Hearing loss is a prevalent sensory disorder that affects approximately 16 million people in the United States alone, with incidence increasing with age. It encompasses a spectrum ranging from mild, temporary impairment to profound, permanent deficits and may involve partial or complete loss of auditory perception. The condition can affect low-, middle-, or high-frequency sound perception, with some patients remaining unaware of the deficit if speech frequencies are preserved.

Physiologically, hearing relies on the precise transmission of sound waves from the external ear through the middle ear to the cochlea of the inner ear, where mechanical vibrations are converted into neural impulses by the hair cells of the organ of Corti. These impulses travel via the cochlear division of the vestibulocochlear nerve (cranial nerve VIII) to the auditory cortex in the temporal lobe. Disruption at any point along this auditory pathway—external ear, middle ear, cochlea, auditory nerve, or central auditory processing centers—can result in hearing loss.

Hearing loss can significantly impact communication, social interaction, and quality of life. In children, undiagnosed hearing deficits can impede speech and language development, while in older adults, it contributes to social isolation, cognitive decline, and increased risk of falls. Etiologies are multifactorial, including age-related degeneration (presbycusis), chronic noise exposure, infections, trauma, congenital anomalies, neoplasms, autoimmune disorders, and ototoxic medications.

From a clinical standpoint, hearing loss is classified into conductive, sensorineural, mixed, and functional types, each with distinct pathophysiological mechanisms, diagnostic features, and therapeutic considerations. Comprehensive evaluation—including detailed history, physical examination, tuning fork tests, audiometry, and, where indicated, imaging—is critical for determining the underlying cause and guiding management. Early identification and intervention can prevent long-term functional deficits and improve patient outcomes.

Pathophysiology

Sound waves normally enter the external auditory canal, striking the tympanic membrane, then transmitting via the ossicles (malleus, incus, stapes) to the cochlea. The cochlear division of cranial nerve VIII (auditory nerve) transmits impulses to the brain.

• Air conduction: Normal sound pathway through external and middle ear to cochlea; generally superior to bone conduction.

• Bone conduction: Sound transmitted directly through cranial bones to cochlea.

• Disruption points: Hearing loss can arise from outer, middle, or inner ear damage or nerve dysfunction.

Types of Hearing Loss

History and Physical Examination

History

• Laterality: unilateral vs. bilateral

• Onset: sudden vs. gradual, intermittent vs. continuous

• Associated symptoms: tinnitus, vertigo, fullness, pain, discharge

• Risk factors: noise exposure, trauma, family history, ototoxic medications, systemic illnesses

Physical Examination

• Inspect external ear for inflammation, foreign bodies, or masses

• Palpate tragus and mastoid for tenderness

• Otoscopic examination: tympanic membrane color, perforation, retraction, bulging

• Hearing tests:

  • Whispered voice and ticking watch tests

  • Weber test (512 Hz): lateralization indicates conductive (same ear) vs sensorineural (opposite ear)

  • Rinne test: AC>BC normal; BC>AC indicates conductive loss

Implications of Results

Medical Causes of Hearing Loss

Special considerations

• Patient communication: Face patient, speak slowly, avoid shouting or chewing.

• Testing: Audiometry, brainstem auditory-evoked responses, cochlear implant evaluation.

• Prevention: Ear protection, avoid chronic loud noise, adherence to prescribed medications.

• Pediatric focus: Early detection critical for speech, language, and cognitive development; use startle reflex or evoked-response testing in infants.

• Geriatric focus: Presbycusis often worsened by noise exposure; amplification or cochlear implants may be needed.

References

1. Neitzel R, Daniell WE, Sheppard L, Davies H, Seixas N. Comparison of perceived and quantitative measures of occupational noise exposure. Ann Occup Hyg. 2009;53:41–54.

2. Rabinowitz PM, Galusha D, Kirsche SR, Cullen MR, Slade MD, Dixon-Ernst C. Effect of daily noise exposure monitoring on annual rates of hearing loss in industrial workers. Occup Environ Med. 2011;68(6):414–418.

3. Ciorba A, Bianchini C, Pelucchi S, Pastore A. The impact of hearing loss on the quality of life of elderly adults. Clin Interv Aging. 2012;7:159–163.

4. Stach BA. Clinical Audiology: An Introduction. 4th edition. San Diego: Plural Publishing; 2014.

5. Ruckenstein MJ. Hearing loss: diagnosis and treatment. Med Clin North Am. 2013;97(5):901–918.