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Cochlea cadaver dissection - part 1

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Cochlea cadaver dissection - part 1

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Cochlea cadaver dissection - part 1

  1. 1. Cochlea Cadaver Dissection- Part 1 12-05-2017 2.35 pm
  2. 2. 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 to slideshare.net with Facebook account after clicking www.skullbase360.in
  3. 3. Part-2 of this PPT present at weblink https://www.slideshare.net/murali chandnallamothu/cochlea-cadaver- dissection-part-2
  4. 4. Throughout our life we have to practice temporal bone
  5. 5. Abnormal cochleas dissection photos added later in few days Essence of abnormal cochleas 1. IP 2 is exactly like normal cochlea 2. IP 3 - wide cochleostomy & precurved electrode 3. 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 electrode 5. common cavity - lateral wall electrode 6. 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
  6. 6. Round window in Cochlear implant
  7. 7. Helicotrema (at right angles to a line between the oval and round windows)
  8. 8. 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 semilunar The thickness of membrane is 60 micro mm The length is 1.70 mm the width is 1.35 mm It contains all three layers like TM The entrance of niche is 2.2 mm.
  9. 9. Still experts opinion has to be taken regarding below line diagram - don’t take it granted – below line diagram is in the process of developing 1. Round window membrane 2. Crista semilunaris 3. 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 bar 5. Vertical bar 6. Cavum anterior 7. Cavum posterior 8. Fustis 9. Opurculum or Crista
  10. 10. 1 Round window membrane 2 Crista semilunaris 3 Fustis 4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista
  11. 11. 1 Round window membrane 2 Crista semilunaris 3 Fustis 4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista
  12. 12. 1 Round window membrane 2 Crista semilunaris 3 Fustis 4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista
  13. 13. 1 Round window membrane 2 Crista semilunaris 3 Fustis 4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Pars anterior 9 Pars posterior 10 Crista
  14. 14. Surgical implications 1) It is a outlet door of sound conduction through cochlea 2) It acts as resonant chamber of sound 3) Sono invertion - sound can be transported through the RWM and passing through cochlea and coming outfrom oval window gives rise to good hearing - reverse way 4) It transports micromolecules to inner ear by eaither diffusion or pinocytosis 5) For cochlear implant surgeons RWM is not directly posteroior to scala tympani So scala is present just antero superior to RWM hence surgeon has to remove crista to insert electrode directly in to scala tympani
  15. 15. • 6) Rwm is divided in to pars anterior and pars posterior by fibrous band arising from crista semilunaris The 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 anterior These bony cavums act like resonant spaces to outlet sound 8) pars anterior always for sound vibration RWM vibration is evident at 1500 to 3000 hzs and at higher frequencies it vibrates irrigularly 9) 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 fluid In posterior part of RWM for better diffusion 10) Most of the round windows have false membranes hence it is better to remove those before instillation of gentamycin.
  16. 16. • 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 posticus 13) 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 fossula 14) 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
  17. 17. 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 loss 18) Gentamycin trans tympanic instillation for menieres disease spreads from pars posterior of RWM to vestibule through the scala rather than diffusion through the helicotrema 19) 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
  18. 18. 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.
  19. 19. Relation of OSL [ = Osseus spiral laminae ] & RW niche [ = opening ]
  20. 20. Anatomy of the human round window (left ear-medial view). A, The RW is fan shaped and conical and opens into the RW niche (*). CA, cochlear aqueduct; ST, scala tympani. B, A CI electrode array has been inserted through the RW. The electrode rides on the crista fenestrae. – from paper title “Is the Human Round Window Really Round? An Anatomic Study With Surgical Implications”
  21. 21. FUSTIS & FINICULUS
  22. 22. 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 are 1) its origin is pylogenically different from other parts of that area hence it behaves differently 2) It contains enzymes which are resistant to cholesteatoma destruction 3) 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 membrane 5) 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.
  23. 23. • 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 RW 10) 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..
  24. 24. Type A fustis. f fustis, sp styloid proeminence, st scala tympani, rw round window
  25. 25. Type B fustis. f fustis, sp styloid proeminence, st scala tympani, rw round window
  26. 26. Right ear. Endoscopic view of fustis type B. ow oval window, st scala tympani, fu fustis, pe pyramidal eminence, rw round window
  27. 27. Right ear. The tool shows the scala tympani. ow oval window, st scala tympani, fu fustis, rw round window
  28. 28. 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.
  29. 29. FUSTIS position must be known for CI surgeons
  30. 30. Sometimes you may not appreciate fustis by Sinus tympani approach but for Veria technique fustis is very important.
