Petrous apex 360°

1. Petrous apex 360° 27-10-2015

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. 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. Approaches to petrous apex LATERAL SKULL BASE From above the labyrinth Middle cranial fossa transpetrous [ = Trans-apical ] approach From posterior to the labyrinth Retrolabyrinthine transpetrous [ = Trans-apical ] approach / endoscopic retrolabyrinthine approach From through the labyrinth Translabyrinthine transpetrous [ = Trans-apical ] approach Transcochlear transpetrous [ = Trans-apical ] approach From below the labyrinth Infralabyrinthine /Infra- otic = Infratemporal fossa type A transpetrous [ = Trans-apical ] approach POTS Infralabyrinthine /Infra- otic = Infratemporal fossa type B & C transpetrous [ = Trans-apical ] approach ANTERIOR SKULL BASE 1. From anterior to the labyrinth Suprapetrous approach Infrapetrous approach

5. Lateral skull base view

6. Middle cranial fossa transpetrous approach

7. Retrolabyrinthine transpetrous approach – dotted red line means trajectory medial to labyrinth & cochlea

8. Tranaslabyrinthine Transpetrous [= Transapical ] approach After drilling the LSC , PSC & SSC – IAC is exposed Transpetrous path is above & below the IAC & medial to cochlea

9. The Enlarged Translabyrinthine Approach with Transpetrous ( = Transapical ) Extension – intradurally above the IAC you will get 5 th nerve where below the IAC you will get 6 th nerve & lower cranial nerves . Schematic drawings showing the amount of bone removal around the internal auditory canal in the different variants of the translabyrinthine approach. Note that in the transapical modification the exposure is 320° and about 360° in types I and II, respectively. Abbreviations as in Fig. 5. 1 . cn , cranial nerve; CN , cochlear nerve; FN , facial nerve; IV , inferior vestibular nerve; SV , superior vestibular nerve.

10. Transcochlear transpetrous approach

11. Infratemporal fossa approach –A & B Transpetrous approach

12. POTS = Petro-occipital trans-sigmoid approach – sigmoid sinus is opened – dotted red line means trajectory medial to labyrinth & cochlea

13. Anterior skull base – suprapetrous & infrapetrous approach

14. The Petrous pyramid has only 3 surfaces unlike E gypt pyramid which has 4 surfaces

15. 3 surfaces 2 upper surfaces 1 basal surface

16. The  petrous portion  of the temporal bone or   pyramid  is pyramidal 

17. Petrous apex = Anterior Triangular ( T ) area + Posterior Quadrangular ( Q ) area

18. Petrous apex = Anterior Triangular ( T ) area + Posterior Quadrangular ( Q ) area

19. Approach through posterior Quadrangular ( Q ) area = Kawase approach or Anterior Transpetrosal approach – click http://aiimsnets.org/AnteriorTranspetrosalapproach.asp #

20. Superior view of the right petroclival area: see the relationships between the petrous apex, the Vth nerve, and the petroclival area. VI 6th Cranial nerve; PCa posterior cerebral artery; RCP right cerebral peduncle; SCA superior cerebellar artery; CO cochlea; GG gasserian ganglion; PCA petrous carotid artery; IPS inferior petrosal sinus; AFB acousticofacial bundles

21. Superior view of a right middle cranial fossa following drilling and dissection of the petrous bone: see the right tympanic cavity, and its relationships. GG Gasserian ganglion; ET Eustachian tube; PCA petrous carotid artery; IPS inferior petrosal sinus; V 5th cranial nerve; PN petrosal nerve; CO cochlea; G geniculate ganglion; CN cochlear nerve; FN facial nerve; ETE Eustachian tube entrance; M malleus; U uncus ; SSCC superior semicircular canal; LSCC lateral semicircular canal; SPS superior petrosal sinus

22. Quadrangular part boarders

23. Petrous apex – Triangular area Petrous apex – Quadrangular area

24. Quadrangular ( Q ) space in anterior skull base – where petrous apex is seen – Supra-petrous approach – space between laceral carotid & Trigeminal ganglion & V3

