Anotia ("no ear") describes a rare

congenital A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

deformity A deformity, dysmorphism, or dysmorphic feature is a major abnormality of an organism that makes a part of the body appear or function differently than how it is supposed to. Causes Deformity can be caused by a variety of factors: *Arthritis a ...

that involves the complete absence of the auricle, the outer projected portion of the ear, and narrowing or absence of the

ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about in length and in diameter. S ...

. This contrasts with

microtia Microtia is a congenital deformity where the auricle (external ear) is underdeveloped. A completely undeveloped auricle is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Micro ...

, in which a small part of the auricle is present. Anotia and microtia may occur unilaterally (only one ear affected) or bilaterally (both ears affected). This deformity results in

conductive hearing loss Conductive hearing loss (CHL) is a type of hearing impairment that occurs when sound waves are unable to efficiently travel through the outer ear, tympanic membrane (eardrum), or middle ear structures such as the ossicles. This blockage or dysfun ...

deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is writte ...

Ear development

Ear development begins in about the third week of human embryonic development, beginning with the formation of the

otic placode In embryology, the otic placode is a thickening of the ectoderm on the outer surface of a developing embryo from which the ear develops. The ear, including both the vestibular system and the auditory system, develops from the otic placode beginni ...

s, an extension of the early hind brain. By the fourth week of development, the otic placodes invaginate, or sink inward forming pits which close themselves off for the outer surface

ectoderm The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...

and begin forming the inner ear labyrinthe on the inside. Outer ear development begins in about the fifth week of human embryonic development. Upon the

pharyngeal arches The pharyngeal arches, also known as visceral arches'','' are transient structures seen in the Animal embryonic development, embryonic development of humans and other vertebrates, that are recognisable precursors for many structures. In fish, t ...

, auricle hillocks begin to form. By the seventh week, the three pairs of hillocks have enlarged differentiated and fused together to start forming the auricle, or outer portion of the ear. Throughout fetal development, the hillocks will move from the sides of the neck to the sides of the head. Simultaneously, in the seventh week of development, the auditory tube begins to form out of the tympanic membrane.

Processing sound

The human ear is divided into three sections. Each section has its own specialized function. #The outer ear acts like a funnel and takes in the sound. #The middle ear holds the

tympanic membrane In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit changes in pressur ...

, or ear drum and several little bones that are moved by the sound waves that have entered the ear via the canal. These movements are very small, like vibrations and are transmitted to the inner ear. #The inner ear contains a structure called the cochlea, which contains small hair- like cells that respond to sound information and transmits it via nerve impulses down the

auditory nerve The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory information ...

and to the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

, where they are processed.

Defects of the ear: anotia/microtia

The isolated cause, a cause not associated with a syndrome, of anotia or microtia is not known, though it is believed to be of genetic basis. Developmentally, anotia/microtia occurs when certain tissues associated with the auricle do not develop. This rare defect may occur as part of a syndrome or as an isolated abnormality. Type I: External portion of the ear is small in size; auricle structure is normal Type II: The auricle is in a hook or 'S' shape; external ear is only moderately abnormal. Type III: Small amount of basic, soft tissue ear structure lacking cartilage; auricle is abnormal in appearance. Type IV: Most severe type, anotia; all external structures of the ears are absent. Defects affecting the external ear such as the auricle results from malformation or suppression of the auricular hillocks, which are small swellings on the embryonic visceral arches or the beginnings of the external ears; the small swellings are derived from the first and second pharyngeal arches. Because the ears and the kidneys develop simultaneously, children with ear defects are often checked for kidney defects at birth.

Related syndromes

"20% to 40% of children with microtia/anotia will have additional defects that could suggest a syndrome."Schoenwolf, Gary C., and William J. Larsen. Larsen's Human Embryology. 4th ed. Philadelphia: Churchill Livingstone/Elsevier, 2009. p601-2. Print.

Treacher-Collins syndrome Treacher Collins syndrome (TCS) is a genetic disorder characterized by deformities of the ears, eyes, cheekbones, and chin. The degree to which a person is affected, however, may vary from mild to severe. Complications may include breathing pr ...

: (TCS) A congenital disorder caused by a defective protein known as

treacle Treacle () is any uncrystallised syrup made during the refining of sugar.Oxford Dictionary The most common forms of treacle are golden syrup, a pale variety, and black treacle, a darker variety similar to molasses. Black treacle has a distinctiv ...

, and is characterized by craniofacial deformities; malformed or absent ears are also seen in this syndrome. The effects may be mild, undiagnosed to severe, leading to death. Because the ear defects are much different in this disorder and not only affect the outer ear, but the middle ear as well, reconstructive surgery may not help with the child's hearing and in this case a

bone-anchored hearing aid A bone-anchored hearing aid (BAHA) is a type of hearing aid based on bone conduction. It is primarily suited for people who have conductive hearing losses, unilateral hearing loss, single-sided deafness and people with mixed hearing losses who c ...

would be best. BAHA will only work, however if the inner ear and nerve are intact.

Goldenhar syndrome Goldenhar syndrome is a rare congenital defect characterized by incomplete development of the ear, nose, soft palate, lip and mandible on usually one side of the body. Common clinical manifestations include limbal dermoids, preauricular skin tag ...

: A rare congenital birth defect that causes abnormalities of facial development. Also known as oculoauricular dysplasia. The facial anomalies include underdeveloped, asymmetric half of the face. The defect is capable of affecting tissue, muscle, and the underlying bone structure of the side of the face with the abnormality.

Ablepharon macrostomia syndrome Ablepharon macrostomia syndrome (AMS) is an extremely rare, autosomal dominant genetic disorder characterized by abnormal phenotypic appearances that primarily affect the head and face as well as the skull, skin, fingers and genitals. AMS general ...

: (AMS) A rare genetic disorder characterized by various physical anomalies which affect the craniofacial area, the skin, the fingers, and the genitals.

Treatment

The treatment will vary with the different grades, but the most common is a surgical repair. The surgical option is cosmetic reconstruction of the external ear's normal shape and repair of the ear canal. In less severe cases, the reconstruction will be sufficient to restore hearing. In grades of anotia/microtia that affect the middle ear, the surgery with the use of a

(BAHA) will likely restore the hearing. The BAHA may be surgically implanted onto the skull which would allow for some hearing repair by conduction through the skull bone. "This allows sound vibrations to travel through bones in the head to the inner ear." BAHA: An implantable hearing device. It is the only hearing aid device that works via direct bone conduction.*

References

External links

* {{Congenital malformations and deformations of ears Congenital disorders of ears