Microtia is a pathologic condition of the external ear, wherein an affected individual is born with a grossly misshapen or absent external ear. It is frequently associated with aural atresia, or the absence of normal ear canal, tympanic membrane, functional ossicles and conductive hearing component.
Microtia is relatively uncommon, occurring in 7- 10,000 live births. It is more common on the right side than on the left, but can be bilateral. Prenatal maternal lifestyle is not associated with microtia.
Microtia is usually broken down into four categories:
- Grade I is a slightly small ear with identifiable structures and a small but present external ear canal.
- Grade II is a partially formed ear, usually with a closed off or stenotic external ear canal producing a conductive hearing loss.
- Grade III is the absence of the external ear with a small "peanut" skin and cartilage structure and the absence of the external ear canal and ear drum.
- Grade IV is absence of the total ear (anotia).
In addition to the severe psychologic effect of a grossly deformed ear, the child or adult with microtia has a moderately severe hearing loss. The patient routinely has an absence of the external ear (or pinna), an absent external canal and ear drum, as well as a small middle ear cavity with fusion of the small middle ear bones (ossicles) and an open (patent) eustachian tube, despite a normal inner ear. Therefore, these children have a maximum conductive hearing loss. Because it is critical for children to have normal hearing in order to have normal speech and bilateral hearing for the ability to detect directionality, the best treatment of microtia is to provide reconstitution of both the external ear and hearing.
The surgical intervention for correction of microtia/atresia at New York Eye and Ear Infirmary of Mount Sinai is performed utilizing a unique and rarely found team approach. Patients who present with microtia/atresia and/or associated hemi-facial deformities are evaluated by the microtia/atresia team of the Otology Center.
Each patient undergoes a thorough team approach evaluation to detect the level of external ear, external ear canal, middle ear and facial and bite deformities through the Otology Center and Facial Plastic Surgery service at New York Eye and Ear Infirmary. The workup for these patients consists of a hearing test, CT scan of the temporal bone to detect the exact course of facial nerve and delineation of the amount of middle ear and external canal deformity, and may include x-rays of the face and mandible to detect hemi-facial deformities and bite irregularities and ultrasound evaluation of the kidneys. Following this evaluation, treatment options are reviewed and recommended to the parents of the child with the ear deformity. Treatment of the microtia may or may not include surgery. Parents of children who do not want surgery can opt for an external prosthesis, which can be fixed to the side of the patient's face with titanium pins or glue. Patients who have the most common auricular deformity, Grade III, require a three to four stage reconstruction procedure performed over a one to two year period to achieve optimal surgical correction.
The primary procedure consists of harvesting cartilage from the sixth, seventh and eighth ribs on the side opposite the deformity. Great care must be taken to ensure adequate cartilage is harvested and preserved without injuring the underlying lung. The chest wound is then closed and a drain inserted. These cartilage pieces are then carefully carved and sutures are placed to form these slightly curved pieces into the complex, multiplanar shape and framework of a normal ear structure. The normal, contralateral ear is copied as closely as possible. A separate incision is made into the scalp overlying the normal position of the ear and a thin layer of scalp skin is carefully elevated in the exact spot the cartilage framework is to be placed; this location is generally determined by the position of the normal ear on the opposite side. At this time, the abnormal, malformed remnant ear cartilage and some skin are removed. The ear framework is then inset into a pocket behind the "peanut" skin vestige and the overlying skin is shrink- wrapped around the framework utilizing suction drains. At the same time, the remaining "peanut" vestige is rotated to form the earlobe. This procedure requires the patient to remain in the hospital two to three days. The patient is sometimes discharged home with the drains in place; these are removed one week postoperatively.
During the intermission between the first and second stages, the patient is encouraged to undergo laser hair removal, as the hair almost always grows down onto the skin that covers the upper part of the ear framework.
Three months after the first procedure (which allows time for the cartilage grafts to heal in place) the second stage is performed. This stage consists of lateralizing, or moving away from the side of the head, the cartilage framework. This is accomplished by elevating the framework away from the deep muscle and soft tissues (preserving a thin layer on the cartilage itself), and then placement of a skin graft and additional cartilage behind the framework to allow for permanent lateralization. This procedure generally does not require hospitalization. At this point, the patient has a relatively natural looking ear.
The third stage operation consists of a drill out procedure in which the external ear canal is actually created by the neuro-otologist. This canal is developed until the location of the bony tympanic plate is detected. The bony plate is removed and a new tympanic membrane or ear drum is made from muscle lining and this is connected to the middle ear ossicles. The newly formed canal is lined with a skin graft and attached to the external framework. This procedure requires the patient to be in the hospital for two to three days and is performed two to three months following the third stage. At this point the patient now has almost normal hearing and a natural ear framework on the side of the head. Alternatively, a bone anchored hearing aid (BAHA) can be placed to allow for hearing amplification without major surgery.
Additional steps may include customizing procedures, including construction of a preauricular tragus and any other finesse procedures needed to be done in order to make the reconstructed ear look as natural as possible. If a patient has an underlying maxillofacial or hemi-facial deformity, these procedures are performed by the oromaxillofacial surgeon during the first, second and third stages of the auricular reconstruction.