Hearing Loss and Deafness
Hearing Loss and Deafness: Excerpt from The Diagnostic Approach to Symptoms and Signs in Pediatrics
Hearingis the perception and interpretation of sound.Because normal hearing is importantin development of language and social interaction, moderate-to-severehearing loss during first 3 yrs of life may seriously impair thisdevelopment.Identifying children with hearing lossis crucial, so that treatment can be given to overcome any lossand counteract its developmental effects.Hearing loss can be classified as conductive,sensorineural, or mixed.Conductive loss is caused by any impedanceof sound wave transmission from external auditory meatus to footplateof stapes. Often reversible with medical or surgical treatment.Sensorineural loss is caused by damageto cochlea, auditory nerve, cochlear branch of auditory nerve, orpathways of auditory transmission, including brainstem nuclei, medialgeniculate body, and auditory cortex. With rare exceptions, usuallynot reversible.Mixed hearing loss has both conductiveand sensorineural components. Principal Causes of Hearing Loss and Deafness
- Conductivehearing loss
- Externalauditory canal disorders
- Atresia of external auditory canal
- Impacted cerumen
- Otitis externa
- Exostosis
- Masses
- Middle ear disorders
- Acuteand chronic otitis media
- Otitis media with effusion
- Tympanic membrane perforation
- Hemotympanum
- Tympanosclerosis
- Ossicular chain defect, disruption,or fixation
- Cholesteatoma and other middle earmasses
- Sensorineural hearing loss
- Sensorineuralhearing loss without associated abnormalities
- Sensorineural hearing loss with associatedabnormalities
- Chromosomal disorders
- Inner ear malformations
- Labyrinthineaplasia
- Common cavity malformation
- Cochlear malformations
- Large vestibular aqueduct
- Prematurity
- Hypoxic-ischemic encephalopathy
- Bilirubin encephalopathy (kernicterus)
- Infection
- Trauma
- Drugs
- Perilymph fistula
- Neoplasm
- Ménière disease
- Unknown
- Mixed hearing loss
Clinical Features and Diagnosis
Conductive Hearing Loss
External Auditory Canal Disorders
Atresia of External Auditory Canal
Absenceof meatus under tragus signifies presence of external auditory canalatresia. External ear is usually small and deformed.CT should be performed to identifyother abnormalities, especially in middle ear, and to help in evaluationof possible surgical repair. Impacted Cerumen
Impacted cerumen (earwax) in external canalis common cause of conductive hearing loss. Hearing returns to normalafter its removal.
Otitis Externa
Inflammationof external auditory canal with discharge and swelling causes obstructionand diminished sound transmission. Hearing returns to normal afterinflammation subsides.See Chap.16, Earache. Exostosis
Exostoses(bone overgrowths) may be found in external auditory canal or middleear but are uncommon in pediatric population.Usually bilateral and close to tympanicmembrane.Although diagnosis is usually clinical,CT may be useful in defining their extent. Masses
Foreignbodies (e.g., cotton balls, erasers, beads, and other small objects)that obstruct external canal can cause decreased hearing. Readilyseen by otoscopy.Polyps are reddish or purplish massesthat bleed easily. Can arise from external canal and tympanic membraneor protrude from middle ear into canal through perforation in membrane.Often associated with cholesteatoma. Excisional biopsy is diagnostic.Neoplasms arising from external auditorycanal are rare in pediatric population but include neurofibromas,eosinophilic granulomas, and rhabdomyosarcomas. CT shows locationand extent of lesion. Histologic diagnosis is definitive. Middle Ear Disorders
Acute and Chronic Otitis Media and Otitis Media with Effusion
Most commoncauses of conductive hearing loss in children are acute and chronicotitis media and otitis media with effusion.See Chap.16, Earache. Tympanic Membrane Perforation
Most common causes of tympanic membrane perforationare acute otitis media and head trauma. The latter causes conductivehearing loss by accumulation of blood in external canal or middleear or by disruption of ossicular chain. Perforation is seen byotoscopy.
