What Causes Hearing Loss?
AURAL ATRESIA means lack of an ear canal. Most children born with microtia also have atresia. Luckily, these children usually have a normal inner ear and hearing nerve (cochlea), which means they are not deaf. Instead they have conductive hearing loss which can be treated by Dr. Bonilla as well.
Aural Atresia (no ear canal)
The left ear has a full aural atresia with absence of the ear canal.
Aural Stenosis (narrowed)
The right ear has a narrowed ear canal but is not closed.
Is a child with microtia deaf? In almost all cases, the answer is no. Why? During in-utero development the outer ear and middle ear form at about the same time. When there is a severe congenital malformation of the outer ear, such as a microtia, then there is usually a malformation of the middle ear as well. Most of the time, the middle ear malformation consists of fused or malformed middle ear bones, a smaller middle ear cavity and an abnormal course of the facial nerve.
Luckily, the inner ear (the location of the hearing and balance organs) forms at a different time as the outer and middle ears. As a result, the inner ear functions at a normal level, even in a child with a microtia. So when someone asks whether your child is deaf, the answer almost always is usually no.
When hearing loss occurs because of an outer or middle ear problem, this is called conductive hearing loss. When hearing loss occurs because of an inner ear problem, this is called sensorineural hearing loss.
In conclusion, a child with a microtia will usually have normal sensorineural hearing and moderate to severe conductive hearing loss. All this means is that the child’s inner ear is normal (normal sensorineural status), but because there is no ear canal, there is no way for sound to “conduct” to the inner ear via the ear canal. As a result, there will be conductive hearing loss.
HOW HEARING WORKS
One of the most viewed videos worlwide explaing how hearing works in children with microtia.
(please note that newer hearing options are now available)
ANATOMY DEMONSTRATION ON AN EAR MODEL
TREATMENT OPTIONS FOR HEARING LOSS
Option 1: No Treatment
This is an option for a child born with unilateral (one-sided) microtia and atresia. Many years ago, this was a common option for several reasons. The first was the worry of risking damage to the facial nerve (the nerve that controls the movements of the face). With much advancement of CT scan technology and facial nerve monitoring during surgery, now it is much easier to evaluate the anatomy of the facial nerve, middle and inner ear. With this important knowledge, now surgeons can discuss whether a child is a good candidate, medium candidate or poor candidate for ear canal surgery. If a parent decides to give a child with unilateral microtia the option of waiting for hearing correction later, it is hard to argue that choice. There MUST be excellent communication between the surgeon and the parents.
“Doing nothing” is NOT a choice on a child with bilateral (both sides) microtia and atresia. These children have severe hearing loss on both sides and must be aided with a bone conduction hearing device.
Option 2: Ear Canal Surgery (Atresiaplasty)
Atresioplasty is a very complex surgical procedure which entails using a specialized drill to burr through the bone behind the microtia to form an ear canal. Once the ear canal is drilled, a skin graft is then placed to line the ear canal and the new eardrum.
Before an atresiaplasty is recommended, a high-resolution CT scan of the temporal bone is performed. There are various grading classifications to determine if a child is a candidate for ear canal surgery. The main factors in determining if a child is a candidate for this type of surgery are:
- Middle ear and mastoid pneumatization
- Anatomy of the ossicles (middle ear bones)
- Inner ear morphology
- Course of the facial nerve
The most common risk of the atresiaplasty is re-narrowing of the new ear canal. The most dangerous risk is actual damage to the facial nerve (although the risk should be low in experienced hands). Therefore, this procedure should only be performed by an experienced otologist.
Option 3: Bone-Conduction Hearing Processors
A child with severe conductive hearing loss due to microtia and atresia can have the ability to hear by simply placing a device on the skull that vibrates with sound. The sound is transmitted directly to the inner ear hearing nerve via vibration.
Children with microtia who are less than 5 years of age and are not yet ready for an implant, can use a vibrating hearing processor through a Softband. This consists of a soft elastic headband with a plastic snap connector that holds the hearing processor in place. The two most common brands are 1) Cochlear America 2) Oticon.
A newer bandless option is also available: Med-El “Adhear):
Dr. Bonilla strongly believes that bone-anchored hearing aid surgeries should be performed ONLY by Board-Certified Otolaryngologists who are trained in hearing disorders and can manage any possible complications during surgery.
Because of Dr. Bonilla’s training and experience in pediatric hearing surgeries, he routinely implants the bone-anchored hearing aids during the microtia surgery.
If the patient chooses to have a surgically implanted hearing device instead of the nonsurgical softband, these are the most common bone-anchored devices placed implanted in surgery:
Cochlear Attract Magnet
(no visible abutment)