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Flashcards in 52 Pediatric Hearing Loss Deck (20):
1

How common is pediatric hearing loss?

How common is pediatric hearing loss?

Hearing loss is the most common birth defect and most prevalent sensorineural disorder in developed countries. Each year in the United States, 4000 infants are born with bilateral profound hearing loss, and 8000 infants are born with unilateral or bilateral mild-to-moderate hearing loss. Pediatric hearing loss can be categorized into congenital and acquired hearing loss. Congenital hearing loss is one of the most common anomalies present at birth and is estimated to occur in 2 to 4 infants per 1000. The overall prevalence of childhood hearing loss including loss present at birth, progressive, and acquired causes is thought to be 2 cases in 100 children.

2

What is universal newborn hearing screening?

What is universal newborn hearing screening?

In 1993, the National Institutes of Health published a consensus statement endorsing screening of all newborns for hearing loss before hospital discharge. Prior to universal newborn hearing screening programs, testing was only conducted on infants who met the criteria of the high-risk register (see Question 7). Currently, 43 states in the United States mandate newborn hearing screening and all have Early Hearing Detection and Intervention programs. Prior to universal newborn hearing screening, nearly 50% of infant hearing loss cases were identified later, after the critical period for speech and language development. Now, greater than 95% of newborns are tested prior to discharge home from the hospital. It has been recommended that all infants should have hearing screening before one month of age. Infants who do not pass newborn screening should have a follow-up medical and audiologic evaluation prior to three months of age.

3

How are neonatal hearing screen tests performed?

How are neonatal hearing screen tests performed?

There are two methods utilized for hearing screening at birth: otoacoustic emissions (OAE) and automated auditory brainstem response (AABR) testing. Both OAEs and AABR tests are noninvasive and can be obtained during normal physiologic sleep in the setting of a newborn nursery or neonatal intensive care unit. Newborns who do not pass their hearing screens are referred to audiologists for further workup, typically with complete diagnostic auditory brainstem response testing.

4

Why is early identification of hearing loss important?

Why is early identification of hearing loss important?

Early identification and subsequent treatment of hearing loss has a substantial impact on the development of speech and language skills. Studies have shown that children with hearing loss who began receiving treatment at or before 6 months of age have language skills comparable to their peers regardless of degree of hearing loss. Patients who were treated early had language skills significantly better than those in whom hearing loss was diagnosed after 6 months of age. Delayed diagnosis is known to have negative impacts not only on language skills, but also academic performance, career opportunities, and psychosocial well-being.

5

Why is it important for physicians to be familiar with the milestones for development of speech and hearing?

What is the most critical period?

Why is it important for physicians to be familiar with the milestones for development of speech and hearing? What is the most critical period?

Familiarity with milestones affords an effective initial screening method for children with hearing loss. Hearing loss may be most detrimental during the critical period between birth and 3 years of age when children develop speech, auditory pathways, and emotional bonds to family members. Infants with profound SNHL are unable to obtain auditory feedback, and without this feedback they cannot acquire the motor speech skills necessary for communication.

6

Summarize the major milestones for development of speech and hearing.

Summarize the major milestones for development of speech and hearing.

Generally, infants younger than 3 months of age are startled by loud sounds and are calmed by familiar voices. At 6 months, infants have the ability to localize sounds, and by 9 months they respond to their names and are able to mimic environmental sounds. By 18 months of age, infants react to sounds from any direction and are capable of following commands to perform simple tasks. Although most infants say “ma-ma” or “da-da” early on, the first obvious speech milestone occurs at about 1 year of age when infants learn their first meaningful words. By age 2, most normally hearing monolingual children have a vocabulary of 20 or more words.

7

What are risk factors for early childhood hearing loss?

What are risk factors for early childhood hearing loss?

