Complete Otosclerosis ENT 2013, 2016, 2019

Otosclerosis is a condition where one or more foci of irregularly laid spongy bone replace part of normally dense enchondral layer of bony otic capsule in the bony labyrinth. This is one of the most common question in DNB ENT THeory and OSCE,We will start with anatomy and then go for clinical findings and treatment options.

Questions on Otosclerosis – Discuss in brief the aetiopathogenesis of otosclerosis. Describe in  brief the management of otosclerosis with special reference to “Revision Surgery”.Q-Clinical features and audiological eligibility for surgery. Define Otospongiosis,     its clinical features, surgical treatment and its complications. Q- a) Describe histopathology & genetic basis for Otosclerosis. Clinical, audiological & radiological diagnosis of Otosclerosis. Surgical challenges in Stapes surgery. Describe the various options to make fenestra during stapes surgery and various prostheses being used with the method of placement. (4+4+2) Dec 2013, Dec 2016, Dec 2018, Dec 2019, June 2019

Anatomy of labyrinth.

• Otic capsule
• Otic labyrinth
• Periotic labyrinth

Otic Capsule

• It is the bony labyrinth
• Ossifies from 14 centres
  • First one > region of cochlea >16 weeks
  • Last one  > posterolateral part of posterior semicircular canal  >  20 weeks
• It has three layers:
  • Endosteal
  • Enchondral
  • Periosteal
    1. Endosteal layer : Innermost layer.It lines the bony labyrinth
    2. Enchondral layer : Develops from cartilage  and later ossifies into bone(ENCHONDRAL LAYER :some islands of cartilage left unossified & give rise to otosclerosis).
    3. Periosteal : Covers the bony labyrinth
• Periotic / Peilymphatic Labylinth : It surrounds the otic labyrinth and is filled with perilymph. It includes vestibule,scala tympani,scala vestibuli,perilymphaticr space of semicircular canals and the periotic duct.

Epidemiology :

• 10% overall prevalence of histologic otosclerosis
• 1% overall prevalence of clinical otosclerosis
• Race(% incidence of otosclerosis)
  • Caucasian(10%)
  • Asian(5%)
  • African american(1%)
• Gender
  • More common in females than males in the ratio 2:1
• Age
  • Most common age of presentation : 15-45yrs
  • Youngest presentation : 7yrs     
  • Oldest presentation : 50yrs

Pathogenesis of Otosclerosis

• Resorption of enchondral bone
• Enlarges perivascular space
• Deposition of immature woven bone
• Further remodelling
• Deposition of mature sclerotic bone
• Bone remodelling controlled by osteoblasts and osteoclasts
• Growth factors,cytokines,enzymes and free radicals
• Failure of regulation of osteoclasts and osteoblasts
• Uncontrolled bone remodelling

Phases of Otosclerosis

• Two phases of disease:
  • Active/Immature/Otospongiosis phase
  • Inactive/Mature/Otosclerotic phase

Active Phase :

• Deposition of immature woven bone
• Increased cellularity
• High vascularity
• Dilatation of vessels
• Schwartz sign

Blue Mantles of Manasse :

Mature Phase :

• Deposition of highly mineralised bone
• Mature bone-thick and cellular
• Osteoclastic activity resolved
• Vascular spaces narrowed

Most common sites of involvement:

• Fissula ante fenestrum- 80-95%
• Round window niche- 30%
• Apical medial wall of cochlear labyrinth- 15%
• Stapes footplate- 12%
• Posterior to oval window
• Anterior wall of IAC,cochlear aqueduct,malleus,incus

Types :

1: Histological

• Stapes not involved
• Diagnosed by postmortem examination of temporal bone

2: Stapedial

• Stapes involved
• Conductive  hearing loss

3: Cochlear

• No stapes fixation
• Involves cochlear endosteum
• Sensorineural hearing loss

Etiology :

Proposed Theories

• Metabolic
• Immune
• Vascular
• Infection
• Trauma
• Anatomical and histological anomalies of temporal bone

Genetic :

