Week 5 - Otosclerosis Flashcards
What is otosclerosis?
- means “hardening of the ear”
- metabolic bone disease of ossicles and otic capsule
- fixation of the ossicles (stapes)
- results in a conductive or mixed HL
Otosclerosis is altered body metabolism in the otic capsule resulting in cyclic _____ and deposition of bone
Reabsorption
T/F: abnormal bone from otosclerosis can also invade the cochlea causing sensorineural damage and a mixed loss
True
What are the two symptom-based classifications of otosclerosis?
Clinical
- symptomatic and presenting with combination of HL, tinnitus, and rarely vertigo
Histological
- asymptomatic, more common, and typically diagnosed postmortem
Besides the symptom-based classification, how else might otosclerosis be classified? What are the two categories of this system?
Site of Lesion Classification
- based on the structure predominantly affected
- losing utility since subtypes are on a continuum
Fenestral - stapes predominantly affected
Retrofenestral - cochlea predominantly affected
The prevalence of histologic otosclerosis is highest in which race?
Caucasian - 10%
Females are more often affected by clinical otosclerosis than males. When is the typical onset for the disease?
15-45 years
Name 3 possible factors implicated in the development of otosclerosis
- hereditary
- endocrine
- metabolic
- infectious (Measles)
- autoimmune
Otosclerosis consists of an early phase an a late phase. Describe them
Early phase - otospongiosis = vascular spongy bone growth
Late phase - dense sclerotic bone in areas of earlier respiration and otospongiosis
Otosclerosis site of lesion is limited to the ___ capsule and stapes
Otic
What structures in the ME are usually affected by otosclerosis?
Oval window
Footplate
Annular Ligament
Round window (less frequent)
What does the cochlear dysfunction portion of otosclerosis consist of?
Invasion of membranous labyrinth
Atrophy of spiral ligament in lateral wall
T/F: Otosclerosis is invisible on high resolution CT scans
False
How does otosclerosis damage the cochlea?
Damage occurs via:
- Bony invasion of membranous labyrinth
- Enzymes produced in otosclerotic foci adjacent to lateral wall of cochlea infiltrate membranous labyrinth
- disrupts cochlear fluid homeostasis
- eventual degeneration of organ of corti
What case history and symptoms would we expect to see with otosclerosis?
- progressive HL (conductive or mixed, SNHL, Carhart notch)
- beginning unilateral, then possibly progressing to bilateral (80% of cases)
- tinnitus (75%)
- vestibular complaints (25%)
In most cases, the physical exam is limited in it’s usefulness, but what is one thing that may be visible with otosclerosis?
Schwartze sign - reddish discolouration of the TM d/t increased vascularity
(10% of cases)
Is imaging usually required for otosclerotic diagnosis?
Not usually
- audiology most useful
- high res CT for surgical planning
Describe the audiometric progression of otosclerosis
Variable
- usually initial conductive HL in low freq
- configuration flattens
- increased conductive component in low freq and decline in BC for high freq
What is Carhart’s notch?
- 2 kHz dip for pure tone BC
- Hallmark feature of otosclerosis
- caused by reduction in BC activated ossicular motion affecting resonance
Describe the audiometry of cochlear otosclerosis
- mixed hearing loss initially
- can advance rapidly
- less common
What type of imminance can we expect with otosclerosis?
- type A or As tymps
- absent or unusual acoustic reflexes (e.g reverse, on-off, or diphasic)
Which is the older method for stapes surgery: Stapedectomy or stapedotomy?
Stapedectomy
- stapes footplate is removed
Describe how stapedotomy is different from stapedectomy
Stapedotomy is:
- more commonly used now
- keeps the footplate intact
- results in less trauma to the oval window
- and less possibility of damaging the inner ear
What is the goal of stapes surgery?
To close the ABG
- otosclerosis can recur and displace prosthesis
- revision surgery may be required (may not fully restore hearing)
What are some non-surgical interventions for patients with otosclerosis?
Medical:
- fluoride (not effective)
- bisphosphonate
Amplification:
- patients who do not want/are not fit for surgery
CI:
- advanced otosclerosis invading the cochlea causing SNHL