  • Family history of permanent childhood hearing loss
  • Birth weight less than 1500 grams
  • Congenital craniofacial anomalies
  • In utero infections (ToRCHeS)
  • Maternal diabetes or alcohol/drug use
  • Hyperbilirubinemia requiring exchange transfusion
  • Apgar scores less than 5 at 1 minute and less than 7 at 5 minutes
  • Neonatal exposure to:
    • Ototoxic agents
    • Mechanical ventilation for 5 days or longer
    • Extracorporeal membrane oxygenation (ECMO)
  • Postnatal infections associated with hearing loss
  • Identified syndromes known to cause sensorineural or conductive hearing loss
  • Neurodegenerative disorders or sensorimotor neuropathies
  • Parental or caregiver concerns regarding hearing
  • Head trauma
  • Recurrent or persistent otitis media with effusion lasting for at least 3 months

8

What are the causes of congenital hearing loss?

What are the causes of congenital hearing loss?

Approximately 50% of all cases of congenital deafness are inherited, about 30% are considered to be from acquired/environmental causes, and 20% are cause unknown.

9

How are genetic causes of hearing loss categorized?

How are genetic causes of hearing loss categorized?

Genetically influenced hearing loss is believed to be responsible for a major portion of pediatric hearing loss and can be grouped into disorders that are syndromic and nonsyndromic. Disorders that cause syndromic hearing loss are associated with congenital anomalies involving other organ systems. Nonsyndromic hearing loss is isolated to anomalies of the middle or inner ear and does not involve other organ systems or the external ear. Approximately 70% of hereditary hearing loss is nonsyndromic.

10

What are the most common syndromes causing sensorineural hearing loss?

Describe their features and modes of inheritance.

What are the most common syndromes causing sensorineural hearing loss? Describe their features and modes of inheritance.

  • Usher syndrome: This syndrome is inherited in an autosomal recessive (AR) pattern and is responsible for up to 10% of congenital deafness. It is the most common type of AR syndromic hearing loss and the degree of hearing loss may vary. It is also associated with retinitis pigmentosa, which can cause progressive blindness, and vestibular dysfunction. Multiple mutations of genes have been associated with Usher syndrome including MYO7A, USH2A, CDH23 and others.
  • Pendred syndrome: This syndrome is transmitted in an AR pattern and is responsible for 5% to 10% of recessive hearing loss. It is associated with multinodular goiter, inner ear malformations including Mondini deformity, and enlarged vestibular aqueducts and abnormal perchlorate testing. Mutations in the SLC26A4 gene are common.
  • Jervell and Lange-Nielsen syndrome: This is the third most common cause of AR syndromic hearing loss and is thought to be responsible for 1% of all cases of recessive hearing loss. This syndrome is associated with congenital severe bilateral hearing loss and a prolonged Q-T interval in ECG, which is associated with sudden death. Mutations in the KCNQ1 and KCNE1 genes are thought to be associated.
  • Waardenburg syndrome: This syndrome is the most common cause of autosomal dominant (AD) hearing loss and accounts for 2% of all cases of congenital hearing loss, which can be variable. Other physical findings may include telecanthus, white forelock, hyperplastic high nasal root, hyperplastic medial eyebrows, and heterochromia irides. Multiple genetic mutations exist, most commonly in PAX3 and MITF genes.
  • Branchio-oto-renal syndrome: This syndrome is inherited in an AD pattern and includes branchial fistulas, renal abnormalities, and abnormal development of the inner, middle or external ears including preauricular pits. It is associated with mutations in EYA1, SIX1, and SIX5 genes.
  • Stickler syndrome: This is an AD inherited syndrome associated with cleft palate, osteoarthritis, myopia, and progressive SNHL. Three types are recognized based on the molecular genetic defect: STL1 (COL2A1), STL2 (COL11A1), and STL3 (COL11A2).

11

How is nonsyndromic hearing loss inherited?

What are some nonsyndromic causes of congenital hearing loss?

How is nonsyndromic hearing loss inherited? What are some nonsyndromic causes of congenital hearing loss?

Most genetically acquired hearing losses are caused by single-gene Mendelian inheritance in the absence of a recognizable syndrome. Nonsyndromic SNHL may be caused by any one of an increasing number of identified genes; currently over 100 SNHL genes have been mapped and over 50% have been identified. Eighty percent of nonsyndromic hearing loss cases follow the autosomal recessive pattern, 15% are autosomal dominant, with the remainder being X-linked or mitochondrial.

