Microtia and Other Congenital Auricular Deformities

and Emir Q. Haxhija2



(1)
Department of Plastic Surgery and Burns, Institute for Mother and Child Health Care of Republic Serbia, University of Belgrade, New Belgrade, Serbia

(2)
Department of Pediatric and Adolescent Surgery, Medical University Graz, Graz, Austria

 



Keywords
MicrotiaCorrectionChildren



3.1 Introduction


A child with malformed ear often attracts attention from curious playmates (usually at 4 or 5 years of age when body image relating to face develops), and very often the child faces rejection, teasing, and name-calling [1, 2]. Early surgery for the deformity is desirable for the child psyche, but it is in vast majority of cases technically impractical [1].

Ear deformities can be classified into anotia, complete hypoplasia or microtia (with or without atresia of external auditory canal), hypoplasia of middle third of the auricle, hypoplasia of superior third of the auricle (constricted ear, cryptotia, hypoplasia of entire superior third), and prominent ear [1, 3]. Other ear anomalies also occur with variable incidence and different treatment options [1, 39].


3.2 Embryology


The auricle, the auditory canal, and the middle ear originate from the first and second branchial arches [1]. At the end of the fifth and the beginning of the sixth embryonic week, mesenchymal proliferation of the first and second branchial arches develops six surface irregularities (hillocks) which fuse into the definitive ear [1, 4]. In case of incomplete fusion, malformation of the external and/or middle ear can occur [1, 3, 4]. External and middle ear has same embryonic origin (microtia is accompanying with anomalies of middle ear), and the inner ear is almost always normal in patients with microtia since it has different embryonic development [3]. The hearing loss in microtia/atresia is conductive in nature [1, 3, 6].


3.3 Anatomy


The structures that formed the auricle are helix, the antihelix, the antihelical scapha, the antihelial crura, the tragus, the antitragus, the cavum conchae, the cymba conchae, and the lobule [3, 79]. Fibroelastic auricular cartilage is medially covered by the connective tissue and skin and laterally covered by skin only, and the lobule itself is mainly composed of adipose and connective tissue [3].


3.4 Microtia


Microtia is severe hypoplasia of external ear with variable deformation of auditory canal [14, 7, 8, 1018].

The incidence of microtia is between 1 in 6000 and 8000 live births [2, 8, 12]. The incidence is low among Caucasians and it’s high in Japanese and among American Indians [1, 8, 15]. Microtia is unilateral in vast majority of cases (80–90%); the right side is involved more often than the left, and boys are affected more often than girls [1, 2, 7, 8].

Microtia is probably multifactorial in etiology with environmental and genetic factors involved, and it counts as a part of the spectrum of hemifacial microsomia deformities (maldevelopment in the first and second branchial arches) [1, 7, 12]. Microtia can be associated with other deformities such as facial skeletal asymmetries, facial nerve paralysis, cleft lip and palate, cardiac anomalies, and urinary tract anomalies [1, 3, 7, 8, 15].

Gilles is credited with the first use of rib cartilage for construction of an auricular framework in 1920, and Tanzer reintroduced the technique of autogenous costal cartilage grafts as a method of auricular reconstruction in 1959 [2, 11, 12]. Brent and Nagata techniques are most widely used for auricular reconstruction, followed by Firmin, Park, and Siegert modifications of these techniques [1, 3, 7, 8, 12, 13, 1517].

Patients with unilateral microtia/atresia usually have normal hearing on the contralateral ear, and hearing rehabilitation in these patients can include observation, band-retained bone conduction sound processor, osseointegrated implant-retained bone conduction sound processor (after 5 years of age), and atresiaplasty [1, 3, 68, 15]. Patients with bilateral microtia/atresia usually have serviceable hearing, and these patients should be fitted with a bone-conduction hearing aid as early as possible in life [1, 3, 68, 15]. Computerized tomography (CT) of temporal bone has to be performed at about 4 years of age prior to surgical treatment [15].

Canal construction (atresiaplasty) and tympanoplasty in children with microtia should be performed only in cases with hearing loss in the contralateral ear or in cases of bilateral microtia, and it is performed in most cases after the microtia reconstruction [1, 7, 15]. Recently some authors proposed that atresiaplasty can be performed before or simultaneously with the microtia reconstruction [15].


3.4.1 Classification


The microtia deformity itself is enormously variable [3]. The most common variety of microtia involves an irregular cartilage remnant with an associated small vertical earlobe with absent auditory canal [1, 3, 4, 8]. There are several classification of microtia derived from any authors: Nagata, Brent, Fukuda, Muerman-Marks, Asse, Firmin, and Marx (Rogers modification) [1, 3, 8, 12, 15].

