AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Of the more than 4000 infants born deaf each year, more than half have a hereditary disorder. Hereditary disorders must be differentiated from acquired hearing losses. Not all hereditary hearing loss is present at birth; some children inherit the tendency to develop hearing loss later in life.

Genetic sensorineural hearing loss (SNHL) includes a broad range of disorders that affect infants, children, and adults. Affected individuals may have unilateral or bilateral hearing loss ranging from mild to profound. This article, like most related discussions, focuses on childhood hearing loss, with consideration of a few forms of adult-onset hearing loss.

Pathophysiology

Disorders of the inner ear, cochlea, cranial nerve VIII, CNS pathways, nuclei, or cerebral processing of sound can cause SNHL.

Genetic hearing loss may be syndromic or nonsyndromic. Patients with syndromic hearing loss have other defining traits, often abnormalities of the external ear or other organ systems. Nonsyndromic hearing impairment is not associated with other defining traits or related medical conditions. Transmission of genetic hearing loss may be dominant, recessive, X-linked, or mitochondrial.

Frequency

United States

According to the National Institute on Deafness and Other Communication Disorders (NIDCD), hearing loss affects approximately 28 million Americans and approximately 17 in 1000 children and adolescents younger than 18 years. About 6 or 7 of every 1000 children in the United States are born with mild-to-moderate  hearing loss and 1 of 1000 are born deaf.

Congenital hereditary hearing loss must be differentiated from acquired hearing loss. More than half of all cases of prelingual deafness are genetic. The remaining 40-50% of all cases of congenital hearing loss are due to nongenetic effects, such as prematurity, postnatal infections, ototoxic drugs, or maternal infection (with cytomegalovirus [CMV] or rubella). Most SNHLs are autosomal recessive and nonsyndromic. Hearing loss that results from abnormalities in connexin 26 and connexin 30 proteins likely accounts for 50% of cases of autosomal recessive nonsyndromic deafness.

The incidence of hearing loss increases with age. Loss affects 314 in 1000 people older than 65 years and 40-50% of people aged 75 years or older. Adult-onset hearing loss can be attributed to normal aging processes and environmental triggers. However, an individual's genetic predisposition should not be underestimated, as illustrated by aminoglycoside-induced ototoxicity and the predisposition to noise-induced hearing loss.

Current statistics can be found on the Early Hearing Detection & Intervention (EHDI) Program Web site published by the Centers for Disease Control and Prevention.

International

Hearing impairment affects up to 30% of the international community. Worldwide, an estimated 70 million persons are deaf. SNHL appears to occur twice as often in developed countries as in underdeveloped countries.

Mortality/Morbidity

The 350,000 individuals who are profoundly deaf in the United States earn approximately 30% less than the general population. Among school-aged children with hearing loss, approximately 52,000 attend schools or programs for the deaf, 100,000 are enrolled in special deaf-education classes, and 250,000 participate in standard public school settings. The overall cost for deafness education is estimated to be $121 billion.

Age

Before universal hearing screening for newborns, less than 50% of children who had hearing impairment were identified before the age of 3 years. Detection of risk factors (eg, prematurity, low birth weight, low Apgar scores) helps in identify less than 50% of infants who have or who are at risk for hearing loss.

In 1 study, 78% of infants identified with hearing loss were in the well-baby nursery and not the neonatal intensive care nursery (Korres, 2005). This finding emphasized the ineffectiveness of screening on the basis of risk identification alone.

Twenty-eight states now mandate universal screening of newborns.  According to the National Newborn Screening Status Report from April 2006, screening is almost universally offered but is not yet required in the remaining states.

At present, the mean age when hearing loss is detected is about 14 months. However, in Virginia,  the mean age at diagnosis decreased from 16.2 to 4.5 months. In this state, universal infant screening was mandated by law on July 1, 2000, and compliance of >98% was achieved by 2004.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

History

Early identification and management of hearing loss in children is critical. Failure to detect congenital or acquired hearing loss may result in deficiency in language development, interruptions in family bonding and social interaction, and poor academic achievement. Physicians must recognize children at risk for hearing loss and support appropriate intervention.

