Hearing loss

Hearing loss is categorized by the anatomical site of damage. Conductive loss involves the outer or middle ear—such as cerumen impaction, otitis media, or otosclerosis—and is often medically or surgically reversible. Sensorineural loss results from damage to the cochlea, hair cells, or auditory nerve, and is typically permanent; common causes include noise exposure, presbycusis, and ototoxic drugs. Mixed loss combines both components.

Within sensorineural loss, the site of lesion can be further specified: cochlear (hair cell or stria vascularis) versus retrocochlear (eighth nerve or brainstem). This distinction guides prognosis and intervention—cochlear losses may benefit from hearing aids or cochlear implants, whereas retrocochlear lesions often require imaging to rule out vestibular schwannoma.²

Age-related hearing loss (presbycusis) is the most common cause, affecting roughly two-thirds of adults over 70. Chronic noise exposure—occupational, recreational, or environmental—damages outer hair cells and is a leading preventable cause. Genetic factors account for over half of congenital cases, with mutations in genes such as GJB2 (connexin 26) being frequent.³

Infections (meningitis, cytomegalovirus, rubella), ototoxic medications (aminoglycosides, platinum-based chemotherapy), and head trauma also contribute. In low- and middle-income countries, chronic suppurative otitis media and cerumen impaction remain major causes.¹

Diagnosis begins with otoscopy and pure-tone audiometry, which measures thresholds across frequencies. Tympanometry and otoacoustic emissions help differentiate conductive from sensorineural loss. For infants, automated auditory brainstem response screening is standard.⁴

Management is tailored to severity and type. Conductive losses may be treated medically or surgically. Sensorineural loss is managed with hearing aids, assistive listening devices, cochlear implants for severe-to-profound cases, and auditory rehabilitation. Early intervention in children is critical for language development.⁵

Beyond the common narrative, several nuances deserve attention. Hidden hearing loss—synaptopathy—refers to cochlear nerve synapse loss that does not appear on standard audiograms but impairs speech-in-noise perception.⁶ Ototoxicity monitoring programs use high-frequency audiometry to detect early damage from chemotherapy, allowing dose adjustments.

Historically, Beethoven's deafness has been debated as possibly caused by lead poisoning or Paget's disease, illustrating the complexity of retrospective diagnosis.⁷ Additionally, unilateral hearing loss, often overlooked, affects sound localization and academic performance in children.

Sensorineural hearing loss

Hearing loss due to damage to the inner ear or auditory nerve, typically permanent.

Conductive hearing loss

Hearing loss due to problems in the outer or middle ear that prevent sound conduction.

Presbycusis

Age-related hearing loss, typically affecting high frequencies.

Ototoxicity

Damage to the inner ear caused by certain medications or chemicals.

Hidden hearing loss

Cochlear synaptopathy that is not detected by standard audiometry but affects speech perception in noise.