Skull base 360°- part 2

SKULL BASE 360°
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SKULL BASE 360°-Part 2
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[ Dated: 1-11-14 ]
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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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Below presentation is
Indetail eloborate description for
each part of skullbase360 done at
www.skullbase360.in
» Presentation by
» Dr. N. Murali Chand DLO MS (ENT) FHM
» Fellowship in HIV medicine, MAMC, New Delhi
» My website = www.integratedmedicine.co.in
• www.skullbase360.in
» Cell= +91 99496 77605

Bulbar fascia includes
1. Tenon’s capsule 2. Tubular sheat for each orbital muscle 3. medial & lateral
check ligament 4. suspensory ligament of lockwood

Superior oblique tendon goes underneath the superior rectus
where are inferior oblique muscle goes below the inferior rectus

Parts of SOF
1. Lateral part- LFT [ Liver functional tests ] Menumonic – Lacrimal N., Frontal
N.,Trochlear N.
2.Middle part
3. Medial/Inferior part

Branches of V 1
1. Lacrimal N.
2.Frontal N.
3. Nasociliary N.
Immediately after removing the
periorbita

Frontal N. devides into Sup.Troch.N.
& Supraorb.N. – NOTE Fal.Lig

A segment of the orbital portion of the optic
nerve has been removed. This exposes the
branch of the inferior division of the
oculomotor nerve, which passes below the
optic nerve and enters the medial rectus
muscle.

When you are approaching endoscopically
the upper most one is Sup.Orb.M
superiorly & Medial rectus inferiorly
The medial approach is directed through the
interval between the superior oblique and the
levator muscles.

Nasociliary N. [ 3rd branch of V1 ]
devides into AEN & PEN

Inferior orbital muscle is completely
muscle , whereas Sup.Obl.M is muscle &
tendinous

Medial
Orbital
Approach-
Periorbita
elevated
from
bone

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.

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

One artery in the head which we can’t move – is
OA – Central retinal artery is avulsed

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

when we are removing a triangular piece of bone in
Transplanum approach , the base of traingle is PEA

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.

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

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

In both type a = intradural type,
b = extradural supra-optic strut types Opthalmic
foramen is in Optic canal

In Type c = extradural trans-optic strut type , the Opthalmic
foramen in Optic strut

http://www.nature.com/eye/journal/v20/n10/fig_tab/6702377f3.html#figure
-title
The upper diagram is Type a or b Opthalmic artery , the lower diagram is Type
c Opthalmic artery
Dup OC = Duplicate Opthalmic
canal

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).

Schematic drawing origin (a medial, b central, c lateral) and exit
(d lateral, emedial) of superior wall of the ophthalmic artery

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).

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).

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%).

The dura over the ACP passes over the
ON, giving the falciform ligament

FCB-Fibrocartilago basalis at junction
of petrous & paraclival carotid
Fibrous tissue surrounds the entrance of
the vertebral artery into the CPA.

Fibrous tissue surrounds the entrance of
the vertebral artery into the CPA.
Left side. Combined transsigmoid, suboccipital
and extreme lateral approaches provide an
overview off the craniocervical junction, the
foramen magnum area, and the surrounding
structures of the medullary stem.

Laceral carotid lies over the Foramen lacerum not passing through
Foramen lacerum - Foramen lacerum floor is occupied by FCB [
Fibrocartilagenous basalis ] -- Note Fibrocartilagenous basalis at
laceral segment in both photos

A nontoothed forceps is used to hold the soft tissues (ST) surrounding
the nerve at the level of the stylomastoid foramen (SMF), and
sharp scissors are used to dissect the soft tissues from the bone at that
level. C Cochlea, FN(m) Mastoid segment of the facial nerve, LSC Lateral
semicircular canal, NC New canal, SS Sigmoid sinus

Rerouting of the facial nerve. FN(m) Mastoid
segment of the
facial nerve, FN(p) Intraparotid facial nerve, SM
Facial nerve at the stylomastoid
level, ST Soft tissues
The facial nerve has been rerouted into the new
canal (*).
FC Fallopian canal, FN(p) Rerouted part of the
intratemporal facial nerve,
FN(t) Rerouted part of the tympanic segment of
the facial nerve, ST Soft
tissues