  31. 31. between fustis & finiculus SCC ( subcochlear canal ) present
  32. 32. SCC = Sub Cochlear Canaliculus,
  33. 33. Between the fustis and the finiculus a subcochlear canaliculus is often seen, which is a tunnel that connects the round window chamber with the petrous apex via a series of pneumatized cells. Right ear. Endoscopic anatomy of inferior retrotympanum. fu fustis, t tegmen, pp posterior pillar, f finiculus, j jacobson’s nerve
  34. 34. Right ear. Endoscopic anatomy of the retrotympanum during dissection for acustic neuroma surgery. fu fustis, fn facial nerve, ow oval window, pr promontory, scc subcochlear canaliculus, et Eustachian tube
  35. 35. Right ear. Endoscopic dissection during surgery, after drilling the promontory. ow oval window, st scala tympani, scc subcochlear canaliculus
  36. 36. Subcochlear canaliculus type A
  37. 37. Subcochlear canaliculus type B
  38. 38. Subcochlear canaliculus type C
  39. 39. Round window types
  40. 40. • So far round window is neglected part in middle ear Now a days it is gaining popularity For type4 and 5 t plasties sono inversion techniques viroplasties gentamycin and other chemical perfusions cochlear implant insertions corticosteroid perfusions in s n d skullbase approaches round window is important There are so many verieties of shapes of r w s I have previously discussed 4 types of r w s
  41. 41. " High arched" round window
  42. 42. " High arched" round window • Dear surgeons it is" High arched" round window it is present 1-3%of cases you can compare this window to normal r w which is shown here The arched round window associated with 1 compressed cochlear capsule in caratico facial angle 2 Deep hypotympanum 3 long trabiculae including trabicula longa 4 wide concomerata lateralis and absent concomireta medialis Wide postis posticus with subcochlear tunnel 5 wide sinus tympani
  43. 43. "PARABOLIC" round window
  44. 44. "PARABOLIC" round window • Dear surgeons it is "PARABOLIC" round window in shape present 1% of cases characterised by 1 two vertical limbs longer than tegmen 2 wide niche 3 Third limb is formed by styloid complex 4 s shaped cochlea including sub vestibular portion 5 wide finiculus with high pavementum pyramidalis 6 deep carotid recess 7 3rd part of facial nerve is nearer to middle ear
  45. 45. • Surgical implications 1 wide angle cochlea hence cochlear implant electrode insertion is easy 2 narrow vestbular window stapes surgery is difficult 3 endoscopic endomeatal f n decompression is easy in these cases 4 vibroplasty is easy 5 infracochlear approach to petrous apex is not possible in this type of round windows 6 endoscopic endomeatal approach to IAC is easy in this type of cases 7 s shaped cochlea here allows wide transcochlear approach to clivus
  46. 46. Inferior cochlear vein
  47. 47. A, Illustration showing the RWM and surrounding structures seen through the facial recess. The red box represents the hook region of the cochlea that was modeled in this study. B, Anatomy of the round window and surrounding structures after removing the bone from the model. C, The RWM and spiral ligament have been removed from the model, and the scala tympani has been made transparent to show the intracochlear structures. BM, basilar membrane; CA, cochlear aqueduct; CT, chorda tympani; DR, ductus reuniens; EAC, external auditory canal; FN, facial nerve; I, incus; ICV, inferior cochlear vein; LSC, lateral semicircular canal; OSL, osseous spiral lamina; PSC, posterior semicircular canal; S, stapes; SL, spiral ligament; SM, scala media; SSC, superior semicircular canal; ST, scala tympani; SV, scala vestibuli; RWM, round window membrane.
  48. 48. A, Illustration showing the RWM and surrounding structures seen through the facial recess. The red box represents the hook region of the cochlea that was modeled in this study. B, Anatomy of the round window and surrounding structures after removing the bone from the model. C, The RWM and spiral ligament have been removed from the model, and the scala tympani has been made transparent to show the intracochlear structures. BM, basilar membrane; CA, cochlear aqueduct; CT, chorda tympani; DR, ductus reuniens; EAC, external auditory canal; FN, facial nerve; I, incus; ICV, inferior cochlear vein; LSC, lateral semicircular canal; OSL, osseous spiral lamina; PSC, posterior semicircular canal; S, stapes; SL, spiral ligament; SM, scala media; SSC, superior semicircular canal; ST, scala tympani; SV, scala vestibuli; RWM, round window membrane.