25. Quadrangular ( Q ) space – where petrous apex is seen – Supra-petrous approach – space between laceral carotid & Trigeminal ganglion & V3 Quadrangular ( Q ) area in middle cranial fossa Quadrangular ( Q ) space in anterior skull base approach

26. Quadrangular ( Q ) space – where petrous apex is seen – Supra-petrous approach – space between laceral carotid & Trigeminal ganglion & V3 Quadrangular ( Q ) area in middle cranial fossa Quadrangular ( Q ) space in anterior skull base approach

27. JT = Jugular Tubercle – Below this tubercle is hypoglossal canal & above is Internal Jugular foramen

28. IPS & HVP hypoglossal venous plexus

29. Petrous apex - Quadrangular area

30. Middle cranial fossa approach

31. the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing. http:// www.worldneurosurgery.org/article/S0090-3019(00)00271-8/fulltext

32. The middle fossa retractor is fixed at the petrous ridge (PR). AE Arcuate eminence, GPN Greater petrosal nerve, M Middle meningeal artery The expected location of the internal auditory canal (IAC). The bar-shaded areas are the locations for drilling. A Anterior, AE Arcuate eminence, GPN Greater petrosal nerve, MMA Middle meningeal artery, P Posterior

33. Approaches to petrous apex LATERAL SKULL BASE From above the labyrinth Middle cranial fossa transpetrous [ = Trans-apical ] approach From posterior to the labyrinth Retrolabyrinthine transpetrous [ = Trans-apical ] approach / endoscopic retrolabyrinthine approach From through the labyrinth Translabyrinthine transpetrous [ = Trans-apical ] approach Transcochlear transpetrous [ = Trans-apical ] approach From below the labyrinth Infralabyrinthine /Infra- otic = Infratemporal fossa type A transpetrous [ = Trans-apical ] approach POTS Infralabyrinthine /Infra- otic = Infratemporal fossa type B & C transpetrous [ = Trans-apical ] approach ANTERIOR SKULL BASE 1. From anterior to the labyrinth Suprapetrous approach Infrapetrous approach

34. Middle cranial fossa Transpetrous ( = Transapical )

35. A right-sided skin incision for the middle cranial fossa approach.

36. The skin and subcutaneous tissues have been elevated as one flap .

37. The temporalis fascia has been harvested and the temporalis muscle cut using monopolar diathermy.

38. The temporalis muscle and periosteum have been elevated as one flap.

39. The craniotomy has been performed using a small drill.

40. The craniotomy flap has been elevated and the middle fossa ( MFD ) can be seen. The branches of the trigeminal nerve ( V1 , V2 , V3 ) can be identified at the anterior part of the approach.

41. The Fukushima middle cranial fossa retractor has been applied to maintain the elevated dura . Three-quarters of the canal circumference is skeletonized, leaving a thin shell of bone over it.

42. The different areas of access for the middle fossa approaches. a Classic middle fossa approach to the internal auditory canal. b Enlarged middle fossa approach for tumor removal. c−e The middle fossa transpetrous approach.

43. The landmarks for the internal auditory canal (arrow) in middle fossa approach. AE , arcuate eminence; gspn , greater superficial petrosal nerve ; MMA , middle meningeal artery. A schematic representation of the position of the internal audi tory canal in middle cranial fossa approach. EAC , external auditory canal; IAC , internal auditory canal; SSC , superior semicircular canal; SPS , superior petrosal sinus.

44. An anatomical dissection carried out through the middle fossa, illustrating the relationships between the various structures in this area. A closer view of the lateral end of the internal auditory canal.

45. The posterior rhomboidal area ( Q ) of the anterior petrous apex. The anterior triangular area has been uncovered by sectioning the mandibular nerve ( V3 ) and reflecting the gasserian ganglion.

46. The amount of circumferential exposure of the internal auditory canal near the fundus is only 180°. Kawase approach The quadrangular area of the petrous apex anterior to the internal auditory canal is drilled and the horizontal segment of the internal carotid artery ( ICA ) is exposed.