Styloid apparatus – superior
view Styloid apparatus – lateral view

After the attached muscles have been dissected away, the
styloid process (SP) is fractured using a rongeur. FC Fallopian canal,
FN Facial nerve, FN(p) Rerouted part of the intraparotid facial nerve,
TB Temporal bone

Fig. 9.21 To obtain control over the vascular structures as they enter
the temporal bone, the tympanic bone (TB), the fallopian canal remnants
(FC), and the infralabyrinthine air cells are all to be removed.
C Basal turn of the cochlea (promontory), IJV Internal jugular vein,
JB Jugular bulb, SS Sigmoid sinus

The view after completely uncovering the lateral surfaces of
the vascular structures. C Basal turn of the cochlea (promontory), ICA
Internal
carotid artery, IJV Internal jugular vein, JB Jugular bulb, SS Sigmoid
sinus

Fig. 9.29 The plane of dissection between the internal carotid artery
(ICA) and the overlying periosteum (P) is best developed at the entrance
of the artery into its canal. C Basal turn of the cochlea (promontory)

Internal carotid artery is deeper to styloid process when we see from laterally &
medial to styloid process when we see from anteriorly – [SP- Styloid process]

Two things protect the parapharyngeal carotid anteriorly
1. Tensor veli palatini & 2. SPHA [ = stylopharyngeal
aponeurosis ]

The Petro-occipital Fissure- contains IPS

The Petro-occipital Fissure- contains
IPS

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

Usually inferior petrosal sinus
opens into jugular bulb
Sometimes along with jugular
bulb opening , it opens into
internal jugular vein also [ lower
single arrow in below photo ]

a. IPS inferior to nerve IX and
superior to nerves X and XII.
b. IPS inferior and medial to all
four nerves.
c. IPS superior and lateral to all
four nerves
d. A second IPS joining the
internal jugular vein passing
medial to IX and lateral to X,
XI, and XII

An anatomical classification according to the level of the inferior
petrosal sinus–internal jugular vein junction has been developed
1. Junction at the level of the
jugular bulb
2. Junction at the level of the anterior
condylar vein junction (extracranial
opening of the hypoglossal canal)

3. Junction at the level of the
lower extracranial jugular vein
• CoC - level of the condylar
canal
• IJV- internal jugular vein
• JF- level of the jugular
foramen
• SS- sigmoid sinus
• VVP- vertebral venous
plexus

4. Multiple junctions: upper junction at the level of the jugular bulb and
lower junction at the level of the anterior condylar vein
a )Multiple upper junctions at the level of the jugular bulb (JB).
b )Multiple junctions: upper junctions at the level of the jugular bulb and lower
junction at the level of the anterior condylar vein.
c) No connection between the internal petrosal sinus and the internal jugular vein. The
sinus drains in the vertebral venous plexus.

In infratemporal fossa [=intact
cochlear approach –
Dr.Morwani ] type B
approach
See IPS in Kawase approach

Right sided anterior petrosectomy on a cadaver dissection: intradural exposure
and operative field. PCA Petrous carotid artery; DPA drilled petrous apex; IPS
inferior petrosal sinus; BA basilar artery; VI 6th cranial nerve; AICA anterior inferior
cerebellar artery; P pons; V 5th cranial nerve

NOTE Inferior petrosal sinus at CLIVUS
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

In middle cranial fossa approach

3rd nerve is sandwiched between posterior
cerebral artery & superior cerebellar artery

3rd nerve is sandwiched between posterior cerebral artery &
superior cerebellar artery

3rd nerve is sandwiched between posterior cerebral artery &
superior cerebellar artery
Through endoscopic lateral skull
base
Through endoscopic anterior
skull base

3rd nerve is sandwiched between posterior cerebral
artery & superior cerebellar artery
Through endoscopic lateral skull
base
Through endoscopic anterior
skull base

P1 in relation to 3rd nerve P2 in relation to 3rd nerve

Relationship of PcomA & 3rd nerve –
parallel to each other

In parasellar pituitary 3rd n & 4th n & Pcom present
in Postero-superior cavernous compartment

