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- Decrease in the ability to perceive and comprehend sound. It can be partial, complete, unilateral, or bilateral.
- Types of hearing loss include conductive hearing loss (CHL or air–bone gap), sensorineural hearing loss (SNHL), or mixed hearing loss.
- System(s) affected: auditory; outer and middle ear (CHL) or inner ear, auditory nerve, and/or brainstem (SNHL)
- All ages affected; common in children (CHL) and elderly (SNHL)
- Usually more severe at an earlier age in men
- Increases with age
- Sudden sensorineural hearing loss (SSHL) occurs in 5 to 20 per 100,000 persons/year.
WHO estimates that 538 million people affected worldwide.
- ~80% of people aged >85 years have hearing loss.
- Hearing aids are underused.
- Loss of communication is a source of emotional stress and a physical risk for the elderly.
- Congenital hearing loss
- 1 to 6/1,000 infants have hearing loss.
- Mandatory screening in >97% of newborns with otoacoustic emission (OAE) and auditory brainstem response (ABR) testing
- Audiologic testing after major intracranial infection (meningitis)
- Significant hearing loss at birth and infancy can lead to speech, language, and cognitive delays. Early diagnosis and treatment improves outcome.
- Otosclerosis can worsen during pregnancy.
- Maternal infections cause permanent pediatric hearing loss.
Etiology and Pathophysiology
- CHL: Hearing loss can result from middle ear effusion, obstruction of canal (cerumen/foreign body, osteomas/exostoses, cholesteatoma, tumor), loss of continuity (ossicular discontinuity), stiffening of the components (myringosclerosis, tympanosclerosis, and otosclerosis), and loss of the pressure differential across the tympanic membrane (TM) (perforation).
- SNHL: damage along the pathway from oval window, cochlea, auditory nerve, and brainstem. Examples include vascular/metabolic insult, mass effect, infection and inflammation, and acoustic trauma.
- Noise-induced hearing loss is caused by acoustic insult that affects outer hair cells in the organ of Corti, causing them to be less stiff. Over time, severe damage occurs with fusion and loss of stereocilia; eventually may progress to inner hair cells and auditory nerve as well
- Large vestibular aqueduct or superior canal dehiscence: Third mobile window shunts acoustic energy away from cochlea.
- Connexin 26 (13q11–13q12): most common cause of nonsyndromic genetic hearing loss
- Mitochondrial disorders (may predispose to aminoglycoside ototoxicity)
- Otosclerosis: familial
- Most common congenital syndromes
- Hemifacial microsomia
- Stickler syndrome
- Congenital cytomegalovirus
- Usher syndrome
- Branchio-oto-renal syndrome
- Pendred syndrome
- CHARGE association
- Neurofibromatosis type 2
- Waardenburg syndrome
- Eustachian tube dysfunction
- Chronic sinusitis; allergy
- Adenoid hypertrophy; nasopharyngeal mass
- Cigarette smoking
- Sleep apnea with continuous positive airway pressure (CPAP) use
- Neuromuscular disease
- Family history/heredity
- Prematurity and low birth weight
- Craniofacial abnormalities (e.g., cleft palate, Down syndrome)
- Third mobile window (superior canal dehiscence or large vestibular aqueduct)
- Eustachian tube dysfunction
- Aging/older age
- Loud noise/acoustic trauma
- Dizziness/vertigo: especially Ménière disease or history of labyrinthitis
- Medications (aminoglycosides, loop diuretics, aspirin, quinine, chemotherapeutic agents, especially cisplatin)
- Bacterial meningitis
- Head trauma
- Vestibular schwannoma/skull base neoplasm
- Previous ear surgery
- Sensorineural, pediatric specific
- Perinatal asphyxia
- Mechanical ventilation lasting ≥5 days
- Congenital infections (toxoplasmosis, other agents, rubella, cytomegalovirus, herpes simplex [TORCH] syndrome)
- Toxemia of pregnancy
- Maternal diabetes
- Rh incompatibility
- Prematurity or birth weight <1,500 g
- Severe hyperbilirubinemia; exchange transfusions
- Anomalous temporal bone (Mondini or large vestibular aqueduct)
- Infectious diseases: chickenpox, measles, encephalitis, influenza, mumps, bacterial meningitis
- Limit noise exposure; use hearing protection.
- Avoid ear canal instrumentation (e.g., cotton swabs).
- Limit ototoxic medications.