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AUD spring 2020 CI > Week 8 Surgery > Flashcards

Week 8 Surgery Flashcards

1
Q

why is imaging important pre, intra, and post op basic

A
  • pre-op= candidacy
  • intra-op monitoring= electrode position
  • post-op= confirmation of electrode position and to see what is happening if there was a malfunction
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2
Q

X-ray

A
  • plain radiography film
  • sends an ionized beam through the body that would be absorbed by the bone and tissue and create a shadow on the film
  • bones appear white, air appears black, and muscles/soft tissue appear gray
  • used to detect bone fractures, arthritis, tumors, osteoporosis, fluid in lunges, and infection
  • ionizing radiation–concern for radiation-induced cancer
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3
Q

CT scan

A
  • computerized tomography
  • takes x-ray 2D slices and changes them to 3d
  • very good at showing bone, soft tissue, and blood vessels (CTA)
  • head: typically used to detect infarction, tumors, calcifications, hemorrhage and bone trauma
  • –hypodense (dark) structures=edema and infarction
  • –hyperdense (bright) structures= calcifications and hemorrhage
  • –disjunction= bone trauma
  • ionizing radiation so concerns for radiation-induced cancer
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4
Q

MRI

A
  • magnetic resonance imaging
  • uses strong magnetic fields and radiowaves to form images of the body
  • soft tissues and blood vessels= MRA
  • head: identify brain tumors, aneurysms, bleeding in the brain, nerve injury, and other problems, such as damage caused by a stroke. also find problems of the ear and auditory nerve, and eye and optic nerve
  • no ionizing radiation
  • there are two different protocols: T1 and T2
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5
Q

T1 MRI

A
  • dark on T1 image
  • –calcification, increased water (as in edema), tumor, infarction, inflammation, infection
  • –gray matter (gray)
  • bright on T1 image
  • –fat, subacute hemorrhage
  • –paramegnetic substances (contrast): gadolinium, manganese, copper
  • –white matter (white)
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6
Q

T2 MRI

A
  • dark on T2 image
  • –calcification, fibrous tissue
  • –paramagnetic substances (contrast): deoxyhemoglabin, methemoglobin
  • –gray matter (gray) and white matter (dark gray)
  • –air and hard bone (black)
  • bright on T2 image
  • –increased water (as in edema), tumor, infarction, inflammation, infection, subdural collection, subacute hemorrhage
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7
Q

embryology of the cochlea

A
  • otic placode form the ectoderm of the neural tube= 3rd week
  • otocyst, VIII n= 4th week
  • cochlear duct= 6th week
  • –2.5-2.75 turns 8th to 10th week
  • organ of corti= 25th week
  • osseous otic capsule= starts at 15th week and completes at 23rd week
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8
Q

the developed cochlea size and orientation

A
  • most lateral
  • 1.5 inch (38 mm)
  • – circumference is 0.1 inch (2.5 mm)
  • points outward and downward
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9
Q

saggital

A

splits left and right

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10
Q

coronal

A

front and back

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11
Q

transverse

A

top and bottom (axial)

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12
Q

specifically what is being looked for in the pre-op assessment

A
  • inner ear abnormalities
  • signs of luminal obstruction
  • other findings that would affect the procedure
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13
Q

what percent of hearing loss are congenital

A

35% (65% of congenital HL is bilateral and 93% of that is symmetrical)

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14
Q

Michel deformity

A

complete absence of the inner ear (labyrinthine aplasia)–before forming otocyst (=3rd week); 6%

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15
Q

cochlear aplasia

A

complete absence of the cochlea (2nd rarest deformity <6th week; 8%

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16
Q

common cavity (CC) deformity

A

general cavity (no differentiation of cochlea and vestibule) 3rd most common; 8%

17
Q

cochlear hypoplasia

A

differentiated cochlea and vestibule with smaller dimensions; 7-15%

18
Q

incomplete partition (IP-I)

A

cochlea lacking the modiolus; 20%

19
Q

incomplete partition (IP-II)

A

mondini malformation (1-1.5 turns) with dialated vestibule and enlarged VAD 7th week; 19%

20
Q

incomplete partition (IP-III)

A

dilated-bulbous IAC, abnormal connection with the basal turn–associate with x-linked HL; 2%