The most common mutation causing congenital profound hearing loss is in the GJB2 gene, which encodes the connexin-26 gap junction protein. This mutation may be responsible for 30% to 50% of all congenital profound hearing loss. SLC26A4 mutations make up the second most common genetic cause of SNHL; this may be present in Pendred syndrome, and patients may also have enlarged vestibular aqueducts.

12

Describe inner and middle ear anomalies that can cause hearing loss.

Describe inner and middle ear anomalies that can cause hearing loss.

Malformations of the inner ear are rare. They can be categorized into malformations of the bony and membranous labyrinth and those limited just to the membranous labyrinth. Michel’s aplasia is complete failure of inner ear development (labyrinthine aplasia), which typically leads to complete deafness. Mondini dysplasia results in an incomplete partition in the cochlea; only the basal turn of the cochlea is developed, and the bony cochlea is restricted to 1.5 turns. This can present in early childhood or later in adult life, with hearing that ranges from complete loss to normal hearing. Mondini dysplasia is inherited in an autosomal dominant pattern.

Membranous labyrinthine anomalies include Siebenmann-Bing (complete membranous labyrinthine) dysplasia, Scheibe (cochleosaccular) dysplasia, and Alexander (cochlear basal turn) dysplasia. Siebenmann-Bing dysplasia is extremely rare, and has been reported in association with Jervell-Nielsen-Lange and Usher syndromes. Scheibe dysplasia is often noted in autosomal recessive congenital hearing losses. Alexander dysplasia may be related to familial high-frequency sensorineural hearing loss. Diagnosis of dysplasia requires examination of the membranous labyrinth and can only be confirmed by post-mortem histopathologic study.

Enlarged vestibular aqueduct (EVA) is the most common inner ear anomaly seen on temporal bone imaging in patients with sensorineural hearing loss. It is described as a vestibular aqueduct that measures 1.5 mm or greater. The clinical presentation of enlarged vestibular aqueduct may be sensorineural or mixed, with hearing loss present either at birth, progressive through childhood, or even fluctuating. Sudden hearing loss can occur spontaneously or with mild head trauma. Patients diagnosed with EVA are urged to avoid contact sports and other situations that may result in head trauma to reduce progression of their hearing loss.

Congenital middle ear ossicular anomalies can also occur and often result in varying degrees of conductive hearing loss. These can include malformed or entirely absent ossicles. Malleus head fixation is likely the most common ossicular abnormality, and occurs secondary to incomplete pneumatization of the epitympanic space. Congenital absence of the incus’ long process can occur, which leads to a maximal conductive hearing loss. Congenital stapes fixation may also be responsible for stable conductive hearing loss and require stapedectomy for hearing restoration.

13

What are the most common causes of acquired pediatric hearing loss?

What are the most common causes of acquired pediatric hearing loss?

Acute otitis media and chronic otitis media with effusion are the most common causes of conductive hearing loss in children. Fluid within the middle ear space can inhibit the vibration of the tympanic membrane, reducing sound conduction. Acquired hearing loss can also be caused by cholesteatoma when desquamated epithelium expands into the middle ear and mastoid spaces, which can erode middle ear ossicles or even into the otic capsule.

14

Which infections can lead to hearing loss in children?

Which infections can lead to hearing loss in children?

Toxoplasmosis, rubella, congenital cytomegalovirus (CMV), herpes, and syphilis (ToRCHeS ) are infections that can be responsible for hearing loss if contracted in the perinatal period. Congenital CMV is the most common cause of nonhereditary sensorineural hearing loss in children. The prevalence of congenital CMV is 0.58%, and among those newborns infected, 12.8% will experience hearing loss. Among patients with symptomatic CMV infections, the majority have bilateral hearing loss; in those with asymptomatic infection, unilateral loss is more common.

Bacterial meningitis is thought to cause hearing loss in approximately 10% of children infected. Bacterial meningitis is usually caused by Streptococcus pneumoniae, Group B streptococcus, Neisseria meningitidis, and less commonly by Haemophilus influenzae type b. Hearing loss is a result of ossification of the cochlea from the inflammatory process. Frequent hearing evaluations are necessary with a CT scan of the temporal bone to look for ossification if hearing loss is found. Cochlear implantation may proceed urgently if ossification is found in order to preserve some membranous cochlear architecture.