Relationship of PcomA & 3rd nerve

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

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 –I think B
is nothing but posterior clinoid process
C window lateral of cn III
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

Note the aperture for 3rd nerve & 4th nerve anterior & posterior to
posterior petro-clival fold [ PPCF ]

Oculomotor cistern
Cranial nerve III enters the roof included in its own cistern
(oculomotor cistern).
Oculomotor cistern goes upto
anterior clinoid tip

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

Fronto-temporal orbitozygomatic
transcavernous approach
COM= Caratico-occulomotor
membrane , DR = dural ring

The oculomotor nerve divides into a
small superior and large inferior division just before passing
through the superior orbital fi ssure.

4th nerve – 5 components – a. cisternal b. tentorial –
see paolo castelneovo book

The TC [ tentorium cerebelli ], with the trochlear nerve inside,
can be visualized passing inferiorly to the IIIcn.
endoscopic transclival view

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.

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.

(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

Trigeminal area at Cerebello Pontine
Angle – along with my voice
Click
http://www.youtube.com/watch?
v=YBqk4Jdnxic

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 origin is above or below AICA or has two
rootlets of origin

6th is appresiated in TA-II [ Transapical type II ]
approach when 360 degrees IAC drilled

6th nerve – enters the dorellos canal –
Intradural course

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

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

When we are doing clival chordoma we have to
anticipate 6th nerve medial to paraclival carotid
which is present in dorellos canal

The basilar artery (BA) can be seen
very tortuous.

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 ).

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 ).

1. 6th N. crossing carotid at Petro-clival junction when viewing in lateral skull base
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 ).

Inferior boarder of L-OCR is by 6th
nerve & V1

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

Blue arrow in Left picture ; * in Right
picture - Gruber’s ligament

Usually, the IPS passes beneath the superior petro-sphenoidal
ligament (l. of Gruber) with the abducens nerve.

6th nerve passing below gruber’s
ligament

ACP anterior clinoid process, APCF anterior petroclinoid fold, DS dorsum sellae, ICF interclinoid
fold, PF pituitary fossa, PLL petrolingual ligament (inferior sphenopetrosal ligament),
PPCF posterior petroclinoid fold, PS planum sphenoidale, SSPL superior sphenopetrosal
ligament (Gruber’s ligament), TS tuberculum sellae, black asterisk middle clinoid process

6th nerve is parallel to V1 – in the same
direction of V1

6th nerve is parallel to V1 – in the same direction of V1

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

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

Vertical part of 7th nerve bissects the
jugular bulb

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

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.

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.

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

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]

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

Drilling has been carried out more
inferiorly to identify the
cochlear aqueduct (CA). Note the
proximity of the aqueduct to the
glossopharyngeal
nerve (IX).

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.

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

Jugular foramen area [
9,10,11,12 nerves]

Superior & inferior ganglion of vagus
at jugular foramen

Jugular tubercle [ JT ] , star = foramen lacerum

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

Note the relationship of clivus &
jugular tubercle

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

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.

Jugular fossa is just lateral to
hypoglossal canal

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.

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.

Through lateral skull base - The
curved vertebral artery displaces
and stretches the hypoglossal
nerve fibers.
Through anterior skull base

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.

HC = hypoglossal canal , JT= Jugular Tubercle

Hypoglossal canals
From front – through nose From back

Coronal cut – hypoglossal canal

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,

Transoral approach to SUPERO-MEDIAL Parapharyngeal
tumors – incision anterior to anterior pillar of tonsil

In infrapetrous approach there are chances of injury to 6th nerve [ in dorello’s
canal medial to paraclival carotid ] & 12th nerve

12th nerve bissecting internal & external carotid

Robbins level II. 1 Sternocleidomastoid muscle, 2
posterior belly of digastric muscle, 3
spinal accessory nerve (common trunk), 4 internal
jugular vein, 5 splenius capitis muscle, 6 levator
scapulae muscle, 7 anterior scalene muscle, 8
transverse process of atlas, 9 hypoglossal nerve, 10
carotid bifurcation, 11 branches of cervical plexus

Superior view of the atlas and the axis.
The atlas consists of two thick lateral masses situated
at the anteromedial part of the ring, which are connected
in front by a short anterior arch and posteriorly
by a longer curved posterior arch. 1, anterior arch
of the atlas; 2, superior articular facet is an oval, concave
facet that articulates with the occipital condyle;
3, posterior arch of the atlas; 4, vertebral artery (VA);
5, transverse foramina; 6, transverse process; 7, dens
of the axis.

