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Cranial nerves 360°

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Cranial nerves 360°

  1. 1. Cranial nerves 360° 29-9-2016 7.59 pm
  2. 2. Great teachers – All this is their work . I am just the reader of their books . Prof. Paolo castelnuovo Prof. Aldo Stamm Prof. Mario Sanna Prof. Magnan
  3. 3. 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 for downloading.
  4. 4. 7up- 7th is above Coca cola – cochlear n. is cola[=lower]
  5. 5. Crannial nerves 360 video Click https://www.youtube.com/watch?v= PSTzJOHpDCM
  6. 6. 1st nerve
  7. 7. After removal of planum 1st nerve seen lateral to gyrus rectus . Car.: carotid; Chiasm.: chiasmatic; Clin.: clinoidal; CN: cranial nerve; Fiss.: fissure; G.: gyrus; ICA: internal carotid artery; Interhem.: interhemispheric; Orb.: orbital; Rec.: recess.
  8. 8. 2nd nerve
  9. 9. The dura over the ACP passes over the ON, giving the falciform ligament
  10. 10. 1. The transplanum route may also facilitate exposing the anterior incisural space. On the center of this space the chiasm helps separate the two major cisternal compartments. Below the chiasm is the chiasmatic cistern, and above it is the center of the lamina terminalis cistern. 2. The pituitary stalk and superior hypophyseal arteries are located into the chiasmatic cistern.
  11. 11. Opening through the planum sphenoidale facilitates approaching the posteromedial portion of the anterior cranial fossa. This area is related to the posterior part of the basal surface of the cerebrum, which presents the rectus gyrus, the olfactory sulcus, and the orbital gyri. The olfactory nerve is related to the olfactory sulcus. The transplanum route may also facilitate exposing the anterior incisural space. On the center of this space the chiasm helps separate the two major cisternal compartments. Below the chiasm is the chiasmatic cistern, and above it is the center of the lamina terminalis cistern. A.: artery; Ant.: anterior; Cer.: cerebral; Com.: communicating; CN: cranial nerve; Fiss.: fissure; G.: gyrus; Hyp.: hypophyseal; Intercav.: intercavernous; Interhem.: interhemispheric; Sup.: superior; Tub.: tuberculum; V.: vein.
  12. 12. Various types of Optic nerve • Type I: The most common type, it occurs in 76% of patients. Here, the nerve courses immediately adjacent to the sphenoid sinus, without indentation of the wall or contact with the posterior ethmoid air cell [Figure 11]. • Type II: The nerve courses adjacent to the sphenoid sinus, causing an indentation of the sinus wall, but without contact with the posterior ethmoid air cell [Figure 12]. • Type III: The nerve courses through the sphenoid sinus with at least 50% of the nerve being surrounded by air [Figure 13]. • Type IV: The nerve course lies immediately adjacent to the sphenoid and posterior ethmoid sinus [Figure 14] and [Figure 15].
  13. 13. Figure 11: Coronal CT showing type I optic nerve (arrows) the nerve is seen to course immediately adjacent to the sphenoid sinus, without contact with the posterior ethmoid air cell
  14. 14. Figure 12: Coronal CT showing type II optic nerve (curved arrows) causing an indentation of the sinus wall, but without contact with the posterior ethmoid air cell
  15. 15. Figure 13: Coronal CT shows type III optic nerve (arrows) where more than 50% of the nerve is surrounded by air
  16. 16. Figure 14: Coronal CT showing type IV optic nerve on the right (arrow) -The nerve course lies immediately adjacent to the sphenoid and posterior ethmoid sinus. O: Onodi cell; S: Sphenoid sinus
  17. 17. Figure 15: Coronal CT showing type IV optic nerve bilaterally (arrows). O: Onodi cell; S: Sphenoid sinus
  18. 18. Delano, et al., found that 85% of optic nerves associated with a pneumatized anterior clinoid process were of type II or type III configuration, and of these, 77% showed dehiscence [Figure 16], indicating the vulnerability of the optic nerve during FESS. Figure 16: Coronal CT shows pneumatisation of anterior clinoid process (stars) with type III optic nerve (stars) with bony canal dehiscence bilaterally
  19. 19. Pneumatization of anterior clinoid process – in various planes + onodi cell on both sides of sphenoid [ when transverse septum present in sphenoid it is onodi cell ] + sphenoid recess on left side between V2 & VN .
  20. 20. The same cadaver photo what you are seeing in CT scan above – Note the supraoptic pneumatisation [ present in anterior clinoid process ] in an onodi cell .
  21. 21. The sphenoid sinus septa may be attached to the bony canal of the optic nerve, predisposing the nerve to injury during surgery . Figure 17: Coronal CT showing sphenoid septa (arrow) attached to the bony walls of type III optic nerve bilaterally (stars)
  22. 22. Accessing intraconal lesions endonasally requires manipulation of the extraocular muscles. The nerve branches that supply the oculomotor muscles run in the medial surface of the muscles. Thus, try to avoid excessive retraction of the extraocular muscles to avoid inadvertent muscle paresis.
  23. 23. Optic tubercle
  24. 24. In 83% the OA passes around the lateral aspect of the optic nerve (b, left); in the remaining cases the OA stays medial to the optic nerve, 17% - this point important in optic nerve decompression
  25. 25. One artery in the head which we can’t move – is OA – Central retinal artery is avulsed
  26. 26. Relation of PEA & ON Anterior limit of Transplanum approach is PEA – when we are removing a triangular piece of bone in Transplanum approach , the base of traingle is PEA
  27. 27. when we are removing a triangular piece of bone in Transplanum approach , the base of traingle is PEA
  28. 28. The sphenoid ostium (SO) is first opened inferiorly (black arrow, 1) then laterally (black arrow, 2). This should afford a clear view into the sphenoid sinus and the remaining anterior face of the sphenoid can be removed up toward the optic tubercle (OT) but usually stopping short of the tubercle to lessen the potential risk to the optic nerve.
