Conductive Hearing Loss

Conductive hearing loss is a type of hearing impairment caused by disruption of sound wave conduction in the external or middle ear. In this condition, the sound-perceiving apparatus — the inner ear (cochlea) and auditory nerve — remains intact.

The underlying problem is a mechanical barrier along the sound pathway. As a result, sound vibrations cannot effectively reach the sensory receptors of the inner ear, and sounds are perceived as muffled. In most cases, this type of hearing loss is reversible and treatable.

Etiology and pathophysiology

Conductive hearing loss is caused by pathology of the structures responsible for conducting and amplifying sound.

• External ear pathologies:
  • Earwax impaction. The most common cause that is easy to treat.
  • Otitis externa. Swelling of the external auditory canal walls.
  • External auditory canal atresia. Congenital absence or closure of the ear canal.
• Middle ear pathologies:
  • Perforated tympanic membrane. Compromised integrity of the tympanic membrane.
  • Otitis media. Accumulation of fluid (exudate) in the tympanic cavity.
  • Otosclerosis. Fixation of the stapes (one of the auditory ossicles), impairing sound transmission.
  • Ossicular chain disruption. Often a consequence of trauma.

Clinical Significance

Patients with conductive hearing loss typically report impaired hearing and a sensation of fullness or pressure in the ear. An enhanced perception of patients’s own voice, which sounds unusually loud (autophony), is also characteristic of the condition.

The gold standard for diagnosis is pure-tone audiometry. The key diagnostic criterion on the audiogram is the presence of an air–bone gap. This is the difference between hearing thresholds measured through air conduction (in headphones) and bone conduction (with a vibrator on the mastoid process).

Unlike sensorineural hearing loss, the conductive form is often successfully treatable. The treatment aims to eliminate the underlying cause: earwax impaction is removed, otitis is treated conservatively, the tympanic membrane may be repaired (myringoplasty), or the ossicular chain reconstructed (ossiculoplasty).