cochlea cadaver dissection - part 1

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Cochlea Cadaver Dissection

Cochlea Cadaver Dissection- Part 1 18-04-20178.29 pm

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For Other powerpoint presentatioins of Skull base 360 I will update continuosly with date tag at the end as I am getting more & more information click www.skullbase360.in- you have to login toslideshare.netwith Facebook account after clickingwww.skullbase360.in

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Throughout our life we have to practice temporal bone

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Abnormal cochleas dissection photos added later in few days Essence of abnormal cochleas

IP 2 is exactly like normal cochleaIP 3 - wide cochleostomy & precurved electrodecochlear hypoplasia -- outcomes depends on how many number of electrodes inserted . Minimum 10 electrodes insertion should be there to get better outcome IP 1 - lateral wall electrodecommon cavity - lateral wall electrodeCHARGE - still try CI , not working then ABI.michel - ABI directly

In all abnormalities see cochlear nerve aplasia .... even absent in MRI , do EABR & keep CI

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Round window in Cochlear implant

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Helicotrema (at right angles to a line between the oval and round windows)

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ROUND WINDOW MEMBRANE SO FAR NEGLECTED PART IN OTOLOGIC SURGERY

Surgeons, so far round window membrane is most neglected part in otological surgery endoscopic visualisation of RWM with 2.7 mm 45 degree scope gives more information

Dear surgeons,These are pictures of round window membrane RWM may be kidney shaped, round or triangular or oval or semilunarThe thickness of membrane is 60 micro mmThe length is 1.70 mm the width is 1.35 mmIt contains all three layers like TMThe entrance of niche is 2.2 mm.

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Still experts opinion has to be taken regarding below line diagram - dont take it granted below line diagram is in the process of developing 1. Round window membrane2. Crista semilunaris3. Fibrous band

Crista semilunaris & fibrous band devides RWM into pars anterior & pars posterior.

Floor of Round window is devided into Horizontal bar & Vertical bar 4. Horizontal bar5. Vertical bar

6. Cavum anterior7. Cavum posterior

8. Fustis9. Opurculum or Crista

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1 Round window membrane 2 Crista semilunaris 3 Fustis4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista

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1 Round window membrane 2 Crista semilunaris 3 Fustis4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista

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1 Round window membrane 2 Crista semilunaris 3 Fustis4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista

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1 Round window membrane 2 Crista semilunaris 3 Fustis4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista

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Surgical implications1) It is a outlet door of sound conduction through cochlea2) It acts as resonant chamber of sound3) Sono invertion - sound can be transported through the RWM and passing through cochlea and coming outfrom oval window gives rise to good hearing - reverse way4) It transports micromolecules to inner ear by eaither diffusion or pinocytosis5) For cochlear implant surgeons RWM is not directly posteroior to scala tympaniSo scala is present just antero superior to RWM hence surgeon has to remove crista to insert electrode directly in to scala tympani

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6) Rwm is divided in to pars anterior and pars posterior by fibrous band arising from crista semilunarisThe implant electrode shoud be introduced from pars anterior to enter the scala if electrode is introduced from pars posterior it touches osseous osseous spiral lamina and electrode does not go into scala.7) The floor of niche divided by horizontal bony bar and small vertical bar into cavum posterior and cavum anteriorThese bony cavums act like resonant spaces to outlet sound8) pars anterior always for sound vibration RWM vibration is evident at 1500 to 3000 hzs and at higher frequencies it vibrates irrigularly9) pars posterior is always tor micromolecules diffusion in to inner ear ant it contains more melanocytes so for gentamycin instillation it is better to place fluidIn posterior part of RWM for better diffusion10) Most of the round windows have false membranes hence it is better to remove those before instillation of gentamycin.

