Friday, September 14, 2007

Microtia

I have not seen any microtia cases in my practice. Most of these, appropriately so, are sent to Children's Hospitals so that a team (ENT, Plastic Surgeons, Audiologist, Speech Therapist, etc) can take care of them. I do find it amazing that this reconstruction can be done so well by those like Dr. Charles Thorne who has a great website on Microtia. I suggest you visit his site (photo from his site).

Severe forms of microtia most likely represent arrests in embryonic development occurring at approximately 6-8 weeks of gestation. Less extreme forms are likely the result of embryonic accidents at a later stage, around the third month of fetal development. Even with extremely small microtic remnants, a lobular component is almost always present, although vertically oriented and superiorly displace. Anotia, the severest of ear deformities, is extremely rare and represents complete failure of development.


The incidence of microtia varies with the extent of the deformity. Severe abnormalities occur in approximately 1 in 7000 to 1 in 8000 births. The occurrence is estimated to be 1 in 4000 for Japanese and as high as one in 900 to 1200 in Javajo Indian. Microtia is nearly twice as likely in male as in females. The right-to-left-to-bilateral ratio is 5:3:1. Ear deformities frequently occur in families of patients with mandibulofacial dysostosis (Treacher Collins syndrome). Many patients with microtia have evidence of the first and second branchial arch syndrome (craniofacial microsomia). In previous studies it is thought that this is multifactorial and there is approximately a 6 % risk of recurrence in first degree relatives.


In 1977 Tanzer proposed a clinical classification of auricular defects which is often used in publications since that time. He classified the congenital ear defects according to the approach necessary for their surgical correction.

I. Anotia
II. Complete hypoplasia (microtia)
A. With atresia of external auditory canal
B. Without atresia of external auditory canal
III. Hypoplasia of middle third of auricle
IV. Hypoplasia of superior third of auricle
A. Constricted (cup or lop) ear
B. Cryptotia
C. Hypoplasia of entire superior third
V. Prominent ear


The term aural atresia refers to the absence of the ear canal. Patients who have microtia usually, but not always, also have aural atresia. Patients who have aural atresia have no hearing on that side but usually have completely normal hearing in the normal ear. Patients who lack the ear canal also have structural abnormalities of the middle ear with absence of the eardrum and incomplete formation of the small middle ear bones, which allow conduction of hearing through the middle ear. Microtia and aural atresia tend to occur together because the outer ear and the middle ear evolve from a common embryologic origin.

"In most patients the only issue which should be addressed early in childhood is an evaluation of the hearing. At What Age Is the External Ear Reconstruction Initiated? This is an important question, which is undergoing some evolution. Up until recently, surgical reconstruction of the outer ear was recommended beginning at the age of six years. At this age the patients were thought to have sufficient cartilage in the rib cage to allow reconstruction of the ear. As surgical techniques have improved, however, it is clear that a better quality, more detailed, ear reconstruction is possible when the surgery is delayed to after the age of ten years. "--Dr. Charles Thorne

There are four elements needed to create the appearance of a "real" ear--a flaplike shape, a helix, a concha, and a lobule. A lack of these essential elements cannot be made up by the addition of small details. Position is also of prime importance. Three key dimensions of correct position include 1) the inclination of the long axis of the pinna, 2) the level on the face (high or low), and 3) the distance from the orbit.

A variety of surgical strategies have been devised for the reconstruction of the external ear. The stages depend largely on the severity of the patient’s deformity; the size, position, and quality of the microtic elements; and the surgeon’s preference. Tanzer advocated a four-stage reconstruction. In the first stage, the lobular remnant was transposed transversely to its correct anatomic position. In the second stage, costal cartilage from the sixth, seventh, and eighth contralateral ribs, was implanted beneath the mastoid skin, using a V-shaped postlobule incision. The sixth and seventh costal cartilages were used for the base and antihelix, and the eighth costal cartilage became the helical rim. The carved cartilage elements were coapted with fine-gauge wire. In the third stage, the construct was elevated from the head by advancement of postauricular skin and placement of a retroauricular, full-thickness skin graft. The concha and tragus were later (fourth stage) created with composite contralateral ear and skin/cartilage grafts. Tanzer later modified this sequence by combining the lobular transposition and placement of the cartilage framework into one stage, prefacing this modification with the admonition that if extensive mobilization or surgical manipulation of the lobule is necessary, it is best to use four separate stages to avoid vascular compromise of the lobular element.

