Introduction:
Branchio Otic syndrome (BOS) is an uncommon genetic disorder that affects the outer, inner, and middle ear resulting in hearing impairment that can be sensorineural (hearing loss due to nerve damage) or conductive (hearing loss due to obstruction in vibrational conduction of sound to the inner ear) or both. It does not involve kidneys. Branchio Otic syndrome (BOS) occurs along with kidney disorder, and it is referred to as Branchio-Oto-Renal Spectrum Disorder (BORSD).
What Is the Incidence of Branchio Otic Syndrome?
Branchio Otic syndrome (BOS) is very uncommon and accounts for one in forty thousand births of the general population.
When Do the Symptoms of Branchio Otic Syndrome (BOS) Begin?
The age of onset of symptoms for Branchio Otic syndrome (BOS) is from newborn to four weeks of life.
What Are the Causes of Branchio Otic Syndrome (BOS)?
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Genetic Mutation: Branchio Otic syndrome is caused due to mutation of gene EYA1 (Eye Absent 1) and SIX1 (Sine Oculis Homeobox 1). The alteration or mutation of these genes can result in the abnormal formation of many tissues during embryological development (development of the fetus), like malformation of structure derived from the second branchial arch (facial muscles, eyes, neck muscles, ears, and kidneys).
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Hereditary: Affected parents have a fifty percent chance of having a child with a similar disorder.
What Are the Signs and Symptoms of Branchio Otic Syndrome (BOS)?
Signs and symptoms of Branchio Otic syndrome mostly occur due to malformation of the second branchial arch (affects the structures derived from the arch) caused by genetic mutation of EYA1 (Eye Absent 1) and SIX1 (Sine Oculis Homeobox 1) gene protein. Affected newborns will show:
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Hearing loss (in one or both ears).
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Preauricular pits (a small hole in front of the ear).
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Abnormalities in the inner, middle, and outer ear.
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Atresia of the auditory canal (malformed ear canals).
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Abnormal nasolacrimal drainage (flow of tears from eyes through the nose).
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Facial asymmetry (difference between left and right side of the face).
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Facial nerve paralysis (damage to the facial nerve due to underdevelopment of the second branchial arch).
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Depression on the lips (lip pits).
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Preauricular skin tags (extra tissue near in front of the ears).
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A branchial cleft cyst (abnormal opening of tissues in the neck leading to the formation of a sinus tract during the development of the fetus).
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Conductive hearing impairment (hearing impairment due to obstruction in vibrational conduction of sound to the inner ear).
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Sensorineural hearing impairment (hearing loss due to damage to the nerve supplying the ears).
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Micrognathia (small jaw).
How Can We Diagnose Branchio Otic Syndrome (BOS)?
Branchio Otic syndrome (BOS) is diagnosed by the following methods:
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History: A detailed history of parents or family members suffering from similar disorders should be noted.
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Clinical Examination: A physical examination of a child is done to rule out the presence of preauricular pits (a hole in front of the ear) and skin tags (extra ear tissue growth in front of the ears). A facial nerve examination is done for the patient complaining of muscle twitching or having an asymmetric face.
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Audiogram (Hearing Test): It is done to rule out the hearing impairment by producing sound in the ears of the patient at different tones or frequencies through a mini earphone, and response to the sound is noted on the graph, which is then assessed.
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Computed Tomographic (CT) Scans: This scan is done for the temporal bone (bone present on the lateral side of the skull) to rule out any deformities present in the outer, middle, and inner ears, like deformed ear canals.
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Molecular Genetic Testing: Molecular genetic test helps to rule out any alteration or mutation of EYA1 and SIX1 gene protein. This test confirms the diagnosis for the presence of Branchio Otic Syndrome.
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Renal (Kidney) Ultrasound: It is done to check for any kidney abnormalities as the branchio otic syndrome may involve the kidney in some cases and is termed Branchio-Oto- Renal- syndrome (patients show all the symptoms of branchio-otic-syndrome with renal dysfunction).
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Computed Tomography (CT) of Neck: It is done in the patients who present with a lump in the neck with continuous pus discharge from the swelling to check for the presence of a branchial cleft cyst or fistula tract (failure of closure of tissues while embryological development of the fetus presents with a lump in the neck). It helps to determine the size of the fistula tract so that surgery can be planned accordingly.
What Is the Treatment of Branchio Otic Syndrome (BOS)?
Branchio Otic syndrome is managed by supportive measures and based on the symptoms present. Various methods to manage are:
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Hearing Aids: If hearing loss is detected while a hearing test, hearing aids like hearing headbands and bone-anchored hearing implants (a device placed in the bones near the ear surgically) are given to the child in the early stages of life (birth to five years of age) to prevent the speech-language disability in the child.
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Surgical Treatment: Surgical removal of the fistula tract in the neck (branchial fistula) is done by excision (cutting with a blade) of the complete tract. The patient is kept on antibiotics after the surgical procedure in case of an infected cyst.
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Kidney Management: The presence of any kidney deformities is managed by the nephrologist (kidney specialist). Dialysis or kidney transplantation is done by the doctor, depending on the symptoms.
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Genetic Counseling: Genetic counseling is done for the patients and their parents.
Conclusion:
Branchio Otic syndrome is a very uncommon genetic disorder affecting newborns. Branchio otic syndrome presents with symptoms like hearing loss, ear deformities, and second branchial arch deformities (malformation of the second branchial arch due to gene mutation affecting the structures derived from the arch during embryonic development). Molecular genetic test showing alteration in EYA1 gene and SIX1 gene confirms the presence of Branchio Otic syndrome. Early diagnosis and management of branchio otic syndrome is important for a satisfactory outcome of the treatment and to prevent the delay of speech-language development in the child.
