DESCRIPTION

• Hearing loss is a broad category and covers a wide range of pathologies. It can be:
  • Purely conductive (e.g., otitis media with effusion [OME] [a.k.a. glue ear] in children)
  • Sensorineural (disruption of the auditory pathway at any point from the cochlea of the inner ear through to the brainstem)
  • Mixed (combination of conductive and sensorineural)
• The severity of hearing loss is also variable, with language, social, and therapeutic implications. The normal hearing range includes 0 to 20 dB, which equates to being able to perceive sound quieter than a whisper. Mild hearing loss corresponds to a range of 20 to 39 dB, moderate is 40 to 69 dB, severe is 70 to 89 dB, and profound is >90 dB.
• Early detection and prompt management are essential for the development of normal language and psychosocial functioning, as well as to identify potentially reversible causes or other underlying problems.

EPIDEMIOLOGY

Hearing loss occurs in 1 to 3 newborns per 1,000 births, with 1 to 2 per 1,000 suffering from permanent childhood hearing impairment. There is a slightly increased prevalence of hearing loss in boys compared to girls with a ratio of 1.16:1.0.

RISK FACTORS

• High-risk factors in neonates
  • Congenital infections: TORCH (toxoplasmosis, other agents, rubella, cytomegalovirus [CMV], and herpes simplex)
  • Family history
  • Craniofacial anomalies
  • Hyperbilirubinemia
  • Prematurity
    • Low birth weight <1,500 g
    • Neonatal intensive care unit (NICU) stay >5 days
    • Use of extracorporeal membrane oxygenation (ECMO)
    • Need for prolonged intubation
  • Perinatal hypoxic ischemic injury
  • Bacterial meningitis
  • Medications (certain antibiotics including, but not limited to, streptomycin, gentamicin, tobramycin, vancomycin)
• High-risk for acquired hearing loss
  • Impacted wax
  • Middle ear effusion (age, immature eustachian tube function, adenoid hypertrophy)
  • Infections (bacterial meningitis, measles, mumps)
  • Cholesteatoma
  • Otosclerosis
  • Trauma
  • Ototoxic medications
  • Pica

PATHOPHYSIOLOGY

• Any condition that impairs the transmission of sound from the external space to the cochlea will cause conductive hearing loss.
  • This includes cerumen, abnormalities of the helix or auricle, middle ear effusions, and ossicular chain abnormalities (fixation, discontinuity).
  • Besides cholesteatoma, other middle ear masses include glomus tumors, schwannomas of the facial nerve, and hemangiomas.
• Sensorineural hearing loss (SNHL) is due to damage to the cochlear hair cells or the cochlear nerve. Even mild distortions in the hair cells can result in severe hearing loss.
• Most acquired hearing loss is conductive, with the OME being the most common etiology. The eustachian tube is positioned more horizontally in younger children, leading to easier entry of nasopharyngeal pathogens into the middle ear space. As the child develops into an adult, the tube elongates and angles caudally. This explains the decline of otitis media cases after the age of 5 years.