This document describes various approaches to the petrous apex, including the middle cranial fossa transpetrous approach. It discusses the landmarks and surgical anatomy relevant to this approach, including exposing the internal auditory canal and petrous apex by drilling bone. It also mentions combining the frontotemporal orbitozygomatic approach with the Kawase approach to access the middle and posterior cranial fossae. Several references are provided with links to videos and papers on these techniques.

1. Petrous apex 360°
11-4-2017
10.49 pm

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

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of
“ Skull base 360° ”
I will update continuosly with date tag at the end as I am
getting more & more information
click
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4. Approaches to petrous apex
LATERAL SKULL BASE
1. From above the labyrinth
a. Middle cranial fossa transpetrous [ =
Trans-apical ] approach
2. From posterior to the labyrinth
a. Retrolabyrinthine transpetrous [ =
Trans-apical ] approach / endoscopic
retrolabyrinthine approach
3. From through the labyrinth
a. Translabyrinthine transpetrous [ =
Trans-apical ] approach
b. Transcochlear transpetrous [ =
Trans-apical ] approach
4. From below the labyrinth
a. INFRA-COCHLEAR approach through
BRACKS MANS TRIANGLE
b. Infralabyrinthine/Infra-otic =
Infratemporal fossa type A transpetrous [
= Trans-apical ] approach
c. POTS
d. Infralabyrinthine/Infra-otic =
Infratemporal fossa type B & C
transpetrous [ = Trans-apical ] approach
ANTERIOR SKULL BASE
1. From anterior to the labyrinth
a. Suprapetrous approach
b. 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 5th nerve
where below the IAC you will get 6th 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 - The ‘infrapetrous’ and
‘suprapetrous’ planes referred to in this discussion pertain to the plane to the
petrous ICA, not necessarily the petrous bone.

14. The mid- coronal and posterior coronal planes are divided into 7 anatomic
zones based on the relationship to the ICA.
• Zone 1 represents the anterior petrous apex.
• Zone 2 represents the mid- body of the petrous bone below the level of the horizontal
• segment of the petrous carotid.
• Zone 3 represents the suprapetrous region consisting of the quadrangular space.
• The quadrangular space is defined medially by the paraclival ICA, inferiorly by the
• horizontal segment of the petrous ICA, laterally by the second division of the trigeminal
• nerve, and superiorly by the course of the sixth cranial nerve within the cavernous
• sinus. Through this approach Meckel’s cave and the gasserian ganglion can be
• reached.
• Zone 4 represents the superior lateral cavernous sinus, representing the region
• through which the oculomotor (III), trochlear (IV), first division of the trigeminal
• nerve, and abducens (VI) nerves traverse.
• Zone 5 represents the transpterygoid /infratemporal space with direct access to the
• middle fossa.
• Zone 6 represents the region of the condyle. It is the paramedian area located
• immediately lateral to the inferior third of the clivus and foramen magnum. It is
• antero- laterally bounded by the eustachian tube and fossa of Rosenmuller that mark
• the parapharyngeal ICA laterally. Superiorly, it has its limit on the petroclival synchondrosis.
• Lesions in this region can involve the hypoglossal canal.
• Zone 7 represents the region lateral to the parapharyngeal ICA. The approach for
• this region extends along the floor of the maxillary sinus and contains the lateral
• pterygoid plate and attached soft tissue. Most importantly, this region contains the
• jugular foramen posteriorly.

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

16. Quadrangular part boarders –
Zone 3 represents the
suprapetrous region
consisting of the
quadrangular space.
The quadrangular space is
defined medially by the
paraclival ICA, inferiorly by
the
horizontal segment of the
petrous ICA, laterally by the
second division of the
trigeminal
nerve, and superiorly by the
course of the sixth cranial
nerve within the cavernous
sinus. Through this approach
Meckel’s cave and the
gasserian ganglion can be
reached.

17. The Petrous
pyramid has only
3 surfaces unlike
Egypt pyramid
which has
4 surfaces

18. 3 surfaces
2 upper surfaces 1 basal surface

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

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

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

22. Approach through posterior Quadrangular ( Q ) area =
Kawase approach or Anterior Transpetrosal approach
Neurosurgeons are doing FTOZ + kawase approach to get control of middle
cranial fossa & posterior cranial fossa respectively
For FTOZ + Kawase approach click
1. https://www.youtube.com/watch?v=qgItZDwRYjk
2. https://www.youtube.com/watch?v=M89uijtuzQA
3. https://www.youtube.com/watch?v=es-U3QitxdY
4. https://www.youtube.com/watch?v=vDGO4kVy0Gc
5. http://www.aiimsnets.org/skull_base_tumors.asp
6. http://aiimsnets.org/AnteriorTranspetrosalapproach.asp#
others
https://www.youtube.com/results?search_query=frontotemporal+orbitozygo
matic+approach
https://www.youtube.com/results?search_query=kawase+approach

23. 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

24. 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

27. Petrous apex – Triangular area
Petrous apex – Quadrangular area

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

29. 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

30. 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

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

33. IPS & HVP hypoglossal
venous plexus

34. Petrous apex - Quadrangular area

37. Middle cranial fossa approach

38. 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

39. 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

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

41. Middle cranial fossa
Transpetrous ( = Transapical )

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

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

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

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

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

47. 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.

48. 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.

49. 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.

50. 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.

51. 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.

52. 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.

53. 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.