Hemotympanum
Direct blowto ear or basilar skull fracture may cause hemotympanum.Tympanic membrane appears red or purplebecause of blood in middle ear space. Other findings that may beseen with basilar skull fracture include ecchymoses behind ear oraround eyes, and CSF drainage from nose or ears.CT helps determine extent of injury. Tympanosclerosis
Characterizedby whitish plaques in tympanic membrane and nodular deposits insubmucosal layers of middle ear. If deposits of calcium and phosphatecrystals involve ossicles, conductive loss can occur.Predisposing factors are chronic otitismedia and tympanostomy tube placement. Ossicular Chain Defect, Disruption, or Fixation
Should besuspected in cases of conductive hearing loss when external auditorycanal and middle ear appear normal on exam.History of head trauma suggests ossiculardisruption.CT of temporal bone shows ossicularchain and any abnormalities of otic capsule. Cholesteatoma and Other Middle Ear Masses
Cholesteatomausually appears as whitish mass in middle ear. Other middle earmasses are discussed by Bellet et al. (1992).Conductive hearing loss, tinnitus,ear fullness, or facial nerve palsy can indicate presence of middleear mass, regardless of whether it is visible by otoscopy.CT is initial imaging exam for middleear masses. Sensorineural Hearing Loss
Sensorineural Hearing Loss without Associated Abnormalities
In the past these disorders were usuallydistinguished from each other by mode of genetic transmission, ageof onset, severity of hearing loss, and type of audiogram (Gorlinet al., 1995). Recently, several genes for hearing loss have beenmapped to different chromosomes, permitting specific diagnosis (Willems,2000).
Sensorineural Hearing Loss with Associated Abnormalities
Several syndromes may be associated withsensorineural hearing loss: Hurler, Hunter, Cockayne, Alport, Klippel-Feil,Wildervanck, Waardenburg, Usher, Pendred, Jervell and Lange-Nielsen,and branchio-oto-renal.
Chromosomal Disorders
Although trisomies 13, 18, 21, and 22 maybe associated with sensorineural hearing loss, conductive loss dueto otitis media with effusion is more common.
Inner Ear Malformations
The following malformations can usually bediagnosed by CT, although sometimes MRI may be necessary.
Labyrinthine Aplasia
Michel malformation consists of aplasia ofcochlea, vestibule, and semicircular canals.
Common Cavity Malformation
Exists when there is single labyrinthinecavity without cochlea or semicircular canals.
Cochlear Malformations
Most commoncochlear malformation observed with imaging studies is Mondini malformation.Axial CT shows single cochlear cavitywith normal cochlear basal turn.Has been reported in many syndromes:DiGeorge, Goldenhar, Pendred, Waardenburg, and CHARGE association.Pseudo-Mondini malformation is presenceof a cochlear vestige that communicates directly with vestibulewithout intervening bony cochlear basal turn.With cochlear aplasia, nidus of scleroticbone replaces cochlea. Large Vestibular Aqueduct
Both the vestibular aqueduct and endolymphsac are enlarged in this malformation Although hearing loss is progressive,it is often fluctuating. Head trauma may result in sudden, irreversible,profound sensorineural hearing loss.
Prematurity
Mechanism of hearing loss in premature infantswithout any other predisposing factor is unknown.
Hypoxic-Ischemic Encephalopathy
Perinatal asphyxia, including birth trauma,may result in hypoxic-ischemic encephalopathy and hearing loss.