21
Q

luminal obstruction in pre op assessment

A
  • ossification: infection or trauma
  • –meningitis–most common cause of acquired HL in children–up to 35% with HL (of them 70% have severe to profound HL)
  • ——most affected–basal turn near the round window (cochlear aqueduct)
  • —–loss of hair cells and spiral ganglion neurons
  • —–starts within 8 days to a few weeks after the infection, detected as early as 2 months
  • –labyrinthitis due to COM or cholesteatoma
  • –metabolic bone disorders (otosclerosis, Paget’s disease)
  • –temporal bone fracture
  • MRI allows to ee the fluid in the cochlea to evaluate patency
22
Q

pre-op conditions that would affect surgery

A
  • vascular anatomy
  • –anterior displacement of sigmoid sinus (1.6%)
  • –high riding jugular bulb (6%) close to the round window
  • –carotid canal dehiscence (close to the round window)
  • facial nerve, mastoid, and tympanic cavity
  • –VII n pathway (cochlear malformation)
  • –enlarged vestibular aqueduct (>1.5mm)
  • —–up to about 15% of children with HL
  • –mastoid pneumatization
23
Q

what can you see with HRCT pre-op

A
  • cochlear deformity
  • facial nerve location
  • ossification (53%-90% sensitivity)
  • aeration of the temporal bone
  • sigmoid sinus location
  • high-riding jugular bulb
  • size of vestibular aqueduct
  • narrowing of the IAC (<2-2.5mm)
  • modiolar deficiency
24
Q

what can you see with MRI pre-op

A
  • cochlear dysplasia
  • ossification (95% sensitivity, 88% specificity)
  • sigmoid sinus location
  • size of vestibular aqeuduct
  • narrowing of the IAC
  • modiolar deficiency
  • evaluate IAC content
  • evaluate the caliber of the cochlear nerve
25
Q

goals of post-op imaging

A
  • proper placement of the electrode
  • role-out movement in case of malfunction
  • –portable plain radiography intra-operative (baseline)
26
Q

imaging of CI placement

A
  • Stenvers= pt laying down facing forward
  • transorbital= pt standing up
  • base= the pt looking up and is at the plane of the array
  • –the first two give a similar view
27
Q

post-op imaging–MRI compatibility

A
  • magnetic field generate torque and force on the ferromagnetic components of implanted device
  • generate current or heat in the electronic device (damage tissue)
  • demagnetize the internal magnet
  • always check for compatibility
28
Q

1st 3 steps of CI surgery

A
  • incision: 4-5 cm (posterior-parallel to post-auricular sulcus)
  • mastoidectomy
  • –identify the facial nerve and location of facial recess
  • –facial recess should be wide (stapes, RW, inferior to RW)
  • pocket (bed) for internal device (angled posterior-superior, 45 degree of canthomeatal line)
  • –2-3 mm deph
  • –children’s skull (1yr) is 2-3 mm (shallow or sit on dura)
  • –lock device in place (tight pocket, sutures, or pins)
  • –a channel for the electrode lead
29
Q

cochleostomy

*4th step of CI surgery (after making pocket for internal device)

A
  • remove the RW niche
  • –identify RW to identify scala tympani
  • –diameter 0.6-1.2 mm
  • –types
  • —–promontory–inferior to RW (floor of scala tympani)
  • ——-anterior and superior placement
  • —–RW-incision to the RW membrane
  • —–extended RW- 1-2 mm inferior (RW and RW niche)
30
Q

5th to 8th steps of CI surgery

after cochleostomy

A
  • electrode insertion:
  • –promontory-tip directed anterior-inferior
  • –RW- tip directed more anterior inferior
  • seal the cochleostomy–soft tissue (periosteum)
  • –stabilize electrde
  • –prevent infections (OM, meningitis)
  • ground electrode inserted beneath the temporalis muscle
  • internal incision is closed using absorbable sutures, then external layer
  • **intra-op testing= impedance and eCAP to make sure electrodes are stimulating the auditory nerve
31
Q

cochlear implant surgery–soft surgery

A
  • identify the RW and appropriate placement of the cochleostomy
  • elimination of bone dust and blood from entering the cochlea (repeated irrigation)
  • low speed drilling
  • avoiding suctioning the perilymph
  • steroids– intratympanic steroids or systematic (before and after)
  • careful and slow insertion
32
Q

cochlear implant surgery–ossified cochlea

A
  • short-array insertion
  • double array
  • –1st arrary= drill a tunnel in the basal turn
  • –2nd array=cochleostomy 2mm anterior to oval window
  • –scala vestibuli insertion= cochleostomy 2 mm anterior to oval window
33
Q

cochlear implant surgery–chronic otitis media

A

*remove the infection

34
Q

cochlear implant surgery early complications

A
  • poor electrode placement
  • infection
  • facial nerve injury
  • chorda tympani nerve injury
  • CSF leak
  • damage to electrode
  • dizziness
35
Q

cochlear implant surgery late complications

A
  • receiver/stimulator extrusion
  • infection
  • facial nerve stimulation
  • CSF lead
  • device failure
  • electrode migration
  • dizziness

AUD spring 2020 CI (16 decks)

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