47. the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing. http:// www.worldneurosurgery.org/article/S0090-3019(00)00271-8/fulltext

48. Videos of kawase approach or Anterior Transpetrosal approach – click http://aiimsnets.org/AnteriorTranspetrosalapproach.asp #

49. The whole length of the horizontal portion of the internal carotid artery ( ICA ) is exposed up to the anterior foramen lacerum ( AFL ). The dura is opened by creating an inferiorly based flap, the dashed lines.

50. Surgical Anatomy after Opening of the Dura The middle fossa transpetrous approach.

51. The anterior inferior cerebellar artery is seen looping around the acousticofacial bundle ( AFB ). At a higher magnification a prominent flocculus ( Fl ) is observed.

52. The distal part of the vertebral artery ( VA ) can be seen. The distal part of the vertebral artery ( VA ) can be seen.

53. After removing the remaining bone of the petrous apex, the basilar artery ( BA ) can be seen in the prepontine cistern. Opening the dura of the middle cranial fossa exposes the third nerve ( III ) and intracavernous portion of the internal carotid artery ( ICA ).

54. A closer view at the level of the fundus of the internal auditory canal. The facial nerve lies anteriorly and superiorly. The vestibular nerve posteriorly is separated from the facial nerve by a plane of cleavage. The cochlear nerve is located inferior to the facial nerve. The cochlear nerve travels along an inferior course in the internal auditory canal. Inferior to the vestibular nerve at the porus acusticus , it becomes inferior to the facial nerve at the lateral end of the internal auditory canal. There is a labyrinthine artery coursing between the cochlear and facial nerves.

55. A closer view at the level of the porus acusticus . The anterior inferior cerebellar artery forms a vascular loop and gives off labyrinthine arteries, which fix the contact between the artery and the inferior surface of the acousticofacial nerve bundle at the inferior lip of the meatus.

56. The root exit zone of the facial nerve is anterior to the root of the cochlear nerve and superior to the rootlets of the lower cranial nerves. 7 Facial nerve 8 Vestibulocochlear nerve 9 Glossopharyngeal nerve 10 Vagus nerve AICA Anterior inferior cerebellar artery IAC Internal auditory canal PICA Posterior inferior cerebellar artery

57. The pontobulbar junction and the roots of the lower cranial nerves are visualized. The loop of the posterior inferior cerebellar artery is seen in the background.

58. Right enlarged middle fossa approach. The internal auditory canal has been opened, revealing the acousticofacial Perve bundle contained within it. The facial nerve runs anteriorly, and the superior vestibular nerve lies posteriorly. The loop of the anterior inferior cerebellar artery runs near the Meatus, below the acousticofacial nerve bundle.

59. Lateral view of CP angle

60. Posterior view of CP angle 1. level 1 = Trigeminal area 2. Level 2 = AFB area 3. Level 3 = Lower cranial nerve area 4. Level 4 = Foramen magnum area

61. Various Transpetrous approaches to get lateral view of CP angle ( = to reach Lateral part of Posterior cranial fossa dura ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area Retrolabyrinthine Transpetrous ( = Transapical ) Translabyrinthine Transpetrous ( = Transapical ) Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 3 = Lower cranial nerve area POTS = Petro-Occipital Trans-Sigmoid approach Infralabyrinthine Transpetrous ( = Transapical ) -- which is nothing but IFTA-A , PONS , IFTA-B Transpetrous approach [ IFTA-A,B = Infratemporal fossa approach A , B / PONS = petro-occipital trans-sigmoid approach ] predominently to reach Level 4 = Foramen magnum area 6. Exrtreme lateral or Far lateral or Transcondylar approach

