What is microtia?

Microtia meaning ‘little ear’ is a congenital deformity ranging from mild reduction in auricle (external ear) size to complete absence of the external ear. Microtia affects only one ear in 90% of the patients, commonly affecting the right side and mostly occurring in males. A narrow (canal stenosis) or an absent (canal atresia) ear canal is frequently present with microtia. Microtia can arise either sporadically or be associated with a family history of the condition.¹

Why is grading microtia severity important?

Microtia grading severity is based on the extent of outer ear deformity and its impact on the hearing process. Children with microtia are at the risk of developing hearing loss with varying degrees. As hearing affects speech and language skills, early severity grading enables timely initiation of appropriate interventions.

Mild cases of microtia may require prosthetic ears or reconstructive surgery, whereas severe cases may require cochlear implants or bone-anchored hearing aids to improve hearing and appearance. In most cases, microtia occurs in isolation but can be associated with craniofacial syndromes such as hemifacial microsomia, Goldenhar Syndrome and Treacher Collins Syndrome; kidney malformation; heart defects; cleft palate or inner ear abnormalities. These conditions must be considered during treatment planning to achieve favourable results and improve the patient’s quality of life.²

Causes

• Decreased oxygen levels during the first trimester
• Lack of blood supply owing to the pressure from foetal positioning against the inside of the mother or from the umbilical cord during the first trimester
• Increased drug or alcohol use
• Teratogens, such as mycophenolate mofetil, thalidomide and isotretinoin
• Advanced paternal or maternal age, low birth weight and high altitude^1,3

Problems associated with microtia

• Most children with microtia exhibit an underdeveloped or absent ear canal causing hearing loss and affecting speech development.
• Children with microtia also develop ear infections
• Children may become self-conscious as they begin to understand the differences in their bodies compared with their peers, hampering their self-confidence.⁴

Grading systems for microtia

Marx classification

This is the most commonly used classification system for microtia. The auricle size and the presence of the subunits are used to grade the severity of microtia (Figure 1).

Grade I: The auricle is slightly small, but all seven subunits are present.

Grade II: The auricle size is smaller than that of Grade 1 and lacks one or two subunits.

Grade III: The auricle is called the ‘peanut ear’ with a small piece of cartilage; only one or two subunits are present, probably the concha or lobule.

Grade IV: The auricle lacks subunits and is called ‘anotia’.³

Figure 1. Marx's classification of microtia. Image taken from Andrews J, Kopacz AA, Hohman MH. Ear microtia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Jun 22]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK563243/ 

Nagata classification

In this classification, each type refers to the surgical approach employed by practitioners while performing an otoplasty (Figure 2).

Lobule type: The remnant ear and lobule are present but lack the concha, acoustic meatus and tragus. This is similar to Grade III of the Marx classification.

Concha type: The auricles have a concha, lobule, tragus and intertragic notch, but the presence of the acoustic meatus and upper auricular pole is variable.

Small concha type: The characteristics resemble the lobule type with an additional indentation representing the concha.

Anotia: The external auricle is absent similar to Marx’s classification.³

Figure 2: Nagata’s classification of microtia. Image adapted from Andrews J, Kopacz AA, Hohman MH. Ear microtia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Jun 22]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK563243/ 

Tanzer classification

Type I: Anotia

Type II Complete hypoplasia either with or without congenital auricular atresia

Type III: Hypoplasia of the middle third of the auricle

Type IV: Hypoplasia of the upper third of the auricle (constricted (cup and lop) ear, cryptotia, or hypoplasia of the superior third

Type V: Prominent ear⁵

Weerda’s classification

This classification includes all the congenital deformities associated with the external ear and is a modification of the Marx and Tanzer classifications based on the surgical approach and embryogenic development.

First-degree dysplasia

General: The normal auricle structures are recognisable, although slightly deformed. As per Tanzer classification, cup ear deformities I, IIa and IIb are observed.

Surgical: Occasionally. additional skin and cartilage are required for reconstruction.

