3D CT images are extremely important in the accurate assessment of the development of the middle ear space and the state of middle ear ossicles. If the middle ear space is totally or almost completely absent, then surgery is usually not advisable.
Atresia left ear
Congenital atresia is the lack of development of the external ear , there is a bony atresia 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.
Atresia left external ear but normal inner ear
In most cases, middle ear ossicles-malleus, incus and stapes- are somewhat deformed. They may or may not be in contact with the stapes bone lying underneath them.
The position of the facial nerve is of great importance. It may sometimes follow an abnormal course. A determination of this course becomes extremely helpful when the ear surgeon is advising parents about surgical reconstruction of the ear.
Normal left inner ear
The inner ear develops early (completed by 4th month) in pregnancy. Thus, there may not be an abnormality of the inner ear structures in most cases of atresia.
Deformed ossicles left ear
About congenital atresia and Microtia
Congenital Atresia, the absence of the external ear canal, is a birth defect which is almost always accompanied by abnormalities of both the middle ear bones in various degrees, as well as the external ear.
The degree of hearing loss brought about by the atresia must be evaluated immediately. If both ears are affected, early hearing aid fitting is called for. Using a bone type of hearing aid which bypasses the obstruction, vibration on the bone allows for normal development of speech in the child.
Microtia
Congenital Microtia, also a birth defect, is an abnormal condition in the growth of the external ear. They can vary from minor abnormalities of the helical ear folds to a marked absence of ear development. The presence of a small tag of skin and cartilage may be the only indication of an external 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.
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.
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.
Surgical correction-
1-Making an ear canal
The plug of solid bone is drilled away by utilizing an air drill. Ear surgeons use the high power operating microscope and diamond dust burrs which gently free the bones of hearing from the bone of the ear canal Once the bones have been fully freed and the middle ear space exposed, the raw surfaces of the bony ear canal must be relined with a skin graft or the ear will close down in a scar.
2-Making an ear drum
A very thin skin graft is generally harvested from behind the ear, is thinned and utilized to create a new eardrum. The facial graft is placed directly on the bones of hearing.
3-Middle ear Reconstruction
Reconstruction of the middle ear may be essential as there is no connection between the hammer and anvil (malleus and incus) and the underlying stapes bone. In addition, these bones may have different degrees of abnormal development, requiring removal and eventual replacement. All attempts are made to reconstruct at the primary procedure if possible.
The position of the facial nerve is continuously monitored with a facial nerve monitor. It is vital to identify the position of the nerve. This is routinely performed in order to avoid damage to it. The external ear canal is then generally packed with firm balls of gelatin sponge and silicone sheeting. When the operation is completed, the external ear canal should be completely covered by skin graft.
Alternative to surgery
Alternatives to surgery include no intervention in a unilateral or one sided atresia, or use of a bone-implantable hearing aid into the mastoid bone behind the external ear.
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