62. Photograph of a cadaveric dissection showing an overview of the temporal bone and depicting the posterior surface of the petrous part. The sphenoid bone, which articulates anteriorly with the petrous and squamous temporal bone, has been removed in this specimen. The pyramidal petrous part, located between the sphenoid and occipital bones, has a base, apex, and three surfaces. The sigmoid sinus descends along the posterior surface of the mastoid part and turns anteriorly toward the jugular foramen. The posterior transpetrosal approaches involve progressive degrees of resection of the petrous temporal bone. The retrolabyrinthine (green outline) dissection exposes the area between the superior petrosal sinus, the sigmoid sinus, and the posterior semicircular canal. The translabyrinthine approach (pink outline) extends more anteriorly to remove all three semicircular canals and to expose the anterior wall of the IAC. The transcochlear (blue outline) dissection extends even more anteriorly to the petrous apex, resulting in an almost complete petrosectomy with the widest and most direct exposure of all the posterior transpetrosal approaches. PET. = petrous/ petrosal ; POST. = posterior; RETROLAB = retrolabyrinthine ; S.C. = semicircular canal; SIG. = sigmoid; SUP. = superior; TRANSLAB = translabyrinthine .

63. Middle cranial fossa Transpetrous approach - the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing. http:// www.worldneurosurgery.org/article/S0090-3019(00)00271-8/fulltext

64. Retrolabyrinthine Transpetrous ( = Transapical )

65. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area ================================================== Infralabyrinthine Transpetrous ( = Transapical ) -- which is nothing but IFTA-A , PONS , IFTA-B Transpetrous approach [ IFTA-A,B = Infratemporal fossa approach A , B / PONS = petro-occipital trans-sigmoid approach ] Predominently to reach Level 3 = Lower cranial nerve area

66. COMBINED APPROACHES Retrolabyrinthine Transpetrous ( = Transapical ) Subtemporal Approach Retrolabyrinthine Transpetrous ( = Transapical ) Subtemporal Transtentorial Approach Retrolabyrinthine Subtemporal Transapical Approach Retrolabyrinthine Subtemporal Transtentorial Approach

67. 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.

68. 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.

69. Retrolabyrinthine Subtemporal Transapical ( Transpetrous Apex) Approach Schematic drawing showing the incision to be performed. A retrolabyrinthine approach is performed.

70. 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.

71. 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 ).

72. The internal auditory canal ( IAC ) is identified. A large diamond burr is used to drill the petrous apex.

73. 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 ).

74. 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.

75. Tilting the microscope downward, the lower cranial nerves are well seen.

76. Retrolabyrinthine Subtemporal Transtentorial Approach The retrolabyrinthine craniotomy has been performed. The petrous apex has been partially drilled. The middle fossa dura ( * ) is incised.

77. 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.

78. Branches of the trigeminal nerve ( V1 , V2 , V3 ) at the level of the lateral wall of the cavernous sinus.

79. Endoscopic Retrolabyrinthine approach – The retrolabyrinthine approach consists of a small posterior fossa craniotomy, between the sigmoid sinus and the otic capsule. It provides limited exposure of the posterior fossa, confined to the region of the entry zone of the trigeminal nerve and acousticofacial nerve bundle. More lateral structures, such as the porus acusticus and the internal auditory canal, cannot be visualized directly, since they are blocked by the otic capsule. In order to reach and inspect the interna ) auditory canal, it is necessary first to enlarge the approach posteriorly, removing the bone overlying the sigmoid sinus and 1-2 cm of the retrosigmoid occipital bone; and secondly, to use the endoscopic procedure .

80. Translabyrinthine Transpetrous ( = Transapical )

81. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area ================================================== Infralabyrinthine Transpetrous ( = Transapical ) -- which is nothing but IFTA-A , PONS , IFTA-B Transpetrous approach [ IFTA-A,B = Infratemporal fossa approach A , B / PONS = petro-occipital trans-sigmoid approach ] Predominently to reach Level 3 = Lower cranial nerve area

82. The Enlarged Translabyrinthine Approach with Transpetrous ( = Transapical ) Extension – intradurally above the IAC you will get 5 th nerve where below the IAC you will get 6 th nerve & lower cranial nerves . Schematic drawings showing the amount of bone removal around the internal auditory canal in the different variants of the translabyrinthine approach. Note that in the transapical modification the exposure is 320° and about 360° in types I and II, respectively. Abbreviations as in Fig. 5. 1 . cn , cranial nerve; CN , cochlear nerve; FN , facial nerve; IV , inferior vestibular nerve; SV , superior vestibular nerve.

83. Drilling inferior to the right internal auditory canal ( IAC ). Further extensive drilling inferior to the internal auditory canal ( IAC ) toward the petrous apex.

