Chapter 13 Etiologies

• Etiologies & High-Risk Factors for Hearing Loss in Children

Hearing Loss Prevalence

• Demographic trends show a high, rising global hearing loss prevalence across life.
• It is projected that the number of people with hearing loss may increase more than 1.5-fold in the next three decades.
• Over 700 million people are likely to experience moderate or higher hearing loss by 2050.
• In 2018, there were an estimated 466 million people with disabling hearing loss worldwide.
• 93% of people with disabling hearing loss are adults, and 7% are children.
• Among adults with disabling hearing loss, more are males (56%) than females (44%).
• Prevalence of hearing loss that is 35 dB or greater: Prevalence of hearing loss 35 dB or greater by age and severity (A) and proportion of individuals with hearing loss by age and cause for all severities (B).
• 3 in 1000 babies are born with hearing loss
• Hearing loss is 10x greater for infants with 1 or more risk factors (2-5%).
• Late onset and acquired hearing loss incidence is 6x higher than HL in the neonatal period.

Etiology of Childhood Hearing Impairments

• 50-55% of childhood hearing impairments are of unknown origin.
• 25-30% of Etiology of Childhood Hearing Impairments is genetic.
• 70% of genetic hearing impairments are recessive traits; 25% are dominant.
• 5% of genetic hearing impairments are X-linked and mitochondrial.
• 5% of the genetic origins in hearing impairments stem from chromosomal aberrations
• Teratogenic agents account for 10% of childhood hearing impairments.
• Maternal infections, chemicals/drugs, and radiation are teratogenic agents.
• Environmental/traumatic factors account for a portion of the childhood hearing impairments
• Loud noise, low birth weight, prematurity, severe neonatal jaundice, medication, and injury are environmental/traumatic factors.

Risk Indicators for Delayed-Onset Hearing Loss

• There are risk indicators that are especially concerning for delayed-onset hearing loss.
• Concerned caregiver regarding hearing, speech, language, or developmental delay is an indicator.
• A family history of permanent childhood hearing loss is an indicator.
• Neonatal intensive care for more than 5 days or any of the following is indicator: assisted ventilation, exposure to ototoxic medications (gentamycin and tobramycin) or loop diuretics (furosemide/Lasix), hyperbilirubinemia that requires exchange transfusion.
• In utero infections, such as CMV, herpes, rubella, syphilis, and toxoplasmosis are indicators
• Craniofacial anomalies, including those that involve the pinna, ear canal, ear tags, and ear pits and temporal bone anomalies are indicators
• Physical findings, such as white forelock, can be associated with a syndrome including sensorineural or permanent conductive hearing loss.
• Syndromes associated with hearing loss or progressive or late-onset hearing loss, such as: neurofibromatosis, osteopetrosis, Usher syndrome; Waardenburg, Alport, Pendred, and Jervell and Lange-Nielson syndromes.
• Neurodegenerative disorders such as Hunter syndrome or sensory motor neuropathies such as Friedreich ataxia and Charcot-Marie-Tooth syndrome are risk indicators.
• Culture-positive postnatal infections associated with sensorineural hearing loss: bacterial and viral (especially herpes viruses and varicella) meningitis.
• Head trauma, especially a basal skull/temporal bone fracture requiring hospitalization, is a risk indicator.
• Chemotherapy (treatment for malignancy/cancers) is a risk indicator.

Prematurity

• Premature infants: gestational age under 37 weeks.
• Moderately premature infants: 31-36 weeks.
• Severely premature infants: 24-30 weeks.
• Newborn is defined as the first day of life.
• Neonate is defined as the first month of life
• Infant is defined as the first year of life.
• Prematurity accounts for 5-10% of live births.
• High morbidity and mortality is attributable to immature organ systems
• Responsible for 75% of perinatal and neonatal deaths
• Immediate/early complications are common

Prematurity: Immediate/early complications.

• Hypoxia/ischemia
• Intraventricular hemorrhage
• Sensorineural injury
• Respiratory failure
• Necrotizing enterocolitis
• Cholestatic liver disease
• Nutrient deficiency
• Social stress

Early complications and associated sequelae

• Hypoxia/ischemia can lead to mental retardation, spastic diplegia, microcephaly, and seizures.
• Intraventricular hemorrhage can lead to metal retardation, spasticity, seizures, and hydrocephalus.
• Sensorineural injury can lead to hearing and visual impairment, retinopathy of prematurity, strabismus, and myopia.
• Social stress can lead to child abuse/neglect and the failure to thrive.

Hyperbilirubinemia (severe neonatal jaundice)

• This condition is marked by high levels of bilirubin in the blood.
• Increased bilirubin causes the infant's skin and whites of the eyes (sclera) to look yellow.
• Causes of jaundice include physiological jaundice, breast-feeding jaundice (slow breakdown of bilirubin); usually not harmful, prematurity (immature blood, liver and enzymes) etc
• Increased red blood cell break down includes: abnormal blood shapes
• Blood type mismatch between the mother and the baby Bleeding underneath the scalp (cephalohematoma) caused by a difficult delivery. Higher levels of red blood cells, more common in small-for-gestational-age babies and some twins Infection . Lack (deficiency) of certain important enzymes.
• Inability to remove bilirubin includes: Certain medications, congenital infections such as rubella, syphilis, and others, diseases that affect the liver or biliary tract, such as hepatitis hypoxia, infections (such as sepsis) , many different genetic or inherited disorders.
• Treatment will involve none, phototherapy, or exchange-transfusion.
• Possible complications include: Cerebral palsy, deafness and Kernicterus ( a severe complication of jaundice caused by too much bilirubin in a child's blood and leading to brain damage).