Autosomal dominant inheritance with incomplete penetrance. Monozygotic twins have 100% concordance rate. Significant association present between both familial and sporadic cases of clinical otosclerosis and COL1A1 gene

Measles Infection :

• Ultrastructural and immunohistochemical evidence of measles like structures and antigenicity in active otosclerotic lesions.
• Measles RNA in footplate specimens with otosclerosis
• Elevated levels of Antimeasles antibodies in perilymph
• Data inconclusive

Clinical Features :

• Conductive or mixed hearing loss
  • Slowly progressive
  • Bilateral,asymmetric
• Paracusis willisii : Patient hears better in noisy surroundings
• Vestibular symptoms
  • Vertigo
• Tinnitus
• Speech : Monotonous,well modulated soft speech

Pathology of Conductive Hearing Loss :

• Fibrous fixation of footplate : 30 db
• Localised bony fixation : 30-40 db
• Bony ankylosis of annular ligament : 40 db
• Impairment of annular ligament at posterior vestibular joint space : 250-2000Hz

Pathology of Sensorineural Hearing Loss :

• Otosclerotic involvement of cochlear endosteum
• Atrophy of spiral ligament and replacement by amorphous eosinophilic substance
• Bony invasion of scala tympani of cochlea
• Circulatory changes in cochlea due to abnormal bone
• Damage to cochlea by metabolic enzymes from abnormal bone

Otomicroscopy :

• Schwartze Sign
  • Reddish hue seen through the tynpanic membrane
  • Also called flamingo sign
  • Indicative of active focus
• Rule out other conditions:
  • Middle ear effusions
  • Tympanosclerosis
  • Tympanic membrane perforations    
  • cholesteatoma or retraction pockets

Tuning Fork Tests

• Show conductive hearing loss

Audiometry :

• Pure tone audiometry
• Impedence audiometry
  • Tympanometry
  • Acoustic reflex

Pure Tone Audiometry :

Air Conduction

• Low frequencies affected first
• Rising air line-stiffness tilt
• Due to stapes fixation
• Disease progression
• Air line flattens •
• Due to mass effect

Bone Conduction :

    Carhart’s Notch -Hallmark audiologic sign of otosclerosis

   Proposed Theory :

• Loss of inertia of stapes
• Fixation disrupts the normal ossicular resonance(2000Hz)
• Normal compressional mode of bone conduction is disrupted because of relative perilymph immobility.
• Reverses with stapes mobilization

Tympanometry :

Acoustic Reflex :

Imaging :

Computed tomography(CT) of the temporal bone for evaluation of otosclerosis

Pre-op:

• Characterize the extent of otosclerosis
• Severe or profound mixed hearing loss
• Evaluate for enlarged cochlear aqueduct •

Post-op:

• Recurrent CHL
• Re-obliteration vs prosthesis dislocation

Axial cuts :

• Patient position- canthomeatal line perpendicular to the table top
• 1mm cuts
• Top of superior semicircular canal to bottom of the cochlea •

Coronal :

• Patient position-supine with head overextended face turned 20 degrees ipsilateral

Fenestral Otosclerosis :

Cochlear Otosclerosis :

Differential Diagnosis :

• Secretory otitis media
• Ossicular discontinuity
• Congenital stapes fixation
• Malleus head fixation
• Tympanosclerosis
• Paget’s disease
• Osteogenesis imperfecta

Treatment Of Otosclerosis

MEDICAL AMPLIFICATION SURGERY

Sodium Flouride

• Mechanism: Flouride ion replaces hydroxyl group in bone forming fluorapatite
• Resistant to resorption
• Increases calcification of new bone •Causes maturation of active foci of otosclerosis
• DOSE – Active lesion-50 to 75mg/day, Maintenance-25mg

Indications of Sodium Flouride

• Surgically confirmed otosclerosis
• Pure SNHL
• Positive radiographic findings
• Positive schwartze sign
• Active focus at surgery-treat for 2 yrs
• Preoperatively

