SENSORINEURAL HEARING LOSS IN CHILDREN

-incidence from 1:1000 to 1:2000

-50% of childhood sensorineural hearing impairment is due to genetic factors;

I. CLASSIFICATION OF CHILDHOOD HEARING LOSS

A. Congenital

1. Genetic

a. Hearing loss alone

b. Hearing loss associated with other abnormalities

2. Acquired

B. Postnatal

1. Genetic

a. Hearing loss alone

b. Hearing loss associated with other abnormalities

2. Acquired

Nb: Differentiation between congenital (before birth) and postnatal deafness is important in management.

II.PATHOEMBRYOLOGY

A. Inner ear has separate development (otic placode) time (4th-20th week gestation) from external & ME,

however inner ear abnormalities do occur in 15-20% of cases of external canal atresia (SNHL in only 6%).

B. Auricle (1st and 2nd branchial arches) is formed early from 6th-12th week gestation and

malformation of auricle implies malformation of middle ear, mastoid, VII nerve.

Normal auricle with external canal (1st branchial groove) atresia indicates abnormal development during 28th week gestation by which time ossicles and middle ear already formed.

Ossicles: 1st arch derivatives: Þ malleus head, incus short process and body;

2nd arch derivatives: Þ manubrium of malleus, incus long process, stapes.

C. Histopathology of Congenital SNHL

1. Abnormal bony labyrinth

a. occurs rarely

b. due to faulty induction of inner ear (bony labyrinth inductor = developing CNS);

nb: fetus with abnormal brain development will often have abnormal bony labyrinth

c. abnormal bony labyrinth seen on radiographic exam of inner ear Þ suspect CNS abnormality

2. Abnormal neuroepithelium

a. occurs more frequently--predominant histopathology in most congenital and postnatal SNHL

b. usually absence of organ of Corti + abnormal surrounding membranous structures

c. thought to be secondary to premature cell death (degeneration) rather than lack of development

d. with abnormal bony labyrinth, neuroepithelium is often normal

e. with loss of organ of Corti and sound deprivation, normal development of CNS may be impaired.

III. GENETIC DEAFNESS

A. General

1. of all congenital deafness, 50% is secondary to acquired disease and 50% is inherited

2. of the inherited congenital deafness,

-75-88% is autosomal recessive (AR),

-12-24% is autosomal dominant (AD),

-1% is X-linked

3. exist in a variety of combinations of types of HL, mode of inheritance, rate of progression

4. majority of hereditary congenital HL is clinically undifferentiated

(not part of recognizable syndrome and does not affect other organ systems)

5. conductive autosomal recessive HL always exists as part of a syndrome;

6. autosomal recessive is usually stable; autosomal dominant tends toward progression

B. No Associated Organ System Involvement

1. Diagnosis: (hereditary HL w/o stigmata)

a. 2 or more siblings affected

b. consanguineous marriage

c. family history of HL

d. audiometric indications of HL in relatives of deaf child not attributable to another cause

2. variable penetrance with AD transmission: unilateral HL may represent incomplete penetrance; 25% of unilateral SNHL is genetic

3. consider X-linked inheritance if only male children deaf with no known diagnosis

C. Inner Ear Aplasia

1. General

-inner ear deformity can occur alone or in association with a recognized syndrome

2. Classification

a. Michel Aplasia

(1) most severe form

(2) complete failure of bony and membranous labyrinth development

(3) no residual hearing

b. Mondini Aplasia

(1) incomplete formation of bony and membranous labyrinth, often asymmetrical

(2) middle and apical turns of cochlea occupy common bony space (cloaca)

(3) cochlea represented by single curved tube with 1 1/2 instead of 2 & 3/4 turns

(4) vestibular structures also underdeveloped

(5) 2nd most common, (autosomal dominant)

c. Scheibe Aplasia

(1) most common, (autosomal recessive)

(2) membranous aplasia of pars inferior (cochlea/saccule)

(3) bony labyrinth normal (no radiographic abnormality)

(4) Audio:-profound SNHL with residual low frequency hearing

d. Alexander Aplasia

(1) least severe

(2) partial aplasia of cochlear duct (basal turn)

