The Congenital Ear
Repair of congenital microtia requires the coordinated efforts of both facial plastic surgeon and ear surgeon. Reconstruction of the microtic ear is usually delayed until the child is four to five years old. At that age, cartilage from the rib is used to reconstruct the external ear. Several operations may be necessary. The ear surgeon will usually delay reconstruction of the external auditory canal, (i.e. correction of the atresia), until the initial phases of the microtia repair are completed.
Microtia does not always occur along with atresia. Isolated atresia can occur in an ear which appears normal. Microtia repair falls under the province of the facial plastic surgeon, so a complete explanation of this surgery will not be offered here. Microtia is a most obvious abnormality. Any child with microtia should be seen early by an ear surgeon in order to coordinate the procedure between the facial plastic surgeon and ear surgeon. In addition, testing for hearing in both ears is indicated early, using Brain Stem Evoked Response Audiometry. This testing must be done early to determine the adequacy of hearing in the "normal" ear, as well as to confirm whether it is really normal.
Congenital artesia can occur without the usual congenital abnormalities of the external ear. Classically, however, atresias occur in conjunction with some deformity or microtia. The degree of microtia or external deformity does not always indicate the degree of abnormalities of the middle ear. A rough estimate of the degree of middle ear abnormalities can usually be made based on the degree of microtia, because both the external ear and the ear canal and bones of hearing occur in pregnancy at about the same time. The ear surgeon should be consulted early, although a commitment for a surgical procedure for correction of the child's atresia usually need not take place until the child is four or five years old.
Parental Reaction and Early Counseling
The birth of a child with an external ear deformity requires early counseling and intervention by the pediatrician who should refer to a team of facial plastic and ear surgeons. They can inform the family of future prospects. The fitting of a bone conducting hearing aid should also be an early decision, particularly in a child with bilateral atresia. If it seems that atresia is unilateral, that it is in one ear only, then the status of normal hearing in the opposite ear must be clearly established.
If normal hearing is determined, then hearing aid amplification is not necessary. These children will develop normal speech patterns without impairment and correction of microtia and atresia becomes an elective choice.
Assessment of the Deformity
Once the child's hearing status has been determined and the ear surgeon consulted, further evaluation is usually deferred until the child is older. In unilateral atresia, the confirmation that the hearing in the opposite ear is normal takes a great deal of pressure off the parents. We know that these children will develop normally. Evaluation for reconstruction can wait until the child is four years old.
In children with bilateral atresia, the anxiety level is significantly higher. Evaluation of the atresia and the development of the middle ear is usually conducted earlier.
CT Scan Findings
When the child is three or four years old, a CT Scan is generally performed. The CT Scan must be of high resolution. It should be performed by a radiologist who is very experienced with scanning the ear and temporal bone. The CT Scan results are extremely important.
In most cases of atresia (or lack of development of the external ear), there is a bony plate which separates the external ear from the contents of the middle ear where the bones of hearing are present. This bony plate varies in thickness. Also, in cases of complete atresia, there is no external ear canal present; there is a complete obstruction of the external opening by skin. Other cases of atresia may demonstrate a small rudimentary external ear canal which is just narrower and much thinner than usual.
Bones of Hearing
The bones of hearing can be properly evaluated as well by an accurate CT Scan. In most cases, the hammer and anvil malleus and incus are somewhat deformed. They may or may not be in contact with the stirrup or stapes bone lying underneath them. The position of the facial nerve is of great importance. The facial nerve follows a course out of the brain and through the temporal bone or bone of the ear. Generally, it courses through the middle ear below the bones of hearing and then exits into the face at the bottom of the mastoid bone which is the pointed tip of bone that is closest to the jaw joint behind the ear.
The facial nerve may be in normal position in cases of atresia. Often, however, it follows an abnormal course. A determination of this course becomes extremely helpful when the ear surgeon is advising parents about surgical reconstruction of the ear. Additional information regarding the formation of the inner ear, cochlea, and labyrinth (i.e. hearing and balance parts of the inner ear) are also obtained from the CT Scan.
The inner ear develops a little earlier in pregnancy. Thus, there may not be an abnormality of the inner ear structures in most cases of atresia. The development of the middle ear space and mastoid bone is also very important in the assessment of reconstructive potential A good estimate of the size and depth of the middle ear cavity can be obtained with the CT Scan.
Surgical Reconstruction: Assessment
The surgical reconstructive potential of congenital atresia is generally made after the CT Scan has been fully evaluated. The parents are advised on the potential for reconstruction, based on the degree of development of the child's middle ear, inner ear, and mastoid, as well as the position of the facial nerve and the relative absence of or deformity of the bones of hearing. The most important factor is the development of a good middle ear cavity, not necessarily the size or shapes of the bones of hearing themselves.
The ear surgeon will see and evaluate the child on a yearly basis until age four. At four, if there is a microtia, plans should have already been made by the facial plastic surgeon for reconstruction of the microtia. Coordination between the ear surgeon and the facial plastic surgeon is essential. Scarring could occur when the ear surgeon performs the initial stages. It could compromise the graft material introduced by the facial plastic surgeon.
Most surgical teams advise that the initial microtia repair be performed prior to the ear surgeon's correction of the atresia. The placement of the position of external ear canal must also be coordinated. Relative risks of the surgery versus benefits must be discussed at length with the family. This must be done prior to surgical intervention. No cases of atresia surgery are routine. Finding the unexpected is routine in these cases. Thus, the ear surgeon must give the family a realistic assessment of the potential for reconstructive success, as well as hearing in the involved ear or ears.