  29. 29. 1. In rare situation we have to anticipate OA in Antero-inferior & Lateral compartments of CS . 2. Opthalmic artery – Retrograde branch of Intracranial carotid Branches of the cavernous internal carotid artery ( ICA ), a rare variation: ophthalmic artery passing through the superior orbital fissure Normal OA above upper dural ring
  30. 30. classification of the ophthalmic artery types http://www.springerimages.com/Images/MedicineAndPublicHealth/1- 10.1007_s10143-006-0028-6-1 a = intradural type, b = extradural supra-optic strut type [ Optic strut = L-OCR ] c = extradural trans-optic strut type on optic nerve, pr proximal ring, cdr carotid dural ring= upper dural ring , ica internal carotid artery I think this variation is type c
  31. 31. In both type a = intradural type, b = extradural supra-optic strut types Opthalmic foramen is in Optic canal
  32. 32. In Type c = extradural trans-optic strut type , the Opthalmic foramen in Optic strut
  33. 33. http://www.nature.com/eye/journal/v20/n10/fig_tab/6702377f3.html#figure -title The upper diagram is Type a or b Opthalmic artery , the lower diagram is Type c Opthalmic artery Dup OC = Duplicate Opthalmic canal
  34. 34. Origin and intracranial and intracanalicular course of the ophthalmic artery and its subdivisions, as seen on opening the optic canal (reproduced from Hayreh67). Both from one specimen. (a) The extradural origin of the right ophthalmic artery, so that no ophthalmic artery is seen even on opening theoptic canal; a thinning of the dural sheath is seen at 'X', indicating the position of the artery. (b) The ophthalmic artery is seen after removing the dural sheath covering it (reproduced from Hayreh and Dass2).
  35. 35. Schematic drawing origin (a medial, b central, c lateral) and exit (d lateral, emedial) of superior wall of the ophthalmic artery
  36. 36. A diagrammatic representation of variations in origin and intraorbital course of ophthalmic artery. (a) Normal pattern. (b–e) The ophthalmic artery arises from the internal carotid artery as usual, but the major contribution comes from the middle meningeal artery. (f and g) The only source of blood supply to the ophthalmic artery is the middle meningeal artery, as the connection with the internal carotid artery is either absent (f) or obliterated (g) (reproduced from Hayreh and Dass3).
  37. 37. Origin, course, and branches of the ophthalmic artery in two adult specimens. Segment Y disappeared in (a) and segment Z disappeared in (b), resulting in the ophthalmic artery crossing under the optic nerve in both. In (b) an anastomosis is seen in lateral wall of the cavernous sinus between the part of the internal carotid artery lying in proximal part of the cavernous sinus and a branch from the ophthalmic artery passing through the superior orbital fissure (reproduced from Hayreh67).
  38. 38. Various relations of OA [ Opthalmic artery ] to ON left figure when it crosses under the optic nerve (in 17.4%) and right figure when it crosses over the optic nerve (in 82.6%).
  39. 39. Give incision in supero-medial area in optic nerve decompression – add scott brown information
  40. 40. 3rd nerve
  41. 41. 3rd & 4th nerves below optic nerve
  42. 42. Lilliquits membrane present over the basillar artery & 3rd N. origin area
  43. 43. 3rd nerve is sandwiched between posterior cerebral artery & superior cerebellar artery
  44. 44. The Type C Modified Transcochlear Approach – after cutting the tentorium With mild retraction of the temporal lobe, the bifurcation of the internal carotid artery (ICA) into the anterior (ACA) and middle cerebral (MCA) arteries is seen. The ipsilateral (ON) and contralateral (ONc) optic nerves are seen. The oculomotor nerve (III) is embraced by the posterior cerebral artery (PCA) superiorly and the superior cerebellar artery (SCA) inferiorly
  45. 45. 3rd nerve is sandwiched between posterior cerebral artery & superior cerebellar artery
  46. 46. 3rd nerve is sandwiched between posterior cerebral artery & superior cerebellar artery Through endoscopic lateral skull base Through endoscopic anterior skull base
  47. 47. 3rd nerve is sandwiched between posterior cerebral artery & superior cerebellar artery Through endoscopic lateral skull base Through endoscopic anterior skull base
  48. 48. Observe here the Pcom (here labelled as ACoP in some language ) is parallel to 3rd nerve in infrachiasmatic cistern . Excellent photo . Other points to note 1. 3rd nerve sandwitched between posterior cerebral artery & superior cerebellar artery . 2. On the left side 2 superior cerebellar arteries present from the origin itself. 3. Diameter of Pcom varies on two sides. 4. Infra-chiasmastic cistern is nothing but suprasellar area
  49. 49. Liliequist membrane Seller segment(S), Mesencephalic segment (M), Diencephalic segment (D Black arrow (D), Arrow head (M), White Arrow (S)
  50. 50. Liliequist membrane
  51. 51. Through Lamina terminalis Through Optic-carotid corridor Liliequist membrane
  52. 52. P1 in relation to 3rd nerve P2 in relation to 3rd nerve
