27 Congenital - Ear Flashcards
Incidence of congenital hearing loss
1:1000
What percent of congenital hearing loss is hereditary and what percent of those are syndromic
> 60% (others say 50%); 30%
What is the typical inheritance pattern of syndromic HL
Auto Dom
Typical inheritance patterns of non-syndromic HL
75% Auto Rec
10-20% Auto Dom
2-3% X-linked
<1% mitochondrial
What genetic mutation is though to be responsible for 50-80% of all AR HL?
Mutation of the DFNB1 gene on chrom 13q encoding for connexin 26 (causes 27% of sporadic cases of congen HL)
T/F: 1 in 31 ppl are carriers for the connexin 26 mutation
True
What is function of connexin 26
Formation of gap jnc in stria vascularis, BM, limbus, and spiral prominence of cochlea (transports K+)
What is the typical severity and pattern of AD HL
Less severe, delayed onset, high-freq HL
What is the typical severity and pattern of X-linked HL
Prelingual and more clinically diverse HL
What is term for complete agenesis of petrous portion of temporal bone
Michel aplasia
What is term for developmentally deformed cochlear where only the basal coil can be identified
Mondini aplasia
What is m/c form of inner ear aplasia
Scheibe aplasia (cochleosaccular dysplasia or pars inferior dysplasia)
Which inner ear aplasia is characterized by high freq HL with nl low freq HL
Alexander
Which inner ear aplasia will not allow cochlear implant or amplification aids
michel aplasia
Mutation of what gene is a/w EVA
Pendrin on chrom 7q31
What inner ear malformation is a/w early onset SNHL, usu b/l and progressive and vertigo
EVA
Which SCC forms first? Last?
Superior canal first; lateral canal last
T/F: Superior SCC deformities are always accompanied by lateral SCC deformities
True
What syndrome accounts for m/c form of hereditary congenital deafness
Waardenburg’s synd (I thought it was Ushers)
What is incidence of Waardenburg’s
1 in 4000
What are the 4 clinical subtypes of Waardenburgs
“1. SNHL (20%), heterochromia irides, pigment anomalies, dystopia canthorum
- As above, without dystopia canthorum (SNHL in >50%).
- Klein–Waardenburg’s syndrome: microcephaly, mental retardation, limb and skeletal abnormalities, in addition to signs of #1.
- Shah-Waardenburg’s syndrome: #2 + Hirschsprung’s disease
What genetic mutation is responsible for most cases of types 1 and 3 Waardenburg’s
Mutation of PAX3 gene on chrom 2q37
What is dystopia canthorum
Shortened and fused medial eyelids resulting in small medial sclera, lateral displacement of inferior puncta and hypertelorism
What synd is characterized by CP, micrognathia, severe myopia, retinal detachments, marganoid habitus, and HL
Stickler
What genetic mutations are responsible for most cases of Stickler synd
Mutations of COL2A1 gene on chrom 12 or COLIIA2 gene on chrom 6
Synd c/b SNHL and RP
Usher’s
3 subtypes of Usher’s
I—Severe–profound hearing loss, absent vestibular function, prepubertal retinitis pigmentosa.
II—Moderate–severe hearing loss, normal vestibular function, postpubertal retinitis pigmentosa.
III—Progressive hearing loss.
