**3. Embryology and etiopathogenesis of CAA**

The mandibular (I) and the hyoid (II) branchial arches contribute to the auricular development, and both may be involved in the etiopathogenesis of CAA. Auricular pinna starts to develop between the third to sixth weeks of embryonic life, when hillocks appear on the arches, and its formation is complete at the fourth month of gestation. The basis of tragus, the helical root, and the superior part of the helix comes from the anterior three hillocks, derived from the first arch. The posterior hillock that derives from second arch is responsible for the formation of the antihelix, antitragus, and lobule. The middle ear cavity derives from the first pharyngeal arch starting from 4 weeks of gestation. The pinna develops around the external meatus which becomes canalized at week 28 of embryologic life. At 8 weeks the middle ear cleft is formed, and the cavity is complete developed at 30 weeks. The first arch cartilage generates malleus and incus by 8 weeks of gestation that start to ossify at the 4 months of pregnancy. From the second arch, cartilage comes out the stapes except the medial lamina of the footplate which derives from the otic capsule [10]. At week 9, ectodermal cells proliferate, fill the meatus lumen, and form the "meatal plug" (MP); then on week 10, the MP extends in a disclike fashion by following a horizontal plane, and the internal part of MP starts to thin for generating the future tympanic membrane. At the same time, the plug in the proximal portion of the neck starts to be resorbed. At week 13 the MP is in contact with the primordial malleus, and this contact will contribute to the thinness of internal part of MP that will create the tympanic membrane at week 15. At week 16 the external ear canal is fully patent but still narrow and curved. At week 18 the meatus is fully extended and starts its opening that will be completed at 28 weeks [11].

Any type of adverse event that occurs during the 4 and 25 weeks of gestation and interrupts one of more of these developments may be responsible for one of the different types of CAA. The adverse event may be related to genetic aberrations, vascular accident (fetal hypoxia), teratogenic substances (aminoglycoside antibiotics, hydantoin, alcohol, nicotine, herbicides), maternal infection (rubella, *Cytomegalovirus*, measles, hepatitis, toxoplasmosis, lues), and maternal metabolic disease (deficiency of thyroid hormone or diabetes) [12].

CAA may be a single malformation or be associated with other malformations as in the case of oto-facial dysostosis (Treacher-Collins syndrome, Goldenhar syndrome), craniofacial dysostosis (Crouzon syndrome, Apert syndrome), otocervical dysostosis (Klippel-Feil syndrome, Wildervanck syndrome), oto-skeletal

*Advances in Rehabilitation of Hearing Loss*

were the most appropriate treatment.

**2. Congenital auris atresia (CCA)**

these systems.

sible for the CCA [5].

the first goal in CAA followed, eventually, before the adolescent age by an esthetic reconstruction of the external ear [2]. In 1992 Jahrsdoerfer et al. [3] proposed a CT grading system for CAA that was shown to correlate with postoperative hearing outcomes, as a supporting method during the decisional process of treatment of CCA malformation; the suggestion of the author was to treat the high score of malformation with external canal bone reconstruction and eventually ossiculoplasty, while in the case of lower scores, the bone-anchored hearing implants (BAHIs)

Other more recent scoring systems as the Lübeck score have been proposed; this system is based on strong analyses conducted on high-resolution CT scan. The proposed method used a 16-score grading for addressing to the best ear implant [4]

In this chapter we discuss the CCA management with BAHIs by illustrating the different implants available on the market and the implantation method and finally reporting the results that we obtained in more than 10 years of experience with

Congenital aural atresia is an ear malformation that may have different severity and may affect the external ear only or the middle ear too. The ear malformation may be a single problem or be part of a syndromic picture. An altered development of the first and second branchial arches and the first branchial cleft may be respon-

Schuknecht [6] classified four degree of severity based on the combination of high-resolution computer tomography (CT) scan and surgical findings: (1) Type

*The image shows the four types of CAA as described by Schuknecht. In Type A, the yellow indicates the presence of the cholesteatoma behind the meatal stenosis. The gray areas in Types B, C, and D represent the portion with* 

*bone atresia. The red dot in type D shows the aberrant exit of facial nerve.*

that has the same efficacy as the Jahrsdoerfer et al. classification [3].

