What is Microtia : Causes, Treatment, Prognosis, Epidemiology, Features, Risk Factors

Microtia is a birth defect in which the proper development of the outer ear is hampered during the first trimester of the pregnancy. The underdevelopment of the outer ear or the pinna may range from complete absence to a small size. Microtia can affect single or both the ears. It may or may not result into hearing loss and can be fixed through effective treatment.

Microtia is a congenital deformation of ear which begins in the early phase of gestation and leads to deformed appearance of ear on the birth of the child and can be accompanied by hearing loss. The deformation can be minor to missing ear lobe but in most cases the inner parts of the ear remain intact. However, in some cases it may result in the narrowing or absence of the ear canal thereby causing hearing loss.

Microtia is namely of two types which is unilateral microtia and bilateral microtia. In case of unilateral microtia, only one ear gets affected, especially the right side. The affected ear may have underdeveloped hearing abilities whereas the unaffected ear has normal hearing capacity, thus sounds are absorbed by the normal ear. On the other hand, the bilateral microtia affects both the ears leading to impaired hearing ability along with poor speech development.

The features of microtia are classified into four categories which are:

• Grade I Microtia: In this type of microtia, there exists minor deformation identified by small ear with almost normal ear anatomy. The ear canal is generally open but narrow.
• Grade II: In grade 2 type of microtia, the tragus is developed with a normal bottom ear. The top ear is mildly deformed with a narrow or no ear canal.
• Grade III: It is the most common of all types which is characterized by small and underdeveloped ear with missing ear canal.
• Grade IV: This type marks the complete absence of the outer ear as well as the ear canal.

The cases of microtia occur as one in eight to ten thousand with about ninety percent cases suffering from unilateral microtia and the rest ten percent suffering from bilateral microtia. Amongst these cases, over forty to fifty percent cases suffer from hearing loss due to the condition. The prominence of the condition is found more in males in comparison to females. The geographical prominence lies towards Asian and South as well as South American regions.

The physical as well as the psychological outlook is very positive for children ailing from microtia, depending on whether the ear reconstruction surgery has be opted or not. Alongside the surgery, the psychological state of the parents and the child are equally important. In case of presence of anxiety issues in parents and low self-esteem in the child, personal counseling becomes very important so that the child can become realistic and deal with social issues.

The cause behind the condition still remains unknown but there are certain speculations that suggest association of microtia to other conditions.

• Chromosomal Aberrations
• Autosomal traits
• Multifactorial inheritance
• Recessive traits
• Goldenhar syndrome
• Treacher Collins syndrome
• Administration of drugs like Thalidomide and Isotretinoin.

Factors that pose a threat of microtia in the new born are:

• Presence of diabetes in the expecting mother
• Low consumption of carbohydrates and folic acid during pregnancy

Evaluation of microtia is required to be done as early as, soon after birth. This helps the parents to understand the condition and the available treatments. To diagnose microtia, the general methods adopted are:

• Audiogram to Diagnose Microtia: It is a test conducted in sound proof environment, to test the hearing ability of an individual. The tests are conducted at regular intervals until steady results are obtained.
• CT Scan for Diagnosing Microtia: This test helps in radiological analysis of the structure of the middle ear and ear canal. This measure is adopted prior to the ear reconstruction surgery.

The treatment opted for microtia depends on the extent of deformity and the severity of hearing impairment. An audiologist can be consulted and accordingly hearing aids can be used to help the child listen as well as aid in the speech development. The deformity can only be treated through ear reconstruction surgery. It needs to be kept in mind that the best time to conduct the surgery is when the ear size of the child is near about that of an adult, which is around eight to ten years. The general reconstruction surgeries opted are:

• Rib Cartilage Graft to Treat Microtia: This surgery aims at reconstructing the ear by utilizing the rib cartilage of the patient and transforms it to an ear. Being a living tissue it grows with the growth of the patient. The surgery is usually taken up after six years of age and is conducted in different stages.
• Medpor Techniques to Treat Microtia: It is an implantation technique which uses polyethylene plastic implants that allows the growth of the patient tissues through its porous framework. This technique allows ear reconstruction in a single surgery.
• Ear Prosthesis as a Method to Treat Microtia: These are opted in case of severely underdeveloped ear, in which silicone prosthetics are attached to the skin with the help of adhesives or titanium screws. These look normal and similar to real ear but the only drawback that remains is that it requires daily care and maintenance.

Microtia is the malformation of external ear since birth, in which the outer ear is either absent or underdeveloped. In some cases, it also contributes to hearing impairment along with hampered speech development, due to absence or narrowness of the ear canal. The condition can be treated effectively with ear reconstruction surgery and usage of hearing aids.

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