Congenital hearing loss is potentially identifiable with newborn screening. High-risk indicators should be used to identify children who are at risk for developing hearing loss after birth. All children should periodically be screened for hearing loss, and any parental concern should be thoroughly addressed with a formal hearing evaluation. Attention to high-risk indicators, to achievement of speech and language milestones, and to the family history are essential in evaluating a child for hearing loss.

The Joint Committee on Infant Hearing developed the following checklist of high-risk indicators for hearing loss in neonates, infants, and children from birth to 24 months:

• Birth to 28 days
• • Family history of SNHL, presumably congenital SNHL
  
  
  • In utero infection associated with SNHL (eg, toxoplasmosis, rubella, CMV infection, herpes, syphilis)
  
  
  • Ear and other craniofacial anomalies
  
  
  • Hyperbilirubinemia at levels that require exchange transfusion
  
  
  • Birth weight <1500 g
  
  
  • Bacterial meningitis
  
  
  • Low Apgar scores (0-3 at 5 minutes, 0-6 at 10 minutes)
  
  
  • Respiratory distress (eg, due to meconium aspiration)
  
  
  • Mechanical ventilation >10 days
  
  
  • Ototoxic medication (eg, gentamicin) administered for >5 days or used in combination with loop diuretics
  
  
  • Physical features or other stigmata associated with a syndrome known to include SNHL (eg, Down syndrome, Waardenburg syndrome)


• 29 days to 24 months
• • Parental or caregiver concern about hearing, speech, or language, and/or developmental delay
  
  
  • Any of the risk factors for newborns listed above
  
  
  • Recurrent or persistent otitis media with effusion (OME) for at least 3 months
  
  
  • Head trauma with fracture of the temporal bone
  
  
  • Childhood infectious diseases associated with SNHL (eg, meningitis, mumps, measles)
  
  
  • Neurodegenerative disorders (eg, Hunter syndrome) or demyelinating diseases (eg, Friedreich ataxia, Charcot-Marie-Tooth syndrome)

Failure to achieve the following speech and language milestones may indicate hearing loss and necessitate a hearing evaluation (Northern, 1991):

• Birth to 3 months
• • Startles to loud noise
  
  
  • Awakens to sounds
  
  
  • Blinks or widens eyes in response to noises


• 3-4 months
• • Quiets to mother's voice
  
  
  • Stops playing, listens to new sounds
  
  
  • Looks for source of new sounds that are not in sight


• 6-9 months
• • Enjoys musical toys
  
  
  • Coos and gurgles with inflection
  
  
  • Says "mama"


• 12-15 months
• • Responds to his or her name and the word "no"
  
  
  • Follows simple requests
  
  
  • Uses expressive vocabulary of 3-5 words
  
  
  • Imitates some sounds


• 18-24 months
• • Knows body parts
  
  
  • Uses expressive vocabulary with 2-word phrases (minimum of 20-50 words)
  
  
  • 50% of speech intelligible is to strangers


• By 36 months
• • Uses expressive vocabulary of 4- to 5-word sentences (approximately 500 words)
  
  
  • 80% of speech is intelligible to strangers
  
  
  • Understands some verbs

A detailed family history to identify affected parents, siblings, and relatives is imperative in the evaluation of the patient with hearing impairment.

Physical

Because SNHL is associated with effects on virtually every organ, the physician must be familiar with the constellation of physical findings that may elucidate the etiology of a patient's hearing impairment.

Physical examination should include a complete evaluation of the ears, nose, throat, head, and neck, along with an overall assessment of the child's general physical and neurologic status.

Findings associated with hearing loss include microtia or atresia of the ear canal, cleft lip or palate, craniofacial abnormalities (eg, micrognathia, facial asymmetry, microcephaly, or craniosynostosis), cranial nerve weakness, heterochromia of the iris or other abnormalities of the ocular structures, vision impairment, goiter, and skeletal abnormalities.

Causes

Approximately 50% of all cases of congenital deafness are inherited. Approximately 70% of cases of hereditary deafness are nonsyndromic, and the remaining 30% are syndromic, being associated with other specific deformities or medical problems. Of nonsyndromic hearing losses, 75-85% are inherited in an autosomal recessive pattern, 15-20% are inherited in an autosomal dominant pattern, and 1-2% are inherited in an X-linked pattern.