54. 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

55. Neurosurgeons are doing FTOZ + kawase approach to
get control of middle cranial fossa & posterior cranial
fossa respectively
For FTOZ + Kawase approach click
1. https://www.youtube.com/watch?v=qgItZDwRYjk
2. https://www.youtube.com/watch?v=M89uijtuzQA
3. https://www.youtube.com/watch?v=es-U3QitxdY
4. https://www.youtube.com/watch?v=vDGO4kVy0Gc
5. http://www.aiimsnets.org/skull_base_tumors.asp
6. http://aiimsnets.org/AnteriorTranspetrosalapproach.asp#
others
https://www.youtube.com/results?search_query=frontotemporal+orbitozygo
matic+approach
https://www.youtube.com/results?search_query=kawase+approach

56. Kawase vs “Modified Anterior Petrosectomy
(MAP) Rhomboid” Approach – get this paper at
www.sci-hub.cc
http://ofuturescholar.com/paperpage?docid=190
5013
Kawase vs Retrosigmoid Transtentorial and
Retrosigmoid Intradural Suprameatal Approaches
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4
067754/

57. To get any paper of any journal free click
www.sci-hub.bz or www.sci-hub.cc
How to get FREE journal papers in www.sci-hub.bz or www.sci-hub.cc
1. When same paper published in different journals , the same paper has
different DOIs -- so we have to try with different DOIs in www.sci-
hub.bz orwww.sci-hub.cc if one of the DOI is not working.
2. If the paper has no DOI , copy & paste URL of that paper from the main
journal website . If you can't get from one journal URL try with different
journal URL when the author publishes in different journals .
3. Usually all new papers have DOIs . Old papers don't have DOIs . Then
search in www.Google.com . Old papers are usually kept them free in Google
by somebody . Sometimes the Old papers which are re-published will have
DOIs. Then keep this DOI in www.sci-hub.bz or www.sci-hub.cc
4. Add " .pdf " to title of the paper & search in www.Google.com if not found
in www.sci-hub.bz or www.sci-hub.cc

58. 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.

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

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

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

62. 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).

64. 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.

65. 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.

66. 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

67. 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.

68. 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.

69. Lateral view of CP angle

70. 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

71. 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
1. Retrolabyrinthine Transpetrous ( =
Transapical )
2. Translabyrinthine Transpetrous ( =
Transapical )
3. Transcochlear Transpetrous ( = Transapical )
predominently to reach Level 3 = Lower cranial
nerve area
4. POTS = Petro-Occipital Trans-Sigmoid
approach
5. 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

72. 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.

73. 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

74. Retrolabyrinthine Transpetrous (
= Transapical )

75. 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

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

77. 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.

78. 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.

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

80. 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.

81. 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).

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

83. 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).

84. 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.

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

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

87. 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.

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

89. 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 .

90. Translabyrinthine 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. The Enlarged Translabyrinthine Approach with Transpetrous ( =
Transapical ) Extension – intradurally above the IAC you will get 5th nerve
where below the IAC you will get 6th 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.

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

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

95. 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.

96. 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.

97. 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.

98. 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.

100. 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.

101. Transcochlear Transpetrous ( =
Transapical )

102. 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

103. 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.

104. 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.

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

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

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

108. 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

109. Removal of the fallopian canal
with a rongeur.

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

111. 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.

112. 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).

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

114. 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.

115. 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

116. Petroclival meningiomas surgery by
Modified transcochlear approach
Click video
https://www.youtube.com/watch?v=
kUa9fQ4_aQY

117. INFRA-COCHLEAR approach
through BRACKS MANS TRIANGLE

118. PETROUS APEX CHOLESTEATOMA - Dear surgeons today we did INFRA-COCHLEAR
approach to petrous apex cholesteatoma through BRACKS MANS TRIANGLE
cholesteatoma is completely removed with microscopic approach passing under the
vertical ica It was communicated intradurally Finally cavityis obliterared with fat Here
are some microscopic pics

122. Prof. Marchioni papers of SCC [ Sub
Cocheolar Canal ]
• http://sci-hub.cc/10.1007/s00405-014-2923-8
• http://sci-hub.cc/10.1007/s00276-016-1662-5

123. 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

124. 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

125. Right ear. Endoscopic dissection during surgery, after drilling the
promontory. ow oval window, st scala tympani, scc subcochlear
canaliculus

126. Subcochlear canaliculus type A

127. Subcochlear canaliculus type B

128. Subcochlear canaliculus type C

130. Temporal bone CT. Look at the sub-cochlear canaliculus or sub-cochlear
tunnel that can allow endoscopic transcanal retrocochlear access to the IAC
and drain the petrous apex cells

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

148. 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).

149. 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.)

150. 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.

151. 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.

152. 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).

153. 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).

154. 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.

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

156. POTS = Petro-Occipital Trans-
sigmoid approach

157. 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

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

159. A U-shaped musculoperiosteal
flap is outlined.

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

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

162. 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).

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

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

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

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

167. 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.

168. 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.

169. 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.

170. 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

171. 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.

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

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

174. 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).

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

176. 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.

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

178. 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).

179. 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).

180. 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.

181. Anterior skull base
Infra-petrous approach

182. Infra-petrous approach
is through Mid Clivus

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

184. 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

185. 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

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

187. IPS & HVP hypoglossal
venous plexus

188. 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

189. 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

190. 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.

191. 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.

192. 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.

193. 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

194. 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.

195. Clival recess

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

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

199. Anterior cranial fossa dura Posterior cranial fossa dura

200. Anterior skull base
Supra-petrous approach

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

202. 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

203. 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

204. Paraclival carotid
PAp = Petrous apex
1. caudal part, the lacerum
segment of the artery
corresponding to the
extracavernous portion of
the vessel, and
2. 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

205. 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.

206. 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.

207. 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

209. 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

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

212. 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
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account for downloading.