Second-degree dysplasia

General: Moderate deformity, although few normal auricle structures are recognisable; cup ear deformity III as per Tanzer classification

Surgical: Additional cartilage and skin are required for partial reconstruction

Third-degree dysplasia

General: Severe malformations and absence of auricular structures, similar to lobule type or Grade III microtia

Surgical: Additional cartilage and skin are required for total reconstruction⁵

Hunter classification

Microtia-First degree: All the normal ear components are present; the median longitudinal length is 2 standard deviations below the mean

Microtia-Second degree: Few normal ear components are present; the median longitudinal length is 2 standard deviations below the mean

Microtia-Third degree: Few auricular structures are present; however, they are not recognisable

Anotia: Complete absence of the ear⁵

Evaluation criteria in grading systems

Patient history

Microtia is identified during newborn screening or a physical examination by the clinician. The clinician should conduct a complete patient history, such as ear infections, developmental milestones of speech and language, and other congenital anomalies, such as craniofacial asymmetry, hearing loss and kidney and heart abnormalities, which may indicate a family history.^4,6

Physical examination

A complete head and neck exam should be performed, including an evaluation of the oral cavity, mandible, palate, facial nerve, eyes, and skin colour and quality. The clinician should also identify if any genetic syndromes are associated with microtia. Hemifacial microsomia, accessory auricular appendages, preauricular pits or aural atresia should be noted. Examination of the auricular components of the ear should be conducted, along with a comparison to the contralateral side. Monitoring the middle ear status of the affected side is essential to ensure the hearing of the unaffected side is optimal.^4.6

Hearing evaluation

As infants with microtia fail the newborn hearing screen, they should be referred to an audiologist as soon as possible for an auditory brainstem response (ABR) test. ABR should be performed by 3 months of age. It can be conducted while the infant is asleep and without sedation from birth till 6 months of age.

Hearing tests are used to determine the grade of microtia. These tests are crucial for children with unilateral or bilateral microtia to measure the frequency of the sound heard by each ear. Doctors also examine the auditory canal to assess any abnormalities present. This is important for patients with higher grades of microtia who may experience complete deafness in one or both ears.

Auditory assessments using appropriate behavioural test methods (visual reinforcement audiometry, standard audiometry and conditioned play audiometry) should be performed in infants older than 6 months. These tests determine the ability to hear different frequencies at different loudness levels, helping doctors assess whether the hearing loss associated with microtia is mild, moderate or severe. For children where auditory evaluation is challenged, a sedated ABR may be performed. Hearing sensitivity should be examined once or twice a year until the child reaches five years of age.

The audiological assessment should be performed within 2-3 months in patients with bilateral microtia. Hearing amplification should be provided within 4 months and enrolment in the early intervention should be done within 6 months to optimise speech and language development.^4,6

Imaging studies

An ultrasound should be performed to rule out any kidney abnormalities. Computed tomography (CT) scans provide detailed images of the ear and its surrounding structures, the size and shape of the external ear and the presence of other deformities, which help the doctors to determine microtia severity. The narrowing or blockage of the ear canal can be determined using a CT scan, indicating the increased risk of conductive hearing loss.

Middle ear infections and fluid build-up can contribute to hearing loss, which can be identified in a CT scan. A temporal bone CT scan is recommended to assess the surgical repair candidacy using the Jahrsdoerfer grading scale. A CT scan should be avoided before the age of 6 years due to radiation risk and because hearing reconstructive surgery is not advisable before that age.^4,6

Consultations

Newborns should be referred to an audiologist and an otolaryngologist to discuss their hearing status, provide adequate rehabilitation services and monitor their auditory progress. A consultation with a geneticist should be conducted if any syndromes are noticed at birth. A plastic or craniofacial surgeon referral is given to patients or parents seeking more information on microtia reconstruction. When surgical reconstruction is unsuitable, an anaplastologist is consulted for prosthetic ears. A referral to the craniofacial clinic is required for adolescents with hemifacial microsomia requiring plastic surgery or oral and maxillofacial surgery. Speech pathologists evaluate speech and language delays and initiate early intervention programs for children up to 3 years with developmental delays. Individualised Education Plan should be pursued through the school system for children older than 3 years.⁶

Counselling

The patient’s parents may experience intense feelings of frustration and guilt. Thus, they require counselling concerning the causes of microtia and its impact on hearing and microtia reconstruction options with the respective timelines. Parents should be advised on the manner of communication with their child, friends and family to prevent feelings of shame due to microtia. Parents should be encouraged to join support groups or online communities, for example, www.earcommunity.org, to avoid isolation and experience positive stories of children with microtia leading a healthy and productive life.⁶

Summary

Microtia is a condition present at birth where the auricle is either underdeveloped or absent. Microtia either occurs in isolation or is associated with other congenital syndromes. The noticeable asymmetry and conductive hearing loss may impact a child’s self-confidence and communication with peers.

Prompt evaluation and collaboration among various specialists is crucial for optimal outcomes, The extent of hearing loss should be evaluated to provide a customised treatment plan for the patient depending on the age, patient preference, microtia severity and associated congenital anomalies. Patients with microtia and their families can benefit from support groups to discuss their emotional or social challenges. Patients should attend regular follow-ups to monitor the outcomes, address their complications, and receive continuous support throughout life.