Syndromic hearing impairment

Autosomal dominant

Waardenburg syndrome is the most common cause of autosomal dominant syndromic hearing loss. The syndrome includes dystopia canthorum, a broad nasal root, confluence of the medial eyebrows, heterochromia irides, a white forelock, and bilateral or unilateral SNHL. Expressivity is extremely variable.

Four subtypes of Waardenburg syndrome are defined. Type I includes dystopia canthorum (ie, lateral displacement of the inner canthus of the eye) and is caused by mutations in PAX3. Type II is characterized by the absence of dystopia canthorum and is caused by mutations in MITF. Type III has associated upper-limb abnormalities and is caused by mutations in PAX3. Type IV is thought to be caused by mutations in EDNRB, EDN3, and SOX10, and patients with type IV have Hirschsprung disease.

Branchio-otorenal syndrome is the second most common cause of autosomal dominant syndromic SNHL. This condition manifests as preauricular pits, deformed auricles, and lateral branchial cysts. The hearing loss may be conductive, SNHL, or mixed. Some patients have Mondini anomalies of the cochlea. Penetrance is high, but expressivity is extremely variable. Mutations in the EYA1 and SIX1 gene have been identified.

Neurofibromatosis type 2 (NF2) is associated with vestibular schwannomas, meningiomas, ependymomas, juvenile cataracts, and other intracranial and spinal tumors. The gene for NF2 has been mapped to chromosome 22q12.2 and is thought to be a tumor-suppressor gene. It has about 50% penetrance. In the Wishart type of NF2, the disease manifests in childhood or early adulthood. As vestibular schwannomas and other tumors develop, this subtype becomes rapidly progressive and often severely disabling. In the Gardner type of NF2, disease is more limited, less disabling, and presents later (in the third or fourth decades) that it is in the Wishart type.

Otosclerosis is a genetic disorder generally associated with adult-onset conductive hearing loss. However, advanced otosclerosis may cause SNHL. The genes responsible for otosclerosis have not been found, but foci on chromosomes 6, 7, and 15 have been implicated.

Achondroplasia may be associated with mixed hearing loss.

Paget disease may result in progressive, adult-onset conductive hearing loss, SNHL, or both. Other common findings of this bone disorder are enlargement of the skull, kyphosis, and shortening of stature. The hearing loss is thought to be due to a cochlear process. Genetic and environmental factors are likely to be contributing factors.

Autosomal recessive syndromic hearing loss

Usher syndrome is the most common cause of autosomal recessive syndromic SNHL. Usher syndrome results in both hearing and visual impairments, and it is the etiology in at least 50% of persons with deafness and blindness.

Three main types of Usher syndrome are described. Type I is characterized by congenital severe-profound hearing loss and vestibular dysfunction. Retinitis pigmentosa (RP) develops in childhood and progresses to blindness. Type II Usher syndrome is characterized by congenital mild-to-severe SNHL but normal vestibular function. Associate RP develops during the later teen years. Type III disease results in progressive hearing loss and vestibular dysfunction. RP begins at puberty.

Twelve loci have been found to cause Usher syndrome. Genes and the proteins that they encode have been identified for 7 of the 12 loci. The genes that cause Usher syndrome are MY07A, USH1C, CDH23, PCDH15, and SANS, which cause USH1, USH2A (which causes USH2), and USH3A (which causes USH3). A mutation, named R245X, of the PCDH15 gene may account for a large percentage of USH1 cases in today's Ashkenazi Jewish population.

Pendred syndrome is the second most common type of AR syndromic hearing loss. It is characterized by congenital severe-to-profound sensorineural hearing impairment and euthyroid goiter. Goiter develops in early puberty or adulthood. Affected individuals have an abnormal perchlorate test indicating delayed organification of iodine by the thyroid. Abnormalities of a temporal bone scan include Mondini dysplasia and dilated vestibular aqueduct. Mutations in SLC26A4 have been identified. Genetic testing is available.

Jervell and Lange-Nielsen syndrome results in congenital SNHL and a prolonged QT interval. Affected individuals have syncopal episodes and may have sudden death. High-risk children (ie, those with a family history that is positive for sudden death, SIDS, syncopal episodes, or long QT syndrome) should have a thorough cardiac evaluation.