  49. 49. Crest of round window
  50. 50. http://sci- hub.cc/10.1016/j.aanat.2005. 09.006 Development of the bony round window niche from the 16th fetal week (A) to newborn (F). The first ossification centers of the otic capsule appear around the round window, but the inferior wall of the niche does not begin to ossify until the 17th fetal week (B). The first sign of the crest of round window can be seen in the 18th week (C) and it develops rapidly up to the 23rd week (D). The walls of the niche show intensive growth during the entire prenatal period but its typical appearance is not complete until the eighth fetal month (E). f – fustis, pa – postis anterior, pp – postis posterior, t – tegmen of the round window, arrow – crest of the round window.
  51. 51. OPERCULUM of round window drilled
  52. 52. Operculam must be drilled even to make cochleostomy ... Cochleostomy notch done
  53. 53. HOOK [ = Crista Semilunaris ] of Round window
  54. 54. http://sci- hub.cc/10.1016/j.aanat.2005. 09.006 Development of the bony round window niche from the 16th fetal week (A) to newborn (F). The first ossification centers of the otic capsule appear around the round window, but the inferior wall of the niche does not begin to ossify until the 17th fetal week (B). The first sign of the crest of round window can be seen in the 18th week (C) and it develops rapidly up to the 23rd week (D). The walls of the niche show intensive growth during the entire prenatal period but its typical appearance is not complete until the eighth fetal month (E). f – fustis, pa – postis anterior, pp – postis posterior, t – tegmen of the round window, arrow – crest of the round window.
  55. 55. COCHLEOSTOMIES 1. INFERIOR Cochleostomy 2. ANTERO-INFERIOR Cochleostomy 3. SUPERIOR Cochleostomy 4. SV[ Scala Vestibular ] Cochleostomy 5. MIDDLE TURN Cochleostomy 6. APICAL TURN/SUPERIOR TURN Cochleostomy
  56. 56. INFERIOR Cochleostomy
  57. 57. INFERIOR cochleostomy
  58. 58. Best / ideal is INFERIOR ( not antero-inferior ) cochleostomy which is direct trajectory to scala tympani
  59. 59. Best / ideal is INFERIOR ( not antero-inferior ) cochleostomy which is direct trajectory to scala tympani ..... See I stopped about to open . Then try pick
  60. 60. Observe operculum drilled. Round window intact . Cochleostimy intact ....... Cochleostomy INFERIOR...... What I realized is cochleotomy opening will not open within seconds . It takes sometime
  61. 61. Posterior tympanotomy
  62. 62. See endoateum of cochleostomy not torn with burr ......... Upper one round window . Lower one cochleostomy
  63. 63. Upper one round window . Lower one cochleostomy .......... Round window is very simple ............. Definitely inferior cochleostomy is direct trajectory but we need to drill more time ........ Residual hearing may damage
  64. 64. Two openings connected......... But drilling is more . I fear residual hearing lost because of more drilling
  65. 65. Amount of drilling is somuch in INFERIOR cochleostomy
  66. 66. Antero-inferior Cochleostomy
  67. 67. The round window niche is visualized through the facial recess. If the round window niche is divided into quadrants, the conchleostomy should be performed in the anterior inferior quadrant.
  68. 68. First using a larger 1.5 to 2 mm bur portion of the bony promontory is removed just anterior to the anterior/inferior annulus of the round window membrane. A 1-mm bur is then used to expose the endosteum of scala tympani.
  69. 69. SUPERIOR Cochleostomy
  70. 70. Superior cochleostomy notch
  71. 71. Yes.. Superior cochleostomy leading to Scala vestibuli & Scala tympani . Observe partition ( osseus spiral lamina ) in superior cochleostomy…… Cochlear electrode array kink if you pass by superior cochleaostomy in scala tympani … so Anterior inferior or INFERIOR is better
  72. 72. Above partition is SV [ scala vestibuli ] & below partition is ST [ scala tympani ]
  73. 73. Incus removed
  74. 74. Incus & incus buttress has to be removed in rotated cochleas grade 3 & 4 before mohnish's technique of posterior canal wall reduction
  75. 75. Stapes dislocated ……Foot plate removed . Now i am going to make cochleostomy in between RW & OW to enter Scala vestibuli in meningitis cases in ossificans cases
  76. 76. Pyramid drilled
  77. 77. SV [ Scala Vestibular ] cochleostomy
  78. 78. Notch between OW & RW
  79. 79. Note cochleostomy between RW & OW leading to Scala vestibuli & separate from superior cochleostomy Note spiral lamina in superior cochleostomy
  80. 80. Note spiral lamina through SV cochleostomy between OW & RW
  81. 81. All opening from above 1. OW 2. SV cochleostomy 3. Superior cochleostomy 4. RW5. INFERIOR cochleostomy
  82. 82. All opening from above 1. OW 2. SV cochleostomy 3. Superior cochleostomy 4. RW5. INFERIOR cochleostomy
  83. 83. MIDDLE TURN cochleostomy & PARISIER'S TRIANGLE (DANGEROUS TRIANGLE)
  84. 84. PARISIER'S TRIANGLE (DANGEROUS TRIANGLE) Perisier's triangle is very important triangle in endoscopic ear surgery 1) Superior limb is formed by inferior part of HFN 2) The apex is formed by the geniculate ganglion 3) The base is formed by the anterior commissure (end) of oval window 4) Inferior limb is formed by tunning point of jocobson's nerve to the the geniculate ganglion.
