Bangalore, India

Visualization of the fetal ear is not a part of the routine assessment, and hence has received little attention in the ultrasound literature. It should be attempted in cases with fetal anomalies, in particular those of the face, as this could help in the differential diagnosis.

Embryology: The external ear consists of:

1. Auricle
2. External acoustic meatus

The auricle arises from a series of elevations termed 'auricular hillocks' around the first pharyngeal cleft. Three elevations on the first pharyngeal arch (mandibular arch) and three elevations on the second pharyngeal arch (hyoid) are seen at 6 weeks. The hillocks are transitory and soon lose their identity to contribute to the various parts of the external ear. At first the auricles are ventrolaterally placed but at the end of the embryonic period they have assumed a dorsolateral position.

The external acoustic meatus arises as a 'key-hole' between the auricular hillocks, which forms the future cartilaginous portion of the meatus. The osseous portion canalizes from a meatal plug of epithelial cells, the medial end of which forms the external layer of the tympanic membrane.

Anatomy

Types of malformations

Malformations of the external ear may be related to:

Abnormal ear shape

Adherent lobule Auricular appendage Ear-lobe groove

Ear cleft Darwinian tubercle Misshapen ear

Malformations of the auricle and bony meatal atresia are often combined and may be associated with anomalies of the middle and internal ear. They often form part of many chromosomal anomalies and syndromes. A brief account of these is presented.

1.      Microtia

Definition: Microtia means small ears. The condition may range in severity from uncomplicated hereditary microtia transmitted as a dominant and rather harmless trait[1] to severe forms with conductive hearing loss.  

Etiology: Non-syndromic microtia has an autosomal dominant transmission in a minority of families[2]. Isolated microtia is uncommon.

Pathogenesis: Abnormal development of the first and second branchial arches. 

Associates anomalies: Commonly associated with the following:

1.1.       Hemifacial microsomia:

The term was first described by Gorlin and Pinbord to describe a condition consisting of unilateral microtia, macrostomia and failure of formation of the mandibular ramus and condyle. The minimal diagnostic criteria and phenotypic spectrum of the variants are:

1.2.       Microtia-anotia

Definition: Deformed or absent pinna with an atretic ear canal. Most forms  are associated with conductive hearing loss.

Inheritance: Autosomal dominant vs. multifactorial. Gupta et al[3] described large kindred with autosomal dominant inheritance of congenital microtia and auditory meatal atresia with conductive deafness. Five generations were affected. Microtia-anotia can occur either as an isolated defect or in association with other defects. Only in a minority of cases has a genetic or environmental cause been found. In these cases, microtia-anotia is usually part of a specific pattern of multiple congenital anomalies. For instance, microtia-anotia is an essential component of isoretinoin embryopathy, is an important manifestation of thalidomide embryopathy, and can be part of the fetal alcohol syndrome and maternal diabetes embryopathy. Microtia-anotia occurs with a number of single gene disorders, such as Treacher-Collins syndrome, or chromosomal syndromes, such as trisomy 18.

Other conditions that may be frequently associated with microtia include:

Three images of the ear of a fetus with Townes syndrome

6.      Dysplastic ear

Definition: Abnormally shaped auricles. Usually  associated with chromosomal anomalies:

• Diastrophic dysplasia (see also) : has a 'cauliflower deformity' due to cystic degeneration of the pinnae of the ear.

• Antley-Bixler syndrome: Dysplastic ears with hypoplasia, brachycephaly, radiohumeral synostosis, and joint contractures.

• Trisomy 13-15: underdevelopment of tragus and lobule.

• Anencephaly: large and fleshy and sometimes folded.

• Mandibulo-facial dysostosis (Treacher-Collins): ears are small and hypoplastic, 'crumpled' and shaped like a shell with no helix or anti-helix.

Dysplatic ear with micrognathia in Nager syndrome

"Elfin" pointed ears (cerebellar anomaly)

7.      Lobe malformations

• Adherent lobe: frequent variation that occurs less often in men than in women.

• Absent lobe: seen in Seckel syndrome.

• Cleft lobe (coloboma): longitudinal cleft of lobe which may be partial but usually extends to but not through , the incisura intertragica.

Auricular cleft (a different entity from the cleft lobe), in a fetus with holoprosencephaly.

• Hypertrophied, thickened lobe: lobe disproportionately large for the overall ear size, is thickened and feels fibrotic in the center. May be associated with hearing loss and secondary speech disorder.

• Wolf-Hirschhorn syndrome: distal deletion of the short arm of chromosome 4 and is characterized by growth deficiency, mental retardation, a distinctive "greek-helmet†facial appearance, microcephaly, ear lobe anomalies, and sacral dimples[13].

• Beckwith-Wiedemann syndrome: a rare genetic overgrowth syndrome presenting with organomegaly, abdominal wall defects, macroglossia, and postnatal hypoglycemia. Head and neck manifestations of this abnormality include flame nevus of the forehead and characteristic sulci of the ear lobe.

8.      Melotia

Definition: Ear located on the cheek.

Pathogenesis: May represent lack of aural ascent due to underdevelopment of the auricle. There is also the embryological evidence, that melotia represents extraordinary big preauricular appendages[14].

9.      Low-set ears

Definition: An ear that is set below an arbitrary line drawn between the lateral canthus of the eye and the occipital protruberance is considered low-set.

Etiology: probably multifactorial.