Mutations in the KCNE1 and KCNQ1 genes cause Jervell and Lange-Nielsen syndrome. About 90% of cases of Jervell and Lange-Nielsen syndrome are caused by mutations in the KCNQ1 gene; KCNE1 mutations are responsible for the remaining 10% of cases. These genes are responsible for coding potassium channel proteins critical for maintaining the normal functions of the inner ear and cardiac muscle. Mutations in these genes alter the usual structure and function of potassium channels or prevent the assembly of normal channels. These changes disrupt the flow of potassium ions in the inner ear and in cardiac muscle, leading to the hearing loss and irregular heart rhythm characteristic of Jervell and Lange-Nielsen syndrome.

X-linked syndromic hearing loss

Alport syndrome is associated with SNHL and hemorrhagic nephritis. The HL is bilateral and slowly progressive in this X-linked dominant disorder. The defect is located near Xq22. Other forms are autosomal dominant or recessive.

Nonsyndromic SNHL

An estimated 70% of hereditary hearing loss is nonsyndromic. Seventy-five percent of nonsyndromic SNHL is autosomal recessive, 20-25% is autosomal dominant, and 1-1.5% is X-linked. When a gene locus for hearing loss is identified, it is named for the inheritance pattern and a consecutive number. DFNA indicates autosomal dominant gene loci, DFNB indicates autosomal recessive loci, and DFN indicates X-linked loci. Mitochondrial disorders also exist. New gene loci are discovered every year.

Mutations in the connexin 26 gene at locus DFNB1 on chromosome 13 is thought to account for about 50% of recessive nonsyndromic hearing loss. 35delG is the most common mutation, but at least 90 different GJB2 mutations have been described. The gene GJB2 codes for connexin 26, a gap junction beta2 protein. These proteins form intercellular channels in the plasma membrane and facilitate the exchange of molecules between cells. Connexin 26 is expressed in the stria vascularis, spiral ligament, spiral limbus, and in supporting cells of the cochlea. It appears to have a role in recycling of potassium. The hearing loss is usually prelingual, progressive, varies from mild to profound. It is usually predominantly high frequency and sloping but may also present with a flat audiometric curve. The ear is usually radiologically normal. Connexin 26-related hearing loss can be inherited by autosomal recessive or dominant patterns.

A common X-linked nonsyndromic mutation at gene locus DFN3 causes a mixed hearing loss. These patients are prone to perilymph gushes during stapedectomy with resulting profound postoperative SNHL. The gene is called POU3F4.

An interesting mitochondrial gene mutation is that for aminoglycoside-induced SNHL. The mutation A1555G in the 12s rRNA gene makes a person susceptible to hearing loss after treatment with gentamicin, neomycin, or other aminoglycosides.

Several Web sites are devoted to cataloging gene mutations, including those of the Harvard Medical School Center for Hereditary Deafness and GeneTests.

Radiologic and pathologic correlates of SNHL include several defined abnormalities.

Michel dysplasia is characterized by complete failure of inner ear development, while the external and middle ears may be normal and functional. Complete unilateral or bilateral deafness may ensue. The diagnosis rests on postmortem histopathology because radiographic studies cannot differentiate between Michel dysplasia and labyrinthitis ossificans.

Mondini dysplasia is possibly due to arrested development of the cochlea in its embryonic stage at approximately the sixth week of gestation. Only the basal turn of the cochlea is developed, and the bony cochlea is restricted to 1.5 turns. Mondini dysplasia may manifest in early childhood or in adulthood, with hearing that ranges from complete loss to normal hearing. It is inherited in an autosomal dominant fashion.

Scheibe dysplasia is the most common form of congenital dysplasia of the inner ear and is also known as cochleosaccular dysplasia. The bony labyrinth, membranous utricle, and semicircular canals are fully formed, while pars inferior structures, namely the saccule and cochlear duct, are poorly differentiated. Scheibe dysplasia is often noted in congenital hearing losses with autosomal recessive inheritance.

Alexander aplasia is characterized by aplasia of the cochlear duct. The organ of Corti, particularly the basal turn of the cochlea and adjacent ganglion cells, is affected most prominently. Hearing loss is most notable with high frequencies, whereas low-frequency hearing is relatively preserved.