  85. 85. • The surgical implications are 1) This triangle contains labyrinthine part of FN. 2) During transotic or transcochlear approaches surgeon should respect this triangle and drill carefully to avoid injury to FN. 3) Clinically labyrinthine part consists of two segments a meatal segment of nerve, labyrinthine part of nerve. total length of this nerve is 3 to 5 mm. Anteriorly we can see these parts clearly through this triangle. 4) 1st part of FN passes close to lower border of precochlear HFN towards anterior end of oval window in this triangle. 5) Irregular drilling of cochlea in this triangle damages FN That is why it is called DANGERS TRIANGLE. 6) During trans meatal endoscopic dissection of IAC, this triangle important for identification of nerves 7) Translabyrinthine approach visualises posterior surface of 1st part of FN, in transcochlear approaches the anterior surface of the nerve is exposed. In transottic approaches 270 to 320 degrees of 1 st part of FN is exposed. 8)Observe closely the labyrinthine part of FN there is a constriction of labyrinthine segment and meatal segment. Facial nerve key points 1) Facial nerve changes direction 5 times during its course from brain stem to styloid foramen. 2) No other nerve in body covers such a long distance in bony canal 3) facial nerve contains 10000 axons that are responsible for the innervation of the face musculature and also for the communications with other nerves human body 4) work with injured facial nerve requires lot of patience.
  86. 86. • RULE OF 2 IN TEMPORAL BONES 1) The diameter of geniculate fossa is 2 mm 2) The distance between between geniculate fossa to anterior wall of vestibule is 2 mm 3) The thickness of geniculate crest is 2 mm 4 ) The diameter of horizontal facial nerve in that area is 2 mm Hence while drilling the bone or curetting the bone at perigeniculate area it is not advisable to use bigger burs more than 2mm diameter 5) The meatal segment of facial nerve is usually 2 mm anterior and superior to superior vestibular nerve. My special thanks to prof Livio presuitti, prof Daniele Marchioni and prof Jao Flavio Nogueira who taught me this Anatomy
  87. 87. While making middle turn cochleostomy we shouldn’t injure the labyrinthine part of facial nerve present in perisier’s triangle
  88. 88. Notch 2 to 3 mm anterior to OW & below the processes cochleriformis leads to middle turn
  89. 89. For middle turn cochleostomy also we need to drill a lot . Not opening that much easily
  90. 90. Still not opened .
  91. 91. Still not opened .
  92. 92. Still not opened .
  93. 93. Now opened . In middle & apical turns SV is more than ST ……I don't know why
  94. 94. See how depth the middle turn cochleostomy
  95. 95. See how depth the middle turn cochleostomy
  96. 96. All opening from above 1. OW 2. Middle turn cochleostomy 3. SV cochleostomy 4.Superior cochleostomy 5. RW 6.INFERIOR cochleostomy
  97. 97. We have to appreciate the same labyrinthine part of facial nerve by perisiers triangle ( dangerous triangle ) also . So we shouldn't go more than 2 to 3 mm to OW while doing middle turn cochleostomy
  98. 98. APICAL TURN / SUPERIOR TURN cochleostomy
  99. 99. here I lifted the tensor tympani muscle & I made cochleostomy exactly in tensor tympani groove which is superior turn cochleostomy
  100. 100. here I lifted the tensor tympani muscle & I made cochleostomy exactly in tensor tympani groove which is superior turn cochleostomy
  101. 101. here I lifted the tensor tympani muscle & I made cochleostomy exactly in tensor tympani groove which is superior turn cochleostomy
  102. 102. here I lifted the tensor tympani muscle & I made cochleostomy exactly in tensor tympani groove which is superior turn cochleostomy
  103. 103. here I lifted the tensor tympani muscle & I made cochleostomy exactly in tensor tympani groove which is superior turn cochleostomy
  104. 104. Labyrinthine part of facial nerve in transmastoid approch by CWU [ Canal Wall Up ] Labyrinthine part of facial nerve decompression
  105. 105. Labyrinthine part of FN can be decompressed by intact bridge transmastoid approach
  106. 106. Labyrinthine part of facial nerve decompression…….. Observe middle cranial fossa bone & dura also decompressed from labyrinthine part of facial nerve
