Otology Flashcards
What type of inheritance is aminoglycoside induced hearing loss?
Mitochondrial mutation
So passed through mom to all of her children
Schiebe aplasia
Membranous aplasia of cochlea and saccule (can’t see on CT scan)
Pendred Syndrome:
Mutation
Characteristics
AR
SNHL, Mondini malformation with enlarged vestibular aqueduct, euthyroid goiter (by age of 10)
SCL26A4 gene mutation for Pendrin - chloride/bicarb exhange protein, iodide exchange too
Most common infectious cause of congenital hearing loss
CMV - Associated with cerebral calcifications, hepatosplenomegaly, jaundice, intellectual disability
What does the inferior vestibular nerve control?
POSTERIOR SSC function + saccule
What does the superior vestibular nerve control?
Lateral and Superior SCC + Utricle
What do aminoglycosides damage?
OUTER hair cells (Amin-O for Outside)!
Medial wall of epitympanum?
Mostly the promontory
MRI findings of cholesterol granuloma
HYPERintense on T1 AND T2
MRI findings of cholesteotomas
HYPOintense T1, HYPERintense T2, diffusion restricted
Where does chorda tympani nerve pass through in the middle ear?
Between manubrium of malleus and long process of incus before exiting through the petrotympanic fissure.
ABR waveforms mnemonic
ECOLI
I+II - 8th nerve
III - Cochlear nucleus/Sup olivary complex
IV - Sup olivary complex
V - Lateral lemniscus
VI, VII - Inferior colliculus
What is Schwartze’s sign?
Red hue seen at the promontory, found in otosclerosis
Characteristics of CENTRAL vertigo etiology
Vertigo that does not extinguish with repeated stimulation, DOWN (vertical) beating nystagmus that does not improve with fixation, NOT associated with hearing loss usually, less severe.
Get MRI!
Most common cause of NON syndromic congenital SNHL?
Connexin 26 mutation, AR
Non functional gap junction protein, product of GJB2 gene
Most common cause of SYNDROMIC congenital SNHL?
Usher syndrome - AR
Usher Type I, Type II and Type III features?
AR
Type I: Congenital profound SNHL, NO vestibular fx (NO)
Type II: Normal vestibular fx, moderate-severe SNHL (YES)
Type III: Like type II but with variable vestibular fx, progressive HL (MAYBE)
Alport syndrome
X linked, mutation of type IV collagen (COL4A3), causes hearing loss and glomerulonephritis, eye lesions
What is directional preponderance and how do you measure it?
It’s the measure of the difference in total eye speeds between slow phases on each side.
Measured with caloric testing data.
What is speech detection threshold?
Level at which patient is aware of speech 50% of the time.
Explain 7 up Coch down!
Sup ant: FN
Sup Post (behind Bill’s bar): SVN
Inf ant: Cochlear nerve
Inf Post: IVN
Transvere crest is between the SVN and IVN
CHARGE Syndrome
Coloboma of eye, heart defects, atresia of nasal choanae, retardation, genital/urinary abnormalities, ear abnormalities (SCC aplasia, deafness)
-Autosomal DOMINANT
Most common cochlear malformation
Incomplete partition type 2 - arrest at 7th week, 1.5 turns of cochlea, associated with EVA, pendred syndrome, predisposition to SNHL
What % of pediatric HL is due to genetic?
50% are genetic
70% of those are NON syndromic
Most common syndromic cause - Usher
Most common NON syndromic cause - Connexin 26
NF-2
AD
Tumor suppressor gene 22
Bilateral acoustic neuromas, cafe au lait spots (less than NF-1), other cranial, etc. schwanommas, intracranial meningiomas, optic gliomas
Stickler Syndrome
AD
Mutation type II and XI collagen genes
Joint hypermobility, retinal detachment, SNHL, micrognathia
Waardenburg Syndrome
MITF gene/PAX3 gene, AD usually
4 types, SNHL, while forelock, iris pigment abnormalities, dystopia canthorum, broad nasal root
Type II - don’t have dystopia canthorum, SNHL more common
Type III - Type I + upper limb abnormalities
Type IV - Type I + Hirschprung’s disease
Treacher Collins Syndrome
AD
CHL secondary to ossicular abnormalities, can also have EAC stenosis
Hypoplastic mandible, cleft palate, downward slanting eyes, coloboma of lower eyelids (in Goldenhar its UNILATERAL)
AR syndromes with SNHL (3)
- Usher - most common syndromic cause of pediatric HL!
- Pendred
- JLNS
JLN Syndrome
AR, severe to profound HL
Cardiac conduction defect –> syncopal episodes and sudden death
Prolonged QT interval
Important to get EKG in infants with severe to profound SNHL!