An enlarged vestibular aqueduct may be inherited or spontaneous. It is typically defined as an anteroposterior diameter >1.5 mm at the operculum, but some clinicians and authors use a definition broader than this. Hearing loss usually is bilateral and progressive, and it may be associated with vertigo. Much is still unknown about this disorder.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Michel dysplasia
Mondini dysplasia
Scheibe dysplasia
Alexander aplasia
Enlarged vestibular aqueduct
Familial progressive sensorineural deafness
Metabolic disorders
Erythroblastosis fetalis
Birth trauma and/or anoxia
Radiation
Prematurity
Congenital ossicular fixation

Prenatal infections

CMV infection
Rubella (German measles)
Toxoplasmosis
Herpes simplex
Syphilis

Exposure to teratogenic agents

Thalidomide
Isotretinoin

Neoplasms

Vestibular schwannoma
Meningioma
Mucosal adenoma
Paraganglioma
Squamous cell carcinoma
Rhabdomyosarcoma

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Lab Studies

Routine series of laboratory tests are not recommended in the evaluation of a hearing impaired patient. Rational assessment of the cost-benefit ratio and the clinician's index of suspicion should guide the selection of laboratory studies for an individual patient. Studies may include those listed below.

• Molecular genetic testing: Assays are available for the GJB2 gene (for connexin 26), the GJB6 gene (for connexin 30), SLC26A4 (related to an enlarged or dilated vestibular aqueduct and Mondini dysplasia associated with Pendred syndrome), mitochondrial gene mutation A1555G (aminoglycoside-sensitive SNHL), and COCH (associated with adult-onset dominant SNHL). Genetic testing is available for a number of other genes, but the infrequency of most of them makes clinical testing impractical.


• CBC with differential


• Chemistries


• Blood sugar determination


• BUN and creatinine measurement


• Thyroid studies


• Urinalysis


• Fluorescent treponemal antibody absorbed (FTA-ABS) test


• Specific immunoglobulin M (IgM) assays for toxoplasmosis, rubella, CMV infection


• Herpes virus autoimmune panel


• Autoimmune profile
• • Test of erythrocyte sedimentation rate (ESR)
  
  
  • Antinuclear antibody (ANA) test
  •  
  
  
  • Rheumatoid factor (RF) test
  
  
  • Measurement of complement levels
  
  
  • Raja-cell studies
  
  
  • Western blot (to identify serum anti-68 kd autoantibody)
  
  
  • Tests for circulating immune complexes

Imaging Studies

• CT scanning offers high-resolution images with 1-mm sections, which permit good visualization of the anatomy of the bones, ossicles, and inner ear.
  
  
  • CT assists in the diagnosis of suspected labyrinthine anomalies, such as a large vestibular aqueduct or Mondini dysplasia. CT scanning also is useful for diagnosing suspected labyrinthine fistula or temporal bone fractures.
  
  
  • CT may help in identifying the relatively nondysplastic and presumably somewhat-hearing ear when auditory habilitation is being considered.


• MRI has high soft tissue contrast, which makes it ideal for evaluation of the inner ear, internal auditory canal, and cerebellopontine angle.
  
  
  • MRI with gadolinium enhancement is the criterion standard for evaluating potential retrocochlear pathology as a cause of hearing loss.
  
  
  • Highly T2-weighted images obtained with appropriate sagittal sections can depict aplasia of the cochlear nerve and subtle malformations of the inner ear.

Other Tests

• Auditory brainstem response (ABR): ABR is most clinically useful for assessment of infants and young children.
  
  
  • Principle areas of application include the evaluation and diagnosis of the peripheral auditory system and related pathology and determination of the neural integrity of the acoustic nerve and brainstem pathway.
  
  
  • ABR provides a valid estimate of auditory sensitivity based on the threshold of response.


• Audiometry: Valid and reliable techniques are presently available to provide information relevant to presence, degree, and nature of hearing impairment in children within the first 24 hours of life.
  
  
  • Visual response audiometry yields precise information regarding auditory sensitivity in infants as young as 6 months. Head-turning responses to sound are conditioned through visual reinforcement, and ultimately the response behavior is controlled.
  