Brent uses a three-stage or four-stage technique, similar to that of Tanzer, although with a slightly varied sequence. In the first stage, a pattern for the construct is made by placing a piece of x-ray film against the normal ear and tracing its anatomic landmarks. The template is then reversed and made several millimeters smaller throughout to accommodate for the thickness of the skin cover. The lobular component is altered depending on the quality and amount of residual lobular tissue. Lobule transposition is the second stage in Brent’s technique. He believes it is safer and easier to position the lobular remnant around an established construct. This stage is performed several months after the initial cartilage grafting.The lobule is rotated and often filleted to receive the end of the framework. The construct is elevated in the third stage to achieve projection of the helical rim. The ear position is stabilized by placing a piece of banked costal cartilage posteriorly beneath the framework in a fascial pocket. The retroauricular scalp is then advanced to minimize visible scarring. The remaining postauricular defect is closed with a “medium-thick” split-thickness skin graft. Tragus construction, conchal excavation, and symmetry adjustment are performed in the fourth stage. The tragus is formed using a composite skin/cartilage graft from the contralateral conchal vault through an anterior approach.

Nagata’s technique involves two stages. It was first introduced in 1993 and has undergone several possible technical refinements, depending on the type of microtia present (ie lobular, small concha, anotia, low hairline).In the first stage, the rib cartilage framework, which incorporates a tragal component, is placed in a subcutaneous pocket and the lobule is transposed. This first stage thus roughly corresponds to the first three stages in Brent’s sequence. Nagata uses the skin of the posterior lobule and mastoid to cover the conchal aspect of the construct. By converting the V-shaped posterior lobule incision used by Tanzer into a “W,” he also increases the surface area of skin available to cover the framework. Six months later the second stage is done. The construct is elevated and symmetry adjustments made.


Complications arising from surgical efforts to reconstruct the external ear may occur both at the ear reconstructive site and at the donor sites for tissue harvest. The complications associated with costal cartilage harvest include the immediate problems of the pneumothorax and atelectasis and the delayed issues of chest wall deformity and scarring. Complications at the ear reconstruction site include exposure of the cartilage framework due to overlying skin flap necrosis. This can be devastating to the reconstruction and may necessitate the complete removal of the framework. In cases of flap compromise, early intervention is mandatory for salvage of the reconstruction. More commonly, small areas of skin loss (less than 1 cm) may be dealt with conservatively with topical and systemic antimicrobial therapy, allowing the area to granulate and heal by secondary intent. Infection is not a common complication (0.5 percent), but it may stem from either construct exposure or pathogens in the vestigial external ear canal. As such, careful assessment of any pathologic findings in the middle ear, such as otitis or cholesteatoma, and preoperative cleaning of the canal are imperative. Hematoma is an infrequent complication (0.3 percent), but its occurrence can have devastating consequences. Long-term complications in the reconstructed ear primarily relate to extrusion of suture material and resorption of the cartilage framework, which may alter the shape and form of the auricular components.

Recent advances in implantology and prosthetic materials have lead to excellent results using osseo-integrated anchoring devices and ear prostheses. The weak link in this technology lies in the quality of the prosthesis itself, the lifelike appearance of which is wholly dependent on the artistry and skill of the anaplastologist. Patients undergoing this approach have been generally quite satisfied with the prostheses and wear them daily and for prolonged periods without difficulty.



References
  • Surgical Procedures of the External Ear Canal and Ear; Dept. of Otolaryngology, UTMB, Grand Rounds; May 5, 1993; Kathleen McDonald M.D., Jeff Vrabec M.D., Melinda McCracken, M.S.
  • Total reconstruction of the auricle: The evolution of a plan of treatment; Plast. Reconstr. Surg. 47: 523, 1971; Tanzer, R. C.
  • Autogenous Rib Cartilage Reconstruction of Congenital Ear Defects: Report of 110 Cases with Brent's Technique; Plastic & Reconstructive Surgery. 104(7):1951-1962, December 1999; Osorno, Gabriel M.D.
  • Auricular Reconstruction: Indications for Autogenous and Prosthetic Techniques; Plastic & Reconstructive Surgery. 107(5):1241-1251, April 15, 2001; Thorne, Charles H. M.D.; Brecht, Lawrence E. D.D.S.; Bradley, James P. M.D.; Levine, Jamie P. M.D.; Hammerschlag, Paul M.D.; Longaker, Michael T. M.D.
  • Auricular Reconstruction for Microtia: Part II. Surgical Techniques; Plastic & Reconstructive Surgery. 110(1):234-251, July 2002; Walton, Robert L. M.D.; Beahm, Elisabeth K. M.D. (bottom two photo composites on technique from this article)
  • Refinements in the Elevation of Reconstructed Auricles in Microtia; Plastic & Reconstructive Surgery. 117(7):2414-2423, June 2006; Tai, Yoshiaki M.D.; Tanaka, Shinsuke M.D.; Fukushima, Junichi M.D.; Kizuka, Yuichiro M.D.; Kiyokawa, Kensuke M.D.; Inoue, Yojiro M.D.; Yamauchi, Toshihiko M.D.

1 comment:

Femail doc said...

I was driving recently and noticed a young male passenger in a car just ahead of me in the next lane over. Something not quite right about what I was seeing. I realized it was his tiny ear, and how just the glimpse of an ear too small made me take note. Correcting this one clearly makes a difference in first impressions made by patient. Interesting post.