ENT: Otosclerosis

 

Otosclerosis

Definition

·         It is a common hereditary disease of localized bone derived from the otic capsule.

·         The normal laminar bone is removed by osteoclasts and replaced b unrecognized bone  of greater thickness, vascularity and cellularity

·         Spongy bone replaces the enchondral layer of the bone

·         It causes fixation of the ossicles (stapes)  

·         It results in conductive or mixed hearing loss.

Epidemiology

·         The incidence of otosclerosis increases with age.

·         The most common age group presenting with hearing loss from otosclerosis is 15-45 years

·         However it has been reported to manifest as early as 7 years and as late as the mid 50’s.(rare)

·         Male: Female = 1:2

Etiology

·         The exact etiology is unknown

·         Hereditary, 54% of patients present with family history

·         Autosomal dominant

·         Race: white race are affected more than negroes

·         Harrnonal: otosclerotic activity is more during pregnancy, puberty & menopause

·         Infectious (viral)  

·         Vascular

Types:

1) Stapedal otosclerosis: causing stapes fixation and conductive deafness

·         Lesions starts just in-front ofÿual window — anterior focus

·         Lesions may starts behind the oval window- posterior focus

·         Around the margin of the stapes foot plate- circumferential

·         In the foot plate but annular ligament being free- biscuit free  

·         Completely obliterate the oval window- obliterative

 2) Cochlear otosclerosis:

It involves region of round window or other areas in the otic capsule and may cause sensorineural hearing loss probably due to liberation of toxic materials in to the inner ear fluid

3) Histologic otosclerosis:

It remains asymptomatic and causes neither conductive nor sensorineural hearing loss Lesions detected only on post-mortem

Histologically Otosclerosis has two main forms:

a. an early of spongiotic phase (otospongiosis)

i. The early phase is characterized by multiple active cell groups including osteocytes, osteoblasts, and histocytes.

ii. It develops a spongy appearance because of vascular dilation secondary to osteocyte resorption of bone surrounding blood vessels.

iii. This can be seen grossly as red hue behind the tympanic membrane termed "Schwartze's sign"

b.  a late or sclerotic phase

i. dense sclerotic bone forms in the areas of previous resorption.

Pathophysiology

Various etiological factors (age, hereditary, hormonal factors etc.)-àAffects the otic and labyrinthine capsuleàEnlargement of the perivascular spaceàBone absorption by osteoclastic activityàNew bone deposition by osteocytes containing vascular spaces in centeràLamellar boneàWith time mucoperiosteum of middle ear increases in thickness and becomes vascularàReddish hue through the translucent ear drum

 As diseases advances

Involvement of the bony labyrinth

Round window involvement

Involvement of footplate

Stapedial otosclerosis

Cochlear otosclerosis

Clinical manifestation:

Symptoms

·         Voice: is low modulated and the patients are soft spoken.

·         Hearing loss: this is the presenting symptom and usually starts in twenties. Mostly it is bilateral and conductive type.

·         Paracuris willisi: an otosclerotic client hears better in noisy environment than in quiet surroundings this is because a normal person will raise his voice in noisy environment

·         Tinnitus: commonly seen among cochlear otosclerosis client  

·         Vertigo

Signs:

·         The tympanic membrane is intact but there will be congested slight reddish discoloration called Schwaltze Sign

·         Eustachian tube function in normal

·         Rime's test is negative: (BC>AC)

·         Webbers test is lateralized more towards the ear which is affected.

·         Pure tone audiometry will show loss of air conduction

Diagnosis

1) History:

·         Slowly progressive, bilateral (80%), asymmetric, conductive hearing loss

ü  Tinnitus is associated with 75% patients 

ü  The age of onset of hearing loss is young

ü  History of significant ear infections.

·         Low-volume speech.

·         Two-thirds of patients will report a family history of hearing loss.

2) Physical examination

·         TM appears normal in the majority of patients S

·         chwartze sign is observed in 10% of patients

·         Weber test: lateralization to the affected ear

·         Rime's test: Negative

·         Absolute bone conduction — Normal

3)Tests

Pure tone audiometry

a.Conductive hearing loss

b.Sensorineural hearing loss

4)Image study: CT scan can characterize the extent of the otosclerotic focus at the oval window

Management

Medical:

·         There is no medical treatment

·         Sodium fluoride 50 mg BD for I to 2 yrs -in cochlear otosclerosis - to hasten the  maturity of active focus and arrest further cochlear loss

Amplification: hearing aide

a.Patients who do not want to undergo surgery

b.Patients who are not fit for surgery.

Surgical treatment

·         Stapedectomy

·         Small fenestra stapedectomy

·         Stapedotomy

·         Stapedotomy with stapedius tendon preservation

·         Vein- graft Teflon interposition operation

·         Laser stapedotomy

Indication

·         Bone conduction of 0 to 25 db and air conduction of 45 to 65 db

·         Speech discrimination score of 60% or more

 

Contraindication

·         Age >70 years

·         Children less than preadolescent age group

·         Otitis media

·         Only hearing ear   Pregnancy

Stapedectomy:

·         Surgical procedure whereby the damaged stapes is removed and replaced with stainless steel or plastic prosthesis. The oval window is grafted with absorbable gelatin sponge or tissue grafts

·         Small fenestra stapedectomy

·         The small fenestra technique involves making a small hole in the footplate of the stapes and inserting the prosthesis through that hole.

Stapes mobilization:

·         It is no longer done these days as it gives temporary results

·         Refixation being quite common

 

Fenestration operation:

·         Making an opening from the external auditory canal to the membranous labyrinth