84. Bone removal superior and inferior to the internal auditory canal (arrows). Further drilling of the petrous apex and clivus .

85. Extensive bone removal inferior and superior to the internal auditory canal ( IAC ). Bone superior to the canal ( * ) is still to be removed. The whole contents of the internal auditory canal ( IAC ) are pushed inferiorly to allow removal of the remaining bone ( * ) superior to the canal.

86. The whole contents of the canal are displaced inferiorly to show the extent of bone removal. The anterior wall of the canal can also be drilled if needed. Schematic drawing showing the technique and extent of bone removal in the type I (green line) and type II (red line) transapical extension . F , facial nerve; C , cochlear nerve; Vs , superior vestibular nerve ; Vi , inferior vestibular nerve.

87. Schematic drawing showing the technique and extent of bone removal in the type I (green line) and type II (red line) transapical extension. F, facial nerve; C, cochlear nerve; Vs , superior vestibular nerve; Vi, inferior vestibular nerve.

88. General view of the structures in the cerebellopontine angle after opening the dura . Note the enhanced exposure of the angle and the excellent exposure of the trigeminal nerve ( V ). The trigeminal nerve ( V ) is pushed superiorly. The basilar artery ( BA ) in the prepontine cistern can be seen well.

89. With more traction of the tentorium, a panoramic view of the structures in the angle is available. The trochlear nerve ( IV ) is seen before piercing the tentorium to gain access to the middle fossa.

90. Transcochlear Transpetrous ( = Transapical )

91. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area ================================================== Infralabyrinthine Transpetrous ( = Transapical ) -- which is nothing but IFTA-A , PONS , IFTA-B Transpetrous approach [ IFTA-A,B = Infratemporal fossa approach A , B / PONS = petro-occipital trans-sigmoid approach ] Predominently to reach Level 3 = Lower cranial nerve area

92. An extended mastoidectomy , labyrinthectomy , identification of the internal auditory canal, and drilling of the cochlea has been performed. The facial nerve ( FN ) has been skeletonized. The facial nerve ( FN ) has been skeletonized.

93. Using a diamond burr to uncover the labyrinthine segment of the facial nerve ( FN ). The facial nerve ( FN ) is completely uncovered. Note Bill’s bar ( BB ) separating the nerve from the superior vestibular nerve ( SVN ) at the level of the fundus of the internal auditory canal.

94. Identification of the greater superficial petrosal nerve ( gspn ). The greater superficial petrosal nerve is ( gspn ) cut.

95. The geniculate ganglion ( GG ) and the labyrinthine portion of the facial nerve ( FN ) are elevated. The tympanic segment is freed.

96. A beaver knife is used to free the mastoid segment. The superior vestibular nerve ( SVN ) is detached from its attachment.

97. The whole contents of the internal auditory canal are transposed posteriorly with the facial nerve ( FN ). New position of the facial nerve ( FN ) after posterior rerouting

98. Removal of the fallopian canal with a rongeur .

99. Surgical Anatomy after Opening the posterior cranial fossa dura Drilling of the cochlea ( Co ). Drilling of the petrous apex ( PA ).

100. View after complete performance of the approach. The dashed lines represent the dural incision. View after opening the dura , showing excellent control of the basilar artery ( BA ) and prepontine cistern.

101. Tilting the microscope downward, both the ipsilateral ( VA ) and contralateral ( VAc ) vertebral arteries come into view. With a slight retraction of the middle fossa dura , the origin of the superior cerebellar artery at the basilar artery ( BA ) can be seen. Note the excellent control of the trigeminal nerve ( V ).

102. Lilliquits membrane present over the basillar artery & 3 rd N. origin area

103. Mild retraction of the tentorium ( Ten ) provides a good view of the oculomotor nerve ( III ) and its relation to the superior cerebellar artery ( SCA ) lying inferiorly and the posterior cerebral artery ( PCA ) lying superiorly. The trochlear nerve ( IV ) is seen running on the undersurface of the tentorium. Meckel’s cave ( MC ) can be opened when necessary.