Associated anomalies: Commonly associated with the following

• Noonan syndrome: webbing of the neck, pectus excavatum, cryptorchidism, pulmonary stenosis. Ears are low-set with or without abnormal auricles. 25% have mental retardation. Koretzy et al. described an unusual type of pulmonary valvular dysplasia which showed a familial tendency with either affected parent and offspring or affected sibs. Other features were retarded growth, abnormal facies (triangular face, hypertelorism, low-set ears and ptosis of the eyelids)

• Pena Shokeir phenotype: Neurogenic arthrogryposis, pulmonary hypoplasia, hypertelorism with low-set malformed ears. 30% are stillborn. Majority of those liveborn die within the first month of life^[15].

• Trisomy 18: Clenched hand, short sternum, low arch dermal ridge patterning on fingertips and low-set malformed auricles. Only 5% to 10% survive the first year as severely mentally defective individuals.

Low set ear in renal agenesis

10. Synotia

Definition: In Agnathia-Synotia-Microstomia, the ears are very close to each other due to absence or hypoplasia of the mandible. The external ears assume a horizontal position with the lobules located near the midline. Severe degree is found in the cyclopia series.

"Bow-tie" ear due to failure of migration in Agnathia-Synotia-Microstomia

11. Auricular fistula

Definition: Blind-ending narrow tubes or pits. Most are harmless, occasionally they can get infected, form retention cysts and cause chronic discharge.

Etiology: Autosomal dominant inheritance with variable expressivity and incomplete penetrance. Many occur sporadically and are associated with hereditary deafness. Report of large kindreds such as that of Bhalla et al , in which there are no associated features or lateral cervical sinuses suggests that this is a distinct mendelian dominant. The pedigree was traced through seven generations indicated in the expression of the occurred bilaterally as a small pit just anterior to the crus at the root of the ascending helix. The abnormality was found to be inherited through an autosomal dominant gene with incomplete penetrance[16].

Incidence: 0.9% in European populations.

Locations:

• Anterior margin of the ascending limb of the helix.

• Center of the lobule "natural earring holeâ€

• Colloaural: from the floor of the external meatus down to the angle of the mandible.

12. Auricular appendages

Definition: tags of skin with or without a cartilaginous base frequently located in the line of junction of the mandibular and hyoid arches. This is a common malformation occurring in approximately 1.5% of the population. May be sessile or pedunculated.

Sites of location:

·                    In front of the auricle

·                    Within the ear

·                    Behind the ear

·                    On the lobule

Appendages on the cheek between the auricle and the angle of the mouth are often associated with microtia, melotia or oblique facial features. True polyotia seems to be extremely rare and has been reported by Bol and Dekleyn (Acta otolaryng 1:187,1918)

Darwinian tubercle: a small projection from the descending part of the helix. Darwin regarded this variation as a remnant of the pointed ears of some arthropods.

13. External acoustic meatus

Atresia: may be of the osseous or membranous portion. Seen in  severe cases of mandibulo-facial dysostosis.

Duplication: Blind ending accessory canal above or below the canal which leads to the drum.

Septa: dividing the external meatus.

References:

[1] Potter E. L:A hereditary ear malformation transmitted through 5 generations. J. Herid 28:255,1937

[2] ML Buyse "Birth Defect Encyclopedia"Blackwell Scoentific Publishing 1990  p592

[3] Gupta, A. ; Patton, M. A. Familial microtia with meatal atresia and conductive deafness in five generations. Am. J. Med. Genet. 59: 238-241, 1995.

[4] Awwad JT, Azar GB, Karam KS, Nicolaides KH. Ear length: a potential sonographic marker for Down syndrome. Int J Gynaecol Obstet. 1994 Mar;44(3):233-8.

[5] Joes KL "Smith’s recognizable patterns of human malformation" p572

[6]ML Buyse " Birth Defect Encyclopedia"Blackwell Scoentific Publishing 1990  p590

[7] lubs HA:A marker X chromosome Am J. Hum. Genet.21:231, 1969

[8] Verloes A, Lesenfants S, Philippet B, Iyawa A, Laloux F, Koulischer L Genet Couns 1996;7(4):277-82

[9] Fryns JP, Legius E, Moerman P, Vandenberghe K, Van den Berghe H Apparently new "anophthalmia-plus" syndrome in sibs. Am J Med Genet 1995 Aug 28;58(2):113-4

[10] Ruzic J:Der SiebenteFall Kompletter Anotie, Acta Otolaryg 36:186,1948

[11] Peterson, D. M.; Schimke, R. N. : Hereditary cup-shaped ears and the Pierre Robin syndrome. J. Med. Genet. 5: 52-55, 1968.

[12] Rogers BO:Microtic, lop, cup and external-ear abnormalities:four directly inheritable deformities. Plast Recontr Surg 1968; 41;208

[13] Kohlschmidt N, Zielinski J, Brude E, Schafer D, Olert J, Hallermann C, Coerdt W, Arnemann J Prenatal diagnosis of a fetus with a cryptic translocation 4p;18p and Wolf-Hirschhorn syndrome (WHS)Prenat Diagn 2000 Feb;20(2):152-5.

[14] Otto HD Pathogenesis of the preauricular appendages, melotia, and poliotia. Arch Otorhinolaryngol 1979;225(1):45-56

[15] Koretzky, E. D.; Moller, J. H.; Korns, M. E.; Schwartz, C. J.; Edwards, J. E. Congenital pulmonary stenosis resulting from dysplasia of valve. Circulation 40: 43-53, 1969.

[16] Bhalla, V.; Roy, S.; Inam, A. S: Familial transmission of preauricular fistula in a seven generation Indian pedigree. Hum. Genet. 48: 339-341, 1979.