Week 8 Surgery Flashcards
why is imaging important pre, intra, and post op basic
- 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
X-ray
- 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
CT scan
- 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
MRI
- 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
T1 MRI
- 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)
T2 MRI
- 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
embryology of the cochlea
- 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
the developed cochlea size and orientation
- most lateral
- 1.5 inch (38 mm)
- – circumference is 0.1 inch (2.5 mm)
- points outward and downward
saggital
splits left and right
coronal
front and back
transverse
top and bottom (axial)
specifically what is being looked for in the pre-op assessment
- inner ear abnormalities
- signs of luminal obstruction
- other findings that would affect the procedure
what percent of hearing loss are congenital
35% (65% of congenital HL is bilateral and 93% of that is symmetrical)
Michel deformity
complete absence of the inner ear (labyrinthine aplasia)–before forming otocyst (=3rd week); 6%
cochlear aplasia
complete absence of the cochlea (2nd rarest deformity <6th week; 8%
common cavity (CC) deformity
general cavity (no differentiation of cochlea and vestibule) 3rd most common; 8%
cochlear hypoplasia
differentiated cochlea and vestibule with smaller dimensions; 7-15%
incomplete partition (IP-I)
cochlea lacking the modiolus; 20%
incomplete partition (IP-II)
mondini malformation (1-1.5 turns) with dialated vestibule and enlarged VAD 7th week; 19%
incomplete partition (IP-III)
dilated-bulbous IAC, abnormal connection with the basal turn–associate with x-linked HL; 2%
luminal obstruction in pre op assessment
- 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
pre-op conditions that would affect surgery
- 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
what can you see with HRCT pre-op
- 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
what can you see with MRI pre-op
- 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
goals of post-op imaging
- proper placement of the electrode
- role-out movement in case of malfunction
- –portable plain radiography intra-operative (baseline)
imaging of CI placement
- 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
post-op imaging–MRI compatibility
- 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
1st 3 steps of CI surgery
- 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
cochleostomy
*4th step of CI surgery (after making pocket for internal device)
- 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)
5th to 8th steps of CI surgery
after cochleostomy
- 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
cochlear implant surgery–soft surgery
- 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
cochlear implant surgery–ossified cochlea
- 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
cochlear implant surgery–chronic otitis media
*remove the infection
cochlear implant surgery early complications
- poor electrode placement
- infection
- facial nerve injury
- chorda tympani nerve injury
- CSF leak
- damage to electrode
- dizziness
cochlear implant surgery late complications
- receiver/stimulator extrusion
- infection
- facial nerve stimulation
- CSF lead
- device failure
- electrode migration
- dizziness