104. 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

105. Infratemporal fossa approach type A [ IFTA-A ] – transpetrous approach There is no need to transpose facial nerve in ITFA-A – Dr. Morwani

106. The structures that impede the lateral access to the lower skull base, namely, the facial nerve ( FN ), the styloid process and attached muscles and ligaments, and the posterior belly of the digastric. ICA , internal carotid artery; IJV , internal jugular vein. The mastoid segment of the facial nerve ( FN ) is centered on the jugular bulb ( JB ).

107. The facial nerve ( FN ) is skeletonized from the geniculate ganglion to the stylomastoid foramen. The mastoid tip is removed, cutting the tough attachments with strong scissors. (Arrow points at the new fallopian canal.)

108. Anterior transposition of the facial nerve ( FN ). (Arrow points at the new fallopian canal.) The tympanic bone (black double arrows) is still to be drilled. The transposed facial nerve (white arrow) is seen in its new canal.

109. The styloid process ( StP ) and attached structures are severed. The tympanic bone (arrowheads) is drilled. The transposed facial nerve is seen in its new canal.

110. Using a large diamond drill, the vertical intrapetrous internal carotid artery is identified. Drilling the petrous apex medial to the internal carotid artery ( ICA ) to remove all the infiltrated bone . The close relation of the cochlea ( Co ) to the internal carotid artery ( ICA ). The close relation of the cochlea ( Co ) to the internal carotid artery ( ICA ).

111. The petrous apex is already drilled. Tumor is still attached to the internal carotid artery. The anterior wall of the external auditory canal is drilled, allowing better control of the internal carotid artery ( ICA ).

112. The petrous apex is now free of tumor. The vertical intrapetrous internal carotid artery has been liberated. Note the tumor ( T ) surrounding the artery. The internal jugular vein is double ligated, cut, and elevated with the attached tumor. The posterior fossa dura ( PFD ) is exposed. The remaining tumor ( T ) is still to be removed. The opened sigmoid sinus ( SS ) can be seen.

113. The tumor ( T ) is seen surrounding the intrapetrous internal carotid artery ( ICA ).

114. POTS = Petro-Occipital Trans-sigmoid approach

115. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area ================================================== Infralabyrinthine Transpetrous ( = Transapical ) -- which is nothing but IFTA-A , PONS , IFTA-B Transpetrous approach [ IFTA-A,B = Infratemporal fossa approach A , B / PONS = petro-occipital trans-sigmoid approach ] Predominently to reach Level 3 = Lower cranial nerve area

116. The C-shaped skin incision. A skin flap is raised.

117. A U-shaped musculoperiosteal flap is outlined.

118. Bone exposure. Note that no retractors are used. The internal jugular vein ( IJV ) is identified.

119. The internal jugular vein is liberated. An extended mastoidectomy has been performed.

120. A wide retrosigmoid craniotomy. The sigmoid sinus ( SS ) is uncovered. Note that the bone overlying the genu from the lateral to the sigmoid sinus is intact (arrowhead).

121. The dura is separated from the overlying bone. The dura is separated from the overlying bone.

122. The endolymphatic sac ( ELS ) is identified. Further separation of dura from the overlying bone.

123. Placement of aluminum to protect the dura from injury. The cochlear aqueduct ( CAq )is identified.

124. Complete drilling of the retrofacial air cells. The approach has been completed. The dotted line representsthe dural incision.

125. The jugulocarotid crest is drilled, exposing the vertical segment of the internal carotid artery. An extended posterior tympanotomy has been performedand the facial nerve transposed laterally .

126. The dura has been opened and the tumor ( T ) can be seen. Closure of the dura . The remaining defect (white arrowheads ), together with the operative cavity, is obliterated with abdominal fat .

127. Surgical Anatomy after Opening the posterior cranial fossa dura General view of the structures that can be visualized after opening the dura . At the superior aspect of the approach, the fourth ( IV ) and fifth ( V ) cranial nerves can be appreciated.