  
  • Play audiometry is ideal for children aged 2-5 years and for older children who are mentally or developmentally delayed. Conventional audiometric techniques are combined with testing situations in which the child can respond appropriately to stimuli by participating in a form of play activity. Hearing levels can be assessed for both speech and pure tone stimuli.
  
  
  • Conventional audiometry is traditionally reserved for children aged 3-5 years and older. Techniques include pure tone and speech audiometry (to determine air and bone conduction thresholds) and speech recognition.
  
  
  • Immittance audiometry provides an objective, rapid, and accurate assessment of middle ear function in infants and children. Immittance audiometry consists of 2 primary techniques, tympanometry and measurement of acoustic-reflex thresholds.
    
    
    • Tympanometry reflects the compliance of the middle ear system as the eardrum is artificially altered with varying degrees of air pressure in the external ear canal (EAC). A noncompliant middle ear is consistent with effusion, which is a typical presentation in the infant population.
    
    
    • The acoustic-reflex threshold measurement is defined as the lowest intensity level that elicits stapedial muscle contraction. The acoustic-reflex response typically is in the range of 85 dB for the midfrequency stimulus. Deviations in the acoustic-reflex response, including elevated or absent thresholds, are synonymous with middle ear dysfunction


• Otoacoustic emissions (OAEs): OAEs are samples of measurable acoustic energy generated by vibratory patterns in the normal cochlea and propagated into the EAC by way of the middle ear apparatus. Emissions provide an objective measure of auditory sensitivity, frequency analysis, and cochlear integrity.
  
  
  • The 2 primary categories of otoacoustic emissions are spontaneous OAEs (SOAEs) and evoked OAEs (EOAEs). EOAEs can be subdivided into transient and distortion product OAEs (DPOAEs) according to the stimulus characteristics used to elicit their response. Clinical application is limited in that SOAEs are recorded in only approximately half of the population.
  
  
  • Transient OAEs and DPOAEs can be recorded in nonpathologic ears that do not have hearing loss >20-30 dB regardless of sex or age. The absence of measurable EOAEs is strongly predictive of a decrease in peripheral hearing, particularly in the 2000- to 4000-Hz range, where EOAEs appear to be most sensitive to dysfunction of the outer hair cells.


• ECG: Consider ECG to detect cardiac conduction anomalies.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical Care

• Treat any middle ear disease, including otitis media, with appropriate medical therapy.


• Hearing amplification, whether with conventional or advanced technologic devices, is critical to the habilitation process. The goal of amplification is to take advantage of any residual hearing the patient may possess. At a minimum, the goal is to orient the patient to an acoustic event in his or her environment. Hearing amplification can usually be implemented with success by the age of 6 weeks.


• Assistive listening devices and personal systems may be helpful.
  
  
  • Personal devices aid in reducing the signal-to-noise ratio in various listening situations, such as watching television, in classrooms, and in auditoriums.
  
  
  • Telephone devices include volume controls and couplers for use with certain hearing aids. For individuals unable to use standard telephone devices, telecommunication devices for the deaf are available.
  
  
  • Captioning allows individuals with severe hearing impaired to watch television.
  
  
  • Signaling devices, which substitute visual signals for auditory signals, are available to detect environmental household sounds such as the doorbell, ringing telephone, alarm from an alarm clock, fire alarm, or a baby's cry.

Surgical Care

Surgical management of external and middle ear deformities may be recommended in bilateral cases.

• Cochlear implantation
• • Consider cochlear implantation for patients who do not demonstrate significant benefit from conventional hearing amplification.
  • Cochlear implants are electronic devices designed to convert mechanical sound energy into electric signals that can be delivered to the cochlear nerve.
  • Perform a CT or MRI scan of the temporal bones prior to cochlear implantation to ensure the presence of an intact cochlea and cochlear nerve.
  • In children, substantially better performance is obtained when auditory input is restored with cochlear implantation in children younger than 2 years.

Consultations

Participation of many members of the medical community is required to offer comprehensive service to the family of a person with hearing loss. Pediatricians, audiologists, speech-language pathologists, educational specialists, and otolaryngologists must contribute to these efforts.

