OTOSCLEROSIS Moderator-Dr.Mohan Presenter-Dr.Razal

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Definition

A primary disease of the bony otic capsule characterized by abnormal removal of mature bone by osteoclasts and replacement with woven bone of greater thickness, cellularity and vascularity.

Clinical Otosclerosis refers to a lesion that involves the stapes bone or stapidovestibular joint.

Most common site is fissula ante fenestram

(anterior to the stapes foot plate) and also seen in the fossula post fenestram (area in front and behind oval window)

The bone of otic capsule is unique that it exhibits very low remodeling and contains small regions of immature cartilaginous tissue called GLOBULI INTEROSSEI.

Blue Mantles, an earliest histological alterations of otic capsule that stain more basophilic.

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Epidemiology

Race % incidence ofCaucasian 10%Asian 5%African American 1%Native American 0%

Epidemiology

Gender Histologic otosclerosis – 1:1 ratio Clinical otosclerosis – 2:1 (W:M)• Increase progression during pregnancy (10%-17%)• Bilaterality more common (89% vs. 65%)

Epidemiology

Age• 15-45 most common age range of presentation• Youngest presentation7 years • Oldest presentation 50s• 0.6% of individuals <5 years old have foci of

otosclerosis

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Etiology

The exact cause is unknown but many factors have been proposed such as:

• Genetic• Autoimmune• Infections• Endocrine (pregnancy)• Trauma• Vascular

• Hereditary(Autosomal Dominant)• More common in whites than blacks• Uncommon in Asian • Sporadic cases were reported.• Defects in COL1A1 Gene• defects in expression of the COLlAl gene has

revealed a significant association between both familial and sporadic cases

Genetic

Type 1 osteogenesis imperfecta shares both

clinical and histologic similarities with otosclerosis.

Half of all patients with type 1 osteogenesis imperfecta develop hearing loss that is clinically indistinguishable from clinical otosclerosis.

Patients with clinical otosclerosis have blue sclera, a feature that is found in all patients with type 1 osteogenesis imperfecta.

Osteogenesis Imperfecta

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Infectious (Measles)

Measles RNA was found in footplate specimens

Elevated levels of anti measles antibody found in perilymph from patent undergoing stapedectomy.

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a form of autoimmune disease with humoral

autoimmunity to Type II collagen.

Elevated circulating antibodies to type II collagen are found in patients of otosclerosis

Autoimmune

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Pathogenesis

Affects the Otic and labyrinth Capsule

Enlargement of the Perivascular SpaceBone Absorption by osteoclast activityNew Bone deposition by osteocytes Containing vascular space in center Lamellar Bone

With time mucoperiostium of middle ear increases in thickness and becomes vascularReddish Hue through the TM and disease advances

Involvement of Bony labyrinth

Involvement of foot plate.

Cochlear Otosclerosis

Stapedial Otosclerosis

Histologically

Lesion can be divided into Active-Spongy structure immature osseous

tissue with numerous dilated vascular channels with osteoclastic giant cells

Inactive/Mature• End stage of bone transformation ,characterized

by solid compact lamellar tissue. Siebenmann – first to describe the microscopic appearance

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The foci demonstrates two phases: Early spongiotic phase (otospongiosis)

Osteocytes, histiocytes, osteoclasts Active reabsorption of bone Stains blue (blue mantles) on using H&E stain Dilated vessels (Schwartze’s sign)

Late or Sclerotic phase Formation of new bone in resorption areas New bone is dense and sclerotic Stains red on using H&E stain Starts in endochondral bone then involves endosteal

& periosteal layers and membranous labyrinth as disease progress

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Anterior Focus

Most common, at fissula ante fenestram Posterior Focus

Lesion spreading from posterior oval window to annular ligament

Circumferential Lesion flows across the ligament totally obliterating

the annular ligament Biscuit type

Lesion replacing entire footplate, but no involvement of annular ligament leading to a solid footplate

Types of Stapedial fixation

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Obliterative

Completely obliterates the oval window Other areas are:

Round window, the apex of the cochlea, the cochlear aqueduct, the semicircular canals, and the stapes footplate itself

Types of Stapedial fixation

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Diagnosis

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Gradual onset of hearing loss progressing

slowly In 70% cases hearing loss is bilateral Usually becomes apparent around the age of

30 Loss noticeable when it reaches 25 to 30 dB Unilateral loss noticed even later, problem

with localization of sound Positive family history

History

SYMPTOMS

Low modulated voice (BC is more ,patients hears their own voice.