-KCNQ1 Gene
Oto-palato-digital Syndrome
X linked, flat midace, cleft palate, short, broad fingers, CHL (ossicular malformation)
What age do you use Behavioral observational audiometry?
Visual response audiometry?
Conditioned play audiometry?
BOA - < 6 months
VRA - Ideal for 6 mo to 30 mo
CPA - > 30 months
Autosomal Dominant congenital HL syndromes (mnemonic)
WANT CBS
Wardenburg, Apert, Neurofibromatosis, Treacher Collins, Crouzon, Branchio-Oto-Renal, Stickler
Also Pfeiffer!
What does the cochlear aquaduct contain?
-The cochlear aqueduct connects the scala tympani to the subarachnoid space via perilymphatic (periotic) duct.
-Parralel to IAC on CT temporal bone
-Has PERILYMPH (Like CSF, NA NA NA)!
What type of fluid is found in the scala tympani and scala vestibuli?
The scala tympani contains perilymph (“Like CSF, NA NA NA - high NA+)
Perilymph vs Endolymph Composition
Perilymph: High Na+, LOW K+, resembles extracellular fluid and CSF. Found in Scala vestibuli and Scala Tympani.
Endolymph: Low Na+, HIGH K+, resembles intracellular fluid. Found in Scala MEDIA.
Characteristics of congenital cholesteotoma (location, mean age, gender ratio, etc).
Location: Most commonly anterior superior quadrant
Mean age: 5
Male to female preponderance (3:1)
Where do cochlear nerve Afferents recieve most input from?
INNER hair cells (90%)
What are the 5 types of tympanoplasties?
- All three ossicles present, involved repair of TM
- Malleus eroded/missing, graft placed over incus
- Malleus + incus removed, graft placed over stapes head.
- Absent or eroded suprastructure, graft placed over mobile foot plate stapes
- Fixed footplate - 5a = placing graft over fenestration made in horizontal SSC. 5b = stapdectomy + graft overlay.
Malignant Otitis Externa: risk factors, likely microorganism, imaging, TX
- Think uncontrolled diabetic or immunosuppressed
- Pseudomonas #1, fungal less likely
- Biopsy - rule out malignancy
- Imaging: CT (bony erosion), MRI to show soft tissue extent (usually 1st choice), Technetium scan (can diagnose bony activity and shows long term change), FOLLOW with gallium scan (and ESR)
- TX: IV antibiotics
Gradinego syndrome (3 things)
Suppurative OM, Retro-orbital pain/pain in distribution of trigeminal nerve, Ipsilateral abducens palsy (eye looking IN due to unopposed medial rectus)
MRI characteristics for Vestibular Schwanomma VS Meningioma?
VS
T1 - Isointense
T2 - Slightly hyperintense
Contrast - Enhances!!!
Meningioma:
T1 - Isointense
T2- Variable
Contrast - mild to moderate enhancement
HAS DURAL TAIL
What does SP/AP ratio relate to and what is considered pathologic?
ECG measures this.
Normal SP/AP ratio ~ 0.4
SP/AP ratio > 0.4 = suggestive of endolymphatic hydrops
What is one ototoxic drugs that affects INNER hair cells?
CARBOplatin. The rest usually affect the OUTER hair cells (of basal turn so starts with high frequency HL or stria vascularis). Use otoacoustic emmissions to monitor this!
What is speech recognition (reception) threshold?
Level at which patient can repeat 50% of speech material.
Reasons for hearing loss after stapedectomy
- Reparative granuloma (seen 1-6 weeks post op) –> usually SNHL
- Obliterative otosclerosis –> Immediate persistent HL post operatively
- Middle ear adhesions, displacement of prosthesis, necrosis of long process incus (recurrent CHL AB gap > 10 dB)
-MOST COMMON: Resorption of incus, followed by prosthesis displacement.
Exostoses vs Osteomata
Exostoses- broad base, often bilateral, multiple lesions along medial EAC. Harder to remove. Cold water exposure.
Osteomata - Pedunculated, single lesions along suture lines. Easier to remove.
What is crossover? When does it occur? What can you do to minimize the risk of it?
When sound presented to test ear stimulates contralateral ear. More likely to happen with external headphones vs internal ones.
Masking should be done when air conduction threshold for test ear exceeds non test ear by 40 dB for external headphones, 70 dB for internal headphones.
Do masking either way if bone conduction exceeds 10 dB in test ear vs non test ear.
OSHA limits for daily noise exposure?
8 hours at 90 dB. Half time for every 5 dB added (ex: 16 hours @ 85 dB. Half time for every 5 dB added)