Otosclerosis
-
Upload
meghna-rai -
Category
Documents
-
view
36 -
download
4
Transcript of Otosclerosis
OTOSCLEROSIS
ANATOMY OF LABYRINTH
Otic capsule It is the bony labyrinth and consists of 3 layers-
endosteal, enchondral, periosteal Otic labyrinth
The endolymphatic/membranous labyrinth. Consists of utricle, saccule, cochlea, Semicircular
canals, endolymphatic duct and sac. Periotic labyrinth
The perilymphatic labyrinth. Surrounds the otic labyrinth and is filled with perilymph. Consists of vestibule, scala vestibula, scala tympani and perilymphatic space around semicircular canals and periotic duct
DEFINITION
Otosclerosis, or Otospongiosis is a primary disease of the bony labyrinth. One or more foci of irregularly laid spongy bone replace part of normally dense enchondral layer of bony otic capsule.
Most often, otosclerotic focus involves the stapes region leading to stapes fixation and conductive deafness.
ETIOLOGY
The exact cause is unknown but many factors have been proposed:
Anatomical basis- Areas of cartilage rests in the bony labyrinth which due to certain non-specific changes are activated to form a new spongy bone. One such area is the fissula ante fenestrum lying in front of the oval window- site of predeliction for stapedial type of otosclerosis
Heredity- 50% show positive family history. Autosomal dominant trait with incomplete penetrance and variable expressivity
Race- Caucasians most commonly affected Age of onset-Hearing loss starts between 20-
40 yrs. Rare before age of 10 and after 40. Endocrine- Pregnancy, increased deafness
during menopause Associated with osteogenesis imperfecta,
viral infection (measles virus- Paget’s disease)
TYPES OF OTOSCLEROSIS
1. Stapedial Otosclerosis 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
Obliterative Completely obliterates the oval window
2. Cochlear Otosclerosis Involves region of round window or other
areas of otic capsule and may cause sensineural hearing loss due to liberation of toxic chemicals into inner ear fluid
3. Histologic Otosclerosis Remains asymptomatic. No deafness.
PATHOLOGY
Gross Otosclerotic lesion appears chalky white,
greyish or yellow. If red in colour indicates active and rapidly progressive otosclerotic focus.
Microscopically Divided in 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
SYMPTOMS
Hearing loss- insidious, painless and progressive. Often bilateral conductive type.
Paracusis Willisii- Hears better in noisy than quiet surroundings
Tinnitus- more common in cochlear type Vertigo- uncommon Speech- monotonous, well modulated, soft
speech
SIGNS
Schwartze sign; red hue occasionally seen over promontory through tympanic membrane. Indicative of active focus with increased vascularity
Eustachian tube function is normal
Tuning fork tests Negative Rinne (BC>AC): First for 256Hz then
512Hz and when stapes fixation complete; for 1024 Hz.
Weber test : will be lateralized to the ear with greater conductive loss.
ABC normal, may be decreased in cochlear otosclerosis with sensineural loss
Audiometry Pure Tone Audiometry
Loss of air conduction at lower frequencies Bone conduction normal, sometimes shows a dip
at 2000 Hz (Cahart’s notch) which disappears after successful surgery.
Speech Audiometry Normal discrimination score except in those with
cochlear involvement.
Tympanometry- Normal in early cases but later shows curve of ossicular stiffness. Stapedial reflex absent when stapes is fixed
TREATMENT
Medical: No treatment for curing otosclerosis. Sodium fluoride has been tried to hasten maturity of active focus., not recommended.
Surgical: Stapedectomy/stapedotomy with placement of prosthesis is the treatment of choice
Hearing aid
Selection criteria Hearing threshold is 30dB or worse
AB gap at least 15dB
Rinne’s negative for 256 Hz and 512 Hz
Speech Discrimination Score is 60% or more
Contraindications Only hearing ear Meniere’s disease Occupation such as athletes, frequent air
travellers, construction workers, divers Experience frequent change in pressure Works in noisy surrounding
Otitis externa Perforated TM Young children Poor state of health
Prosthesis Teflon piston
Stainless steel piston
Platinum Teflon piston
Titanium Teflon piston
STEPS OF STAPEDECTOMY
1. Meatal incision and elevation of tympanomeatal flap
2. Exposure of stapes area. This may require removal of posterosuperior bony overhang of canal
3. Removal of stapes superstructure4. Creation of a hole in the footplate of the
stapes (stapedotomy) or removal of part of footplate (stapedectomy)
5. Placement of prosthesis6. Repositioning of tympanomeatal flap
COMPLICATIONS OF STAPEDECTOMY
1. Tear of tympanomeatal flap and perforation of TM
2. Injury to chorda tympani with taste disturbance3. Incus dislocation4. Injury to facial nerve5. Vertigo6. Perilymph fistula/granuloma7. Conductive loss- short, loose or displacement of
prosthesis, incus erosion (late)8. Sensineural hearing loss- intraoperative trama,
labyrinthitis, perilymph fistula9. Dead ear
Thank you