OTOSCLEROSIS

Lecture

BY Dr Mazhar

Iftikhar

Anatomy

Otic Labyrinth Periotic Labyrinth Otic Capsule

Definition

Primary localized disease of bony otic capsule

Irregular spongy bone replaces dense enchondral bone

Characterised by; Spongy bone Hearing loss

Aetiology

Anatomical basis Hereditary 50% Race white> negroes Sex females> males Age of onset 20 - 30 Autoimmune type II collagen Measles virus antibodies

Incidence

Clinical otosclerosis upto 3.5%

Histological otosclerosis upto 13%

Pathology

Grossly; Chalky white May be Red /inc vascularity Spongy bone

Histopathology

Globuli Interossei Areas of;

Bone resorption New bone formation Vascular proliferation Connective tissue stroma

Spongiotic bone

Distribution of lesion

Anterior to oval window 90% Round window 30% Cochlear labyrinth 25% Stapes footplate 12% Posterior to oval window 5-10%

Pathology of CHL

Conductive hearing loss 5-60 dB

Expansion to ant of oval window 30-40dB

Bony ankylosis >40dB Narrowing & impairment of annular

lig at post stapediovestibular joint

Pathology of SNHL

Subject of much controversy Atrophy /Hylinization of spiral

ligament cytokines

Pathology of vestibular symptoms

Scarpa’s ganglion Soluble toxic substances Direct invasion

Symptomatology

Slowly progressive hearing loss Apparent at 25 – 30 dB loss

Paracusis Willisii Characteristic soft speech Tinnitis Dizziness & vertigo rarely

Physical Exam

Careful Otoscopic Exam Microscopic Exam

Rule out other causes Tympanic memb normal Middle ear pneumatized Reddish blush (schwartze sign )

Classic Audiometric Findings

Negative Rinne test Low frequency CHL Carhart notch Type A/As tympanogram Diphasic or absent reflexes

Imaging Studies

CT Scanning MRI

Treatment

A. Observation

Least risky Least expensive When no intervention recquired Audiogram on yearly basis

B. Nonsurgical Measures.

1. Sodium Flouride Therapy Reduces bone resorption Inc bone formation Inhibit proteolytic enzymes

2. Bisphosphonates Anti resorptive/inhibit osteoclasts

B. Nonsurgical Measures

3. Amplification Conventional hearing aid Bone-anchored hearing aids

C. Surgical Measures

Indications Air conduction level 45 – 65 dB Bone conduction level 0 – 25 dB Air-Bone Gap 15 dB Discrimination score >60%

Surgical technique

Anaesthesia Tympanomeatal flap raised Ossicular chain inspected & palpated Divisionh of stapedius tendon Crurectomy Stapedotomy Insertion of prothesis & packing

Recent Advances

LASER use Cochlear Implantation

Revision Surgery

Encourage to use hearing aids Failure may be due to

Incus erosion Poorly positioned prosthesis Mallius or Incus fixation Reobliteration

Prognosis

Immediate success Decline slowly After Stapedotomy 3dB decline per

decade After stapedectomy 9dB decline

per decade