Hearing Loss

Key Features

Essentials of Diagnosis

• Two main types of hearing loss

  • Conductive

  • Sensorineural

• Most commonly caused by cerumen impaction, transient eustachian tube dysfunction, or age-related hearing loss

General Considerations

Conductive hearing loss

• Results from a mechanical disruption of the external auditory canal or middle ear

• Four mechanisms, each resulting in impairment of the passage of sound vibrations to the inner ear

  • Obstruction (eg, cerumen impaction)

  • Mass loading (eg, middle ear effusion)

  • Stiffness (eg, otosclerosis)

  • Discontinuity (eg, ossicular disruption)

• Causes include

  • Cerumen impaction

  • Transient eustachian tube dysfunction due to upper respiratory tract infection

  • Chronic ear infection

  • Trauma

  • Otosclerosis

  • Perforations of the tympanic membrane

• Often correctable with medical or surgical therapy, or both

Sensorineural hearing loss

• Common in adults and generally results from deficits of the inner ear or central (brain) auditory pathway

• Age-related hearing loss

  • Most common form of sensorineural hearing loss

  • Manifests as a gradually progressive, predominantly high-frequency hearing loss

• Rate of hearing loss

  • Hearing loss may be gradual or sudden

  • Sudden (idiopathic) sensorineural hearing loss is an otologic emergency

• Causes are either sensory or central and include

  • Deterioration of the cochlea, usually due to loss of sensory hair cells within the organ of Corti

  • Excessive noise exposure

  • Head trauma

  • Ototoxic medications (eg, cisplatin-based chemotherapy)

  • Systemic diseases

  • Deficits at the level of the central auditory pathway (eg, lesions involving the eighth cranial nerve, auditory nuclei, ascending tracts, or auditory cortex)

    • Acoustic neuroma

    • Multiple sclerosis

    • Auditory neuropathy

Clinical Findings

Symptoms and Signs

• Reduction in hearing level

• Weber test

  • Tuning fork is placed directly on the forehead or front teeth

  • In conductive hearing losses, the sound appears louder in the poorer-hearing ear, whereas in sensorineural hearing losses it radiates to the better-hearing ear

• Rinne test

  • Tuning fork is placed alternately on the mastoid bone (bone conduction) and in front of the ear canal (air conduction)

  • In conductive losses > 25dB, bone conduction sounds louder than air conduction

Differential Diagnosis

Conductive (external or middle ear)

• Cerumen (ear wax) impaction

• Transient auditory tube dysfunction

• Acute or chronic otitis media

• Mastoiditis

• Otosclerosis

• Disruption of ossicles

• Trauma or barotrauma

• Glomus tympanicum (middle ear tumor)

• Paget disease

Sensory

• Presbycusis (age related)

• Excessive noise exposure

• Ménière disease (endolymphatic hydrops)

• Labyrinthitis

• Head trauma

• Ototoxicity

• Occlusion of ipsilateral auditory artery

• Hereditary hearing loss

• Autoimmune

  • Systemic lupus erythematosus

  • Granulomatosis with polyangiitis

  • Cogan syndrome

• Other systemic causes

  • Diabetes mellitus

  • Hypothyroidism

  • Hyperlipidemia

  • Chronic kidney disease

  • Infections

Neural

• Acoustic neuroma

• Multiple sclerosis

• Cerebrovascular disease

Diagnosis

Diagnostic Procedures