M/c syndromic cause of HL
Pendred synd, accounting for 10% of cases
What inner ear malformations are more common in pts with Pendred
Mondini aplasia and EVA
What gene is a/w both Pendred synd and EVA
PDS gene, encoding for pendrin protein, on chrom 7q31
What are the clinical features of Alport synd
SNHL and renal failure (presenting as hematuria)
What is basic defect causing Alport
Mutation of COL4A5 gene producing the alpha chain of Type IV collage in BM
What syndrome is c/b HL, renal defects, and cervical fistulas
BOR (branchiootorenal)
What is inheritance of BOR
Auto Dom
What percent of BOR pts have HL
80% (50% mixed, 30% CHL, 20% SNHL)
What is gene responsible for BOR
EYA1 on chrom 8q13.3
Clinical features of Jervell and Lange-Nielsen’s synd
Prolonged QT, syncope, sudden death, HL
What is basic defect causing JLN
Abnl K+ channels
What % of pts with NF1 have AN
5% and usu u/l
What % of pts with NF2 have AN
95% and usu b/l
Which type of NF is c/b cutaneous neurofirbromas
NF1
Genetic mutations for NF1 and NF2
- NF1 gene (nerve growth factor gene) on chrom 17q11.2
- NF2 gene (tsg) on chrom 22q12.2
WHat is name for subtype of osteogenesis imperfecta in which progressive HL begins in early childhood
Van der Hoeve’s synd
Genetic mutations for osteogenesis imperfecta
- COLIA1 on chrom 17q
- COLIA2 on chrom 7q
What dz is c/b cranial synostosis, exophthalmos, parrot-beak nose, and hypoplastic mandible
Crouzon
What is basic defect of Crouzon’s
Abnl fibroblast growth factor receptors
What is Norrie synd
X-linked dz c/b blindness, progressive MR, and HL
What synd is c/b hypertelorism, short stature, broad fingers and toes, CP, and CHL
Otopalatodigital synd
X-linked synd a/w Klippel-Fiel synd, SNHL, CN VI paralysis
Wildervanck synd
What dz is c/b lower lid colobomas, downward slanting palpebral fissures, hypoplastic mandible, malformations of external ear, CP, HL
Treacher-Collins (auto dom)
Treacher collins mutation
TCOF1 on 5q (protein Treacle)
“What do Keams–Sayre, MELAS, MERRF, and Leber’s hereditary optic neuropathy all have in common?
All mitochondrial d/o w/ varying degrees of HL
What organism is m/c a/w virus-induced congenital deafness
CMV
what percent of kids with congenital CMV have HL
10% are born with HL, 10-15% eventually develop HL
What manifestation of congen syphilis is m/c related to SNHL
Interstitial keratitis
3 classic findings of congen rubella synd
SNHL, cataracts, heart malformations
If one parent and one sibling are deaf, what is risk of HL for subsequent offspring
40%
What percent of infants w/ sig congen HL will not have RF
50%
What is incidence of congen aural atresia
1:10,000-20,000
What % of aural atresia is b/l
33%
What does stenosis of EAC predispose to
canal cholesteatoma
Which portion of ossicular chain is least likely to be malformed in pts with congenital aural atresia
stapes footplate
What is incidence of FN displacement in congen aural atresia
25-30%
What is a congenital cholesteatoma
embryonal inclusion of undifferentiated squamous epith in ME behind intact TM, usu w/ no h/o OM
Other than middle ear, where else may congen cholesteatomas arise
petrous apex, CPA, mastoid, EAC
What % of congen cholesteatoma is b/l
3%
T/F: Mastoid bones of pt w/ congen cholesteatoma are most often well aerated
true
What is thought to be cause of congen malleus ankylosis
“Poor development of the epitympanic space leaves the head of the incus and malleus in close contact with the tegmen; a bony bridge can result between the epitympanum and the head of the malleus.
“True/False: Histologically, the bony structures are normal, without evidence of otosclerosis, in cases of malleus ankylosis.
true
What is optimal tx for malleus fixation
removal of head of malleus and interpositionof incus b/w manubrium and stapes head
“What genetic defect results in either Jansen’s chondrodystrophy or Blomstrand’s chondrodystrophy?
“Mutation of the type 1 parathyroid hormone receptor.
What is ciliary defect in pts with Kartagener’s
Absence of dynein side arms on A-tubules
What is m/c site of CSF leak from inner ear into middle ear in kids
oval window (esp if mondini malformation)
What are 2 types of congen defects that lead to spontaneous CSF otorrhea
preformed bony pathway around the bony labryinth (a/w meningitis), often a/w meningocele and aberrant arachnoid granulations located over a pneumatized area of skull
Why does CSF otorrhea present late (50s) when caused by arachnoid granulations
Arachnoid granulations become larger with time; the nl pulsation of CSF pressure can cause bony erosion
What synd is c/b recurrent episodes of vertigo and ataxia in several members of a family?
Familial ataxia syndrome
“Of the four variants of this syndrome (EA1, EA2, EA3, EA4), which one does not respond to acetazolamide?
EA3 of periodic vestibulocerebellar ataxia
“Which of these 4 variants is caused by mutations in a potassium channel gene (KCNA1) on 12p13?
EA1
What are the 2 m/c variants of this syndrome
EA1 and EA2
Which of these is a/w vertigo and results from mutations of a calcium channel gene of 19p
EA2
What gene mutation is behind EA1
K+ channel gene KCNA1 on 12p13
Which variant is a/w migraine
EA2