The entrance of the vertebral artery is the boundary between the foramen
magnum and the spinal part of the accessory nerve.
The root fibers of the spinal accessory
nerve and the fibres of C1 and C2

Anterior & Posterior perforated
substance

Anterior perforated substance &
olfactory track relation

Superior hypophyseal artery =
SHA

Superior Hypophyseal Arteries [ SHAs ]
- more commonly arise from the paraclinoid ICA - In rare cases SHAs originate
from the intracavernous segment of the ICA

LT lamina terminalis cistern=
Suprachiasmatic cistern

LT lamina terminalis cistern –
The lamina terminalis cistern is situated above the optic chiasm (Martins etal.
2011 ) . Within this cistern, A1 and A2, as well as the anterior communicating
artery and the first part of the recurrent artery of Heubner, are evident.

The space between a & oc is Lamina terminalis
Neuroendoscopic view of the third ventricle floor-----Infundibular recess (i), optic chiasm (oc)
and a prominent anterior commissure (a) are seen anterior to the opaque and narrow tuber cinereum (t). B
Neuroendoscopic view of the third ventricle floor in another myelomeningocele patient. A non-transparent
tuber cinereum (t) and a dilated infundibular recess (i) are seen anterior to the mamillary bodies (m). Note to
the vascular structure of the third ventricle floor. cNeuroendoscopic view showing a steep third ventricle
floor in a myelomeningocele patient. A narrow tuber cinereum (t) is visible just anterior to the mamillary
bodies (m). dNeuroendoscopic view through a very narrow prepontine cistern. Note the close proximity of
the basillary artery (ba) and clivus (cl)

Endoscopic third ventricle from
posteriorly -- a. Infundibular
recess b. tuber cinereum c.
mammillary bodies
left posterior communicating artery (a),
mammillary body (b), and right posterior
hypoplasic communicating artery (c) ---
measurement performed between the
posterior communicating arteries using
Geogebra software (a-b = 11.3 mm),

Endoscopic third
ventricle from
posteriorly --
a. Infundibular recess b.
tuber cinereum c.
mammillary bodies
From front – through
lamina terminalis

In the descriptive analysis of the 20 specimens, the PCoAs
distance was 9 to 18.9 mm, mean of 12.5 mm, median of 12.2
mm, standard deviation of 2.3 mm.

Optic chiasma – infundibulum – Mamillary
bodies

The AcomA complex is usually above the optic chiasm (70 % of cases)
(Rhoton 2003 ) . The AcomA is similar to the textbook description in three-
fourths of cases. In about 10 % of cases, it can be hypoplastic or even
duplicated and triplicated (Lang 1995 ) .
• 1. Supra-chiasmatic
cistern
• 2. Chiasmatic cistern
• 3. Sub -chiasmatic
cistern

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.

Below the OT & A1 you will see PComA
Endoscopic view of the anterior part of the Left Suprasellar area [ = Sub-
Chiasmatic Cisttern ] . A1 first segment of the anterior cerebral artery, AChA
anterior choroidal artery, GR gyrus rectus, ICA internal carotid artery, OC optic chiasm,
ON optic nerve, OT optic tract, PCoA posterior communicating artery, PG pituitary
gland, PitS pituitary stalk, MB midbrain, U uncus

Chiasmatic cistern –
The chiasmatic cistern is located in front of the
optic chiasm and above the sella turcica. In the lateral border of the
chiasmatic cistern the first part of the ICAi is visible.
lt ICA SEEN ON LT SIDE.. A HOLE IN THE ARACHNOID..
THE STALK JUST BEHIND IT.. THE DIAPHRAGM SEEN IN
5/6 O CLOCK POSITION..