TORCH Infections

• TORCH infections are a group of congenital infections passed from mother to child during pregnancy, delivery, or after birth:
• T = toxoplasmosis
• O = other (syphilis)
• R = rubella
• C = cytomegalovirus (CMV)
• H = herpes simplex (HSV)

Suspecting TORCH

• Intra-uterine growth restriction (IUGR), Small for Gestational age
• Hepato-spleeno megaly (enlarged liver & spleen)
• Thrombocytopenia (low platelet level)
• Unusual rash
• Maternal history
• “Classic” findings of any specific infection

Diagnosing TORCH

• Maternal/prenatal history
• Remember most infections are mild illnesses often unrecognized
• Thorough examination of infant
• Laboratory tests

Toxoplasmosis

• Caused by protozoan Toxoplasma gondii.
• Domestic cat is the definitive host with infections via ingestion of cysts (uncooked meats, garden products) and contact with oocysts in cat feces.
• The prevalence of infection is much higher in European countries
• Acute infection usually asymptomatic
• There is a 1/3 risk of fetal infection with primary maternal infection in pregnancy
• Infection rate is higher in the 3rd trimester and fetal death is higher with infection in the 1st trimester.

Clinical Manifestations

• Most cases (70-90%) are asymptomatic at birth.
• Classic triad of symptoms includes chorioretinitis, hydrocephalus, and intracranial calcifications
• Other signs include fever, rash, enlarged liver & spleen, microcephaly, seizures, jaundice, thrombocytopenia, enlarged lymph nodes.
• Initially asymptomatic infants are still at high risk of developing abnormalities, such as chorioretinitis and 25% have sensorineural HL.
• Diagnosis is made via Maternal IgG testing, isolation of toxoplasma in culture from placenta and umbilical cord, or newborn with IgM/IgA serologies.
• Treatment of pregnant can reduce congenital transmission by 50% and symptomatic infants should be treated.

Rubella

• A single-stranded RNA virus, it's also a vaccine-preventable disease and a mild, self-limiting illness.
• Infection earlier in pregnancy has a higher probability of affecting the infant.

Clinical Manifestations of Rubella

• Sensorineural hearing loss (50-75%)
• Cataracts and glaucoma (20-50%)
• Cardiac malformations(20-50%)
• Neurologic (10-20%)
• Others include growth retardation, bone disease, Hepato-Splenomegaly, and Thrombocytopenia with “blueberry muffin” lesions
• Maternal IgG may represent immunization or past infection, it cannot be determined accurately.
• Viruses can be isolated by nasal secretions, CSF is less frequent
• Detection of IgM= recent postnatal or congenital infection and Rising monthly IgG suggest congenital, but diagnosis is hard to establish after 1 year.
• Prevention can be done by immunization , can provide supporting care when infected.

Cytomegalovirus (CMV)

• The most common congenital viral infection: with ~40,000 infants per year in U.S.
• Mild, self-limiting illness.
• Transmission can occur with primary infection or reactivation of virus.
• 40% risk of transmission in primary infection. and increased risk of transmission later in pregnancy.
• More severe sequalae is associated with earlier infection.
• 90% are Asymptomatic at birth, up to 15% develop symptoms later, notably sensorineural hearing loss.
• In Symptomatic infection includes SGA, HSM, petechiae, and jaundice.
• Other symptoms include chorioretinitis, periventricular calcifications, and neurological deficits
• Over 80% develop long-term complications like hearing loss, vision impairment, and developmental delay.
• Diagnosis can be done using Maternal IgG shows , but the result is common and not helpful (infection). Viral isolation done from urine or saliva in 1st 3 weeks of life.
• Treatment is currently not recommended in asymptomatic infants due to side effects.

Herpes Simplex (HSV)

• HSV1 or HSV2 are primarily transmitted through infected maternal genital tract and are rationale for C-section delivery prior to membrane rupture.
• Most are asymptomatic at birth, with Three patterns with equal frequency of symptoms between birth and 4 wks: Skin, eyes, mouth (SEM), CNS disease.
• Disseminated disease occurs earliest. with Initial manifestations including nonspecific skin lesions (not necessarily present).
• Diagnoses and Culture of maternal lesions take place if culture is not present in mother. Cultures in infant will be taken at lesion,oro/nasopharynx and CSF.
• Treatment: High dose of antiviral drug .

Syphilis

• Treponema pallidum (spirochete transmitted sexually.
• Placental transmission early as 6 weeks gestation.
• This occurs during the later half of pregnancy.
• Mothers with primary or secondary syphilis more likely to transmit than latent disease.
• Congenital syphilis affects about 2/ 3 of affected live-born infants (asymptomatic at birth), and later develop clinical with symptoms split in 2 years. Early congenital cases includes cutaneous lesions.
• 5 weeks ofJaundice, anemia and snuffles or rhinitis,Periostis and metaphyseal dystrophy. Late congential cases include, Fontal bossing ,Short maxilla ,High Palatial arch .
• Defined by T. palldium identified in skin lesions.
• Penicillin G is the drug of choice.
• Maternal treatments during pregnancy, effective (98%).

Preventable TORCH Infections

• Rubella and Syphilis are preventable.