Otosclerosis ent

📌 Definition: Primary disease of the bony labyrinth. One or more foci of irregularly laid spongy bone replace the normally dense enchondral bone of the otic capsule.
Most common outcome: Stapes fixation → Conductive Deafness.

Aetiology

• Anatomical Basis: Predilection for Fissula Ante Fenestram (just in front of oval window). Contains cartilage rests.
• Heredity: 50% have +ve family history. Autosomal Dominant.
• Race: White > Black. Common in Indians. Rare in Chinese/Japanese.
• Sex: F:M = 2:1. (But in India, Males > Females).
• Age: Onset 20–30 years.
• Aggravating Factors: Pregnancy, Menopause, Trauma/Surgery.
• Viral: Measles RNA found in osteoblasts.

Types & Pathology

Types

1. Stapedial: (Most common). Fixes stapes footplate.
   Sites: Anterior focus (Fissula ante fenestram), Posterior focus, Circumferential, Biscuit type.
2. Cochlear: Involves round window/otic capsule. Causes SNHL due to toxic enzymes.
3. Histologic: Asymptomatic.

Microscopic Appearance

• Immature (Active): Vascular spaces + Osteoblasts. Stains Blue (Blue Mantles).
• Mature (Inactive): Fibrillar bone + less vascularity. Stains Red.

Clinical Features

Symptoms:

• Hearing Loss: Bilateral, conductive, painless, progressive.
• Paracusis Willisii: Patient hears better in noisy surroundings.
• Speech: Soft, monotonous, well-modulated volume.
• Tinnitus: Common (especially in active lesions).

Signs:

• Tympanic Membrane: Normal and mobile.
• Schwartze Sign: Reddish hue seen on the promontory through the TM. Indicates Active Focus (increased vascularity).
• Tuning Fork: Rinne Negative (BC > AC). Weber lateralized to worse ear.

Audiometry Findings

1. Pure Tone Audiometry:

• Air conduction loss (esp. lower frequencies).
• Carhart's Notch: A dip in the Bone Conduction curve.
  Specifics: Max dip at 2000 Hz (15 dB).
  Note: It is an artifact; disappears after stapedectomy.

2. Tympanometry: Normal (Type A) or Type As (Stiffness curve). Stapedial reflex is absent.

Treatment

A. Medical

• Sodium Fluoride: Used to arrest active cochlear otosclerosis (controversial). Hastens maturity of the focus.

B. Surgical (Treatment of Choice)

Operation: Stapedectomy or Stapedotomy.

• Procedure: Remove fixed stapes → Insert prosthesis (Teflon/Titanium piston) between Incus and Oval Window.
• Success: 90% get good hearing improvement.

Contraindications to Surgery:

• Only hearing ear.
• Associated Meniere's disease.
• Young children.
• Professional athletes / Divers / Pilots (risk of vertigo/barotrauma).

Complications of Stapedectomy

• Dead Ear: 1 in 200 patients (Total SNHL).
• Vertigo.
• Facial Nerve Injury.
• Perilymph Fistula.
• Taste disturbance (Chorda tympani injury).

C. Hearing Aid

For patients unfit or unwilling for surgery.