Bilirubin Encephalopathy (Kernicterus)
Usuallycauses bilateral high-frequency hearing loss. Possible mechanismsinclude damage to cochlear nuclei and auditory pathways in brain.See Chap.3, Alteration in Consciousness. Infection
Congenitalinfection with rubella, cytomegalovirus, herpes simplex virus, toxoplasmosis,or syphilis (see Chap. 36, Jaundice)sometimes produces hearing loss and deafness.Although acute and chronic otitis mediacause conductive hearing loss, it is postulated that inflammatorymediators or toxins pass from middle ear to inner ear through roundwindow membrane to cause sensorineural hearing loss.Bacterial meningitis and encephalitiscan cause sensorineural hearing loss that can range from mild toprofound. Trauma
Loud noiseof sufficient duration and intensity can destroy organ of Cortiand its associated neural connections in base of cochlea.Tinnitus almost always occurs in noise-inducedhearing loss.Direct trauma including temporal bonefractures and penetrating wounds may disrupt bony and membranouslabyrinth to cause sensorineural hearing loss. CT is imaging procedureof choice. Drugs
Drugs takenduring pregnancy that may cause hearing loss in neonates includequinine, chloroquine, and isotretinoin.Aminoglycosides (streptomycin, kanamycin,gentamicin, amikacin, neomycin), loop diuretics (furosemide, ethacrynicacid), and cisplatin can cause sensorineural loss in infants andchildren. Perilymph Fistula
Abnormalleak of perilymph (cerebrospinal fluid) into middle ear or mastoidair cell system is caused by defects in temporal bone, particularlyin region of stapes footplate or round window.Defects may be congenital or acquired(secondary to trauma of the temporal bone). They are associatedwith sudden fluctuating or progressive sensorineural hearing lossand can predispose to recurrent meningitis. Vertigo also may occurbut is rare.Injection of intrathecal radioisotopeor dye with subsequent nuclear scintigraphy or CT, respectively,often identifies site of leak. See Chap.41, Nasal Discharge. Neoplasm
Some neoplasticdiseases (e.g., leukemia and neuroblastoma) can invade temporal boneand damage cochlea or auditory pathways.Acoustic neuroma, a benign tumor ofeighth cranial nerve, can cause sensorineural hearing loss, tinnitus,vertigo, and facial nerve paralysis. Presence of bilateral tumorssignifies neurofibromatosis.Posterior fossa tumors in area of cerebellopontineangle (e.g., meningioma) can cause hearing loss, tinnitus and ataxia.CT and MRI can locate and define extent of tumor. Histologic diagnosisis definitive. Ménière Disease
Sensorineural fluctuating hearing loss, tinnitus,and vertigo characterize Ménière disease.
Unknown
There are a number of cases of hearing lossin which the etiology is unknown.
Mixed Hearing Loss
In children with sensorineural hearing loss,presence of acute otitis media or otitis with effusion may produceconductive hearing loss.
Diagnostic Approach
Auditoryand language findings listed in Table26.1 are indications for possible hearing loss or deafness.Suspected hearing loss should be investigatedto determine the type, severity, and cause.Any child with suspected hearing lossshould be referred for audiologic evaluation. Speech and languageassessment is often necessary. Neurologic and otolaryngologic consultationmay be required, depending on suspected problem. Table 26.1. Indications of Possible Hearing Loss or Deafness
| Age | Indications |
| Newborn | No startle after a hand clap 3–6 ft away |
| 1 mo | Failure to alert to sound of a voice |
| 4–12 mos | Failure to turn to someone speaking; failure to make soundsor babble |
| 12 mos | Failure to respond to 1-step command (e.g., "giveme" or "bring me") with a gesture |
| 15 mos | Failure to follow same 1-step command without a gesture |
| 18 mos | Failure to use single words |
| 2 yrs | Failure to repeat phrases or follow simple commands |
| 3 yrs | Failure to locate source of a sound |
| 4 yrs | Failure to give account of recent experience |
| 5 yrs | Failure to carry out simple conversation or difficult to understand speech |
| 6 yrs | Failure to concentrate or be attentive in school |
| Any age | Reliance on gestures rather than on speaking for communication;inadequate understanding of speech; poor articulation; inattentionto faint sounds but more appropriate response to louder sounds |
Hearing Assessment
