there is no tympanic membrane (Zhang et al., 2019). The Jahrsdoerfer score, based on computed tomography (CT) findings, is used to select surgical candidates (Jahrsdoerfer et al., 1992).

Symptoms and signs

Microtia is visible at birth and is often noticed in the delivery room. Even when the pinna looks close to normal, an invisible or very narrow canal opening suggests atresia. Where the tympanic membrane is preserved (stenosis) the loss is usually mild to moderate; in partial and complete atresia a moderate or moderately severe conductive hearing loss is expected in the affected ear (Zhang et al., 2019).

In unilateral cases the other ear hears normally, so the baby responds to sound and the loss may go unnoticed in everyday life. As the child grows, difficulty understanding speech in noise, locating sounds and listening in a busy classroom becomes more apparent. In bilateral atresia, speech and language development is delayed unless amplification is started early.

Skin debris can collect in a narrow canal and a cholesteatoma can develop, so ear discharge (otorrhoea), a bad smell or ear pain (otalgia) from a stenotic ear needs attention (Zhang et al., 2019). Facial asymmetry, a small jaw, preauricular tags or pits, or eye or kidney anomalies should raise the possibility of a syndrome.

Causes and risk factors

The pinna, the external canal and the middle ear develop from the first and second pharyngeal arches and the first pharyngeal cleft, so a disturbance at this stage can affect the pinna, canal and ossicles together. The inner ear develops from a separate structure (the otic placode) and is spared in most cases. There is evidence for both genetic and environmental contributions to microtia, but no causal mutation has yet been firmly established for isolated cases (Luquetti et al., 2012).

Proposed mechanisms include disturbed migration of neural crest cells and vascular disruption during development; environmental factors such as living at high altitude have also been discussed (Luquetti et al., 2012). Exposure to teratogenic medicines in pregnancy is another recognised cause.

Microtia and atresia can be part of conditions such as oculo-auriculo-vertebral spectrum (Goldenhar syndrome) and Treacher Collins and BOR syndromes. Genetic assessment and investigations such as renal ultrasound are therefore considered, especially in bilateral cases or when other anomalies are present.

Audiological and clinical assessment

Every baby with microtia or atresia should be referred for diagnostic audiology whatever the newborn hearing screen result. The JCIH recommends diagnosis by 3 months and intervention by 6 months of age (Joint Committee on Infant Hearing, 2019). OAEs and tympanometry cannot be recorded in an atretic ear, so the core task is to show, ear by ear, that cochlear function is present and how large the conductive loss is.

• Air conduction ABR: thresholds are raised in the atretic ear; in complete atresia the result is usually consistent with a moderate or moderately severe conductive loss.
• Bone conduction ABR: the cornerstone of diagnosis because it shows cochlear function directly. Bone-conducted tone burst ABR separated normal from elevated cochlear sensitivity in infants with 98% accuracy at 500 and 2000 Hz (Hatton et al., 2012).
• The other ear: in unilateral cases, normal hearing in the apparently normal ear is documented with OAEs, tympanometry and ABR; middle ear effusion in this ear leaves the child with a temporary bilateral loss.
• Behavioural testing: visual reinforcement audiometry and later conditioned play audiometry give ear-specific air and bone conduction thresholds. A masking dilemma can arise with bilateral maximal conductive loss.
• Imaging: temporal bone CT shows the middle ear space, ossicles, facial nerve course and inner ear before surgery or implant planning (Zhang et al., 2019); its timing is decided by the surgeon according to the surgical plan and any suspicion of cholesteatoma.

The Jahrsdoerfer score rates the middle ear structures seen on CT and the external ear appearance out of 10; the presence of the stapes scores 2 points and each other item 1 point (Jahrsdoerfer et al., 1992). The international consensus recommends a score of 7 or more for atresiaplasty; a mild rise in bone conduction thresholds alone does not exclude a candidate, as it may reflect the missing inertial contribution of the ossicular chain (Zhang et al., 2019).

The differential diagnosis includes acquired canal stenosis (after chronic inflammation or trauma), external auditory canal cholesteatoma and conductive loss from ossicular anomalies with an open canal. Clearly raised bone conduction thresholds should prompt a search for an associated inner ear anomaly.

Treatment and audiological rehabilitation

In bilateral atresia the goal is access to sound in the first months for speech and language development. The international consensus strongly recommends bone conduction technology in bilateral cases; in young children the device is worn on a softband or an adhesive pad, and implanted systems or middle ear implants can be considered after the age of five (Zhang et al., 2019). A bone conduction hearing aid on a softband also serves as a trial before any later implantation.

Bone conduction implants deliver sound vibration through the skull directly to the inner ear; there are percutaneous models with an abutment through the skin and transcutaneous models that sit entirely under the skin. The implant site should be planned with the reconstructive surgeon so that it does not compromise a later pinna reconstruction (Zhang et al., 2019). In Türkiye, reimbursement for these systems is governed by the current Health Implementation Communiqué (SUT) of the national health insurer (SGK) and depends on a physician’s report.

Atresiaplasty creates a new ear canal and tympanic membrane. Normal inner ear function, well-developed middle ear structures and a Jahrsdoerfer score of 7 or more are required; surgery is recommended after the age of six, and revision may be needed because bone can regrow around puberty (Zhang et al., 2019). Restenosis of the canal, infection, lateralisation of the tympanic membrane, facial nerve injury and a disappointing hearing result are possible problems, so the decision is made with the surgeon and the family in an experienced centre.

Pinna reconstruction uses the patient’s own rib cartilage or a porous polyethylene framework. Rib cartilage is considered adequately developed from about six years, with nine years or older regarded as ideal; porous polyethylene can be used from three years but is recommended after five. Atresiaplasty should be done at the same time as, or after, rib cartilage reconstruction, but before porous polyethylene reconstruction (Zhang et al., 2019). This sequence needs to be discussed early between the audiologist, the ENT surgeon and the plastic surgeon.

In unilateral atresia the benefit of a bone conduction device is less clear. The consensus advises that the decision is made by the family together with the otologist, audiologist, speech and language therapist and school staff, and that families are offered a trial because benefit in noise has been shown (Zhang et al., 2019). For the wider picture, see unilateral hearing loss.

Impact on quality of life and advice

Children with unilateral atresia rarely repeat a school year, but their need for support is considerable. In a study of 40 children none had repeated a year, yet 65% had used school support services: 47.5% had an individualised education programme, 45% had speech therapy and 32.5% had used a remote microphone (FM) system at school (Kesser et al., 2013). Language development and school progress should therefore be reviewed regularly in unilateral cases.

Practical advice: seat the child so that the hearing ear faces the teacher, use a remote microphone system in noisy settings, treat temporary problems in the hearing ear such as middle ear infection or earwax impaction promptly, and protect that ear from noise. In bilateral cases the device should be worn all day, and the softband needs readjusting as the head grows.

Concerns about the appearance of the ear often grow during the school years. The timing of reconstruction is planned around the child’s own wishes and psychosocial situation as well as surgical factors. Meeting the multidisciplinary team and other families with similar experience helps families make decisions.