Week 8 Surgery

Question 1

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

Answer 1

• 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

Question 2

X-ray

Answer 2

• 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

Question 3

CT scan

Answer 3

• 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

Question 4

MRI

Answer 4

• 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

Question 5

T1 MRI

Answer 5

• 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)

Question 6

T2 MRI

Answer 6

• 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

Question 7

embryology of the cochlea

Answer 7

• 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

Question 8

the developed cochlea size and orientation

Answer 8

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

Question 9

saggital

Answer 9

splits left and right

Question 10

coronal

Answer 10

front and back

Question 11

transverse

Answer 11

top and bottom (axial)

Question 12

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

Answer 12

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

Question 13

what percent of hearing loss are congenital

Answer 13

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

Question 14

Michel deformity

Answer 14

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

Question 15

cochlear aplasia

Answer 15

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

Question 16

common cavity (CC) deformity

Answer 16

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

Question 17

cochlear hypoplasia

Answer 17

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

Question 18

incomplete partition (IP-I)

Answer 18

cochlea lacking the modiolus; 20%

Question 19

incomplete partition (IP-II)

Answer 19

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

Question 20

incomplete partition (IP-III)

Answer 20

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

Question 21

luminal obstruction in pre op assessment

Answer 21

• 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

Question 22

pre-op conditions that would affect surgery

Answer 22

• 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

Question 23

what can you see with HRCT pre-op

Answer 23

• 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

Question 24

what can you see with MRI pre-op

Answer 24

• 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

Question 25

goals of post-op imaging

Answer 25

* proper placement of the electrode * role-out movement in case of malfunction - --portable plain radiography intra-operative (baseline)

Question 26

imaging of CI placement

Answer 26

* 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

Question 27

post-op imaging--MRI compatibility

Answer 27

* 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

Question 28

1st 3 steps of CI surgery

Answer 28

* 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

Question 29

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

Answer 29

* 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)

Question 30

5th to 8th steps of CI surgery | after cochleostomy

Answer 30

* 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

Question 31

cochlear implant surgery--soft surgery

Answer 31

* 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

Question 32

cochlear implant surgery--ossified cochlea

Answer 32

* 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

Question 33

cochlear implant surgery--chronic otitis media

Answer 33

*remove the infection

Question 34

cochlear implant surgery early complications

Answer 34

* poor electrode placement * infection * facial nerve injury * chorda tympani nerve injury * CSF leak * damage to electrode * dizziness

Question 35

cochlear implant surgery late complications

Answer 35

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