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11) Micro molecules of 1mue easily passes through the RWM but micromolecules more than 3 mue can not pass through the membrane so surgeon during instillation of intratympanic gentamycin has to observe this point (not to add sodium bicarb in gentamycin solution )12) Rupture of RWM occur in pars anterior it looks like a slit with leak into cavum anticus and cavum posticus13) Cochlear aqueduct inner opening is present in scala tympani just anterior to crista semilunaris still inside is opening of cochlear vein so obstruction to cochlear vein causes sensory neural learing loss outer opening of cochlear aqueduct is present in pyramidal fossula14) Fustis gives strong support to RWM unnecessory excessive drilling of fustis in cholesteatoma surgery causes may accidentally rwm rupture.15) rupture of RWM is one of the causes for sudden SN loss

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16)Fustis gives strong support to rwm unnecessory excessive drilling of fustis in cholesteatoma surgery causes may accidentally RWM rupture.17) Rupture of RWM is one of the causes for sudden sn loss18) Gentamycin trans tympanic instillation for menieres disease spreads from pars posterior of RWM to vestibule through the scala rather than diffusion through the helicotrema19) complete closure of round window is the good alternative treatment in SSCS (superior semicircularcanal fistula syndrome)20) The second most common site of otosclerosis is round window During stapes surgery it is better to visualise the round window for better results

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what a great great description in paper http://sci-hub.cc/10.1016/j.aanat.2005.09.006

Schematic drawings showing variations of the round window niche in adults (right side). The tegmen (t) andthe postis anterior (pa) of the normal niche are formed completely by membranous bone while the postis posterior (pp)and the fundus (f) are formed by chondral bone but covered superficially with membranous bone. The first two rowsdemonstrate alterations within the entrance of the niche and the lower row represents structures outside the nichewhich hide its entrance.

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FUSTIS & FINICULUS

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FUSTIS

it is fustis a solid bony column connecting the retrotympanum to round window niche. So far this structure is neglected Microscopically it may not be clearly visible, but endoscopically it is seen clearly The surgical implications of this structure are1) its origin is pylogenically different from other parts of that area hence it behaves differently2) It contains enzymes which are resistant to cholesteatoma destruction3) it prevents sinus cholesteatoma extending downwards..4) This structure is directed towards round window, in narrow round window niche by following its upper border, we can identify the round window membrane5) It divides upper part of subtympanic sinus, concomerata into medialis and lateralis. C medialis is site for posterior ampullary nerve section.6) Fustis regulates smooth out flow of sound waves from round window membrane.

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7) It helps in creation of pressure difference between round and oval windows encourages acoustic coupling.8) It gives support round window niche because both postis anticus and postis posticus contains cochlea and subcochlear portion that are hollow structures.9) This structure modulates according to round window niche i. e, "V" shaped, square shaped, triangular gothic shaped, like that, to have a relation with RW10) In absent sibiculum, the fustis gives support.11) Fustis narrows the round window niche there by protects the round window membrane (rupture)normally.12) embryologically fustis develops between periosteal layer of the labyrinthine capsule and the thin smooth plate of Pavementum Pyramidalis and it is ontogenically important structure.So surgeons, fustis is very important structure at outflow gate of sound in middle ear.In 1968 Bruce Proctor mentioned, Recently prof Presutti, Prof Marchioni and Prof Joao F Nogueira described this part.so surgeons please look this important but poor part while performing surgeries because it is present in all middle ears..

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Type A fustis. f fustis, sp styloid proeminence, st scala tympani, rw round window

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Type B fustis. f fustis, sp styloid proeminence, st scala tympani, rw round window

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Right ear. Endoscopic view of fustis type B. ow oval window, st scala tympani, fu fustis, pe pyramidal eminence, rw round window

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Right ear. The tool shows the scala tympani. ow oval window, st scala tympani, fu fustis, rw round window

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A. Original round window. B. Basilar membrane. C. Osseous spiral lamina. D. Reflection of perilymphatic fluid. E. Darker area of first curve of the basal turn of the scala tympani. F. Blood vessels. G. Modiolus. H. Removed bone of round window overhang.

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FUSTIS position must be known for CI surgeons

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Sometimes you may not appreciate fustis by Sinus tympani approach but for Veria technique fustis is very important.

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between fustis & finiculus SCC ( subcochlear canal ) present

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SCC = Sub Cochlear Canaliculus,

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Between the