128. The facial nerve can be clearly seen in the middle part of the approach after retracting the posteriorly lying cochlear nerve . Separation of the glossopharyngeal nerve ( IX ) from the vagus ( X ) and accessory ( XI ) nerves at the medial aspect of the jugular foramen. Further inferiorly, the ninth ( IX ), tenth ( X ), and eleventh ( XI ) cranial nerves can be seen exiting the skull through the jugular foramen

129. At the inferior part of the approach the lower cranial nerves can be appreciated. The relation between the inferior petrosal sinus ( ips ) and the lower cranial nerves.

130. The origin of the hypoglossal nerve ( XII ). . The drilled occipital condyle ( OC ) and the hypoglossal canal ( HC ).

131. Infratemporal fossa approach type B &C [ IFTA – B & C ]– transpetrous approach

132. The petrous apex as viewed through the infratemporal fossa type B approach. Structures lying lateral to the internal carotid artery ( ICA ). The mandibular nerve ( V3 ) and the middle meningeal artery have been cut. The instrument points to the position of the already drilled bony eustachian tube ( ET ).

133. Cutting the middle meningeal artery ( MMA ). The mandibular nerve ( V3 ) is cut.

134. Suturing the eustachian tube ( ET ) at the end of the procedure The internal carotid artery ( ICA ) has been exposed anterior to the cochlea ( Co ). Note the tumor ( T ) occupying the petrous apex.

135. The artery is retracted posterolaterally . The petrous apex is drilled.

136. Neurosurgical cottonoids placed in the petrous apex for hemostasis. At higher magnification, residual tumor ( T ) is seen at the mid- clivus and medial to the cartilaginous eustachian tube ( ET ).

137. The internal carotid artery ( ICA ) is displaced laterally to ascertain total tumor removal. The tumor has been totally removed. Note the excellent control of the vertical and horizontal segments of the internal carotid artery ( ICA ). The cartilaginous eustachian tube has been sutured (arrow).

138. The internal carotid artery ( ICA ) has been displaced laterally using an umbilical tape. This allows better exposure of the petrous apex ( PA ) to assure complete tumor removal.

139. Anterior skull base Infra-petrous approach

140. Infra-petrous approach is through Mid Clivus

141. 1. Upper clivus – Upto 6 th nerve entry dorello’s canal (petro- clival junction) 2. Middle clivus – from 6 th nerve to jugular foramen 3. Lower clivus – from jugular foramen to foramen magnum Lateral skull base Anterior skull base

142. The middle third ( M. 1/3rd) begins at the sella floor ( SF) and extends to the floor of the sphenoid sinus (SSF), and the lower third (L. 1/3rd) extends from the floor of the sphenoid sinus to the foramen magnum ( FM). Lateral skull base Anterior skull base

143. Lower half of paraclival carotid - caudal part, the lacerum segment of the paraclival carotid   ”The unsolved surgical problem remains the medial wall of the ICA at the level of the anterior foramen lacerum , until now unreachable with the available surgical approaches."  - In lateral skull base by Prof. Mario sanna – this unreachable is Carotid- Clival window which is accessable in Anterior skull base Infrapetrous Approach Carotid- Clival window – Mid clivus a. Petrosal face b.Clival face

144. JT = jugular tubercle separates the hypoglossal canal from Jugular foramen

145. IPS & HVP hypoglossal venous plexus

146. 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

147. The foramen lacerum (FL) is located lateral to the floor of the sphenoid sinus at the level of the spheno -petro- clival confuence . JT jugular tubercle, HC hypoglossal canal – addFig 3.78 also

148. Pontomedullary junction = Vertebro-basillar junction = Junction of Mid clivus & Lower clivus = foramen lacerum area The pontomedullary junction. The vertebral artery junction is at the level of the junction of the inferior and midclivus . The basilar artery runs in a straight line on the surface of the pons. The exit zones of the hypoglossal and abducent nerves are at the same level. The abducent nerve exits from the pontomedullary junction, and ascends in a rostral and lateral direction toward the clivus .

149. Very rare specimen..The vbj is far inferior to floor of sphenoid sinus Cadaveric dissection image demonstrating structures seen following dissection of the lower third of the clivus . Note how thebasilar arteries and vertebral arteries can be extremely tortuous in their course.

