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
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account for downloading.
4.
5. 7up- 7th is above
Coca cola – cochlear n. is cola[=lower]
11. The dura over the ACP passes over the
ON, giving the falciform ligament
12. 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.
13. 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.
14.
15. 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].
16. 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
17. 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
18. Figure 13: Coronal CT shows type III optic nerve (arrows) where more than 50% of the
nerve is surrounded by air
19. 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
20. Figure 15: Coronal CT showing type IV optic nerve bilaterally (arrows). O: Onodi cell; S:
Sphenoid sinus
21. 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
22. 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 .
23. 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 .
24. 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)
25.
26.
27.
28. 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.
30. 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
31. One artery in the head which we can’t move – is
OA – Central retinal artery is avulsed
32. 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
33. when we are removing a triangular piece of bone in
Transplanum approach , the base of traingle is PEA
34. 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.
35.
36.
37. 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
38. 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
39. In both type a = intradural type,
b = extradural supra-optic strut types Opthalmic
foramen is in Optic canal
40. In Type c = extradural trans-optic strut type , the Opthalmic
foramen in Optic strut
42. 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).
43. Schematic drawing origin (a medial, b central, c lateral) and exit
(d lateral, emedial) of superior wall of the ophthalmic artery
44. 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).
45. 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).
46.
47. 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%).
48. Give incision in supero-medial area
in optic nerve decompression – add
scott brown information
53. 3rd nerve is sandwiched between posterior
cerebral artery & superior cerebellar artery
54. 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
55. 3rd nerve is sandwiched between posterior cerebral artery &
superior cerebellar artery
56. 3rd nerve is sandwiched between posterior cerebral artery &
superior cerebellar artery
Through endoscopic lateral skull
base
Through endoscopic anterior
skull base
57. 3rd nerve is sandwiched between posterior cerebral
artery & superior cerebellar artery
Through endoscopic lateral skull
base
Through endoscopic anterior
skull base
58. 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
69. 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
70. 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
71.
72. Note the aperture for 3rd nerve & 4th nerve anterior & posterior to
posterior petro-clival fold [ PPCF ]
73.
74.
75. Oculomotor cistern
Cranial nerve III enters the roof included in its own cistern
(oculomotor cistern).
Oculomotor cistern goes upto
anterior clinoid tip
76. 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
83. 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 )
84. 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 ).
85. Endoscopic lateral skull base – 4th
coming from posteriorly over the
superior cerebellar artery [ in this
picture has 2 branches
86. 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
87. 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 ]
88. The TC [ tentorium cerebelli ], with the trochlear nerve inside,
can be visualized passing inferiorly to the IIIcn.
endoscopic transclival view
89. 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.
90. 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.
91. 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.
92. (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
99. 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
100. 6th nerve origin is above or below AICA or has two
rootlets of origin
101. 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.
102. 6th is appresiated in TA-II [ Transapical type II ]
approach when 360 degrees IAC drilled
104. 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
105. 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
106. When we are doing clival chordoma we have to
anticipate 6th nerve medial to paraclival carotid
which is present in dorellos canal
109. 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.
110. 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.
111. 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).
112. 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 ).
113. 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 ).
114. 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 ).
115. 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. ]
116. 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
117. Blue arrow in Left picture ; * in Right
picture - Gruber’s ligament
118. Usually, the IPS passes beneath the superior petro-sphenoidal
ligament (l. of Gruber) with the abducens nerve.
Anterior skull base Lateral skull base
119. From lateral skull base - The lateral aspect of the parasellar &
paraclival carotid junction is crossed by the abducent nerve (VI)
123. 6th nerve is parallel to V1 – in the same
direction of V1
124. Middle cranial fossa approach - 6th nerve is
parallel to V1 – in the same direction of V1
125. 6th nerve is parallel to V1 – in the same direction of V1
126. 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
127. 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
130. 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
131. 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.
132.
133. Bottle neck concept – junction of labyrinthine & internal
auditory canal facial nerve is narrow [ bottle neck ]
134. 7up- 7th is above
Coca cola – cochlear n. is cola[=lower]
137. 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.
138. 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
139. 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]
140. 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
141. Drilling has been carried out more
inferiorly to identify the
cochlear aqueduct (CA). Note the
proximity of the aqueduct to the
glossopharyngeal
nerve (IX).
142. 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.
143. 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
149. 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
151. 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
152. 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
153. 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
154.
155.
156. 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.
157. The glossopharyngeal and vagus nerves are well
identified in the cerebellomedullary cistern before
entering the jugular foramen.
159. 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
160. 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).
161. 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
162. 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).
163. 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
166. 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.
167. 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
168. 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
169. C2 nerve root below the 11th nerve
in posterior triangle clearance in SLD
the C2 nerve root is seen crossing
the vertebral artery (VA).
170. 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
173. 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.
174. 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.
175. 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.
176. 90 degree turn of 12th nerve medial to medial wall of
jugular bulb – Dr.Satish Jain
177. ITFA with Transcondylar [ = TC ]
Transtubercular [ = TT ] approach
Here Transcondylar is through Occipital Condyle ;
Transtubercular is through Jugular tubercle &
lateral pharyngeal tubercle
178. 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.)
179. Note 12th nerve in between JT ( Jugular tubercle ) & OC
( Occipital condyle ) in both lateral & anterior skull base
Lateral skull base Anterior skull base
180. 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
181. Through endoscopic lateral skull
base - The curved vertebral
artery displaces and stretches
the hypoglossal nerve fibers.
Through anterior skull base
182. 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.
189. 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,
190.
191. Transoral approach to SUPERO-MEDIAL Parapharyngeal
tumors – incision anterior to anterior pillar of tonsil
192. 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.
193. 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.
194. 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
195. Far lateral approach – photo from
3D Neuroanatomy medical atlas
http://www.3dneuroanatomy.com
196. Hypoglossal is just behind the upper end of
parapharyngel carotid – very easy way to
identify 12th nerve in paraphayrngeal space
– Dr.Satish jain
197.
198. In infrapetrous approach there are chances of injury to 6th nerve [ in dorello’s
canal medial to paraclival carotid ] & 12th nerve
199. 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
200.
201. 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.)
204. 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.
205. 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.
207. 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.
208. 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).
209. The internal auditory canal (IAC)
is identified.
A large diamond burr is used to
drill the petrous apex.
210. 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).
211. 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.
214. 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.
215. Branches of the trigeminal nerve (V1, V2, V3) at the level of
the lateral wall of the cavernous sinus.
216. After this PPT must read “REZ 360” . Click
http://www.slideshare.net/muralichandnal
lamothu/rez-360
217. 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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