**74**

**Figure 1.**

dysostosis (Van der Hoeve-De Klein syndrome, Albers-Schonberg disease), and chromosomal syndromes (trisomy 13, 18, 21, and 18q syndrome) [2].

### **4. Indications to use BAHI in patients with CAA**

CAA is predominantly unilateral (ca. 70–90%) and the malformation mostly affects the right ear, perhaps because this side can suffer more frequently of hypoperfusion even rather that the left side in which the heart is located and that generally has a pressure 10 mmHg higher to the right side. The incidence of ear malformations is approximately 1 in 3800 newborns. Some children may present a bilateral CAA, when the malformation is not an isolated disease, but it is contextualized in a syndrome as, for example, CHARGE syndrome, in which children are affected by bilateral atresia up to 60% of cases [13].

Patients may be affected from different severity of external and middle ear malformation (**Figure 1**): due to the severity we can identify different forms of hearing loss. CAA typically results in conductive hearing loss (CHL) in 80–90% of the cases with the remaining patients demonstrating a sensorineural hearing loss (SNHL) component [10]. The CHL is typically in the moderate hearing loss range of 40–60 dB; this is the range in which BAHIs work better (**Figure 2**).

In the case of children suffering from unilateral CAA [14] and sensorineural hearing loss (10–20% of children with CAA), BAHI may be used for restoring the hearing function if the contralateral normal hearing function is preserved [15–17].

We use to utilize the Jahrsdoerfer et al. method during our decisional process for identifying the most appropriate surgery technique that has to be used. The authors proposed a CT grading system for CAA that was shown to correlate with postoperative hearing outcomes; based on the scores reached in the preliminary

#### **Figure 2.**

*The back image shows the ideal condition to use BAHI, while the supra-impressed yellow banana illustrates the distribution of vocal frequency. CHL that presents an auditory threshold within 45 dB may benefit from a BAHI because the implant guarantees a good recover of auditory functions in the range between 500 and 4000 Hz.*

**77**

**Table 2.**

**Table 1.**

*Congenital Aural Atresia: Hearing Rehabilitation by Bone-Anchored Hearing Implant (BAHI)*

patient evaluation, the authors proposed different surgical options. In the case of high scores (better option), a canaloplasty with eventual ossiculoplasty may be a good option for the treatment of CAA, while, in the case of low scores, the authors' suggestion is to use a BAHI [3]. Specifically, the authors concluded that the patient with a score of 8–9 is a very good candidate (80% chance to reach postoperative PTA threshold of 30 dB or lower) for surgical reconstruction of the auditory canal and the middle ear, while a score of 5/6 or less disqualifies patients for surgery. Furthermore, they identified that syndromic patients rarely present a grade higher

Anyway even in the case of success (**Table 2**), a surgical reconstruction presents a several postsurgical complication as stenosis of the new external auditory canal (15–20%), recurrent otitis externa (10%), sensorineural hearing loss (5%) cholesteatoma (2–4%), and facial nerve injury (0.1%), and often a hearing aid is necessary

**Parameter Points** Stapes present 2 Oval window open 1 Middle ear space 1 Facial nerve normal 1 Malleus/incus complex presence 1 Mastoid well pneumatized 1 Incus-stapes connection 1 Round window normal 1 Appearance external ear 1 Total available points 10

**Authors and year Number of patients Mean PTA ≤ 30 dB HL** Lambert, 1988 16 12 (67%) Bellucci, 1981 71 39 (55%) Mattox and Fisch, 1986 11 5 (45%) De la Cruz et al., 1985 56 41 (73%) Schuknecht, 1989 50 15 (50%) Jahrsdoerfer, 1992 126 61 (48%) Murphy et al., 1997 19 4 (21%) (20 dB) Teufert and De la Cruz, 2004 115 55 (48%) Digoy and Cueva, 2007 54 27 (50%) El-Hoshy, 2008 40 26 (65%) Yellon et al., 2011 19 8 (45%) Nadaraja et al., 2013 390 235 (60.3%)

*The experiences of different authors on the surgical reconstruction of external ear canal are reported.*

than 6/7 and, in general, are poor surgical candidates (**Table 1**).

