Introduction

Microtia is a type of ear defect characterized by a malformation and underdevelopment of the outer ear called “the pinna." Its severity ranges from a decrease in the size of the external ear to a total absence of the external ear, which is the most severe form of microtia.¹

This condition can occur as an isolated birth defect or be caused by other reasons such as genetics or a syndrome.

Microtia in its severe form can lead to loss of hearing, which requires treatments for ear impairment and/or surgical ear reconstruction.²

This article seeks to explore the various methods and technologies used in diagnosing microtia, with a particular focus on advancements in prenatal diagnosis. Diagnostic approaches include clinical evaluation, imaging techniques such as ultrasound and MRI, genetic testing to identify associated syndromes, and advancements in prenatal screening methods.

By discussing these diagnostic modalities comprehensively, this article aims to provide healthcare professionals and families with an understanding of how microtia is diagnosed, the implications for early intervention, and the role of prenatal diagnosis in improving outcomes for affected individuals.

Classification of microtia

Many classification systems have been proposed by different scientists in the medical field. However, there are four major scientists whose theories are widely known.

Hermann Marx (1926) did his classification method based on the degree of deformity. This method provided the background work of modern methods of classification, offering more detailed categorisation based on advancements in medical understanding and surgical techniques.

Robert B. Tanzer (1978) developed his form of classification, categorizing the degrees of congenital ear deformity according to their levels of severity.

The Weerda classification for microtia was introduced by Professor Heinz Weerda in 1988. It provides a method for classifying the severity of microtia based on the level of deformity in the outer ear.

The Hunter et al. classification for microtia was introduced in 2009. This classification system is known for its detailed assessment of congenital (from birth) ear deformities, taking into account both the anatomical deformities of the outer ear and any associated anomalies. It is the most recent form of classification.³

He classified his into three groups:

• First degree: presence of all the normal ear components; only a small part of the ear is out; its full shape can still be recognized
• Second degree: median longitudinal length of the ear in the presence of some, but not all, parts of the normal ear
• Third degree: presence of some structures of the outer ear, but none of these structures conforms to recognized ear components

Anotia: Complete absence of the ear.³

Diagnosis of microtia

Prenatal diagnosis

Prenatal diagnosis is a method used to check the health state of an unborn baby (fetus) in the mother's womb. The primary goal of this type of diagnosis is to detect any form of abnormalities or conditions that could affect the baby's development and overall health.

This allows the parents and caregivers to gather information and make decisions about the management of the pregnancy and prepare for any special needs the baby might have after birth.

Prenatal diagnosis can be performed in three ways:

• Ultrasound
• MRIs
• Genetic testing

Ultrasound

Ultrasonography (the use of ultrasound) is the use of high-frequency sound waves to produce images of structure inside the body. It is usually done in the early stages, first, second, and third trimesters of pregnancy.

In this method, pregnant women are made to lie in a supine position (lie on their backs), and then they are screened by ultrasound to check the development of the babies and measure certain parts of their bodies.

The ears of the babies were looked at from the side to see both ears clearly. If they suspected there was something wrong with the ears, then extra images are taken from different angles and 3D imaging is used for a clearer view.⁴

MRI (magnetic resonance imaging)

MRI is the use of strong magnetic fields and radio waves to generate detailed images of organs and tissues.

Fetal MRI is used alongside ultrasound to diagnose fetal abnormalities. It provides detailed images from different angles, which can show the size, shape, and position of the ears and any related birth defects. MRI can also show and measure the status of the external auditory canal (EAC) and identify the type of microtia.⁵

This is a more preferred method for the diagnosis of fetal microtia.

Genetic testing

Genetic testing is a medical test that analyzes DNA, the chemical compound that carries the genetic instructions for the development and functioning of living organisms. It is used to identify changes in genes, chromosomes, or proteins. These changes can indicate a person’s risk of developing certain genetic disorders, help diagnose existing conditions, and guide medical treatment.

Genetic testing for microtia can help identify any underlying genetic causes or syndromes associated with the condition.

This is the best method of diagnosis that can be used for fetal microtia.

Postnatal and adult diagnoses

Postnatal and adult diagnosis involve the use of physical examinations and utilizing diagnostic tests such as blood tests, imaging, and biopsies. The goal of such diagnosis is to accurately identify health issues to develop effective treatment plans, manage chronic conditions, and maintain overall health and well-being.

Postnatal and adult diagnoses can be performed in:

• Physical Examination
• Audiology brainstem response and otoacoustic emissions
• Imaging Studies
• Genetic Testing

Physical examination

A physical examination is done to inspect the outer parts of the ear. It is usually done by an audiologist.

To examine the ears, the doctor makes the patient sit facing him/her. Differences in ear shape or size and the presence of facial asymmetry (facial differences between both sides of the face) are checked for. An otoscope is also used to inspect the ear area for scars, bumps, pits, skin changes, or redness. The presence of birth defects, redness, swelling, bumps, or discharge are also looked out for.⁶

Audiology, brainstem response, and otoacoustic emissions

Audiology, brainstem response, and otoacoustic emissions are procedures used to detect ear defects in neonates. It is done between 3 and 6 months after birth.

Audiology brainstem response

A child's hearing ability often relies on their ability to respond to sounds. For very young children. Doctors use the Auditory Brainstem Response (ABR) test to measure electrical signals from the scalp when sounds are played in the ear. The waves seen in the test show how well the hearing nerve and brainstem processes sound. These responses are not affected by sleep or sedation, which is why doctors often test while the child is sedated to get accurate results if the child cannot cooperate well.⁷

Otoacoustic emissions

Otoacoustic emissions (OAE) are sounds produced from the cochlea, transmitted across the middle ear to the external ear canal, where they can be recorded. The production of an OAE is a marker for inner ear health and a simple way to screen for hearing loss.

There are two types of OAE: spontaneous OAE (SOAE), which occurs continuously without external stimuli, and evoked OAE (EOAE), which requires an acoustic stimulus prior to its measurement.⁸

Image studies

This involves the use of various techniques such as x-rays, CT scans, ultrasound e.t.c. to see the visual representations of the interior parts of the body. It can be used to detect abnormalities in the ears as well as other parts on the body.

Genetic testing

Genetic testing is not only for unborn babies. It can be used for anyone.

The aim of genetic testing is to help identify any underlying genetic causes or syndromes associated with microtia.

Treatment

The treatment for microtia is chosen according to the level of severity and the availability of treatment methods present.

These methods include surgical reconstruction of the ear, the use of prosthetic ears, hearing aids to address hearing loss, and sometimes autologous rib cartilage grafting to build a new ear structure.

Conclusion

In the past, individuals with microtia faced many challenges, including social stigma and hearing difficulties, which affected their quality of life. However, recent medical advancements have improved the quality of life for those diagnosed with microtia. They can now live normal lives without the interference of this condition in their daily activities and social interactions.

As ongoing research continues to progress in tissue engineering and regenerative medicine, the future promises more natural and less invasive reconstruction techniques. These advancements could potentially eliminate the need for rib cartilage grafting, offering more advanced treatment methods and natural solutions.

Summary

The help of modern medical techniques and supportive care has transformed the management of microtia, allowing individuals to live life well without the burden of their condition affecting their lives. As technology and medicine continue to improve, treatment increases, making it more accessible to everyone affected by this disorder.