CHL Flashcards
Discuss the differential diagnosis of fixed CHL
- Ossicular Discontinuity: Incus necrosis due to recurrent otitis media; 60dB HL (maximal CHL) and type Ad tympanogram
- Fibrous union of the incudostapedial joint: Greater CHL in the higher frequencies
- Tympanosclerosis
- Malleus Head Fixation: If congenital, high incidence of aural atresia, Type As tympanogram (only seen in the most advanced otosclerosis with tympanosclerosis)
- Congenital Stapes Fixation: Usually diagnosed in first decade of life; non-progressive HL; only 10% family history (vs. 66% with otosclerosis)
- Otitis Media: Can be recurrent, chronic ± cholesteatoma, or with effusion
- Middle ear neoplasm: Glomus or facial nerve tumor
- Paget’s disease: Increased Alk Phos; CT findings seen on bilateral petrous bones (Demineralization); typically causes crowding of the ossicles in the epitympanum
- Osteogenesis Imperfecta - Blue sclera, history of multiple bone fractures
- TM perforation
Discuss the differential diagnosis of variable CHL
- EAC collapse
- Increased perilymph pressure
- Inner ear conductive hearing loss
- Ossicular chain discontinuity
- Superior semicircular canal dehiscence syndrome
Describe Austin’s classification of middle ear conductive apparatus lesions and associated hearing loss
- TM Perforation - Loss is proportional to the size of the perforation
- 0-25% ~10dB
- 25-50% ~20 dB
- 50-100% ~ 30dB - TM perforation with ossicular interruption ~40dB
- Total loss of TM and ossicular chain ~50dB loss
- Ossicular interruption with intact TM ~50-60dB
- Ossicular interruption with intact TM and closure of oval window - ~50-60dB loss
If a patient has a small TM perforation, which hearing frequencies does this selectively reduce?
Lower frequencies more affected
Discuss the classification of traumatic tympanic membrane perforations
- Compression
- Penetrating
- Thermal
- Lightening
- Chemical
If a patient has a new TM perforation, how long do you wait until repair?
3-6 months
What are the two main goals of tympanoplasty?
- Re-establish intact TM
- Prevent epithelial ingrowth and infection - Hearing improvement
- Reconstitute hydraulic and catenary lever
Name and discuss the classification of tympanoplasties
Wullstein Classification
- Type I: Myringoplasty (perforation only requiring TM flap and graft only, ossicular chain intact - no ossicular reconstruction)
- Type II: Myringoincudopexy (malleus eroded, incus in tact; graft laid on the IS joint)
- Type III: Myringostapedopexy or PROP (loss of malleus and incus); divided into:
- Stapes columella: Graft placed over intact stapes superstructure (Myringostapediopexy)
- Minor columella: Interpositional graft or PORP (partial ossicular reconstruction prosthesis) between stapes and tympanic membrane
- Major columella: TORP between intact stapes footplate and tympanic membrane - Type IV: Graft laid on stapes mobile footplate (loss of stapes superstructure, footplate is mobile)
- Graft placed on mobile footplate/oval window directly for acoustic coupling
- A “Cavum minor” (a small pneumatized cavity) is created over the RW niche and eustachian tube for acoustic shielding - Type V: Stapes footplate is fixed
- Va in Tos classification: Lateral /horizontal SSC fenestration
- Vb in Tos classification: Removal of stapes footplate (stapes fenestratin) and soft tissue seal over oval window (ie. stapedectomy or stapedotomy)
https://ars.els-cdn.com/content/image/1-s2.0-S1043181003000927-gr2.jpg
https://www.youtube.com/watch?v=cMgw1sJDaDg
What anesthetic agents should be avoided during a tympanoplasty, and why?
NITROUS OXIDE (NO2)
- NO2 expands in closed spaces (such as the middle ear)
- Therefore, may lift off and displace newly placed TM graft
- Easily reversible with administration of 100% O2
What are the possible surgical approaches for tympanoplasty?
EQUIPMENT: Microscopic or Endoscopic
SURGICAL APPROACHES:
1. Postauricular
2. Endaural
3. Transcanal
TM APPROACHES:
1. Overlay
2. Underlay
3. Interlay
What are the materials that can be used for grafting in myringoplasty/tympanoplasty?
MYRINGOPLASTY:
1. Epidisc (hyaluronic acid)
2. Biodesign (porous collagen matrix from porcine small intestine)
3. Gelfoam
4. Steri-strip or cigarette paper (lol Kevan)
TYMPANOPLASTY:
1. Biodesign
2. Temporalis fascia
3. Perichondrium
4. Periosteum
5. Cartilage
What are the advantages and disadvantages of overlay vs. underlay tympanoplasty?
OVERLAY GRAFTING (graft placed over the annulus, only a skin flap needs to be raised):
A. Advantages
1. Excellent exposure
2. High graft take rate
3. Applicable to all cases
B. Disadvantages
1. Requires precision
2. Longer healing time (months vs. weeks)
3. Possibility of blunting, lateralization, or epithelial pearls
UNDERLAY GRAFTING (graft placed under the annulus, tympanomeatal flap):
A. Advantages
1. Less blunting or lateralization
2. High graft take rate
3. Simpler technique
B. Disadvantages
1. Limited visualization
2. Large, anterior perforation less suitable
3. Difficult with small external auditory canal
https://www.youtube.com/watch?v=cMgw1sJDaDg
Six most common causes of malleus head fixation
- Otosclerosis
- Osteodystrophies
- Tympanosclerosis
- Postinfectious adhesions
- Congenital fixation
- Trauma
What are the typical lengths of ossicular prostheses?
PORP ~2.5-3mm
TORP ~5-6mm
Stapes ~4.5mm
Discuss the prognosis of ossicular chain reconstruction
- 61% of partial and 38% of total reconstruction have an ABG of > 20 at 5 years
- Loss of stapes arch and the presence of a mastoid cavity are associated with poorer outcomes
- Patients are likely to report a benefit if they follow the belfast rule of thumb
Belfast rule of thumb:
- Post-op AC PTA is < 30dB or the interaural AC difference is < 15dB
