Microtia is a congenital ear deformity where the outer ear does not fully develop during the first trimester of pregnancy. As a result, the external ear is small and doesn not form properly.

Atresia is the absence of an ear canal. It is almost always accompanied by microtia of the outer ear.

Microtia and Aural Atresia may be unilateral (one ear) or bilateral (both ears).

Of the thousands of microtia patients Dr. Bonilla has evaluated, approximately 10% are bilateral.

Microtia Classifications

Grade 1 Microtia

The ear looks slightly normal, although smaller. Many of the normal features of the ear are preserved. An ear canal may or may not be present (aural atresia).

Grade 2 Microtia

The ear is missing more of the normal features. The earlobe is present. The helix (rim) of the ear is not fully developed on the top. An ear canal may or may not be present (aural atresia).

Grade 3 Microtia

Grade 3 Microtia is the MOST COMMON or “classic” ear deformity. The top half is composed of disorganized cartilage while the bottom half usually has a relatively normal earlobe that has a more vertical direction. An ear canal is almost always missing (aural atresia).

Grade 4 Microtia

Grade 4 Microtia is also called “Anotia”, which means total absence of the external ear. This is the most severe ear deformity. It is common to have a low-set hairline. An ear canal is usually missing (aural atresia).

What is the Cause of Microtia?

  • The most common possible explanation of the cause of microtia is a decreased blood supply to the developing ear in-utero. Others have theorized certain medications taken by the mother during pregnancy such as Accutane, Thalidomide and Retinoic Acid. Environmental factors have also been questioned.
  • Microtia Incidence: 6,000 to 12,000 births.
  • Microtia occurs most commonly on one side (unilateral) in males and on the right side.
  • Approximately 10% of patients with microtia may occur on both sides (bilateral).
  • Most patients with microtia also have aural atresia (no ear canal).
  • Microtia may be part of other syndromes such as hemifacial microsomia, Goldenhar syndrome and Treacher-Collins syndrome.


External Ear Options

  1. No Surgery
  2. Surgery with Natural Cartilage (99% of surgeries worldwide)
  3. Polyethylene implant (material made of plastic)
  4. Ear prosthetic
  5. Future Option: 3-D printed ear (FDA study in progress)

Hearing Options

  1. Unilateral (one-sided): no intervention if unilateral
  2. Bilateral (both sides): intervention is required
  3. Non-surgical: Bone-conduction hearing aid via a softband
  4. Surgical: Bone-conduction implanted hearing aid
  5. Atresiaplasty or Canalplasty (surgical opening of ear canal)

Bilateral Microtia

Children born with bilateral microtia (both sides affected) are managed slightly differently than those with unilateral (one-sided) microtia.

Luckily, children with unilateral microtia have the other normal side to hear good, crisp, clean sounds. Children with bilateral microtia don’t have that luxury. Their hearing loss requires amplification with a bone-conduction hearing aid. There are usually three specialists involved in obtaining a bone-conduction hearing aid. The primary care doctor usually refers the child to an ear, nose and throat specialist. A hearing test is performed by an audiologist and this person is usually the one that dispenses and tests the hearing aid.

If one wants to know what a child with bilateral microtia hears, it is rather simple to reproduce this hearing loss. If one places a finger in each ear in order to totally occlude the ear canal, that is what a child with bilateral microtia and atresia hears. One may ask, then how can the child hear if both ear canals are occluded. The answer is simple: Bone Conduction. Because the vast majority of children with microtia have normal inner ears (where the hearing nerve is located), sound travels via the skull via vibrations. In other words, a sound will strike the skull, nose, jaw, etc. and a vibration gets transmitted straight to the inner ears, totally bypassing the ear canals.

Microtia Ultrasound During Pregnancy Why was the microtia missed during the ultrasound?

It is important to understand why the ultrasound is performed in the first place. The ultrasound is meant to evaluate several functional and anatomic components such as:

  1. Delivery Date
  2. Detect ectopic pregnancies
  3. Detect heart rate
  4. Confirm normal anatomy of vital structures such as the heart, brain, lungs, kidneys, etc...


This is one of Dr. Bonilla's patients who underwent a 4-D ultrasound where the microtia on the right ear can be seen.

Natural cartilage versus plastic polyethylene implants

Dr. Bonilla is a strong beiever in using our own natural cartilage for ear reconstruction instead of a manufactured product which is composed of a hard, plastic material. Our own living tissues have a much longer life.
Using the rib cartilage technique, the cartilage bends naturally, which is more realistic and makes the ear much safer to trauma for the rest of the patient’s life.
The plastic polyethylene implant has the risk of exposure or fracture for the rest of the patient’s life.
​Dr. Arturo Bonilla smiling in a lab coat

Microtia - Congenital Ear Institute ​Dr. Arturo Bonilla

Microtia - Congenital Ear Institute, led by Dr. Bonilla, is the largest exclusive pediatric microtia center in North America. Dr. Bonilla has been recognized as the leading pediatric microtia surgeon, performing thousands of surgeries for children all over the world. His affiliations include: American Medical Association | American Academy of Otolaryngology

You can contact our office online or by calling (210) 477-3277.

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