Nonsyndromic HL

Question 1

Otosclerosis

Answer 1

Autosomal dominant inheritance pattern (incomplete penetrance and variable expressivity)
More commonly presents as complex genetic disorder (mix of genetics, environment, etc)
Disease of abnormal bone remodeling/metabolism in the otic capsule
Audiologic features:
- conductive hearing loss
- mean age of onset is around 20 to 30 yrs

Question 2

Connexin (Cx) Deafness

Answer 2

Autosomal recessive inheritance pattern
Connexin 26 is a protein product of gene GJB2
Mutation (deletion) in this gene disrupts gap junction causing poor ion transportation/cellular communication (affects potassium channel in the inner ear)
Audiological features:
- congenital HL
- mild to profound HL depending on genotype
- typically bilateral
- can be progressive or sudden
- some cases report vertigo or tinnitus
- in some syndromic variations, they have reported skin issues making CI candidacy unlikely

Question 3

X-linked Congenital Stapes Fixation with Perilymph Gusher

Answer 3

X-linked inheritance pattern
Disorder where perilymph leaks from oval window
Audiologic features:
- mixed hearing loss (may be progressive)
- sudden loss of perilymph and hearing if inner ear surgery is conducted when mistaken for otosclerosis

Question 4

Aminoglycoside-induced Toxicity

Answer 4

Mitochondrial inheritance pattern
Mutation that causes hearing loss if aminoglycoside is taken
Audiologic features:
- permanent severe to profound SNHL (generally not progressive), preventable