  53. 53. Relationship of PcomA & 3rd nerve – parallel or cross each other
  54. 54. Relationship of PcomA & 3rd nerve – parallel or cross each other in Kernochan's Notch diagram http://en.wikipedia.org/wiki/Kernohan%27s_notch
  55. 55. In parasellar pituitary 3rd n & 4th n & Pcom present in Postero-superior cavernous compartment
  56. 56. Relationship of PcomA & 3rd nerve
  57. 57. Relationship of PcomA & 3rd nerve
  58. 58. a,b Intraoperative image of the fenestration of deep cystic membrane using different microsurgical instruments (forceps and scissors). Asterisks posterior communicating artery and anterior choroidal artery. c Fenestration of the cisternal layer (cross Liliequist’s membrane). d Intraoperative picture at the end of the procedure http://www.springerimages.com/Images/MedicineAndPublicHealth/1-10.1007_s00381-004-0940-4-0
  59. 59. Right supraorbital approach (0 optic). 1 Diaphragma sellae, 2 cn II, 3 optic tract, 4 ICA, 5 A1, 6 M1, 7 C. N.III, 8 anterior petroclinoid fold, 9 anterior clinoid process. A Optocarotid window, B window between ICA and cn III C window lateral of cn III –I think B is nothing but posterior clinoid process Right supraorbital approach (30 optic). Window between ICA and cn III : 1 tuber cinereum, 2 left P1, 3 left cn III, 4 BA, 5 right P1, 6 right SCA, 7 right cn III
  60. 60. Note the aperture for 3rd nerve & 4th nerve anterior & posterior to posterior petro-clival fold [ PPCF ]
  61. 61. Oculomotor cistern Cranial nerve III enters the roof included in its own cistern (oculomotor cistern). Oculomotor cistern goes upto anterior clinoid tip
  62. 62. The lower dural ring is given by the COM [ Carotid-oculomotor membrane ] , that lines the inferior surface of the ACP. It can be visible, through a transcranial route, only by removing the ACP. The lower dural ring is also called Perneczky’s ring. Medially the COM blends with the dura that lines the carotid sulcus (Yasuda et al. 2005 ) Endoscopic supraorbital view with a 30° down-facing lens -The right portion of the planum sphenoidale is seen from above. Right side
  63. 63. Fronto-temporal orbitozygomatic transcavernous approach COM= Caratico-occulomotor membrane , DR = dural ring
  64. 64. The oculomotor nerve divides into a small superior and large inferior division just before passing through the superior orbital fi ssure.
  65. 65. 4th nerve
  66. 66. The trochlear nerve in 80 % of cases enters at the posterior end of the roof of the cavernous sinus ( CS ) and in 20 % at the lower surface of the TC (Lang 1995 ) . 80 % of cases enters at the posterior end of the roof of the cavernous sinus ( CS ) --- ---Note the aperture for 3rd nerve & 4th nerve anterior & posterior to posterior petro-clival fold [ PPCF ] in 20 % at the lower surface of the TC (Lang 1995 )
  67. 67. The trochlear nerve is divided into 5 segments: cisternal, tentorial, cavernous, fissural ( in superior orbital fissure ) and orbital. The cisternal segment exits the midbrain and courses through the quadrigeminal and ambiens cisterns towards the TC. The tentorial segment starts when the nerve pierces the TC, usually posterior to the postero-lateral margin of the oculomotor triangle. This segment ends at the level of the anterior petroclinoid fold. This portion is in close relationship with the spheno-petro-clival venous gulf and the petrous apex (Iaconetta et al. 2012 ).
  68. 68. Endoscopic lateral skull base – 4th coming from posteriorly over the superior cerebellar artery [ in this picture has 2 branches
  69. 69. The superior cerebellar artery (SCA) and the trochlear nerve (IV) are well observed superior to the trigeminal nerve (V) – in accoustic neroma surgery by translabyrinthine approach
  70. 70. 4th nerve under tentorium in subtemporal approach after cutting the tentorium & lifting it , you are seeing 4th nerve insertion [ yellow arrow = REZ of 4th nerve ]
  71. 71. The TC [ tentorium cerebelli ], with the trochlear nerve inside, can be visualized passing inferiorly to the IIIcn. endoscopic transclival view
  72. 72. 1. In the posterior part of the CS the trochlear nerve is below the oculomotor nerve, while anteriorly it turns upward and becomes the most superior structure of the CS (at the level of the optic strut) (Iaconetta et al. 2012 ) . 2. Trochlear nerve is always superior to V1.
  73. 73. 1. In the posterior part of the CS the trochlear nerve is below the oculomotor nerve, while anteriorly it turns upward and becomes the most superior structure of the CS (at the level of the optic strut) (Iaconetta et al. 2012 ) . 2. Trochlear nerve is always superior to V1.
  74. 74. Observe 4th nerve in tentorium Cadaveric dissection image taken with a 30-degree endoscope following removal of the superior third of the clivus, visualizing the small trochlear nerve seen running along the tentorial membrane edge. BA, basilar artery; PCA, posterior cerebral artery; SCA, superior cerebellar artery; CN III, occulomotor nerve; CN IV, trochlear nerve; CN V, trigeminal nerve; TM, tentorial membrane; PComA, posterior communicating artery; MB, mamillary body.