  107. 107. This labyrinthine part of facial nerve stimulated in cochlear implant by electrodes especially in common cavity & other abnormal cochleas . Then we have to deactivate that electrode
  108. 108. CWD [ canal wall down ] + SP [ subtotal petrosectomy ]
  109. 109. CWD bone dust ………CWD + SP ( subtotal petrosectomy ) has to be done in CSOM + CSF leak + abnormal cochleas
  110. 110. SP = subtotal petrosectomy
  111. 111. DRILLOUTS 1. BASAL TURN drillout 2.MIDDLE TURN drillout 3. APICAL TURN / SUPERIOR TURN drillout
  112. 112. BASAL TURN drillout
  113. 113. Without doing CWD you can't do basal turn drilling So CWD + SP is vital in CI surgery
  114. 114. Without doing CWD you can't do basal turn drilling So CWD + SP is vital in CI surgery
  115. 115. Note scala vestibular & superior cochleostomy leading to Scala vestibuli & Inferior cochleostomy leading to Scala tympani
  116. 116. Note scala vestibular & superior cochleostomy leading to Scala vestibuli & Inferior cochleostomy leading to Scala tympani
  117. 117. The current drilling is called apex of basal turn
  118. 118. The current drilling is called apex of basal turn
  119. 119. MIDDLE TURN drillout
  120. 120. Note the drilling direction of middle turn is in the same curvature of basal turn
  121. 121. Note the drilling direction of middle turn is in the same curvature of basal turn
  122. 122. Note the drilling direction of middle turn is in the same curvature of basal turn
  123. 123. Note the drilling direction of middle turn is in the same curvature of basal turn
  124. 124. Note the drilling direction of middle turn is in the same curvature of basal turn ( scala vestibuli turn )
  125. 125. Scale vestibuli of middle turn is more wider than scala vestibuli of basal turn
  126. 126. Scale vestibuli of middle turn is more wider than scala vestibuli of basal turn
  127. 127. Scale vestibuli of middle turn is more wider than scala vestibuli of basal turn
  128. 128. Scale vestibuli of middle turn is more wider than scala vestibuli of basal turn
  129. 129. Observe middle turn drillout meeting superior cochleostomy
  130. 130. Observe middle turn drillout meeting superior cochleostomy
  131. 131. 1mm cutting burr is the key for CI surgery First time burr head broken
  132. 132. Chaaa.... no another 1mm cutting burr . 1mm diamond causing charring . So we have to keep minimum three sets of 1mm & lesser size to start CI surgery .
  133. 133. I am amazed the human hearing frequency in middle turn & facial associated with middle turn only .
  134. 134. Note horizontal part of facial nerve , tensor tympani muscle , middle turn drill , basal turn drill from above downwards
  135. 135. Note horizontal part of facial nerve , tensor tympani muscle , middle turn drill , basal turn drill from above downwards
  136. 136. PERISIER’S [ DANGEROUS ] TRIANGLE
  137. 137. Observe here 1. Middle turn wall associated with horizontal part of facial nerve 2. Middle turn cavity associated with labyrinthine part of facial nerve in perisiers ( dangerous ) triangle . So main culprit is labyrinthine part of facial nerve in post CI facial nerve stimulation
  138. 138. Perisiers triangle also important in malignancy of ear
  139. 139. See ... how the basal turn keeping middle turn in her lap & inturn middle turn keeping apical turn in her lap So in HRCT in axial section in both cranial & caudal sections you will see basal turn only . Don't confuse that in cranial section you will see apical turn .
  140. 140. Perisier's triangle ( dangerous triangle ) which denotes labyrinthine part of facial nerve …… Corresponds exactly to middle turn drillout
  141. 141. Perisier's triangle ( dangerous triangle ) which denotes labyrinthine part of facial nerve…….. Corresponds exactly to middle turn drillout
  142. 142. Perisier's triangle ( dangerous triangle ) which denotes labyrinthine part of facial nerve…….. Corresponds exactly to middle turn drillout
  143. 143. APICAL TURN/ SUPERIOR TURN drillout
  144. 144. Gross picture of CI drillouts
  145. 145. Part-2 of this PPT present at weblink https://www.slideshare.net/murali chandnallamothu/cochlea-cadaver- dissection-part-2

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