(3) high frequency HL

D. Associated Organ System Involvement

1. Integumentary System

a. Waardenburg Syndrome

(1) autosomal dominant-variable penetrance

(2) most frequently diagnosed hereditary deafness syndrome (1-2% of all congenital deafness)

(3) 6 predominant features: 1. widely spaced medial canthi with shortening of palpebral fissures;

2. prominent, broad nasal route;

3. hypertrichosis of eyebrows;

4. white forelock;

5. heterochromia of irides;

6. SNHL (total or subtotal) in 20% of cases

(4) other features: cleft lip/palate, high arched palate, areas of depigmentation, absent vestib response

(5) Diagnosis: observing stigmata in patient or family (dystrophic canthi and increased intercanthal distance are most common expressions of syndrome)

b. LEOPARD Syndrome

(1) autosomal dominant

(2) lentigines, EKG abnormality, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, bilateral sensorineural deafness (25% affected)

2. Skeletal Dysplasia

a. Klippel-Feil Syndrome

(1) autosomal recessive; females > males

(2) severe progressive SNHL with middle ear anomalies (conductive component),

short neck due to fused cervical vertebrae, spina bifida, EAC atresia

b. Pierre Robin Syndrome

(1) autosomal dominant

(2) main features: cleft palate (50%), micrognathia, glossoptosis

(3) mixed hearing loss, malformed auricles, mental retardation, hypoplastic mandible,

aspiration is a common cause of death

c. Van der Hoeve's Syndrome (Osteogenesis imperfecta)

(1) autosomal dominant, bone fragility, blue sclera

(2) progressive deafness: -CHL, SNHL, or mixed beginning in childhood (50% affected)

3. Craniofacial Anomalies

a. Treacher-Collins Syndrome (Mandibulofacial dysostosis)

(1) autosomal dominant

(2) auricle malformed and small; preauricular fistulas; EAC atresia

(3) mandibular and malar hypoplasia--fishmouth

(4) usually bilateral involvement

(5) down sloping palpebral fissures; notched lower lids

(6) CHL due to malformed malleus/incus (stapes normal)--30% have significant HL

b. Goldenhar's Syndrome (Oculoauriculovertebral dysplasia)

(1) autosomal dominant or autosomal recessive

(2) 1st and 2nd arch abnormality

(3) often unilateral (hemifacial microsomia)

(4) malformed auricles/microtia; malformed middle ear/ossicles; possible underdeveloped inner ear

(5) mostly CHL--40% affected

(6) upper lid colobomas, epibulbar dermoids, hypoplasia of mand/maxilla, cleft pal, spinal anomalies

c. Crouzon's Syndrome (Craniofacial dysostosis)

(1) autosomal dominant

(2) CHL due to EAC atresia or middle ear malformations--30% affected

(3) premature closure of cranial suture lines, midface hypoplasia, bulging eyes--"frog face"

d. Apert's Syndrome (Acrocephalysyndactyly)

(1) autosomal dominant

(2) facial morphology similar to Crouzon's syndrome, but also syndactyly of hands and feet

(3) mental retardation common

4. Ocular Abnormalities

a. Usher's Syndrome

(1) autosomal recessive

(2) 4% of congenital deafness

(3) cxts: congenital SNHL, progressive retinitis pigmentosa, night blindness & tunnel vision, cataracts, mental retardation, psychosis, spinocerebellar ataxia \

(4) vestibular dysfunction--almost all will have no vestibular response to caloric test or ice water

calorics; helps in diagnosis when etiology unknown

(5) usually born deaf due to atrophy of organ of Corti with progressive vision loss from retinitis pigmentosa; night blindness is 1st retinal sign (before age 10) with 50% patients having decreased visual acuity by 2nd decade

(6) retinal findings: granular accumulation of pigment beginning at fundus and extending to periphery

b. Alstrom's Syndrome

(1) autosomal recessive

(2) progressive SNHL beginning in childhood, obesity, diabetes, retinal pigmentation

c. Refsum's Disease

(1) autosomal recessive

(2) progressive aymmetric SNHL (50%), neurologic dysfunction, retinitis pigmentosa, ichthyosis beginning late childhood

(3) absence of enzyme for phytanic acid metabolism (from chlorophyll)