  75. 75. (A) Intraoperative endoscopic close-up view showing the trigeminal nenre and the related neurovascular anatomy. a Trigeminal nerve (V). b Superior aspect of cerebellum. c Petrosal veins. d Petrous apex. e Dense araclmoid adhesions (post-Gamma KnifeX2). f Trochlear nerve (IV). g Brainstem. h Tentorium. i Tentorial incisura. From Prof.shahanian endoskull base book pg 127
  76. 76. 5th nerve
  77. 77. Trigeminal area at Cerebello Pontine Angle – along with my voice Click http://www.youtube.com/watch? v=YBqk4Jdnxic
  78. 78. Dv = Dandy’s vein
  79. 79. Dv = Dandy’s vein
  80. 80. 6th nerve (the snake nerve) 6th nerve originates above the VBJ [ vertebro-basillar junction ] – Prof. Amin Kassam
  81. 81. GL = Gruber’s ligament
  82. 82. The pontomedullary junction. 1. The exit zones of the hypoglossal and abducent nerves are at the same level [ same vertical line when view from Transclival approah ( through lower clivus ) ] 2. The abducent nerve exits from the pontomedullary junction, and ascends in a rostral and lateral direction toward the clivus. 6th nerve originates above the VBJ [ vertebro-basillar junction ] – Prof. Amin Kassam
  83. 83. 6th nerve origin is above or below AICA or has two rootlets of origin
  84. 84. Closer view of the inferior area of the left CPA, with tip of the endoscope between the acousticofacial nerve bundle and lower cranial nerves. PICA originating from the vertebral arterycan be seen forming a loop near the REZ of the facial nerve. AICA arises from the more medial basilar artery and traverses under the acousticofacial nerve bundle to supply the anterior surface of cerebellum. Abducens nerve (VI) is occasionally formed by two different nerve bundles as seen here.
  85. 85. 6th is appresiated in TA-II [ Transapical type II ] approach when 360 degrees IAC drilled
  86. 86. 6th nerve – enters the dorellos canal – Intradural course
  87. 87. 6th nerve – enters the dorellos canal – Intradural course clinical importance = Gradenigo Syndrome - Infection & inflammation of petrous apex involves 6th cranial nerve at the Dorello's canal and 5th cranial nerve in the Meckel's cave
  88. 88. The DMA is in close relationship with the abducens nerve at the level of petrous apex (Cavallo et al. 2011 ) . The DMA is the main feeder of the Dorello’s segment of Vicn (Martins et al. 2011 ) . DMA & 6TH NERVE DMA & 6TH NERVE
  89. 89. When we are doing clival chordoma we have to anticipate 6th nerve medial to paraclival carotid which is present in dorellos canal
  90. 90. Courtesy Dr. Tomasz Skibinski
  91. 91. The basilar artery (BA) can be seen very tortuous.
  92. 92. Cadaveric dissection of the middle third of the clivus with removal of the basilar plexus and exposing the dura. The abducens nerves (CN VI) can be seen bilaterally as they perforate the meningeal dura and become the interdural segments of CN VI. CS, cavernous sinus; PCA, paraclival carotid arteries; P, pituitary gland.
  93. 93. Note 1. Basillar artery is kinky , not always straight 2. observe bilateral hypoglossal canals Cadaveric dissection following the removal of the apical and alar ligaments, and the odontoid process has been drilled away (OP). This re veals the strong and thick transverse portion of the cruciform ligament (CL). Behind this is located the tectorial membrane (TM). ET, eustachian tube; SP, soft palate; HC, hypoglossal canal; VA, vertebral artery; BA, basilar artery.
  94. 94. Gulfar segment of 6th nerve (GS in left picture ) ( gVIcn in right picture ) - The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges-Coll et al. 2010 ). 6th nerve enters dorello’s canal between the meningeal layer of dura and the periosteal layer of dura (POD).
  95. 95. ICAc cavernous portion of the internal carotid artery, IPS inferior petrosal sinus, PAp petrous apex, SPCG sphenopetroclival gulf, cVIcn cisternal segment of the abducens nerve, gVIcn gulfar segment of the abducens nerve, pVIcn petrosal segment of the abducens nerve, white asterisks dura of the posterior cranial fossa – The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges-Coll et al. 2010 ).
  96. 96. 1. 6th N. crossing carotid at Petro-clival junction when viewing in lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve (VI) at the entrance of both [ 6th nerve & carotid ] structures into the cavernous sinus. 2. The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges-Coll et al. 2010 ).
  97. 97. 1. 6th N. crossing carotid at Petro-clival junction when viewing in lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve (VI) at the entrance of both [ 6th nerve & carotid ] structures into the cavernous sinus. 2. The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges-Coll et al. 2010 ).
