What is Atresia
Aural atresia is the lack of a fully developed ear canal, eardrum, middle ear space, and ear bones. Aural atresia is often accompanied by microtia, a congenital deformity of the outer ear. Microtia and atresia may be unilateral (one ear) or bilateral (both ears).
Surgical repair of congenital aural atresia attempts to restore natural hearing to the ear by opening an ear canal, freeing the ear bones (“ossicles”), constructing a tympanic membrane (eardrum), lining the new bony ear canal with a very thin skin graft, and creating an opening (“meatus”) in the reconstructed auricle that is aligned with the new bony ear canal. The finished result is a healthy skin-lined ear canal with tympanic membrane and ossicles that vibrate freely allowing sound energy to be conducted efficiently to the inner ear. In selected patients, the chances of achieving normal or near normal hearing with surgery approach 90-95%.
Not all children are candidates for atresia surgery. A child’s candidacy for this delicate operation lies in two important tests: the hearing test (“audiogram”) and the computed tomographic (CT) scan. The audiogram ensures that the child has normal inner ear (“cochlear”) function, and the CT scan allows me to “see” the development of the middle ear space and the ossicles. I judge a child’s candidacy for atresia surgery based on the development and anatomy of the middle ear space, facial nerve, and inner ear structures. I use the grading scale originally published in 1992 by my mentor, Dr. Robert Jahrsdoerfer. The child’s ear anatomy is graded on a 10 point scale, the higher the number, the better and more favorable the score. We predict that a child with a 7/10 has a 70% chance of achieving normal or near normal hearing; an 8 out of 10 portends an 80% chance; a 9/10 predicts a 90% chance. A recent analysis of our surgical hearing results actually shows that a child with a 7 or better has an 80-90% chance of achieving normal or near-normal hearing.
The timing of atresia repair depends on many factors – age of the patient, maturity of the patient, and type of outer ear reconstruction (microtia repair – see http://www.microtia-atresia.com for details) the family has chosen, to name a few. I generally do not recommend atresia repair, either in children with unilateral or bilateral atresia, until the child is old enough to cooperate with the postoperative care that is absolutely necessary to ensure an excellent result. One week after surgery, the child must sit still for me to remove the packing and clean the new ear canal in the office. One month after surgery, the child must sit still for me to clean and debride the ear canal of the sloughed layer of dead skin that develops in the postoperative period. I have found that children ages 5 and older are old enough and mature enough to let me do the necessary postoperative care in the office. That said, I have met many mature 3-4 year olds who might be able to sit still (and I have a handful of 7-9 year olds who cannot sit still for me to clean the ear!), but I cannot take a chance and jeopardize a successful surgery with poor or incomplete postoperative care. Children over 5 consistently will allow me to do what is necessary to ensure the best surgical outcome by removing packing and cleaning and debriding the ear in the office. For the child not able to tolerate these office procedures, I must return the child to the operating room with the added risk of more general anesthesia.
I see no physiological advantage to repairing unilateral or bilateral atresia any earlier than age 5. If the child has bilateral atresia, the bone conductor is worn until the child is ready for surgery. The magnificent thing about the auditory system is that both sides of the brain receive auditory information from both ears, and the auditory information that goes to the opposite side of the brain crosses the midline very early (or soon) in the neural auditory pathway from the ear to the brain. Unlike the eye, where if the brain does not receive input from one eye (a “lazy” eye, or amblyopia) the eye is functionally blind, both sides of the brain learn to receive and process auditory information from both ears. So as long as one ear is working well (either a normal ear in unilateral atresia cases or an ear with a bone conductor in bilateral cases) the auditory centers on BOTH sides of the brain will develop normally. There is no advantage, as far as the auditory centers of the brain are concerned, in receiving auditory input from both ears as early in life as possible, as long as the brain is receiving auditory input from at least one ear. The advantages of binaural hearing, which is why we correct unilateral atresia cases, include better ability to hear when there is background noise (and we live in a very noisy world!) and the ability to locate sound in space. We are currently testing our unilateral atresia patients with special audiological tests before and after atresia surgery to validate and reinforce this statement.