Contraindications of Sodium Flouride

• Chronic nephritis with nitrogen retention where urinary excretion of fluoride may be impaired
• Chronic rheumatoid arthritis
• Pregnant or lactating women
• Children before skeletal growth completed
• Allergy to fluoride
• Skeletal fluorosis

Benefit is demonstrated by:

• Fading of positive schwartze sign
• Stabilization of progressive SNHL
• Reduction of tinnitus
• Improvement of mild vestibular symptoms
• X-ray demonstration of recalcification of the focus

Side Effects -Gastric intolerance, skeletal flurosis

Surgery for Otosclerosis

Indications of Surgery :

• Bone conduction of 0-25dB
• Air conduction of 45-65dB
• Air-bone gap of atleast 15dB
• Speech discrimination of 60% should be present for good hearing improvement

Contraindications :

• Presence of general medical disease
• Old age > 70 yrs
• Conductive losses from other causes
• Presence of otitis externa,tympanic membrane perforation
• Presence of only hearing ear
• Unilateral otosclerosis
• Stapedial and cochlear otosclerosis with poor air-bone gap
• Pregnancy
• Presence of labyrinthine hydrops
• Positive Schwartze sign
• Patients with occupation related to sports,flying aircraft

Informed Consent

• Patient should be informed about amplification as an alternative mode
• Description of the procedure
• Advantages and possible disadvantages of surgery
• Discussion of all potential risks
• Proper counselling for patients with occupations exposing  them to significant pressure variations-pilots,divers,parachuters

Anesthesia :

Choice of anesthesia depends on patient’s and surgeon’s preferences .

Local Anaesthesia -Intraoperative reports of vestibular stimulation can be identified

General Anaesthesia– Provides assurance against pain and head movement

Proper Positioning of Patient: Essential for good visualization of middle ear structures •Head of the patient is turned towards the contralateral shoulder •Head tilted downwards 10 to 15 degrees •Use of separate head rest

Canal Wall Injection :

• Infiltration using 1%lidocaine and 1:1,00,000 adrenaline
• Four quadrants of external auditory canal injected
• Infiltration of the canal skin at the level of bony and cartilaginous junction

Elevation of Tympanomeatal Flap

• 6 o’clock to 12 o’clock positions
• 6-8mm lateral to the annulus
• Elevation of flap proceeds anteriorly
• Fibrous annulus displaced from its sulcus
• Posterior half of tympanic membrane folded forwards over handle of malleus

Curettage of Scutum

• Chorda tympani nerve is gently freed from any mucosal folds
• Postero-superior bony annulus removed using bone curette or drill
• To provide exposure of long process of incus,stapes,oval window,facial nerve and base of the pyramid

Middle Ear Exammination :

1. Mobility of ossicles
2. Confirm stapes fixation
3. Evaluate for malleus or incus fixation •Anatomical anomalies
4. Dehiscent facial nerve
5. Overhanging facial nerve
6. Persistent stapedial artery  
7. Tympanosclerosis

Separation of Incudostapedial Joint

1. Stapedial tendon is cut with scissors as close as possible to the pyramidal eminence
2. Incudostapedial joint is separated with a joint knife
3. Posterior crus is fragmented near its base using crurotomy scissors
4. Suprastructure is fractured downward toward promontory and removed from middle ear
5. Footplate is transected transversely using sharp angled and straight picks into 2 or 3 pieces
6. Gently extracted from the oval window using right angled hooks or microforceps
7. Soft tissue graft is used to cover or fill the oval window and prosthesis positioned
8. If anterior fragment of footplate is fixed,partial  oval window defect covered with soft tissue graft
9. Tympanomeatal flap is replaced and the external ear canal packed

Stapedotomy :

• Instrumentation
  • Manual/handheld perforator
  • Burr with low speed micromotor
  • Laser
• Site of fenestration
• Size of fenestration and prosthesis
• Techniques :
  • Conventional technique
  • Fisch technique

Stapedotomy – Conventional Technique :

Stapedotomy-Fisch Technique

Stapedectomy v/s Stapedotomy :