*DOI: http://dx.doi.org/10.5772/intechopen.88201*

to allow a good hearing function [15, 18–21].

*The Jahrsdoerfer grading system of candidacy for CAA repair.*

#### *Congenital Aural Atresia: Hearing Rehabilitation by Bone-Anchored Hearing Implant (BAHI) DOI: http://dx.doi.org/10.5772/intechopen.88201*

patient evaluation, the authors proposed different surgical options. In the case of high scores (better option), a canaloplasty with eventual ossiculoplasty may be a good option for the treatment of CAA, while, in the case of low scores, the authors' suggestion is to use a BAHI [3]. Specifically, the authors concluded that the patient with a score of 8–9 is a very good candidate (80% chance to reach postoperative PTA threshold of 30 dB or lower) for surgical reconstruction of the auditory canal and the middle ear, while a score of 5/6 or less disqualifies patients for surgery. Furthermore, they identified that syndromic patients rarely present a grade higher than 6/7 and, in general, are poor surgical candidates (**Table 1**).

Anyway even in the case of success (**Table 2**), a surgical reconstruction presents a several postsurgical complication as stenosis of the new external auditory canal (15–20%), recurrent otitis externa (10%), sensorineural hearing loss (5%) cholesteatoma (2–4%), and facial nerve injury (0.1%), and often a hearing aid is necessary to allow a good hearing function [15, 18–21].


#### **Table 1.**

*Advances in Rehabilitation of Hearing Loss*

dysostosis (Van der Hoeve-De Klein syndrome, Albers-Schonberg disease), and

CAA is predominantly unilateral (ca. 70–90%) and the malformation mostly

Patients may be affected from different severity of external and middle ear malformation (**Figure 1**): due to the severity we can identify different forms of hearing loss. CAA typically results in conductive hearing loss (CHL) in 80–90% of the cases with the remaining patients demonstrating a sensorineural hearing loss (SNHL) component [10]. The CHL is typically in the moderate hearing loss range of

In the case of children suffering from unilateral CAA [14] and sensorineural hearing loss (10–20% of children with CAA), BAHI may be used for restoring the hearing function if the contralateral normal hearing function is preserved

We use to utilize the Jahrsdoerfer et al. method during our decisional process for identifying the most appropriate surgery technique that has to be used. The authors proposed a CT grading system for CAA that was shown to correlate with postoperative hearing outcomes; based on the scores reached in the preliminary

*The back image shows the ideal condition to use BAHI, while the supra-impressed yellow banana illustrates the distribution of vocal frequency. CHL that presents an auditory threshold within 45 dB may benefit from a BAHI because the implant guarantees a good recover of auditory functions in the range between 500 and* 

40–60 dB; this is the range in which BAHIs work better (**Figure 2**).

affects the right ear, perhaps because this side can suffer more frequently of hypoperfusion even rather that the left side in which the heart is located and that generally has a pressure 10 mmHg higher to the right side. The incidence of ear malformations is approximately 1 in 3800 newborns. Some children may present a bilateral CAA, when the malformation is not an isolated disease, but it is contextualized in a syndrome as, for example, CHARGE syndrome, in which children are

chromosomal syndromes (trisomy 13, 18, 21, and 18q syndrome) [2].

**4. Indications to use BAHI in patients with CAA**

affected by bilateral atresia up to 60% of cases [13].

**76**

**Figure 2.**

*4000 Hz.*

[15–17].

*The Jahrsdoerfer grading system of candidacy for CAA repair.*


#### **Table 2.**

*The experiences of different authors on the surgical reconstruction of external ear canal are reported.*

Based on our experience and according to the Jahrsdoerfer study, we can affirm that patients with CAA and a score of < 7 rarely benefit from an external and middle ear reconstruction with good functional results. In such cases, the implantation of a BAHI is a viable option for obtaining a stable, satisfactory, and long-term result in terms of hearing function recovery [18]. In conclusion we think that BAHI could be quite always the best method for restoring hearing function in patients with CAA, even in the case of high score in the Jahrsdoerfer grading system.
