ENT · Otology
The facts most likely to be tested
The Weber test lateralizes to the affected ear in patients with unilateral conductive hearing loss.
The Rinne test demonstrates bone conduction (BC) greater than air conduction (AC) in the affected ear, which is an abnormal Rinne result.
Cerumen impaction is the most common cause of conductive hearing loss in the primary care setting.
Otosclerosis is a common cause of conductive hearing loss in young adults characterized by fixation of the stapes and a carhart notch on audiometry.
Cholesteatoma presents as a pearly white mass behind the tympanic membrane and can cause ossicular chain erosion.
Tympanometry in conductive hearing loss typically reveals a Type B or Type C tympanogram, indicating middle ear effusion or negative pressure.
Otitis media with effusion is the most frequent cause of conductive hearing loss in children following an episode of acute otitis media.
Vignette unlocked
A 28-year-old female presents with a progressive, painless decrease in hearing in her left ear over the past year. She denies any history of ear infections, trauma, or vertigo. Physical examination reveals a normal-appearing tympanic membrane with no evidence of fluid or inflammation. The Weber test lateralizes to the left ear, and the Rinne test shows bone conduction greater than air conduction on the left side. Audiometry reveals a low-frequency air-bone gap.
What is the most likely diagnosis?
Otosclerosis
The patient's presentation of conductive hearing loss with a normal tympanic membrane and the classic Rinne/Weber findings is highly suggestive of otosclerosis, which is caused by abnormal bone remodeling of the stapes.
Full handout
High yield triage
Etiology / Epidemiology
Caused by cerumen impaction, otitis media, or otosclerosis. Common in pediatric populations and elderly patients.
Clinical Manifestations
Patients report muffled hearing and Weber lateralization to the affected ear. Bone conduction > air conduction on Rinne test.
Diagnosis
Audiometry is the gold standard. Conductive loss shows air-bone gap > 10 dB with normal bone conduction.
Treatment
Treat underlying cause: cerumen removal, antibiotics for infection, or stapedectomy for otosclerosis. Avoid aminoglycosides in perforated TM.
Prognosis
Most cases are reversible. Cholesteatoma is a serious complication requiring surgical excision.
Full handout
Epidemiology & Etiology
Conductive hearing loss (CHL) results from external or middle ear pathology preventing sound transmission. Cerumen impaction is the most common cause in primary care. Otosclerosis is a common genetic cause in young adults, while eustachian tube dysfunction is prevalent post-viral infection.
Pertinent Anatomy
The conductive apparatus includes the external auditory canal, the tympanic membrane, and the ossicular chain (malleus, incus, stapes). Pathology here prevents sound waves from reaching the cochlea.
Pathophysiology
Mechanical obstruction or ossicular fixation increases the impedance of sound transmission. This results in a loss of sound intensity, typically affecting low-frequency sounds first. Unlike sensorineural loss, the cochlear hair cells remain intact, allowing for normal sound perception if the sound is delivered via bone conduction.
Clinical Manifestations
Patients often describe hearing better in noisy environments (paracusis willisii). Weber test lateralizes to the affected ear, while the Rinne test shows bone conduction > air conduction. Red flags include otorrhea, severe otalgia, or sudden onset, which may indicate cholesteatoma or malignancy.
Diagnosis
Audiometry is the definitive diagnostic tool. A conductive gap (air-bone gap) of > 10 dB confirms the diagnosis. Tympanometry helps differentiate between eustachian tube dysfunction (negative pressure) and ossicular fixation (reduced compliance).
Treatment
Management is etiology-specific: cerumenolytic agents or irrigation for impaction, and myringotomy for persistent effusion. Stapedectomy is the definitive treatment for otosclerosis. Avoid topical aminoglycosides if the tympanic membrane is perforated due to ototoxicity.
Prognosis
Prognosis is excellent for most mechanical obstructions. Cholesteatoma is a critical complication that can erode the ossicles and mastoid bone, requiring surgical mastoidectomy to prevent intracranial spread.
Differential Diagnosis
Cerumen impaction: visualized obstruction on otoscopy
Otitis media: erythematous, bulging tympanic membrane
Otosclerosis: progressive loss with normal otoscopy
Cholesteatoma: pearly white mass behind the tympanic membrane
Eustachian tube dysfunction: retracted tympanic membrane