CSF rhinorrhoea case
Closed with hadad flap
lt ICA SEEN ON LT SIDE.. A HOLE IN THE ARACHNOID..
THE STALK JUST BEHIND IT.. THE DIAPHRAGM SEEN IN
5/6 O CLOCK POSITION..

Sub-chiasmatic cistern = Supra
sellar area = Supr-sellar cistern

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

Interpeduncular cistern[ = basal
cistern ]

Interpeduncular cistern
IR = infundibulum

Interpeduncular cistern -- Removal of the upper clivus (dorsum sella and
posterior clinoids) provides an excellent view of the interpeduncular cistern
Once the gland has been completely dissected from
the surrounding dura, the pituitary aperture or
diaphragm should be transected along with the
superior intercavernous sinus. This allows the
transposition of the gland into the suprasellar space,
between the optic nerves. This maneuver exposes the
dorsum sella and posterior clinoids that can now be
safely removed. An osteotomy between the dorsum
sella and the posterior clinoids is advised to avoid
excessive traction while removing the clinoid, which
can be risky for the third nerve and carotid artery.

Right supraorbital approach (30 optic).
Window between cn II and ICA: 1 left
PCoA, 2 left P2, 3 left cn III, 4 left P1, 5
left SCA, 6 BA, 7 doubled right SCA, 8
right cn III, 9 right P1, 10 mammillary
bodies, 11 tuber cinereum, 12 right
PCoA, 13 right M1.* sucker

Mammillary bodies
Without removing the DS ,
Subchiasmatic view downwards
After removing the DS &
midclivus

Craniopharyngioma
https://www.facebook.com/groups/4
05175366256295/permalink/552393
251534505/?stream_ref=2

CRANIOPHARYNGIOMAS-Removal corridors.

https://www.scienceopen.com/document_file/84699ab2-4980-4f70-a5b0-
c8d95a1fb6a2/PubMedCentral/84699ab2-4980-4f70-a5b0-c8d95a1fb6a2.pdf
FIGURE 4. The capsule of the cystic craniopharyngioma was firmly attached to the left
hypothalamus, the stalk was dislocated to the right side (Patient 6). The outgrowth of the
craniopharyngioma from proximal stalk is recognizable A. Complete removal of the capsule was
possible, but produced subpial blood injection over the left hypothalamic surface B. MRI scan
revealed a small ischemic injury in the left hypothalamus C. This patient had transient sleep
disorder, moderate hyperphagia and memory problems (see also a supplemented video
material 1).

FIGURE 2. In this cystic craniopharyngioma (Patient 5), the stalk was centrally
infiltrated close to the pituitary and could not be preserved A. The incipient third
ventricle entrance is seen from intracavitary view. The slit into the third ventricle is
still covered with tumour capsule B. Complete removal of the capsule opened the
third ventricle C. Petehiae in the hypothalamus bilaterally resulted from apparently
gentle traction and blunt dissection of the capsule away from the hypothalamus
D. Psychoorganic change, disorientation and memory deficits were noticed in less
than a week after surgery, the transient sleep disorder become apparent in the
second week postoperatively (see also a supplemented video material 2).

FIGURE 3. Large craniopharyngioma (Patient 3) produced unilateral hydrocephalus
by obstructing the right formen of Monro A. The dome was filled with soft
cholesterine cristals B, which were easily removed. Lower limbus of the right foramen
of Monro is seen through the empty third ventricle D. Despite bilateral preservation
of anteromedial hypothalamus C and stalk preservation E, the patient developed
panhypopituitarism and diabetes insipidus with long lasting psychoorganic change

Supratentorial arteries
• http://dc496.4shared.com/doc/2vRIALeU/pre
view.html

Interpeduncular cistern
3rd ventricle is visualised
..through the tuber cinereum

Recurrent artery of Anterior cerebral
artery = Recurrent artery of Heubner

The recurrent artery of Heubner usually origins from the post-communicating segment of the anterior
cerebral artery (ACA). It doubles back the ACA to reach the medial part of the Sylvian fi ssure, below
the anterior perforated substance. Sometimes its path is so long that the artery loops below the basal
surface of the frontal lobes. Not frequently more than one recurrent arteries can be present (Rhoton
2003 ). According to Lang the artery is double in about 30% of cases (Lang 1995 ) .

