What are the etiology, types, symptoms, and treatment options for a 30-year-old female patient with suspected otosclerosis (abnormal bone growth in the middle ear) and a history of progressive hearing loss, vertigo, and tinnitus?

Otosclerosis: Etiology, Types, Symptoms, and Treatment

Etiology

Otosclerosis is a primary osteodystrophy of the otic capsule characterized by abnormal bone remodeling, including pathological bone resorption, new bone deposition, and vascular proliferation in the temporal bone. 1, 2

• The exact cause remains incompletely understood, but the disease represents a complex and progressive pathological process limited to the otic capsule 1, 3
• Genetic factors play a significant role, with family history being a key risk factor 3
• Hormonal and endocrine activity influences disease progression, with worsening often observed during periods of intense hormonal activity (pregnancy, puberty) 3
• Onset typically occurs between the third and fifth decades of life 3

Types and Patterns

Two main clinical presentations exist: stapedial (conductive) otosclerosis and cochlear (sensorineural) otosclerosis, though mixed patterns are common. 3, 2

Stapedial Otosclerosis

• Involves the stapes footplate and oval window, causing mechanical fixation 4, 5
• Results in conductive hearing loss with air-bone gap typically ≥30 dB 4
• Most common presentation requiring surgical intervention 4, 5

Cochlear Otosclerosis

• Involves extension to the cochlear endosteum with degenerative changes in the spiral ligament, stria vascularis, organ of Corti, and cochlear neurons 3, 2
• Causes progressive sensorineural hearing loss 3, 2
• The existence of "pure labyrinthine otosclerosis" is debated, though clinical and histologic evidence supports it 3

Clinical Symptoms

Progressive hearing loss is the hallmark symptom, with the pattern depending on the location and extent of otosclerotic involvement. 6, 3

Hearing Loss Characteristics

• Progressive, bilateral hearing loss (often asymmetric, worse in one ear) 4, 6
• Conductive component when stapedial fixation is present 4, 5
• Sensorineural component when cochlear endosteum is involved 3, 2
• Speech discrimination often remains unusually good for the degree of sensorineural loss 3
• Recruitment is frequently absent, unlike other sensorineural hearing losses 3

Associated Symptoms

• Tinnitus (ringing, buzzing) is common and may worsen with disease progression 7, 6, 1
• Vertigo and vestibular symptoms occur in some patients 6, 1
• Schwartze sign (reddish hue behind tympanic membrane from vascular otospongiotic foci) may be visible on otoscopy 3

Audiometric Patterns

• Classic "Carhart notch" (bone conduction dip at 2000 Hz) in stapedial otosclerosis 4
• "Bite-type" curve most frequent in cochlear otosclerosis, though flat or rising configurations also occur 3
• Type A tympanograms showing normal tympanic membrane mobility despite stapedial fixation 4
• Absent stapedial reflexes 4

Diagnostic Approach

High-resolution CT of the temporal bone without contrast is the first-line imaging modality for confirming otosclerosis and is required before surgical intervention. 7, 4, 8, 5

Clinical Evaluation

• Detailed otoscopic examination to identify normal ear canals, intact tympanic membranes, and possible Schwartze sign 4, 6, 3
• Comprehensive audiometry including pure tone thresholds, speech discrimination, and tympanometry 4, 6
• Tuning fork tests to differentiate conductive from sensorineural components 8
• Family history assessment for otosclerosis and hearing loss patterns 6, 3

Imaging Requirements

• CT temporal bone demonstrates otosclerotic foci ≥1 mm in diameter, altered capsule density, partially or completely erased capsule contour, double ring effect, bony neoformation in labyrinthine spaces, and increased cochlear capsule thickness 3, 5
• CT has 100% positive predictive value for otosclerosis diagnosis when characteristic findings are present 5
• CT identifies clinically significant extensions including endosteal involvement, which predicts lower bone conduction thresholds 5, 2
• CT prevents unnecessary exploratory surgery and identifies alternative diagnoses in 33% of clinically suspected cases 5
• MRI is not appropriate for diagnosing otosclerosis, as it cannot adequately visualize the bony changes 7, 8

Diagnostic Pitfalls to Avoid

• Do not rely solely on clinical examination and audiometry without CT confirmation before surgery 4, 5
• CT-positive ears cannot be predicted from baseline clinical or audiometric criteria alone 5
• Standard head CT lacks the resolution needed for temporal bone structures 7, 8

Treatment Options

Treatment selection depends on the degree of hearing loss, patient preference, and surgical candidacy, with stapedectomy being the definitive treatment for conductive otosclerosis and medical therapy reserved for cochlear involvement. 4, 1, 3

Surgical Management

Stapedectomy is the gold standard for conductive otosclerosis with air-bone gap ≥30 dB and documented stapedial fixation or CT evidence of otosclerosis. 4, 5

• Surgery is indicated when hearing loss significantly impacts quality of life and hearing aid use is inadequate 4
• Type A tympanograms (normal tympanic membrane mobility) must be documented preoperatively 4
• Favorable speech discrimination scores predict better surgical outcomes 4
• Cartilage grafts show better structural outcomes than temporalis fascia, though hearing outcomes are similar 4
• Surgery may benefit patients with severe mixed hearing loss where bone thresholds cannot be evaluated, potentially improving hearing to levels useful for hearing aid application 3

Common surgical complications include incomplete footplate fenestration, poor incus-prosthesis connection, and incus resorption leading to persistent or recurrent conductive hearing loss. 2

Medical Management

Sodium fluoride (NaF) in combination with calcium and vitamin D is the primary medical therapy for cochlear otosclerosis, requiring at least 6 months of treatment. 1, 3

• NaF stabilizes hearing thresholds, improves vestibular symptoms, and delays tinnitus worsening 1
• The rationale is to slow and eventually stop the bone resorption phase 1
• Bisphosphonates administered for at least 6 months show significant improvement in hearing loss, dizziness, and tinnitus remission 1
• Double-blind studies demonstrate that 24 months of bisphosphonate therapy provides greater stabilization of air and bone conduction thresholds compared to placebo 1
• Medical therapy is particularly indicated for pure cochlear otosclerosis without conductive component 3

Hearing Rehabilitation

• Modern hearing aid technology provides effective amplification for patients who decline surgery or are not surgical candidates 9
• Cochlear implants may be considered for severe-to-profound sensorineural hearing loss from advanced cochlear otosclerosis 9

Treatment Algorithm

1. For conductive or mixed hearing loss with air-bone gap ≥30 dB:

   • Obtain high-resolution CT temporal bone to confirm diagnosis and assess extent 4, 5
   • Document stapedial reflexes and tympanometry 4
   • Offer stapedectomy as first-line treatment if surgical candidate 4, 5
   • Consider hearing aids if surgery declined or contraindicated 9

2. For progressive sensorineural hearing loss with CT-confirmed cochlear otosclerosis:

   • Initiate sodium fluoride with calcium and vitamin D for minimum 6 months 1, 3
   • Consider bisphosphonates as alternative or adjunct therapy 1
   • Monitor audiometry every 6-12 months to assess stabilization 1
   • Offer cochlear implantation for severe-to-profound hearing loss 9

3. For patients with vestibular symptoms and tinnitus:

   • Medical therapy with NaF or bisphosphonates addresses these symptoms in addition to hearing stabilization 1
   • Vestibular rehabilitation may be beneficial as adjunct 1