(4) Dx.: high phytanic acid plasma level

(5) Tx.: eliminate phytanic acid from diet

5. Cardiac Abnormalities

a. Jervell and Lange-Nielsen Syndrome

(1) autosomal recessive

(2) cxtcs: profound bilateral SNHL (high frequency worst),recurrent syncope (prominent feature), usually terminates in sudden death--early detection important to preserve life

(3) suspect with family history of SIDS

(4) EKG abnormalities: large T waves, prolonged QT interval

(5) syncopal episodes usually begin 2nd or 3rd decade, last 5-10 minutes

(6) 50% die before age 15 w/o treatment

(7) Rx: 1. propanolol +/- phenobarbital 2. implant cardioverter defibrillator when refractory to drugs

(8) Diagnosis: all patients with idiopathic SNHL should have at least 1 EKG

6. Renal Abnormalities

a. Alport's Syndrome

(1) autosomal dominant

(2) most common progressive inherited cause of SNHL in children

(3) characteristics: progressive SNHL usually beginning age 10, progressive nephritis with hematuria and proteinuria beginning 1st or 2nd decade

(4) males more severely affected--if untreated usually die by 3rd decade;

females often have normal life span with toxemia duringpregnancy

(5) Diagnosis: consider Alport's in any child with SNHL of recent onset;

UA : >3 RBCs/HPF, >5 WBCs/HPF, proteinuria; serum Cr/BUN abnormal;

IVP: atrophy or lobulated kidney with advanced disease

(6) HL usually progresses with age, predominant in HF, affects 50%, correlation between HL severity and renal disease severity; seldom more than severe HL

(7) ocular abnormality may also occur.

(8) histopathology: degeneration of organ of Corti, atrophy of spiral ganglion.

7. Endocrine Dysfunction

a. Pendred's Syndrome

(1) autosomal recessive

(2) variable bilateral SNHL (atrophy of organ of Corti) -- usually severe to profound, esp high freq

(3) develop goiter which usually apparent before age 8; usually euthyroid

(4) comprise 1-7% severe to profoundly deaf children

(5) U-shaped audiogram, vestibular response variable

(6) Mx: exogenous thyroid hormone; total or partial thyroidectomy is contraindicated -- goiter returns

8. Metabolic Storage Diseases

a. Mucopolysaccharidoses

(1) ie., Hurler's Syndrome (Gargoylism); Hunter's Syndrome is same but X-linked

(2) characterized by excessive urinary excretion of glycosaminoglycans

(3) abnormal mucopolysaccharides are deposited in tissues

(4) all autosomal recessive (except Hunter's)

(5) hearing loss is conductive or mixed with air-bone gap in high frequencies

(6) dwarfism, forehead prominence, low set ears, mental retardation,hepatosplenomegaly, coarsening of facial features, corneal opacities

(7) death in early adolescence

9. Chromosomal Abnormalities

a. Trisomy 13 and 18

b. lethal in infancy

c. mixed hearing loss (may also occur in children with Down's Syndrome

IV. ACQUIRED CONGENITAL DEAFNESS

A. Maternal ingestion of teratogens/ototoxins

1. Thalidomide

2. Streptomycin

3. Quinine, Chloroquine phosphate

B. Intrauterine infection

1. Rubella

a. most common cause of acquired congenital SNHL

b. earlier in intrauterine life--more severe effects, 5-10% of mothers with rubella in 1st trimester give birth to children with deafness

c. clinical presentation: (after 1 week of inapparent viral infection)- posterior cervical and retroauricular adenopathy followed by mild URI, then rash which on face & disappears rapidly in 72 hrs.

d. Diagnosis: physical exam +immunologic techniques, maternal rash or exposure history

e. Findings: pigmentary retinitis ("salt and pepper"): most common and consistent finding; congenital cataracts, microcephaly (mentalretardation), cvs anomalies, IUGR, jaundice, long bone lesions

f. all pregnant women have rubella titers drawn at beginning of pregnancy & follow-up titers later

h. severe to profound SNHL, may be assymetric, may be progressive;

may have CHL--fixed stapes or CSOM secondary to high arched palate

2. Cytomegalic inclusion disease

a. CMV;55-72% pregnant women have positiveCMV titers Þ 10% of their offspring have CMV infection; -majority ofCMV infected infants appear normal but 10-15% develop disabilities from CNS damage

b. CMV can infect neonate when mother has a primary or subsequent infection (consecutive pregnancies with infected children).