• Obtain an otolaryngology consult when hearing loss is suspected or diagnosed. The otolaryngologist identifies the hearing loss, assesses the cause, identifies risk factors, and obtains appropriate medical tests.


• A geneticist may offer assistance in establishing the etiology of SNHL. The geneticist can also provide genetic counseling to address a family's questions about the etiology of the patient's hearing loss and the risk of hearing loss in future children.


• The audiologist is responsible for selection of the appropriate aid, which is a critical decision. Once hearing amplification is in place, systematic monitoring is necessary to ensure proper function of the device while monitoring speech and language development.


• A speech and language pathologist can provide appropriate educational programs necessary to enrich social, emotional, and academic development. The patient's linguistic and communicative skills must be analyzed with the understanding that the final indication of the success of the habilitative program is the patient's language capability and not the level of hearing. As a general rule, initially present language to children who are hearing impaired using all available inputs, including auditory, visual, and tactile stimuli.


• An ophthalmology evaluation is important to assess visual acuity and to evaluate any possible ocular components of syndromic hearing loss.

Activity

Anecdotal reports associate increased risk of hearing loss with patients who have enlarged vestibular aqueducts and participate in contact sports.

FOLLOW-UP

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Further Outpatient Care

• Otologist
• • Encourage follow-up annually and as needed.
  
  
  • Frequent findings include problems with the hearing aid, disease of the external or middle ear, and progressive hearing loss.
  
  
  • Follow-up must also reassess the accuracy of the initial diagnosis with appropriate modifications made to the habilitative plan.


• Audiologist
• • After a device hearing amplification is in place, systematic monitoring is necessary to ensure proper function of the device while monitoring speech and language development.
  
  
  • Schedule audiologic reevaluation every 3 months during the first year and then every 6 months thereafter.
  
  
  • Calibrate hearing aids periodically and fit new molds when necessary.
  
  
  • Periodic audiometric testing is necessary to rule out fluctuation or progression of hearing loss.


• Speech and language pathologist
  
  
  • Speech and language therapy is imperative to promote proper language and communication skills.
  
  
  • A plan for systematic monitoring is required to ensure that a child with hearing impairment develops the necessary speech and communication skills to meet his or her daily communication needs.

Deterrence/Prevention

• The patient must avoid ototoxic medications and loud noise exposure in the absence of hearing protection.

Complications

• Children with unilateral hearing loss have difficulty with sound localization and with hearing in settings with background noise that can make school life difficult. Among such children, the incidence of school-grade failure, distractibility, daydreaming, inability to follow directions, and behavioral problems increases.


• Children with profound bilateral hearing loss have reductions in receptive and expressive language skills, rates of graduation from high school, reading levels, and math skills. Deaf individuals may have low rates of employment, few opportunities for financial gain, restricted socialization, language barriers that resulting in limited social groups and reduced quality of life.

Prognosis

With proper amplification, speech and language therapy, and an educational program, a patient with SNHL may participate in mainstream society, obtain gainful employment, and be competent in adult life. Children with profound deafness that is rehabilitated with cochlear implants achieve language development on par with that of their peers.

Patient Education

• When counseling the parents of a child who is hearing impaired, one must address the probability of having subsequent affected children. This risk depends on the status of the parents and on the number of affected offspring.


• For excellent patient education resources, visit eMedicine's Ear, Nose, and Throat Center. Also, see eMedicine's patient education article Hearing Loss.

MISCELLANEOUS

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Frustration, demoralization, poor self-esteem, and eventual social isolation are common outcomes for children with SNHL when identification of hearing impairment is delayed or misdiagnosed.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

• Anagnostakis D, Petmezakis J, Papazissis G, et al. Hearing loss in low-birth-weight infants. Am J Dis Child. Jul 1982;136(7):602-4. [Medline].
• Bergstrom L, Hemenway WG, Downs MP. A high risk registry to find congenital deafness. Otolaryngol Clin North Am. Jun 1971;4(2):369-99. [Medline].
• Cohn ES, Kelley PM, Fowler TW, et al. Clinical studies of families with hearing loss attributable to mutations in the connexin 26 gene (GJB2/DFNB1). Pediatrics. Mar 1999;103(3):546-50. [Medline].
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Article Last Updated: May 7, 2007