  98. 98. L-OCR – Triangle 1. Upper boarder – Optic nerve & Opthalmic artery 2. Posterior boarder – Clinoidal carotid 3. Lower boarder – 3rd N. [ COM – Carotico-Occulomotor membrane seperates 3rd N from Clinoidal carotid ] [ 6th N. & 4th N. & V1 present inferior to 3rd N. ]
  99. 99. AICA anterior-inferior cerebellar artery, Cl clivus, CS cavernous sinus, ICAc cavernous portion of the internal carotid artery, IPS inferior petrosal sinus, LPMVN lateropontomesencephalic venous network, PBs pontine branches, PG pituitary gland, TPV transverse pontine vein, VA vertebral artery, VN vidian nerve (bordered in yellow ), Vcn trigeminal nerve, VIcn abducens nerve, yellow arrow cavernous portion of the abducens nerve
  100. 100. Blue arrow in Left picture ; * in Right picture - Gruber’s ligament
  101. 101. Usually, the IPS passes beneath the superior petro-sphenoidal ligament (l. of Gruber) with the abducens nerve. Anterior skull base Lateral skull base
  102. 102. From lateral skull base - The lateral aspect of the parasellar & paraclival carotid junction is crossed by the abducent nerve (VI)
  103. 103. Grubers ligament
  104. 104. 6th nerve passing below gruber’s ligament
  105. 105. ACP anterior clinoid process, APCF anterior petroclinoid fold, DS dorsum sellae, ICF interclinoid fold, PF pituitary fossa, PLL petrolingual ligament (inferior sphenopetrosal ligament), PPCF posterior petroclinoid fold, PS planum sphenoidale, SSPL superior sphenopetrosal ligament (Gruber’s ligament), TS tuberculum sellae, black asterisk middle clinoid process
  106. 106. 6th nerve is parallel to V1 – in the same direction of V1
  107. 107. Middle cranial fossa approach - 6th nerve is parallel to V1 – in the same direction of V1
  108. 108. 6th nerve is parallel to V1 – in the same direction of V1
  109. 109. http://www.slideshare.net/INUB/endoscopic-anatomy-and-approaches-of-the-cavernous-sinus- cadaver-study - Endoscopic view of the right cavernous sinus and neurovascular relations, demonstrating the ‘S’ shaped configuration formed by the oculomotor, the abducens and the vidian nerves. III oculomotor nerve, V1 ophthalmic nerve, V2 maxillary nerve, V3 mandibular nerve, VI abducens nerve, C clivus, ICA-Sa anterior bend of the internal carotid artery–parasellar segment, ICA-Sp posterior bend of the internal carotid artery–parasellar segment, ICA-C paraclival segment of the internal carotid artery, ICA-L lacerum segment of the internal carotid artery, ICA-P petrous segment of the internal carotid artery, PG pituitary gland, VC vidian canal, VN vidian nerve 6th nerve is parallel to V1 – in the same direction of V1
  110. 110. Upper part of S-shaped configuration – 3rd & 6th nerves. 6th nerve is freely hanging in the cavernous injury when compared to 3rd & 4th nerve – so postential for injury in tumor dissection
  111. 111. 7th nerve
  112. 112. Vertical part of 7th nerve bissects the jugular bulb
  113. 113. In 50% of the cases mastoid segment of Facial nerve travels lateral to level of annulus – This is important while removing the 1. EAC in temporal bone malignancy 2. while decompressing the nerve in malignant otitis externa 3. very careful in children Click http://www.youtube.com/ watch?v=f0cblTWJQ4k
  114. 114. 3rd GENU When facial nerve exists the temporal bone , the main trunk of the facial nerve is the perpendicular bisection of a line joining the cartilagenous pointer to the mastoid tip – some surgeons call this bend as 3rd genu.
  115. 115. Bottle neck concept – junction of labyrinthine & internal auditory canal facial nerve is narrow [ bottle neck ]
  116. 116. 7up- 7th is above Coca cola – cochlear n. is cola[=lower]
  117. 117. 9th nerve
  118. 118. A closer view of the pars nervosa of the jugular foramen. The glossopharyngeal nerve has its own dural porus, which is situated 0-3 mm upwards from the dural porus of the tenth cranial nerve. The vagus and the accessory nerve exit the posterior fossa together in a sleeve of dura through the jugular foramen. Left side. The 30° angled endoscope provides an overview of the inferior part of the CPA. On the right lies the acousticofacial nerve bundle, with the anterior inferior cerebellar artery; the glossopharyngeal nerve and the vagus nerve, as multiple filaments, form three to five major nerve bundles and the accessory nerve.
  119. 119. Note the bone (>, <) left to protect the dura from the drill. AC Supralabyrinthine air cells, CA Cochlear aqueduct, FN Facial nerve, SA Ampulla of the superior canal, V Vestibule Fig. 4.30 The internal auditory canal (IAC) has been identified, but the overlying bone needs to be thinned further. CA Cochlear aqueduct, FN Facial nerve, V Vestibule
  120. 120. Fig. 2.57 After rerouting the facial nerve and drilling away the fallopian canal of a left temporal bone, the cochlear aqueduct (CA) has been opened. The proximity of the glossopharyngeal nerve (IX) can be well appreciated. Since the nerve lies just inferior to the cochlear aqueduct, the latter is used as a landmark to the nerve in the translabyrinthine approach, indicating the lower limit of drilling in order to avoid injury to the glossopharyngeal nerve. ICA Internal carotid artery, JB Jugular bulb, SMF Stylomastoid foramen Retrosigmoid approach – observe 9th nerve near cochlear aqueduct [CA]
  121. 121. The cochlear aqueduct is a bony channel with a pyramidal shape connecting the perilymphatic space of the scala tympani in close proximity to the round window with the subarachnoid space at the level of the JF
  122. 122. Drilling has been carried out more inferiorly to identify the cochlear aqueduct (CA). Note the proximity of the aqueduct to the glossopharyngeal nerve (IX).
  123. 123. The bone overlying the transitional zone from the jugular bulb (JB) to the internal jugular vein (IJV) has been drilled away. The hook can be seen underneath the fibrous band covering the exit of the bulb from the bone. The jugulocarotid spine of bone (<) can be seen lying between the internal carotid artery (ICA) and the jugular bulb. * The fibrous band covering the entrance of the internal carotid artery into the temporal bone.
