8.12 Pediatric Hearing Loss
Key Features
Age at identification has significantly decreased since the advent of newborn hearing screening.
Early identification and treatment of hearing loss is essential to obtain an optimal outcome.
Connexin-26–related deafness is the most common cause of inherited hearing loss.
Acquired hearing loss often occurs within the antenatal period.
Perinatal history is the key to identifying risk factors for both congenital and acquired hearing loss.
The onset of hearing loss in children regardless of etiology often occurs prior to the development of language. The disorders causing both congenital and acquired hearing loss range from the simple and common to the rare and complex. The list of potential diagnoses in this chapter is not exhaustive; additional syndromes with hearing loss as a minor characteristic can be found in Chapter 8.9. For the purpose of this chapter, we will examine hearing loss using the structure seen in Fig. 8.3 , with the caveat that some diagnoses may fall under more than one category.
Epidemiology
Hearing loss is the most common congenital sensory deficit, with an estimated incidence of 2 per 1,000 children. Likewise, acquired loss is exceedingly common, with most children experiencing at a minimum a transient conductive hearing loss (CHL) due to chronic serous otitis. An estimated 50% of childhood sensorineural hearing loss (SNHL) is due to genetic factors, with this proportion increasing with the ongoing detection of new mutations. Genetic causes may eventually account for a large proportion of the hearing loss currently labeled as unknown in etiology. For cases of congenital hereditary hearing loss, about two-thirds are nonsyndromic. In the setting of genetic-related deafness, most cases (70–80%) are autosomal recessive, roughly 20% are autosomal dominant, and the remainder are due to X-linked chromosomal or mitochondrial anomalies. About 50% of the cases of congenital SNHL are considered nonhereditary (i.e., acquired), and most of these are due to TORCHES (to xoplasmosis, r ubella, c ytomegalovirus, h erpes simplex e ncephalitis, and oto s yphilis) infections, sepsis, or severe prematurity.
Clinical
Signs
Speech delay or regression of speech
Vestibular dysfunction
Delays in ambulation
Gait disturbances
Otorrhea
Symptoms
Hearing loss (may be progressive or fluctuating)
Tinnitus
Vertigo
Otalgia
Aural fullness
Congenital Sensorineural Hearing Loss
Dysmorphologies
Most cochlear dysmorphologies are membranous in nature (80–90%) and not identifiable on computed tomography (CT); the remainder have a discernible bony anomaly that is identifiable on CT imaging.
Mondini Deformity
Incomplete partition of cochlea
Autosomal dominant
Unilateral or bilateral hearing loss may be progressive or fluctuating (interspersed with normal hearing).
CT: Cystic dilation of cochlea with absence of modiolus, enlarged vestibular aqueduct, semicircular canal anomalies
Associated with Pendred′s, Waardenburg′s, and Treacher Collins′s syndromes and branchio-oto-renal syndrome (described subsequently)
Michel Aplasia
Autosomal dominant
Anacusis
CT: Absent cochlea and labyrinth, hypoplasia of petrous pyramid
Alexander Deafness
Autosomal recessive or sporadic inheritance
Most common inner ear aplasia
High-frequency loss with residual low-frequency hearing
Aplasia of cochlear duct (membranous defect)
CT: No characteristic features
Associated with congenital rubella and Jervell and Lange-Neilsen′s, Usher′s, and Waardenburg′s syndromes
Scheibe Aplasia
Autosomal recessive
Most common inner ear dysplasia
Partial to complete aplasia of cochlea and saccule (pars inferior) with normal semicircular canals and utricle (pars superior)
CT: No characteristic features (membranous defect)
Associated with Usher′s and Waardenburg′s syndromes
Enlarged Vestibular Aqueduct
Most common radiologic deformity of the inner ear
Progressive SNHL that may be sudden or stepwise decrease
Can occur in isolation or with Mondini deformity
Associated with progressive and/or fluctuating vestibular dysfunction and Pendred′s syndrome
Associated with perilymph gusher
Bing-Siebenmann Dysplasia
Rare, complete dysplasia of membranous labyrinth
Inherited Disorders
Autosomal Recessive
Connexin 26
Chromosomal mutation on 13q11
Most common genetic cause of deafness (> 50% of recessive nonsyndromic hearing loss)
Most commonly autosomal recessive (90 mutations identified)
Can be autosomal dominant (nine mutations identified)
Quantitative and qualitative defects in protein coding for gap junctions (GJB2), which are responsible for maintaining endolymphatic potential in the cochlea [K+], caused by the gene mutation
35delG the most common mutation (however, > 100 mutations have been identified)
Usher′s Syndrome
Chromosome arm 14q (type I), chromosome arm 1q32 (type II)
SNHL, retinitis pigmentosa with or without mental retardation, and cataracts
See Table 8.7 .
Type | Sensorineural hearing loss | Vestibular function | Blindness |
I | Profound | Areflexia | Early adulthood |
II | Moderate to severe | Normal | Midadulthood |
III | Progressive | Progressive | Variable |
Pendred′s Syndrome
Chromosomal mutation on 7q coding for pendrin (sulfate transporter)
SLC26A4 the most common mutation
Defect in tyrosine iodination
Severe to profound SNHL
CT: Mondini deformity or isolated enlarged vestibular aqueduct
Associated with euthyroid multinodular goiter in childhood
Jervell and Lange-Nielsen′s Syndrome
Chromosomal mutation on 11p15 as well as 3, 4, 7, 21
Bilateral SNHL
Long Q-T syndrome (treated with β-blockers)
Goldenhar′s Syndrome
Hemifacial microsomia
Chromosomal mutation on 9
Developmental anomalies of the first and second branchial arches affecting facial nerve, stapedius muscle, semicircular canals, and oval window
Associated with preauricular tags, pinnae anomalies, aural atresia, facial asymmetry, colobomas, and mental retardation
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