cochlea cadaver dissection - part 2
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Cochlea Cadaver Dissection- Part 2
18-04-20178.26 pm
Middle cranial fossa approach for
Cochlear implant
APICAL TURN / SUPERIOR TURN cochleostomy in middle cranial fossa approach
So the indication of middle cranial fossa superior cochleostomy insertion is in infected cases after CWD + SP ( subtotal
petrosectomy ) We can do redo by fat risnced in rifampacin . But if you want to go by sterile area middle cranial fossa superior
cochleostomy & reverse insertion & reverse programming
Superior cochleostomy in middle cranial fossa is just below origin of GSPN Don't fear about carotid ( metal probe ) . Petrous carotid
is 1 cm anterior to origin of GSPN
Superior cochleostomy in middle cranial fossa is just below origin of GSPN Don't fear about carotid ( metal probe ) . Petrous carotid
is 1 cm anterior to origin of GSPN
Superior cochleostomy in middle cranial fossa is just below origin of GSPN Don't fear about carotid ( metal probe ) . Petrous carotid
is 1 cm anterior to origin of GSPN
Probe in Superior cochleostomy in middle cranial fossa is just below origin of GSPN
Superior cochleostomy in middle cranial fossa is just below origin of GSPN
Superior cochleostomy in middle cranial fossa is just below origin of GSPN
See the probe inserted through superior cochleostomy from middle cranial fossa exactly corresponds to superior
cochleostomy just below tensor tympani from middle ear
See the probe inserted through superior cochleostomy from middle cranial fossa exactly corresponds to superior
cochleostomy just below tensor tympani from middle ear
See the probe inserted through superior cochleostomy from middle cranial fossa exactly corresponds to superior cochleostomy just below tensor
tympani from middle ear
See the probe inserted through superior cochleostomy from middle cranial fossa exactly corresponds to
superior cochleostomy just below tensor tympani from middle ear
Labyrinthine part of facial nerve in middle cranial fossa
Just now i fractured tegmen of middle ear with my finger nail … it is so thin …………..So identify ossicles of middle ear through very thin middle ear tegmen & then identify horizontal facial nerve & then 1st genu & then labyrinthine facial nerve ...... simplest way to decompress labyrinthine Or else if you come from medically you may injure cochlea or SSC
Note horizontal part of facial nerve through middle cranial fossa as continuation of GSPN
tegmen of middle ear is so thin …………..So identify ossicles of middle ear through very thin middle ear tegmen & then identify horizontal facial nerve & then 1st genu & then labyrinthine facial nerve ...... simplest way to decompress labyrinthine Or else if you
come from medically you may injure cochlea or SSC
Note horizontal part of facial nerve through middle cranial fossa as continuation of GSPN
facial nerve in lateral part of IAC decompression is difficult even in middle cranial fossa. It is between two solid bones of cochlea & SSC
facial nerve in lateral part of IAC decompression is difficult even in middle cranial fossa. It is between two solid bones of cochlea
& SSC
IAC [ Internal Auditory Canal ] Drilling
IAC conical tube present in angle of SSC crest & GSPN ( more than 50 % dehiscent )
IAC conical tube present in angle of SSC crest & GSPN ( more than 50 % dehiscent )
IAC has to be drilled from medial to lateral IAC first must be opened medially & then only tracked along the direction of IAC ( postero-laterally ) Unless you injure cochlea
basal & medial turns
IAC has to be drilled from medial to lateral IAC first must be opened medially & then only tracked along the direction of IAC
( postero-laterally ) Unless you injure cochlea basal & medial turns
KAWASE APPROACH
The pit infront of cochlea & IAC is kawase approach
The pit infront of cochlea & IAC is kawase approach
Here I am expanding kawase approach . In few minutes I show you COA ( cochlear aperture)
Here I am expanding kawase approach . In few minutes I show you COA ( cochlear aperture)
Probing in middle turn
Observe metal probe in perisiers ( dangerous) triangle
Observe metal probe in perisiers ( dangerous) triangle
Observe metal probe in perisiers ( dangerous) triangle
Perisiers triangle corresponds to labyrinthine part of facial nerve
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array of CI stimulates
labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array
of CI stimulates labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array of CI stimulates
labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array
of CI stimulates labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array of CI stimulates
labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array
of CI stimulates labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array
of CI stimulates labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array of CI stimulates labyrinthine part of facial
nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
So the metal probe in perisiers triangle goes to the middle turn of cochlea & exactly corresponds to labyrinthine part of facial nerve So middle turn array
of CI stimulates labyrinthine part of facial nerve causing twitchings in post-op . Then we have to switch off those electrodes in software programming .