3rd ventricle entered through
1. Supra optic chiasmic route – by Lamina terminalis
2. Infra optic chiasmic route – by Tuber cinerereum
Infra optic chiasmic route – by
Tuber cinerereum

3rd ventricle entry by - Supra optic chiasmic route – by
Lamina terminalis

CC corpus callosum, CP choroid plexus, MI massa intermedia, PC posterior commissure, T
thalamus, ThV fl floor of the third ventricle, yellow arrow opening of the Silvius aqueduct, red
asterisk suprapineal recess, white asterisk ( left ) lateral ventricle, white circles foramen of
Monro

Different positions of the anterior inferior cerebellar artery (AICA) in relation to the
internal auditory meatus.

Don’t use cutting bur while drilling “Frontal T” in
Draf 3 – Use only diamond bur – we may injure
the dura .

HADAD FLAP ---1, area
of origin of the nasoseptal flap (dotted line); 1b, area of origin of the
extended nasoseptal flap, including the floor of the nasal fossa, and if
necessary, the mucosa of the inferior meatus; 2, position of the nasoseptal
flap used for repair of the anterior and posterior ethmoid roof and
cribriform plate; when bilateral flaps are taken, the anterior skull base
can be repaired from orbit to orbit; 3, position of the nasoseptal flap
used for repair of the sellar and parasellar regions; 4, position of the nasoseptal
flap used for repair of the region of the clivus; the arrows indicate
the different ways in which the nasoseptal flap (HBF) can be rotated
from the nasal septum for repair of different zones of the cranial base.

pituitary tumors schematic diagram.

Fig. 13.17 Classification of Knosp et al.10 grading the cavernous sinus extension
when compared with lines drawn medial through the
middle and on the lateral aspect of the carotid arteries—grades 0 to 3. Grade 4
encases the carotid.

Liliequist membrane - Interpeduncolar cistern separated from prepontine
cistern by the mesencephalic leaf of LM.
Liliequist

Craniopharyngioma removal -
Lilliquest membrane & Basillar artery

LM through subtemporal approach

1st olfactory neuron seen in draft 3

Outside-in approach of draf III –
similar like outside-in mastoid
Inside-out approach of draf III –
similar like Inside-out mastoid

The wedge bone between V2 & Vidian nerve
decreases as we go posteriorly towards petrous
carotid

The wedge bone between V2 & Vidian nerve decreases
as we go posteriorly towards petrous carotid

anterior ethmoidal artery ( AEA) and nerve
(AEN) , anterior falcine artery (AFA)

Trigeminal area at Cerebello Pontine
Angle – along with my voice
Click
http://www.youtube
.com/watch?v=YBqk
4Jdnxic

CAROTID COURSE
Click
http://www.youtube.c
om/watch?v=JlNmSI3t
S8Q

PETROCLIVAL MENINGIOMA DECISION
MAKING
•Click
http://www.youtube.com
/watch?v=kUa9fQ4_aQY

Frontal sinus surgery concepts – must for to do DRAF-III
– Don’t use cutting burr while drilling the Frontal-T ,
high chances of injuring the dura -- use only dimond
drill
Click
http://www.youtube.com
/watch?v=2rhafq3Ur0s

Hemifacial spasm
Video-1
http://www.youtube.com/watc
h?v=-zlymD2LYsM
Video-2
http://www.youtube.com/watc
h?v=gGyQFh3PqPg

Mandibulotomy [ Mental nerve
bilaterally ]

Fig. 74a, b The reference level is the acousticofacial nerve
bundle. The anterior inferior cerebellar artery, lying between
the auditory and facial nerves, is found in 38% of cases.

7up- 7th is above
Coca cola – cochlear n. is cola[=lower]

SKULL BASE 360°
Above presentation is
For
Please click or copy/paste in URL or weblink area
http://www.slideshare.net/muralichandnallamoth
u/edit_my_uploads
[ Dated: 19-4-14 ]
I will update continuosly with date tag at the end as I am getting more
& more information

Skull base 360°- part 2

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Skull base 360°- part 2