**5. Management of patients with congenital microtia**

**3. Hearing level**

50 An Excursus into Hearing Loss

The pure-tone hearing average (average air conduction threshold at 0.5, 1, and 2 kHz) is used as a representative value for the hearing level, and the normal hearing range is generally defined as greater than 20 dB with an air-bone gap within 15 dB. We investigated the hearing levels for our patients with congenital microtia and compared these hearing levels with Marx's classification results (**Table 2**). Marx's classification scores did not show a correlation with the pure-tone hearing level. A previous report also found that the hearing level in

**Marx's classification Air conduction threshold (dB) Bone conduction threshold (dB) Air-bone gap (dB)**

Grade I 27.5 5.8 21.7 Grade II 60.9 12.8 48.1 Grade III 76.8 11.9 64.9

Facial nerve palsy and chorda tympani are also known to occur in some cases of congenital microtia. In our study [5], facial nerve paralysis (House-Brackmann grade more than III) and change in taste detection threshold due to chorda tympani nerve dysfunction were found in 8 and 10% of patients with microtia, respectively. We found that chorda tympani nerve dysfunction did not correlate significantly with the anatomic structure of the ear anomalies based on Jahrsdoerfer scores. On the other hand, facial nerve paralysis was significantly correlated with the presence of a malleus-incus complex, a pneumatized mastoid, an incus-stapes connection, and an external auditory canal, and facial nerve paralysis patients had a higher

The facial nerve canal arises initially as a sulcus in the cartilaginous otic capsule, and ossification begins from two distinct sites, such as anteriorly near the apex of the cochlea and posteriorly at the pyramidal eminence, at 20 and 25 weeks' gestation, respectively. The bone progressively covers the facial nerve, and the process is usually complete by 3 months after birth. Since the mastoid process and tympanic ring grow after birth, they displace the nerve medially. Therefore, the development of the facial nerve is closely related to the development of the middle ear and the mastoid process. Meanwhile, the chorda tympani branches from the facial nerve at 5 weeks' gestation and subsequently separates the stapes primordium and the incus primordium from the hyoid visceral bar. Unlike the facial nerve, the chorda tympani in the middle ear is not encased by a bony wall. This early branching and development of the chorda tympani may be one of the reasons why our study did not show a significant correlation between chorda tympani nerve dysfunction and facial nerve paralysis; 83% of patients

microtic ears does not correlate with the degree of microtia [7].

**4. Facial nerve and chorda tympani nerve palsy**

**Table 2.** Average hearing level in patients with microtia.

Jahrsdoerfer score than the chorda tympani nerve dysfunction patients.

Because approximately 20–60% of patients with congenital microtia are known to have associated anomalies or an identifiable syndrome [8], patients with microtia should be examined for other dysmorphic features. In our patients, although there were no cases complicated by anomalies in the kidney and spine, there were some children complicated by esophageal atresia, ventricular septal defect, funnel chest, and cleft lip and palate. Especially, symptomatic microtia, which includes Goldenhar syndrome, hemifacial microsomia, trisomy 21, trisomy 18, and Treacher Collins syndrome, may have additional associated congenital anomalies.

Gorlin et al. [9] proposed an encompassing term "oculo-auriculo-vertebral spectrum (OAVS)," which is characterized by facial asymmetry, microtia, ear and facial tags, epibulbar dermoids, microphthalmia, and macrostomia. Hemifacial microsomia, Goldenhar syndrome, and all of its associated anomalies and variations are thought to be included in this spectrum. Extracranial features include renal, cardiac, and vertebral anomalies; at present, there is no consensus on the minimal diagnostic criteria for OAVS [10]. OAVS and microtia share the following characteristics: (1) variable phenotypic expression, (2) asymmetric involvement of facial structures, (3) right-side preponderance, (4) male predilection, and (5) familial occurrence of microtia or related anomalies, such as preauricular tags and pits [10]. Thus, isolated microtia represents a milder phenotype of OAVS.