• STAPEDECTOMY : •
  • Better low frequency hearing gain
  • May be only method technically possible
• STAPEDOTOMY :
  • Better high frequency hearing gain
  • Low incidence of perilymph fistula,SNHL,lateralization of graft
  • More stable hearing gain •
  • Less labyrinthine trauma

Lasers :

Four important laser qualities for stapedectomy/stapedotomy:

1. Precise optics and tissue interaction
2. Vapourisation without adjacent thermal spread
3. No heating of perilymph
4. No penetration of perilymph

Types of Lasers :

1. Visible Laser
   • short wavelength
   • Argon 514nm,KTP 532nm:
   • ideal optical properties,effective delivery,visible-working and aiming beam are same
2. Infrared Laser
   • long wavelength
   • Co2 laser: 10,600nm   
   • Invisible:aiming beam required

Connective Tissue Seal :

• Vein
• Temporalis fascia
• Tragal perichondrium
• Blood clot
• fat

Site of Fenestration :

• Fenestra is placed in the posterior half of the footplate •
• Posterior fenestra– 0.8mm diameter
• Prosthesi– 0.6mm diameter

Reasons for Posterior Fenestra :

• Minimizes the chance of damaging the saccule
• reconstruction of the annular ligament with restoration of proper acoustic impedance
• Adhesions may be present between the saccule and the footplate at the level of the annular ligament anteriorly
• Avoidance of anterior otosclerotic foci reduces the risk of releasing proteolytic enzymes into the inner ear and reduces the chance of bleeding

Measurement for Prosthesis :

• Distance between the lateral aspect of long process of incus and footplate should be measured
• Prosthesis selected should be 0.25mm longer than the distance
• Usually ,4.5mm prosthesis will be selected

Types of Prosthesis :

1. Robinson prosthesis(metal)-does not require crimping,easy to insert and self centering
2. Causse type(teflon)-memory,no crimping
3. Fisch/Mcgee -malleable ribbon like crook connected to metal or teflon stem,crimping required
4. House type(wire prosthesis)
5. Titanium prosthesis

Post Operative Care :

• Keep ears dry
• Avoid strenuous physical activities
• Avoid nose blowing and forceful sneezing
• Avoid air travel
• Oral antibiotics for 1 week

Intraoperative Complications :

• Tears in tympanomeatal flap
• Subluxation of incus
• Overhanging facial nerve
• Obliterative Otosclerosis of oval window
• Otosclerosis involving the round window
• Persistent stapedial Artery
• Malleus Ankylosis
• Perilymph gusher
• Floating Footplate

Postoperative Complications :

• Facial palsy
• Chorda tympani dysfunction
• Otitis media
• Vertigo
• Reparative Granuloma
• Sensorineural Hearing loss
• Conductive Hearing loss

Tears in Tympanomeatal Flap :

• REASONS:
  • Elevation of the flap in a limited segment,not in a broad front
  • Elevation of tympanic membrane without the annulus
• REPAIR:
  • Placement of a medially placed tragal perichondrium or fascia graft
  • Small tears-closed with piece of gelfoam
  • Small linear tears-Avoid infolding of the edges of the tear

Subluxation of Incus :

• Reasons:
  • During curettage of the bony annulus
  • Separation of the incudostapedial joint
  • Manipulation around oval window
  • During crimping
• Treatment
  • Incus attachment prosthesis
  • Malleus attachment prosthesis

Overhanging Facial Nerve :

• If the prolapsed nerve abuts the promontory inferior to the oval window,surgery should not be completed
• Surgery can be completed by drilling a small fenestra that includes the inferior aspect of the annular ligament
• Prosthesis must be longer than usual to accomodate bending inferiorly to avoid the nerve

Obliterative Otosclerosis of Oval Window :

• Oval window niche can be obliterated by severe thickening of the stapedial footplate or margins of niche
• Fenestration can be achieved after first saucerizing the obliterated niche and thinning the obstructing bone
• If obliterative otosclerosis is found in one ear, 50% chance of the same finding to be present in other ear

Otosclerosis Involving the Round Window :

• Round window can be partially or completely obliterated by otosclerosis
• Surgery should be completed and the finding noted in the operative note
• residual conductive loss is present following surgery,revision surgery is not recommended