c. Stigmata: microcephaly, hydrocephaly, mental retardation, palatal abnormalits, intracereb calcifications, prematurity, low birth weight, chorioretinitis, jaundice with hepatosplenomegaly, petechiae

d. Diagnosis: positive titers (CMV specific IgM) from mother and child (sometimes deceiving)

3. Other Intrauterine Infections

a. Toxoplasmosis

b. Influenza

c. Herpes 1 and 2--history of labial or vaginal lesions

d. Syphilis

C. Perinatal Causes

1. Prematurity:

a. most common cause due to factors including: anoxia, kernicterus, ototoxic medication, labyrinthitis, meningitis, temporal bone fractures

b. prematurity as a factor in SNHL is 10%

c. 2% children less than 1.36 kg (3 lbs.) have significant SNHL

d. premature infant has 20x greater chance of deafness than normal birth weight child

e. usually severe SNHL especially HF

2. Anoxia

a. most important factor in SNHL of premature infant;

asphyxia is likely if cord blood pH <7.25, 5 minute & Apgar <5

b. pathologic lesion probably lies in cochlear nucleus and other portions of CNS (not cochlea)

c. high rate of other CNS handicaps

3. Kernicterus

a. many are also premature

b. few cases of RH incompatibility, but ABO and other blood group incompatabilties assoc. with kernicterus + SNHL

c. hearing loss--bilateral HF SNHL with little loss of speech discrimination

d. Histopath: abnormal CNS with greatest nerve cell injury in ventral cochlear nucleus

e. exchange transfusion --if serum bilirubin >20mg/dl

D. Other Causes

1. Placental/umbilical cord disruption--interference with fetal oxygenation

2. Irradiation (1st trimester)

3. Maternal alcoholism--nutritional disturbances

4. Endocrine disease (maternal): thyrotoxicosis, diabetes, pseudohypoparathyroidism

5. Immunologic disorders

V. GENETIC COUNSELING

A. Extremely important aspect of patient care

B. Clinically, 40% of congenital HL cases will not be found to have a known cause

C. Children born to older parents may be affected through new dominant mutations

D. Risk: (for other children)

1. AD--50%, AR--25%

2. may be altered by incomplete penetrance

3. unknown etiology--presume genetic cause (AD, AR, X-linked)--risk >1 in 1000 and <1 in 2 or 1 in 4

4. informing parents--must give estimate of overall risk = 10%; varies with birth order

(first child after affected sibling--12.5%, second child--10%, third child--7.5%, fourth child--5%)

VI. DIAGNOSIS AND MANAGEMENT OF CHILDHOOD DEAFNESS

-Early signs of abnormal speech/language development:

6 months--no response to sound or voice,

9 mos.--no response to name,

12 mos.--does not babble,

15 mos.--does not understand or respond to "no" or "bye-bye",

18 mos.--no words other than "ma-ma" or "da-da",

2 years--no 2-word phrases or less than 25 words,

3yrs.--no simple questions,

4 yrs.-- consistent articulation errors (except "r", "s", "th"),

5 yrs.--awkward sentence structure or dysfluency

nb: most common cause of HL in children = otitis media,

if suspected congenital or postnatal SNHL, then obtain history in orderly manner:

HISTORY

-See adult Hx & Risk factors in Congen deafness tute.

-try to determine time of onset,

-(1) gestational--identify factors which may have caused HL during fetal development;

1st trimester most important; causes include maternal infections, maternal ingestion of ototoxic drugs,

interference with fetal oxygenation (placental disruption), irradiation, maternal alcoholism, immunologic or endocrine disorders

(2) perinatal--include prematurity, anoxia (placeta previa, abruptio placentae, difficult labor, prolapsed cord), kernicterus, ototoxic med., birth trauma

(3) postnatal--causes include viral labyrinthitis (measles, mumps, chicken pox, influenza), encephalitis, meningitis, sickle cell anemia, head trauma, sound trauma, congenital syphilis, perilymph fistula

(4) family- history of HL.

EXAMINATION:

-detailed otologic exam, & review of all organ systems for abnormalities suggesting a syndrome.

Ix:

-as for adults SNHL

-Audiology: SEE my tute notes on this!!!!

Bibliography:

Cummings, C. Otolaryngology.  chapter 176