  124. 124. 9th nerve present between internal carotid & jugular bulb at carotid canal area[extra-cranially] View from anterior skull base approach View from Lateral skull base approach
  125. 125. 9th nerve – in cadaver
  126. 126. Jugular foramen area [ 9,10,11,12 nerves]
  127. 127. Superior & inferior ganglion of vagus at jugular foramen
  128. 128. Jugular tubercle [ JT ] , star = foramen lacerum
  129. 129. In the cerebello-medullary cistern the LCNs cross the posterior surface of the JT on their way to JF (Fernandez- Miranda et al. 2012 ). Trans-clival approach Retrosigmoid approach Lateral skull base approach
  130. 130. Note the relationship of clivus & jugular tubercle
  131. 131. Jugular tubercle [ JT ] AICA antero-inferior cerebellar artery, ASC anterior semicircular canal, BA basilar artery, HC hypoglossal canal, IAC internal acoustic canal, ICAh horizontal portion of the internal carotid artery, JT jugular tubercle, LCNs lower cranial nerves, LSC lateral semicircular canal, P pons, PICA postero-inferior cerebellar artery, PSC posterior semicircular canal, VIcn abducens nerve, VIIcn facial nerve, white arrow vestibolocochlear nerve
  132. 132. Jugular tubercle [ JT ] - Endoscopic endonasal views of the hypoglossal canal and nerve (extracranial segment) C1 atlas, Cl clivus, CS cavernous sinus, CV condylar vein, FCB fi brocartilago basalis, HC hypoglossal canal, ICAc cavernous portion of the internal carotid artery, ICAp parapharyngeal portion of the internal carotid artery, JT jugular tubercle, OC occipital condyle, XIIcn hypoglossal nerve, violet arrow atlanto-occipital joint
  133. 133. Exocranial & Endocranial views of Jugular Foramen : Within the JF area 2 venous compartement can be identified: a large postero- lateral_SIGMOID_venous channel and a small antero-medial_PETROSAL_venous channel which can receive the drainage of the inferior petrosal sinus (IPS). An intermediary neural compartment is located between the venous ones and houses lower cranial nerves (IX, X, XI). CC carotid canal, CR carotid ridge, ESF endolymphatic sac fossa, FS foramen spinosum, IAM internal acoustic meatus, JT jugular tubercle, OC occipital condyle, PCF petroclival fi ssure, SAF subarcuate fossa, SP styloid process, SSG sigmoid sinus groove, TB tympanic bone, VPTB vaginal process of the tympanic bone, white arrow intrajugular process of the temporal bone, red arrow external ori fi ce of the hypoglossal canal, violet arrow petroclival fi ssure, blue-sky arrow tubal isthmus, black arrow endocranial orifice of the hypoglossal canal, orange arrow trigeminal impression, green arrow pyramidal fossa, black asterisks intrajugular ridge, black circle intrajugularprocess of the occipital bone
  134. 134. The glossopharyngeal nerve has its own dural porus, which is situated 0- 3 mm upwards from the duralporus of the tenth cranial nerve. The vagus and the accessory nerve exit the posterior fossa together in a sleeve of dura through the jugular foramen.
  135. 135. The glossopharyngeal and vagus nerves are well identified in the cerebellomedullary cistern before entering the jugular foramen.
  136. 136. Jugular fossa is just lateral to hypoglossal canal
  137. 137. The jugular bulb lies beneath the fl oor of the middle ear cavity (Roche et al. 2008 ) . It can be of variable shape and size. All the lower cranial nerves ( LCNs ) exit the foramen anteromedially to the jugular bulb, separated from it by connective tissue. The superior ganglion of the vagus nerve is within the jugular foramen ( JF ). At the level of the intraforaminal course, there is a strict connection between the LCNs. The vagus nerve exits the JF vertically, behind IXcn and ICAp (Roche et al. 2008 ) and gives its inferior ganglion on the outer skull base surface. The accessory nerve lies immediately lateral to the vagus nerve. CR carotid ridge, DM digastric muscle (posterior belly), ICAp parapharyngeal portion of the internal carotid artery, IJV internal jugular vein, JB jugular bulb, MMA middle meningeal artery, VIIcn facial nerve, IX glossopharyngeal nerve, X vagus nerve, XI accessory nerve, XII hypoglossal nerve, black arrow inferior ganglion of vagus nerve
  138. 138. When they exit from the skull base, the glossopharyngeal nerve is the most lateral, while the hypoglossal nerve is the most medial. The glossopharyngeal nerve crosses the internal carotid artery shortly after exiting the skull base.Thehypoglossal nerve turns inferiorly to run together with the vagus nerve for a short distance in the upper neck (Fig. 8.4).
  139. 139. The glossopharyngeal nerve is seen crossing the internal carotid artery. More inferiorly, the hypoglossal nerve crosses the artery and passes anteriorly. The vagus nerve is seen coursing between the internal jugular vein and the internal carotid artery. The accessory nerve crosses anterolateral to the internal jugular vein and travels posteriorly (Fig. 8.5). Mneumonic = 9th N. & 12th N. supplies tongue , so 9th N & 12th N. goes anteriorly , 9th N. is superiorly & 12th N. inferiorly crossing carotid . 11th N is for shrugging of shoulders so goes posteriorly , 10th goes down to diaphragm
  140. 140. In about half the cases, the accessory nerve crosses posteromedial to the internal jugular vein. In all cases, it passes anterolateral to the transverse process of the atlas. Note the close relation between the vertebral artery and the internal jugular vein. In extensive cases of posteriorly located glomus tumors, the vertebral artery may be involved (Fig. 8.6).