Deafness-Mainly Conductive hearing loss, Paracussis Willisi-Patient will hear better in

noisy surroundings. Tinnitus Vertigo

Clinical Features

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Hearing Loss

Conducting Hearing Loss (CHL)• Stapedial fixation• Hearing impairment ranging from 5dB to 60dB.• Caused primarily by narrowing and impairment of the

annular ligament, at the posterior stapediovestibular joint space.

Sensorineural Hearing Loss (SNHL)• Cochlear otosclerosis • the sensory and neural elements of the cochlea, such

as hair cells, spiral ganglion cells and stria vascularis, are intact or their impairment is insufficient to account for the observed sensorineural hearing impairment.

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OTOSCOPY• SCHWARTZE SIGN:- red blush color occasionally

seen over promontory or anterior to oval window• Pneumo-otoscopy used to rule out other causes of

CHL such as middle ear serous fluid or small perforation

TUNING FORK TEST• Hearing loss progresses form low frequencies to high frequencies• Rinne Test-Negative• Weber Test-Laterlized to worst ear.• ABC-Normal

Physical Examination

Pure Tone Audiometry

CARHART’S NOTCH Proposed theory

Stapes fixation disrupts the normal ossicular resonance (2000 Hz)

Normal compressional mode of bone conduction is disturbed because of relative perilymph immobility

Mechanical artifact Reverses with stapes mobilization

Speech Audiometry Normal except in those with cochlear

involvement.

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Tympanometry : As type curve

Impedance

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High resolution CT scan

Shows subtle areas of demineralization In case of cochlear involvement it shows

“double ring sign” MRI

Done for patients with unusual presentation Detects congenital anomalies of cochlea Excludes retrocochlear pathology eg. Acoustic

neuroma

Radiological Investigations

Differential Diagnosis

Ossicular discontinuity Congenital stapes fixation Malleus head fixation Paget’s disease Osteogenesis imperfecta

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TREATMENT

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Treatment Options

Hearing aid

Medical management

Surgical management-The ‘Gold’ reference standard of Diagnosis is Surgery

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Hearing Aid

Very effective in early stage of disease But can be used in advance stage, if:

Surgery is contraindicated Patient refuses the surgery In far-advance cases it is required, even

after stapedotomy

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Medical Management Aim is to Stabilize the disease by

reduction of the osteoclastic bone resorption increase osteoblastic bone formation

Inhibits proteolytic enzymes that are cytotoxic to cochlea.

Slows the progression of sensorineural hearing loss

Not commonly used

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Tab. Sodium fluoride

Dose : 50 – 75 mg/day ODDuration : 3 months – 2 years

Function helps to hasten the maturity of active focus and arrest further progression of cochlear loss

It has antienzymatic action on proteolytic enzymes which are cytotoxic to cochlea.

Indications: Cochlear otosclerosis Active stapedial otosclerosis

Sodium Fluoride Therapy

Side effects : Fracture of long bones and spine due to fluorosis. Nephritis. Gastritis

Contraindications: Pregnancy & lactation Patient with kidney stones / nephritis Patient with RA

Sodium Fluoride Therapy

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Surgical Management Poorer ear always chosen for surgery Done preferably under local anesthesia so patient

can notify surgeon if vertigo occurs during procedure

Options are: Stapedotomy Stapedectomy

Lasers -Lesser complications

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