Probing in basal turn
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
Probe in basal turn opens into basal turn cochleostomy in middle cranial fossa
See all the turns of cochlea from middle fossa
SVN & FN converge
Superior Vestibular nerve ( SVN ) & facial nerve separatedby bills bar , that I drilled . Observe here SVN & FN converge . Where as IVN & cochlear nerve
diverge ……….. This convergence of SVN & FN very useful in MRI reading
See horizontal Septum in IAC below SVN & FN ; I cut superior Vestibular nerve ( SVN ) & FN
IVN & CN diverge
Observe here the IVN & cochlear nerve diverge ( not so clear in cadaver )
Observe here the IVN & cochlear nerve diverge ( not so clear in cadaver )
Observe here the IVN & cochlear nerve diverge ( not so clear in cadaver )
Observe here the IVN & cochlear nerve diverge ( not so clear in cadaver )
COA [ Cochlear aperture ]
Observe here cochlear nerve fibres going through the cibriform area ( entry point of modiolus ) In COA ( cochlear aperture )
Observe in this one COA is 2.5 to 3 mm roughtly. If COA less than 1.5 mm it is cochlear nerve aplasia
Cochlear implant after
Translabyrinthine approach
PSC is deeper than LSC & SSC is deeper than PSC
Intact facial canal technique of Skull base .If you transpose grade 3 facial palsy comes .
Ampulla of PSC bisects vertical part of facial nerve exactly at midpoint
See probe coming to Sinus tympani So while clearing Sinus tympani PSC exposed ... becareful
CI after LABYRINTHECTOMY
Only two is enough for CI – one is cochlea & another cochlear nerve – so even in vestibular schwannoma excision by translabyrinthine exposure we can do CI & patient hears
Bills bar between FN & SVN
Labyrinthectomy done to enter Posterior cranial fossa
VA [ Vestibular Aqueduct ]
https://drive.google.com/file/d/0B7F_FcpOJCfpS2lJa3NBNkVDeVE/view?usp=sharing
IAC & VA are two eyes of baby in temporal boone
IAC & VA are two eyes of baby in temporal boone
Endolymphatic duct & Vestibular aqueduct both are same or not ........ I have to refer . ....... but clearly there is duct from vestibule to endolymphatic sac area . If it is
more than 1.5 mm it is " dilated Vestibular aqueduct " Another 1.5mm is ........, if COA ( cochlear aperture ) less than 1.5mm it is cochlear nerve aplasia.
Mario sanna book mention >1.5 mm VA dilated . For mnemonic sake 1.5 mm is there at both VA & COA . One is more & one is less respectively
Radiologically if the width of the Vestibular aqueduct is more than the width of the PSC, then it is dilated. -----Satish jain sir says >2mm VA dilated in any
section .
In HRCT Temporal bone Vestibular aqueduct ( VA )is seen parallel to PSC ( Posterior semi circular canal ) Here also after drilling PSC
we are seeing VA
anatomically also after drilling PSC we are seeing VA .... so radiologically also both sizes same [ my mnemonic & philosophy ] ..... if VA more than PSC it is
dilated
Abnormal cochleas dissection photos added later in few days
Essence of abnormal cochleas
1. IP 2 is exactly like normal cochlea2. IP 3 - wide cochleostomy & precurved electrode3. cochlear hypoplasia -- outcomes depends on how many number of electrodes
inserted . Minimum 10 electrodes insertion should be there to get better outcome
4. IP 1 - lateral wall electrode5. common cavity - lateral wall electrode6. CHARGE - still try CI , not working then ABI.7. michel - ABI directly
In all abnormalities see cochlear nerve aplasia .... even absent in MRI , do EABR & keep CI
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