Persistent Stapedial Artery :

• Arises from the internal carotid artery, often seen running across the footplate
• Incidence: 1 in 5000 to 10,000 ears
• Cannot be safely coagulated with bipolar cautery or laser
• Often it occupies only the anterior half of the footplate and fenestration can be completed in the posterior half

Malleus Anklosis :

• Head of malleus  ankylosed  to the roof of epitympanum by a spur or bar of bone
• Etiology not associated with that of otosclerosis
• Incidence of malleus fixation: 0.5%
• Unilateral in contrast to otosclerosis
• Fixation of the malleus can be corrected by removing the incus  and head of malleus and reconstruction with a malleus attachment prosthesis

Perilymphatic Gusher :

• Associated with patent cochlear aqueduct
• More common on the left
• Increased incidence with congenital stapes fixation
• Increased risk of SNHL

Management :

• Rapid placement of the soft tissue seal over oval window,then the prosthesis
• Elevation of head end
• Bed rest
• Avoid valsalva

Floating Footplate :

• Footplate dislodges from the surrounding OW niche
  • More commonly iatrogenic
• Prevention
  • Use of laser
  • Preliminary footplate control hole
• Management
  • Abort and place soft tissue
  • Small drill hole at margin of oval window and hook to remove

Perilymphatic Fistula :

• Most common single complication of stapedectomy:9-10%
• Potentially dangerous risk of meningitis,hearing loss and dysequilibrium

Etiology :

Primary Fistula :

Presesnt at end of surgery •Syrgeon creates and relies on healing process •Fistula common with plastic prosthesis •Small fistula becomes large with barotraumas •

Secondary Fistula :

Appears  many months or years after surgery-usually due to barotraumas Common when stapedial tendon is cut

Diagnosis :

Symptoms :

• Dysequilibrium
• Hearing loss
• Tinnitus
• Fluctuating hearing •

Audiometric Tests :

• PTA- Sensorineural loss in low frequency
• Speech discrimination- initially fluctuates,later reduced

Treatment :

• Tympanotomy •
• Excision of tract,removal of  prosthesis,covering the defect by soft tissue

Facial Nerve Injury :

• Temporary injury
  • Immediate facial nerve palsy postoperatively due to local anaesthetic infiltration
  • Delayed facial palsy between days 4 and 10 postoperatively
  • Due to facial nerve swelling,resulting from the nerve being heated by a drill or laser
• Permanant injury
  • rare
  • Associated with laser or burr injury in the presence of a dehiscent canal

Chorda Tympani Dysfunction :

• Damage to chorda tympani nerve is seen in 30% of procedures
• Sectioning or stretching the nerve leads to:
  • Metallic taste
  • Impairment of taste
  • Dry mouth
  • soreness of tongue
• Stretching produces more symptoms than sectioning

Post operative Vertigo :

• Serous labyrinthitis – 1week post op
• Reparative granuloma
• Depressed footplate
• Bony fragments compressing the saccule
• Suppurative labyrinthitis
• Endolymphatic hydrops

Post opretive conduction Hearing Loss :

• Displacement or dislodgement of the prosthesis from oval window area(36%)
• Necrosis of long process of incus
• Loose attachment between incus and prosthesis
• Detachment of prosthesis from incus
• Recurrence of otosclerosis and oval window closure

Post Operative Sensorineural Hearing Loss :

• Incidence-0.6%
• Temporary-serous labyrinyhitis
• Permanent
  • Surgical trauma
  • Sudden release of perilymph pressure
  • Excessive movement of stapes
  • Rupture of membranes of inner ear   
  • Vascular compromise

Reparative Granuloma :

• Granulation tissue formation around the prosthesis and incus
• 1-2 weeks postop
• Initial good hearing results followed hearing loss
• Associated tinnitus and vertigo
• O/E: Dull and reddish discolouration of tympanic membrane in postero-superior quadrant
• Treatment: Immediate exploration and removal of granulation tissue
• Prognosis: Hearing returns with early excision