According to Nagata classification, there are five types of microtia: lobule type (the patient has an ear remnant and malpositioned lobule but has no concha, acoustic meatus, or tragus), concha type (the patient presents with ear remnant, malpositioned earlobe, concha, tragus, and antitragus with an incisura antitragica), small concha type (the patient presents with an ear remnant, malpositioned earlobe, and a small indentation instead of concha), anotia (the patient is present with no, or only a minute, ear remnant), and atypical microtia (the patient presents with deformities that do not fit into any of the above categories) (Fig. 3.1a–d) [1, 7, 8, 12, 15]. There is a four-grade classification proposed by Marx (modified by Rogers), detailed classification of microtia proposed by Firmin, and also a classification of hemifacial microsomia associated with microtia proposed by Mulliken et al., named OMENS (Orbital asymmetry, Mandibular hypoplasia, Ear deformity, Nerve involvement, Soft tissue deficiency) [7, 11, 15].

A393954_1_En_3_Fig1_HTML.gif


Fig. 3.1
Different types of microtia: (a) lobule type; (b) anotia; (c, d) atypical microtia


3.4.2 Patient Evaluation


These patients are usually seen within the first 12 months of age, and parents are instructed to return annually until the age for surgery [8]. The recommended age for surgery is at least 6 years, and in most cases, it is around 10 years of age [6, 8, 15]. Alloplastic reconstruction is possible from 3 years of age [15]. Preoperative photographs are obtained, and normal ear side is evaluated (position and anatomy of normal ear), since it is the model for opposite side [1, 3, 7, 8, 14, 15]. At opposite side with microtia, we examine the skin quality, presence of external auditory canal, hair line position, and scar presence [7, 8, 14]. During the exam, the chest wall has to be checked in every detail, and we need to establish any deformity that may complicate chondral graft taking [1, 3, 7, 11, 15]. Treatment options should be discussed with the patient and parents [3, 8, 15].


3.4.3 Surgical Reconstruction


Indications for surgical treatment are aesthetic, functional, and psychosocial [15]. Reconstruction of the architectural structure of the auricle and the projection of auricle are two important topics in this surgery [13, 68, 1015]. There are three options for auricular reconstruction of microtia: autogenous reconstruction, composite autogenous/alloplastic reconstruction (using an alloplastic ear framework), and prosthetic reconstruction [14, 68, 1018]. Reconstructed ear in the long term is usually more bulky with lack of the flexibility of the normal ear [7].


3.4.3.1 Autogenous Reconstruction


This is the most widely used approach [13, 7, 8, 11, 13, 15, 17]. Two techniques for autogenous reconstruction of the auricle, using a rib cartilage framework, described by Brent and Nagata were dominant for a long period of time [1, 3, 7, 8, 12]. Firmin adopted Nagata’s two-stage approach and modified it, and Park used a three-stage procedure for patients with microtia, with tissue expansion during the first stage [7, 1113, 18]. Siegert and colleagues also described a technique for microtia reconstruction [15]. The Brent technique involves four stages: creation and placement of a rib cartilage auricular framework, rotation of malpositioned ear lobule into the correct position, elevation of the reconstructed auricle, and deepening of the concha with creation of the tragus [3, 7]. The Nagata technique encompasses two stages [3, 8, 15]. The first stage is performed not earlier than 10 years of age (chest circumference at the level of the xiphoid has to be at least 60 cm) [8, 12]. In the first stage, creation of costal cartilage framework is performed, including the rotation of the lobule into the correct position [7, 8, 12, 15]. The second stage involves elevation of the reconstructed ear and creation of retroauricular sulcus [7, 8, 12, 15, 18].


3.4.3.2 Preoperative Marking


The location of the earlobe on the normal side is transferred to the affected side (reconstructed ear has to be in symmetrical position with unaffected ear) [7, 8, 14]. The normal ear is traced on the x-ray film, thin plastic film, or paper pattern and sterilized, and by using these tracing, a template of the desired framework is fashioned, it’s reversed, and framework pattern is designed for the new ear [3, 7, 8, 14, 15]. An acrylic or plaster replica of normal ear can also be used (Fig. 3.2a–c) [3]. The exact location and orientation of the desired auricle are drawn on the patient [3, 7, 8, 11]. Different incisions on the skin are made depending on the technique that is used; cartilage remnant is removed preserving the skin, and the pocket is dissected beyond the outline of the eventual auricle [3, 7, 8, 11, 13, 1518].
Oct 28, 2017 | Posted by in Pediatric plastic surgery | Comments Off on Microtia and Other Congenital Auricular Deformities
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