15

What is the role of radiographic imaging in pediatric hearing loss?

What is the role of radiographic imaging in pediatric hearing loss?

Temporal bone computed tomography (CT) and brain/internal auditory canal magnetic resonance imaging (MRI) are the imaging modalities of choice to evaluate hearing loss. Either CT or MRI is the only way to determine presence of an enlarged vestibular aqueduct, vestibular anomalies, or absent cochlear nerves. Some debate exists as to which modality should be obtained primarily, but in general, weighing the differential diagnosis should drive which study should be ordered. For example, CT has been demonstrated to have a greater yield for identifying enlarged vestibular aqueduct; thus if this is suspected by clinical presentation, obtaining a CT of the temporal bones would be recommended.

16

What are some other adjunctive tests that may be helpful to obtain after hearing loss is diagnosed?

What are some other adjunctive tests that may be helpful to obtain after hearing loss is diagnosed?

In children with profound congenital deafness and absent vestibular function, an electrocardiogram (EKG) and/or cardiology consultation should be obtained to evaluate for prolonged Q-T interval that can be found in Jervell-Nielsen-Lange syndrome. Urinalysis may be obtained to evaluate for microscopic hematuria in Alport syndrome. If hearing loss is present along with cleft palate, ophthalmologic consultation can be important in evaluating for Stickler syndrome.

17

What are some medications used in the pediatric population that can cause ototoxicity?

What are some medications used in the pediatric population that can cause ototoxicity?

Aminoglycosides, erythromycin, cisplatin and other platinum-derived chemotherapeutics, and loop diuretics (e.g., furosemide) can all have ototoxic effects.

18

What is auditory neuropathy spectrum disorder (ANSD)?

What is auditory neuropathy spectrum disorder (ANSD)?

Patients with ANSD may display robust OAEs but have either an absent or a markedly dysmorphic AABR response in combination with varying degrees of hearing loss (as demonstrated by behavioral threshold testing).

19

What role does genetic testing play in the diagnosis of congenital hearing loss?

What role does genetic testing play in the diagnosis of congenital hearing loss?

Recent advances in genetic testing for hearing loss have drastically improved the feasibility and yield of identifying etiology of congenital hearing loss. If a mutation is found, it may explain why the person has hearing loss. In some cases it may explain how severe a condition may become or other associated problems that may occur in association with the mutation. From a counseling standpoint, finding out about a genetic condition can help families know the chances of having another child with the same condition or of that child passing on the mutation to their own offspring. Not all the genes the cause hearing loss are known, so it may not be possible to find the mutation that causes it. Additionally, since genetic testing provides information about the family as a whole, the wants and concerns of the whole family must be addressed. That is why counseling should be an integral part of the genetic testing process.

20

What are the treatments for pediatric hearing loss?

What are the treatments for pediatric hearing loss?

Depending on the type and degree of hearing loss, there are a variety of treatments for hearing loss. Conductive hearing loss caused by otitis media and/or eustachian tube dysfunction may be improved with tympanostomy tube placement. Other causes of conductive hearing loss (middle ear malformations) may require middle ear exploration with ossicular reconstruction or stapedectomy.

Hearing aids are frequently used in children to amplify sound. Behind-the-ear hearing aids are most often used in children as they are more adaptable to a child’s growing ear canal.

Bone anchored hearing aids (BAHA) are devices that can be used to restore conductive hearing loss that cannot be treated with traditional hearing aids, such as external auditory canal atresia or in patients with chronic otorrhea. Osseointegrated implants are placed into the skull and a sound processor is attached to provide conducted sound amplification through the bone.

Cochlear implants are a treatment for patients in whom surgical hearing reconstruction or hearing aids are not an option. A cochlear implant bypasses the nonfunctional cochlea and directly stimulates the cochlear nerve. In patients with bilateral profound hearing loss, excellent speech and language outcomes can be achieved with early implantation, often prior to one year of age.
 

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