Hearingthresholds in decibels (dB) correspond to various degrees of hearingloss:Normal: <20dBMild: 21–40 dBModerate: 41–60 dBModerately severe: 61–80 dBSevere: 81–100 dBProfound: >100 dB With pure conductive hearing loss,bone conduction threshold is normal, while air conduction thresholdis increased.Both air and bone conduction thresholdsare increased but within 10 dB of each other with pure sensorineuralloss.With mixed hearing loss, air and boneconduction thresholds are increased but differ by >10 dB.Behavioral observation audiometry canbe used to evaluate hearing in infants <6 mos of age. Loudenough sound with toy bell or calibrated noisemaker provokes arousal.Response may be generalized body movement, startle reflex or jump,eye blinking when awake, or eye tightening when asleep. This testingestimates functioning of child's better ear and measuresleast level of sound stimulus for noting response (minimal responselevel).Reinforcement audiometry can be usedto test hearing in children 6–24 mos of age. Child is placedbetween 2 speakers in sound-proof room. Usual stimuli are speechor narrow bands of noise at different frequencies. To help maintainchild's attention, activating animated toy each time childresponds to test stimulus is useful.Play audiometry may be used with children2–4 yrs of age. Each ear can be tested, and positive responsescan be noted by having child identify a toy or point to a picture.Conventional audiometry may be usedin children >4 yrs of age. What is obtained in standardtesting are air-conducted and bone-conducted pure tone thresholdsfor each ear, speech reception thresholds for each ear, and speechdiscrimination scores.Auditory brainstem response testingis most frequently used objective test to determine hearing sensitivityin young infants or in children unable to cooperate for behavioraltest measurements. Specific Diagnosis
Otoscopicexam of external canal and middle ear can diagnose causes of conductive hearingloss except for ossicular chain defect or disruption, when temporalbone CT is necessary.Tympanic membrane mobility can be assessedby pneumatic otoscopy. Impedance audiometry (tympanometry) is anothermethod to assess and quantitate tympanic membrane mobility.With sensorineural hearing loss, historyand physical exam may provide clues for specific diagnosis. Anyinvestigation will be guided by these findings. However, some childrenwith sensorineural loss have no other abnormalities.CT of temporal bone should be obtainedto search for any anatomic abnormalities. References
- Bellet PS, et al. The evaluation of earcanal, middle ear, temporal bone, and cerebellopontine masses ininfants, children, and adolescents. Adv Pediatr 1992;39:167–205.
- Benton C, Bellet PS. The ear and temporal bone. In:Ball WS Jr, ed. Pediatric neuroradiology. Philadelphia: Lippincott-Raven,1997:607–669.
- Bluestone CD, et al., eds. Pediatric otolaryngology,3rd ed. Philadelphia: WB Saunders, 1996.
- Brookhauser PE. Sensorineural hearing loss in children.Pediatr Clin North Am 1996;43:1195–1216.
- Chan KH. Sensorineural hearing loss in children: classificationand evaluation. Otolaryngol Clin North Am 1994;27:473–486.
- Cotton RT, Myer CM III, eds. Practical pediatric otolaryngology,Philadelphia: Lippincott-Raven, 1999.
- Epstein S, Reilly JS. Sensorineural hearing loss. PediatrClin North Am 1989;36:1501–1520.
- Fleisher GR, Ludwig S, eds. Textbook of pediatric emergencymedicine, 4th ed. Philadelphia: Lippincott Williams & Wilkins,2000:287–291.
- Gorlin RJ, et al. Hereditary hearing loss and its syndromes.New York: Oxford University Press, 1995.
- Parving A, Newton V. Guidelines for description ofinherited hearing loss. J Audiol Med 1995;4:2–5.
- Rudolph EA, ed. Rudolph's pediatrics, 20thed. Stamford, CT: Appleton & Lange, 1996.
- Todd NW. At-risk populations for hearing impairmentin infants and young children. Int J Pediatr Otorhinolaryngol 1994;29:11–21.
- Willems PJ. Genetic causes of hearing loss. N EnglJ Med 2000;342:1101–1109.
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Book Source Details
- Book Title: The Diagnostic Approach to Symptoms and Signs in Pediatrics
- Author(s): Paul S. Bellet
- Year of Publication: 2006
- Copyright Details: The Diagnostic Approach to Symptoms and Signs in Pediatrics, Copyright © 2006 Lippincott Williams & Wilkins.
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