The clinical expression of congenital microtia and OAVS overlap; hence, clinicians should consider multiple medical assessments when examining patients with microtia. First, all patients with microtia should have a diagnostic ear-specific hearing assessment within the first 6 months of age, to identify hearing loss and to assess the type and severity of hearing impairment. In children with conductive hearing loss, high-resolution CT examination of the temporal bone is useful for evaluating the middle and inner ear structures when the child is of preschool or school age. Renal ultrasound, cardiovascular examination at diagnosis, and cervical spine films at the age of 3 years are also recommended [11]. Treatment for atresia should be considered in the context of hearing, speech and language development, and reconstructive surgery at approximately 10 years of age.

Since lack of landmarks, abnormal anatomies of the facial nerve and middle ear structures, and limited space for sound reconstruction, surgical correction of hearing improvement is sometimes difficult and challenging. Therefore, not only surgery but also hearing acquisition through the use of a device should be considered. To date, osseointegrated implants known as bone-anchored hearing aids (BAHA® by Cochlear) and active middle ear implants known as Vibrant Soundbridge® (VSB by Med-El) have been the most reliable method of hearing habilitation. These devices have been shown to improve hearing outcomes and quality of life in patients with microtia who might not otherwise benefit from traditional hearing aids. However, in order to use these implants, patients need to underwent surgery, and the portion of the implant exposed to open air has a risk of infection.

**Pharyngeal pouch:** Saclike diverticula that formed on the endodermal side between the pha-

Hearing Loss in Congenital Microtia http://dx.doi.org/10.5772/intechopen.72429 53

**Mesenchyme:** A type of undifferentiated connective tissue comprised of loose cells embed-

**Otic capsule:** The cartilage that surrounds the developing otic vesicle and develops into the

Department of Otolaryngology, Sapporo Medical University, School of Medicine, Sapporo,

[1] Luquetti DV, Leoncini E, Mastroiacovo P. Microtia-anotia: A global review of prevalence rates. Birth Defects Research Part A: Clinical and Molecular Teratology. 2011;**91**:813-822

[2] Harris J, Kallen B, Robert E. The epidemiology of anotia and microtia. Journal of Medical

[3] Okajima H, Takeichi Y, Umeda K, Baba S. Clinical analysis of 592 patients with microtia.

[4] Takano K, Takahashi N, Ogasawara N, Himi T. The association of external and middle ear anomaly and mandibular morphology in congenital microtia. Otology & Neurotology.

[5] Takano K, Takahashi N, Ogasawara N, Yotsuyanagi T, Himi T. Chorda tympani nerve dysfunction associated with congenital microtia. Acta Otorrinolaringológica.

[6] Jahrsdoerfer RA, Yeakly JW, Guilar EA, Cole RR, Gray LC. Grading system for the selection of patients with congenital aural atresia. The American Journal of Otology.

[7] Ishimoto S, Ito K, Karino S, Takegoshi H, Kaga K, Yamasoba T. Hearing levels in patients with microtia: Correlation with temporal bone malformation. The Laryngoscope. 2007;

Acta Oto-Laryngologica. Supplementum. 1996;**525**:18-24

**Primordium:** An organ or part in the earliest recognizable stage of development

**Microtia:** A congenital malformation of variable severity of the ear

ryngeal arches

**Author details**

Kenichi Takano

Hokkaido, Japan

**References**

ded in the extracellular matrix

bony labyrinth of the internal ear

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Address all correspondence to: kent@sapmed.ac.jp

More recently, a new hearing device utilizing cartilage conduction has been developed [12]. Since the transducer is not necessarily fixed with pressure, the attachment causes no pain, unlike conventional bone conduction. Moreover, this cartilage conduction device does not require surgery. Cartilage conduction hearing aids have a potential as a useful amplification device for patients with congenital microtia and aural atresia.
