Discomfort to noise by zG50te0

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									Otosclerosis

Steven Powell
  SpR ENT
                   Outline
•   Viva
•   Questions
•   Definitions
•   Anatomy and Physiology
•   Pathology
•   Aetiology
•   Clinical Features
•   Diagnosis
•   Treatment Options
               Take Homes
•   Exam!
•   Cahart effect/ notch
•   Multisided surgery
•   Glasgow benefit plot
    Paradoxes and questions
• Is otosclerotic bone sclerotic?
• Is a reparative granuloma a granuloma?

• Why aren’t people as grateful when you do
  the second side?
• How can the bone conduction be better
  than the air conduction in these patients?
Explain this
               Definitions
• A localised hereditary disorder affecting
  endochondral bone of the otic capsule
  which is characterised by disordered
  resorption and deposition of bone.
             Embryology
• Ectoderm forms otic pit and otocyst
• With neural crest cells forms membranous
  labyrinth
• Mesenchyme enclosing otocyst becomes
  chondrified to form otic capusle
• Ossification begins 16 weeks
• Dense bone- petrous
• Channels remain- oval window (footplate
  and annular ligament)
Anatomy
Anatomy
                  Anatomy
• Stapes
  – Anterior crura, posterior crura, footplate
  – Anterior crus thinner
  – Stapedius inserts posteriorly into neck and
    posterior crus
  – Footplate convex superiorly, straight inferiorly
  – 3mm long, 1.4 mm wide
  – Attached to bony margins by annular ligament
               Physiology
• Middle ear is impedance matching system
  – Higher impedance of fluid
  – Size differential
  – Lever action


• Couples sound preferentially to one
  window of cochlea
Bone Conduction- Cahart Effect
                  Pathology
•   Normally very little remodelling of bone
•   Bone remodelling (blasts and clasts)
•   Active (spongiotic) areas
•   Inactive (sclerotic) areas

• Commonest sites
    – Anterior to oval window 80-90%
    – Round window niche 30%
Histology
                Pathology
• Clinical otosclerosis
• Histological otosclerosis
• Cochlear otosclerosis
       Pathophysiology CHL
• Original thinking progressive air bone gap
• Bony ankylosis>otosclerosis>fibrous

• Now appears to be associated with
  stapedovestibular joint space

• Mucosa fibroproliferative
• Schwarte’s sign
      Pathophysiology SNHL
• Otosclerosis in cochlear endosteum
• Action on spiral ligament
• Cytokine mediated

• Rare without cochlear otosclerosis
Pathophysiology SNHL
            Epidemiology
• British Study of Hearing
• 2% M=F, but at CHL >30dB 3F:1M

• 10% prevalence in temporal bones, but ?
  selection
                    Aetiology
• Genetics
    – Autosomal dominant, incomplete penetrance
    – Sporadic
    – COL1A1 gene defects


•   Measles
•   Autoimmune
•   Biochemical factors
•   Pregnancy
            Clinical Features
• Decreased hearing
• Tinnitus (50-70%)

•   May be no clinical signs
•   Schwartze’s rare
•   Normal TM
•   Abnormal TM
Schwartze’s Sign
             Investigations
• Pure tone audiogram
  – Conductive hearing loss
  – Mixed hearing loss
• Tympanometry
• CT
• MRI
Conductive Hearing Loss
Mixed Hearing Loss
CT
         Differential Diagnosis
•   Congenital ossicular abnormalities
•   Ossicular fixation
•   Ossicular errosion
•   Ossicular dislocation

• Tympanosclerosis
• Osteogenesis imperfecta type 1!
         Management Options
•   Watch- natural history
•   Conventional hearing aids
•   BAHA
•   Cochlear implant
•   Stapes surgery

• Fluorides
                Hearing Aids
• 4 scenarios
  – Primary treatment CHL
  – Mixed hearing loss
  – Combination after surgery to reduce CHL to
    serviceable level
  – Rescue treatment

• BAHA
• Cochlear implant (not a hearing aid)
           History of Surgery
•   1876 Kessel- removed footplate
•   1888 Boucheron- rocked footplate
•   Fell into disrepute
•   1938 Lempert- Fenestration
•   1952 Rosen- Mobilisation
•   1956 Shea- stapedectomy and prosthesis
                   Surgery
• Used to be threshold of 20dB gap for
  operating, but now CHL of 10dB may be
  operated on

• Contraindictions
  – Pregnancy
  – Active infection
                  Surgery
•   Anaesthesia general v local
•   Per-meatal or endaural
•   Tympanomeatal flap
•   Curette bone
•   Assess ossicular chain

• Measure distance
Surgical Techniques- stapedotomy
    Stapedotomy Techniques
• Drill
• Lasers

• Tissue to seal- vein

• Type of piston
• Size of piston
Surgical Techniques-
   Stapedectomy
CT
           Surgical Problems
•   Floating footplate
•   Obliterated footplate
•   CSF gusher
•   Facial nerve dehiscence/ prolapse
 Post-Operative Complications
• Conductive Hearing Loss
  – Displacement of Prosthesis
  – Necrosis LPI
  – Bony regrowth
  Postoperative Complications
• Sensorineural hearing loss- rates vary
  depending on paper 1-10%
• Extensive drilling
• Floating footplates
• Perilymph leak

• Delayed SNHL
    Post- Operative Complications
•   Facial nerve injury
•   Vertigo
•   Perilymph fistula
•   Reparative granuloma

•   Discomfort to noise
•   Taste changes
•   Cholesteatoma
•   Meningitis
 Stapedectomy v stapedotomy
• Stapedectomy
  – Better low frequency hearing gain
• Stapedotomy
  – Better HF gain
  – Lower incidence: perilymph fistula, SNH
    impairment, post-op vertigo, revision surgery
           Surgical Issues
• Unilateral
• Second side surgery
Glasgow Benefit Plot
      Belfast Rule of Thumb
• Operated ear brought to 30dB or better or
  within 15dB of contralateral ear
          Revision Surgery
• 92% for CHL
• 2% dizziness/ SNHL/ fistula

• More problems
  – Adhesions
  – Ossicular problems
  – Higher risk SNHL
    Paradoxes and questions
• Is otosclerotic bone sclerotic?
• Is a reparative granuloma a granuloma?

• Why aren’t people as grateful when you do
  the second side?
• How can the bone conduction be better
  than the air conduction in these patients?
               Questions
• Otosclerosis is only partially sclerotic. A
  larger part may be spongiotic
• A reparative granuloma is a misnomer and
  is granulation tissue
• “Over correction” of the air bone gap is
  explained by the Cahart effect
• Second side surgery often doesn’t improve
  overall hearing level as demonstrated by
  Glasgow Benefit Plot
               Summary
• Otosclerosis is a disorder of bone
  resorption and deposition in the otic
  capsule bone/ petrous temporal bone
• Its commonest manifestation is conductive
  hearing loss +/- sensorineural loss
• Treatment options of aiding versus surgery
  should be weighed up in context of the
  audiometry, contralateral ear and patient
  preference.
Thankyou

								
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