Congenital hearing loss, microtia and preauricular pits !

Malformation

Some babies are born not hearing well, with a small ear or with a tiny pit in front of the ear; all of them deserve a hearing test.

Updated 2026-11-01

See it in 3D: Auricle · Ear canal · Eardrum · Malleus · Incus · Stapes · Cochlea · Vestibulocochlear nerve (VIII)

What it is

Congenital hearing loss can be sensorineural (hair cells or nerve, from the inner ear) or conductive (canal, eardrum or ossicles). Microtia is a small, malformed auricle, often with canal atresia; preauricular pits and tags are remnants of the auricular hillocks. Any of them is a clue to look for other malformations and a reason for newborn hearing screening.

Key facts

Congenital hearing loss: about 2 to 3 per 1000 births; about half is genetic.
GJB2 (connexin 26) variants cause about half of autosomal recessive nonsyndromic deafness.
Congenital CMV: a common infectious cause; hearing loss can appear after a normal screen.
Other causes: rubella, prematurity, maternal diabetes, retinoids (isotretinoin).
Microtia: types 1 (small, normally shaped ear) to 4 (anotia); usually one-sided; about 1 in 3800 US births.
Preauricular pits: common and usually harmless; they can become infected.

Embryological cause

Sensorineural: failure of the otic vesicle, of organ of Corti hair cells or of the vestibulocochlear ganglion.
Conductive: defects of the first cleft (canal atresia), the tympanic membrane or the ossicles of arches 1 and 2.
Microtia: the six auricular hillocks (arches 1 and 2, with neural crest) do not grow or fuse properly in weeks 6–8.
Preauricular pit: incomplete fusion of the hillocks; tags come from accessory hillocks.
Because the auricle depends on neural crest, its defects travel with face, kidney or heart anomalies.

Markers

GJB2
SLC26A4
EYA1
HOXA2

How it presents

Hearing loss: failed newborn screen, a baby who does not react to sounds, delayed speech.
Microtia: small auricle, often with a narrow or absent canal and conductive loss on that side.
Microtia associations: oculo-auriculo-vertebral spectrum, oral clefts, facial asymmetry, kidney and heart anomalies.
Pits and tags: in front of the tragus; discharge or swelling may mean an infected tract.

Diagnosis

Newborn hearing screening with otoacoustic emissions or automated auditory brainstem response.
Audiology referral if the screen fails or if there is microtia, a pit or a tag.
CMV testing in the first weeks of life if the hearing screen fails.
Temporal bone CT to plan canal surgery; kidney ultrasound if other findings are present.

Test yourself

Think of the answer, then tap the question to see it.

Which gene is the most common genetic cause of nonsyndromic deafness?

GJB2, which encodes connexin 26.

What type of hearing loss does microtia with canal atresia cause?

Conductive hearing loss, because sound cannot reach the middle ear.

Why does microtia prompt a search for other malformations?

Because the auricle depends on neural crest of arches 1 and 2, which also builds the face and contributes to other organs.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

Microorganisms

← All of embryology

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Anotia/Microtia (Centers for Disease Control and Prevention, 2024); Ear tag: MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine, 2024); Nonsyndromic hearing loss: MedlinePlus Genetics (U.S. National Library of Medicine, 2024); CMV in Newborns (Centers for Disease Control and Prevention, 2024).

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Representative model, for educational purposes only.