Otosclerosis

Written by

in

 

Otosclerosis (Otospongiosis)

High-Yield Revision Notes for NEET PG / NEXT

Otosclerosis is a primary osteodystrophy localized strictly to the **otic capsule** (bony labyrinth). It is characterized by alternating phases of bone resorption (otospongiosis) and abnormal new bone deposition (otosclerosis), leading to **stapes fixation** within the oval window.

High-resolution axial CT scan of the temporal bone showing a lucent demineralized focus at the anterior margin of the oval window, confirming otosclerosis at the fissula ante fenestram.

Radiological Target: Axial HRCT demonstrating the classic pathognomonic lucent focus at the **fissula ante fenestram** (anterior to the oval window ring).

Epidemiology & Etiology

  • Inheritance Pattern: Most frequently presents as an **Autosomal Dominant** trait with incomplete penetrance and variable expressivity.
  • Patient Profile: Classically targets **young white females** (female-to-male ratio is roughly 2:1). Clinical onset typically surfaces between the 2nd and 4th decades of life.
  • Hormonal Aggravation: Rate of clinical progression and hearing impairment significantly **accelerates or spikes during pregnancy** and state alterations like puberty or menopause.

Clinical Manifestations & Named Signs

Clinical Finding / Sign Diagnostic Description & Pathomechanism
Conductive Hearing Loss Characteristically **bilateral (80%), slowly progressive, and asymmetric**. It begins in low frequencies before involving high frequencies.
Paracusis Willisii A paradoxical clinical phenomenon where the patient reports **hearing better in noisy environments**. Occurs because normal individuals raise their voice volume in noise, which overrides the patient’s conductive barrier.
Schwartze’s Sign
(Flamingo Flush)		 A reddish, pinkish glow was visualized through an intact tympanic membrane on otoscopy. Indicates the **active, highly vascular otospongiotic phase** where hyperemic promontory bone shines through.
Tinnitus Often present; typically describes a low-pitched, subjective roaring sound that correlates with the severity of mechanical stapes fixation.

Diagnostic Workup & Audiometry Traps

    1. Tuning Fork Tests: **Rinne test is negative** (Bone Conduction > Air Conduction) for frequencies 256 Hz, 512 Hz, and 1024 Hz as the air-bone gap widens beyond 15-20 dB. **Weber test** lateralizes to the ear with the greater conductive deficit.
    2. Carhart’s Notch (Pathognomonic Board Target):

Pure Tone Audiometry (PTA) demonstrates a characteristically selective, artificial dip in the **bone conduction curve peaking at 2000 Hz**. This does not reflect true sensorineural damage; it is a mechanical artifact caused by the loss of normal stapes footplate resonance. It completely reverses following successful stapes surgery.

  1. Impedance Audiometry: Reveals a characteristic **As type tympanogram** (normal peak pressure, but static compliance is significantly stiffened or reduced due to ossicular fixation). The **acoustic stapedial reflex is absent**.
  2. High-Resolution CT (HRCT): Exceptional tool for diagnosis and surgical planning. Demonstrates focal demineralization areas in active disease or “halo signs” surrounding the cochlea in advanced **cochlear otosclerosis** (which causes sensorineural hearing loss).

Management Protocol

1. Surgical Intervention (Treatment of Choice)

    • Stapedotomy: The modern standard of care. It involves micro-drilling or laser-creating a tiny fenestration (hole) directly through the fixed stapes footplate, bypassing the crura, and inserting a **Teflon or titanium piston piston-prosthesis** from the long process of the incus into the hole. Over 90% success rate in closing the air-bone gap.
    • Stapedectomy: Involves total or partial surgical removal of the stapes footplate and covering the window with a tissue graft prior to piston placement. Carries a higher incidence of inner ear trauma compared to stapedotomy.
    • Absolute Surgical Contraindications:

Only remaining hearing ear (dead ear risk), concurrent active Meniere’s disease, professional pilots/divers, or presence of active middle ear infections.

2. Non-Surgical Alternatives

  • Hearing Aids: An excellent, completely safe non-invasive choice for patients who refuse surgery or exhibit definitive surgical contraindications.
  • Medical Therapy (Sodium Fluoride): Reserved specifically for patients presenting with active otospongiosis (marked Schwartze’s sign) or progressive cochlear otosclerosis. Fluoride ion converts bone matrix hydroapatite into **fluorapatite**, which resists osteoclastic enzymatic degradation and halts spongy progression.