150. Cadaveric dissection demonstrating the osteotomies at the base of the posterior clinoids ( PC ) for separation with the body of the dorsum sella ( DS ). P. CCA , posterior genu of the intracavernous carotid artery; PCA , paraclival carotid artery; ICCA , intracranial carotid artery; BA , basilar artery; PL , posterior lobe of the pituitary gland; AL , anterior lobe of the pituitary gland.

151. Cadaveric dissection image demonstrating the close anatomical relationship of the posterior clinoid ( PC ) with both the intracranial carotid artery ( ICCA ) and the posterior genu of the intracavernous carotid artery ( P. CCA ). AL , anterior lobe of the pituitary gland ; PL , posterior lobe of the pituitary gland; BA , basilar artery. green dotted triangle area for entry of the endoscope into the interpeduncular fossa

152. 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.

153. Clival recess

154. See the relationship between lower boarder of posterior end of vomer & clivus – vomer lower boarder is at junction of mid & lower clivus – my understanding

155. http://www.neurosurgicalapproaches.com/2013/08/25/

156. Anterior cranial fossa dura Posterior cranial fossa dura

157. Anterior skull base Supra-petrous approach

158. Quadrangular ( Q ) space – where petrous apex is seen – Supra-petrous approach – space between laceral carotid & Trigeminal ganglion & V3

159. Quadrangular ( Q ) space – where petrous apex is seen – Supra-petrous approach – space between laceral carotid & Trigeminal ganglion & V3 Quadrangular ( Q ) area in middle cranial fossa Quadrangular ( Q ) space in anterior skull base approach

160. Quadrangular ( Q ) space – where petrous apex is seen – Supra-petrous approach – space between laceral carotid & Trigeminal ganglion & V3 Quadrangular ( Q ) area in middle cranial fossa Quadrangular ( Q ) space in anterior skull base approach

161. Paraclival carotid PAp = Petrous apex caudal part, the lacerum segment of the artery corresponding to the extracavernous portion of the vessel, and rostral part, the trigeminal , intracavernous portion of the artery, so- called because the Gasserian ganglion is posterior to it and the trigeminal divisions are lateral to it. CR clival recess, ICAc cavernous portion of the internal carotid artery, ICAh horizontal portion of the internal carotid artery, PAp petrous apex , VN vidian nerve , MC Mevkels cave

162. CR clival recess, ET eustachian tube, ICAc cavernous portion of the internal carotid artery, ICAh horizontal portion of the internal carotid artery, PAp petrous apex , PLL petrolingual ligament, VN vidian nerve, V2 second branch of the trigeminal nerve, red arrow artery for the foramen rotundum , yellow arrow greater petrosal nerve. The petrolingual ligament connects the petrous apex and the lingula of the sphenoid. It can be considered the border between the horizontal and cavernous portions of the internal carotid artery.

163. Endoscopic vision of the suprapetrous window. The dura of the middle cranial fossa has been displaced upward, and the greater petrosal nerve coming out from the geniculate ganglion is evident . The black arrow in the small picture indicates the perspective of the vision in the bigger image ET eustachian tube, GPN greater petrosal nerve, MCFd dura of the middle cranial fossa, MMA middle meningeal artery, SPS superior petrosal surface, TI trigeminal impression, V3 third branch of the trigeminal nerve, yellow arrow accessory middle meningeal artery, white asterisks greater petrosal nerve groove The skull base given by the sphenoid bone has been drilled away, and the third branch of the trigeminal nerve and the MMA have been freed from their canals. An accessory MMA is seen in close relationship to V3. When present, it passes through the foramen ovale .

164. The space above transverse line of V2 is Middle cranial fossa ( Meckel’s cave ) – Read the CT – scan/ Plane the surgery by using these lines

165. Upper half of paraclival carotid – rostral part , the trigeminal segment of the paraclival carotid TG ( Trigeminal ganglion ) is lateral to upper half [ rostral part ] of Paraclival carotid Anterior skull base Lateral skull base

166. Carotid transposition – need to refer literature regarding “ How far it is SAFE ” in anterior skull base approach

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