  141. 141. In 50% cases 11th nerve crosses antero-lateral & in 50% cases postero-medial to upper part of IJV Antero-lateral crossing to IJV Postero-medial crossing to IJV
  142. 142. 11th nerve
  143. 143. 11th nerve behind left vertebral artery at cervico-medullary junction – listen lecture at 23.25 min in this Prof. Amin Kassam video https://www.youtube.com/watch?v=QoMCqwJ6Ke0 Through anterior skull base approach Through endoscopic lateral skull base approach – The entrance of the vertebral artery is the boundary between the foramen magnum and the spinal part of the accessory nerve.
  144. 144. The accessory nerve (XI) is closely related to the vertebral artery (VA) at the point of dural entrance. Note the dura attached to the artery at this level. Endoscopic lateral skull base approach
  145. 145. The accessory nerve (XI) is closely related to the vertebral artery (VA) at the point of dural entrance. Note the dura attached to the artery at this level. In far lateral approach
  146. 146. C2 nerve root below the 11th nerve in posterior triangle clearance in SLD the C2 nerve root is seen crossing the vertebral artery (VA).
  147. 147. In 50% cases 11th nerve crosses antero-lateral & in 50% cases postero-medial to upper part of IJV Antero-lateral crossing to IJV Postero-medial crossing to IJV
  148. 148. 12th nerve
  149. 149. MINIMALLY INVASIVE RETROSIGMOID APPROACH (MIRA) - Port of entry to Endoscopic Lateral Skull Base
  150. 150. The pontomedullary junction. 1. The exit zones of the hypoglossal and abducent nerves are at the same level [ same vertical line when view from Transclival approah ( through lower clivus ) ] 2. The abducent nerve exits from the pontomedullary junction, and ascends in a rostral and lateral direction toward the clivus.
  151. 151. A closer view of the anterior border of the pontomedullary stem and the vertebral artery junction and origin of the basilar artery. Perforating arteries arise from the vertebral and basilar arteries. The endoscope is focusing on the hypoglossal nerve area. The posterior inferior cerebellar artery arises from the vertebral artery in the background, and runs between the two bundles of the hypoglossal nerve.
  152. 152. Fig. 26a, b Right side. The root fibers of the hypoglossal nerve (12) collect in two bundles, which pierce the dura in two dural pori. The hypoglossal nerve is situated more anteriorly and medially than the root fibers of the lower cranial nerves. The arterial relationship is the vertebral artery, with perforating arteries to the brain stem. The curved vertebral artery displaces and stretches the hypoglossal nerve fibers.
  153. 153. 90 degree turn of 12th nerve medial to medial wall of jugular bulb – Dr.Satish Jain
  154. 154. ITFA with Transcondylar [ = TC ] Transtubercular [ = TT ] approach Here Transcondylar is through Occipital Condyle ; Transtubercular is through Jugular tubercle & lateral pharyngeal tubercle
  155. 155. Endoscopic endonasal view of a cadaveric dissection showing transection of the right eustachian tube (ET) attachment to foramen lacerum (FL). The hypoglossal nerve (XII) enters the hypoglossal canal just deep to the ET and separates the occipital condyle (OC) and the jugular tubercle (JT). (BA, basilar artery; ICA, internal carotid artery [paraclival segment]; IPS, inferior petrosal sinus; VN, vidian nerve.) B. Endoscopic endonasal view of cadaveric dissection showing the parapharyngeal internal carotid artery (ICA) and jugular foramen (JF) following transection and removal of the eustachian tube. (BA, basilar artery; IPS, inferior petrosal sinus; FL, foramen lacerum; JT, jugular tubercle; OC, occipital condyle; XII, hypoglossal nerve.)
  156. 156. Note 12th nerve in between JT ( Jugular tubercle ) & OC ( Occipital condyle ) in both lateral & anterior skull base Lateral skull base Anterior skull base
  157. 157. The accessory nerve (XI) is closely related to the vertebral artery (VA) at the point of dural entrance. Note the dura attached to the artery at this level. Endoscopic lateral skull base approach
  158. 158. Through endoscopic lateral skull base - The curved vertebral artery displaces and stretches the hypoglossal nerve fibers. Through anterior skull base
  159. 159. Through lateral skull base - The curved vertebral artery displaces and stretches the hypoglossal nerve fibers. Through lateral skull base - The opposite vertebral artery exits from the dural porus and stretches /raises the hypoglossal nerve.
  160. 160. HC = hypoglossal canal , JT= Jugular Tubercle
  161. 161. SCG = Supracondylar groove – is an important landmark to hypoglossal canal
  162. 162. Jugular fossa is just lateral to hypoglossal canal
  163. 163. Hypoglossal canals From front – through nose From back
  164. 164. Coronal cut – hypoglossal canal
  165. 165. Hypoglossal nerve in relation to vertebral artery
  166. 166. 1. The SCG [Supracondylar groove] represents a reliable landmark for hypoglossal canal (HC) identification (red arrow) (Morera et al. 2010 ) . 2. The HC divides the condylar region into the tubercular compartment (superior) and the condylar compartment (inferior). Tubercular compartment contains LPT lateral pharyngeal tubercle, PT pharyngeal tubercle,
  167. 167. Transoral approach to SUPERO-MEDIAL Parapharyngeal tumors – incision anterior to anterior pillar of tonsil
  168. 168. Cadaveric dissection image showing the hypoglossal nerve exiting the hypoglossal foramen with its corresponding vein that communicates the internal jugular vein with the basilar plexus. HC, hypoglossal canal; CN XII, hypoglossal nerve and rootlets; FM, foramen magnum; VA, vertebral artery; PICA, posterior inferior cerebellar artery; BA, basilar artery; CN X, vagus nerve.
  169. 169. Note 1. Basillar artery is kinky , not always straight 2. observe bilateral hypoglossal canals Cadaveric dissection following the removal of the apical and alar ligaments, and the odontoid process has been drilled away (OP). This re veals the strong and thick transverse portion of the cruciform ligament (CL). Behind this is located the tectorial membrane (TM). ET, eustachian tube; SP, soft palate; HC, hypoglossal canal; VA, vertebral artery; BA, basilar artery.
  170. 170. IPS & HVP hypoglossal venous plexus Cadaveric dissection image showing the hypoglossal nerve exiting the hypoglossal foramen with its corresponding vein that communicates the internal jugular vein with the basilar plexus
  171. 171. Far lateral approach – photo from 3D Neuroanatomy medical atlas http://www.3dneuroanatomy.com
  172. 172. Hypoglossal is just behind the upper end of parapharyngel carotid – very easy way to identify 12th nerve in paraphayrngeal space – Dr.Satish jain
  173. 173. In infrapetrous approach there are chances of injury to 6th nerve [ in dorello’s canal medial to paraclival carotid ] & 12th nerve
  174. 174. The hypoglossal nerve exits from the hypoglossal canal medial to the ICAp. It lies posteriorly to the vagus nerve and passes laterally between the internal jugular vein and ICAp. The hypoglossal nerve is usually accompained, within the hypoglossal canal, by an emissary vein and arterial branches from ascending pharyngeal artery and occipital artery. C1 atlas, Cl clivus, CS cavernous sinus, CV condylar vein, FCB fi brocartilago basalis, HC hypoglossal canal, ICAc cavernous portion of the internal carotid artery, ICAp parapharyngeal portion of the internal carotid artery, JT jugular tubercle, OC occipital condyle, XIIcn hypoglossal nerve, violet arrow atlanto-occipital joint
  175. 175. Endoscopic endonasal view of a cadaveric dissection showing transection of the right eustachian tube (ET) attachment to foramen lacerum (FL). The hypoglossal nerve (XII) enters the hypoglossal canal just deep to the ET and separates the occipital condyle (OC) and the jugular tubercle (JT). (BA, basilar artery; ICA, internal carotid artery [paraclival segment]; IPS, inferior petrosal sinus; VN, vidian nerve.) B. Endoscopic endonasal view of cadaveric dissection showing the parapharyngeal internal carotid artery (ICA) and jugular foramen (JF) following transection and removal of the eustachian tube. (BA, basilar artery; IPS, inferior petrosal sinus; FL, foramen lacerum; JT, jugular tubercle; OC, occipital condyle; XII, hypoglossal nerve.)
  176. 176. 12th nerve bissecting internal & external carotid
  177. 177. COMBINED APPROACHES 1. Retrolabyrinthine Subtemporal Transapical Approach 2. Retrolabyrinthine Subtemporal Transtentorial Approach Retrolabyrinthine Subtemporal Transapical Approach Retrolabyrinthine Subtemporal Transtentorial Approach
  178. 178. A view of the cerebellopontine angle through the retrolabyrinthine approach Note the narrow field and limited control. Posterior fossa dura (PFD) structures exposed through the standard retrolabyrinthine approach. A view of the posterior fossa dura through the combined retrolabyrinthine subtemporal transapical approach.
  179. 179. The middle fossa dura has been cut. The oculomotor nerve (III) is clearly seen. With more retraction of the temporal lobe and the tentorium (*), the optic nerve (II) is seen.
  180. 180. Retrolabyrinthine Subtemporal Transapical (Transpetrous Apex) Approach Schematic drawing showing the incision to be performed. A retrolabyrinthine approach is performed.
  181. 181. The dura of the middle fossa is detached from the superior surface of the temporal bone from posterior to anterior. With further detachment of the dura, the middle meningeal (MMA) artery is clearly identified.
  182. 182. The middle meningeal artery (MMA) and the three branches (V1, V2, V3) of the trigeminal nerve are identified. View after cutting the middle meningeal artery (MMA) and the mandibular branch of the trigeminal nerve (V).
  183. 183. The internal auditory canal (IAC) is identified. A large diamond burr is used to drill the petrous apex.
  184. 184. The petrous apex has been drilled. The internal carotid artery (ICA) is identified. At higher magnification, the abducent nerve (VI) is identified at the level of the tip of the petrous apex (PA).
  185. 185. Panoramic view showing the structures after opening of the posterior fossa dura. At higher magnification, the anterior inferior cerebellar artery (AICA)is seen stemming from the basilar artery (BA) at the prepontine cistern. The artery is crossed by the abducent nerve (VI). Note the good control of the prepontine cistern through this approach.
  186. 186. Tilting the microscope downward, the lower cranial nerves are well seen.
  187. 187. Retrolabyrinthine Subtemporal Transtentorial Approach The retrolabyrinthine craniotomy has been performed. The petrous apex has been partially drilled. The middle fossa dura (*) is incised.
  188. 188. The tentorium (*) is cut, taking care not to injure the trochlear nerve. The tentorium is further cut until the tentorial notch is reached. With retraction of the temporal lobe the optic (II), oculomotor (III) and contralateral oculomotor (IIIc) nerves are seen.
  189. 189. Branches of the trigeminal nerve (V1, V2, V3) at the level of the lateral wall of the cavernous sinus.
  190. 190. After this PPT must read “REZ 360” . Click http://www.slideshare.net/muralichandnal lamothu/rez-360
  191. 191. 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 for downloading.

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