SKULL BASE 360° Below presentation is

SKULL BASE 360°-Part 2For

SKULL BASE 360°-Part 1Please click or copy/paste in URL or weblink area

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[ Dated: 21-9-14 ] I will update continuosly with date tag at the end as I am getting more

& more information

Below presentation is

SKULL BASE 360°-Part 2

Endoscopic Lateral Skull base (Neuro-otology)Endoscopic Anterior skull base & Microscopic Lateral skull base &Middle cranial fossa skull base &

Open skull base approaches

Art & Presentation by Dr. N. Murali Chand DLO FHM

Fellowship in HIV medicine, MAMC, New DelhiMy website = www.integratedmedicine.co.in

Cell= +91 99496 77605

Orbit

Orbital fascia = Periorbita

Bulbar fascia includes1. 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

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 11. 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- Periorbitaelevated

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.

OPTIC NERVE DECOMPRESSION

Optic tubercle

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 & ONAnterior 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 –

Dr.Janakiram

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 internalcarotid artery ( ICA ), a rare variation: ophthalmicartery passing through the superiororbital 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 typeon 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

Fibrous tissue

FCB-Fibrocartilago basalis at junction of petrous & paraclival carotid

Fibrous tissue surrounds the entrance ofthe vertebral artery into the CPA.

Fibrous tissue surrounds the entrance ofthe vertebral artery into the CPA.

Left side. Combined transsigmoid, suboccipitaland 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) surroundingthe nerve at the level of the stylomastoid foramen (SMF), and

sharp scissors are used to dissect the soft tissues from the bone at thatlevel. 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 thefacial nerve, FN(p) Intraparotid facial nerve, SM Facial nerve at the stylomastoidlevel, 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 Softtissues

Styloid process

Styloid apparatus – superior view Styloid apparatus – lateral view

After the attached muscles have been dissected away, thestyloid 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 enterthe 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 ofthe vascular structures. C Basal turn of the cochlea (promontory), ICA

Internalcarotid 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 ]

Inferior petrosal sinus

HVP hypoglossalvenous plexus

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 ]

Inferior petrosal sinus

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 Transcochlear approach

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 exposureand operative field. PCA Petrous carotid artery; DPA drilled petrous apex; IPS

inferior petrosal sinus; BA basilar artery; VI 6th cranial nerve; AICA anterior inferiorcerebellar 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 gulfarsegment of the abducens nerve, pVIcn petrosal segment of the abducens nerve, white asterisks

dura of the posterior cranial fossa

In middle cranial fossa approach

In middle cranial fossa approach

3rd nerve

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

Relationship of PcomA & 3rd nerve

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 procedurehttp://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).

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 asmall superior and large inferior division just before passing

through the superior orbital fi ssure.

4th nerve

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

Endoscopic lateral skull base

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

5th nerve

Trigeminal area at Cerebello Pontine Angle – along with my voice

Click http://www.youtube.com/watch?v=YBqk4Jdnxic

171

175

6th nerve

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 levelof 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

Courtesy Dr. Tomasz Skibinski

The basilar artery (BA) can be seenvery tortuous.

Gulfar segment of 6th nerve (GS in left picture ) ( gVIcn in right picture )

ICAc cavernous portion of the internal carotid artery, IPS inferior petrosal sinus, PAp petrousapex, SPCG sphenopetroclival gulf, cVIcn cisternal segment of the abducens nerve, gVIcn gulfarsegment of the abducens nerve, pVIcn petrosal segment of the abducens nerve, white asterisks

dura of the posterior cranial fossa

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

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

AICA anterior-inferior cerebellar artery, Cl clivus, CS cavernous sinus, ICAc cavernous portionof the internal carotid artery, IPS inferior petrosal sinus, LPMVN lateropontomesencephalicvenous network, PBs pontine branches, PG pituitary gland, TPV transverse pontine vein, VAvertebral 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.

Grubers ligament

6th nerve passing below gruber’s ligament

ACP anterior clinoid process, APCF anterior petroclinoid fold, DS dorsum sellae, ICF interclinoidfold, 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

6th nerve is freely hanging in the cavernous injury when compared to 3rd & 4th nerve – so postential for injury in

tumor dissection

7th nerve

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

Clickhttp://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.

9th nerve

A closer view of the pars nervosa of the jugularforamen. The glossopharyngeal nerve has its own duralporus, which is situated 0-3 mm upwards from the duralporus of the tenth cranial nerve. The vagus and the accessorynerve exit the posterior fossa together in a sleeve of durathrough the jugular foramen.

Left side. The 30° angled endoscope provides anoverview of the inferior part of the CPA. On the right lies theacousticofacial nerve bundle, with the anterior inferior cerebellarartery; the glossopharyngeal nerve and the vagus nerve,as multiple filaments, form three to five major nerve bundlesand 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 theoverlying 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 thecochlear aqueduct (CA). Note the proximity of the aqueduct to the glossopharyngealnerve (IX).

The bone overlying the transitional zone from the jugularbulb (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 bulbfrom the bone. The jugulocarotid spine of bone (<) can be seen lying between

the internal carotid artery (ICA) and the jugular bulb. * Thefibrous 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

9th nerve – in cadaver

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 theposterior 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, HChypoglossal canal, IAC internal acoustic canal, ICAh horizontal portion of the internal carotidartery, 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

Jugular tubercle [ JT ]

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

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.

JF= Jugular foramen

12th nerve

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.

A closer view of the anterior border of the pontomedullary stem and the vertebral artery junction and originof 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 hypoglossalnerve (12) collect in two bundles, which pierce the dura in

two dural pori. The hypoglossal nerve is situated more anteriorlyand medially than the root fibers of the lower cranial

nerves. The arterial relationship is the vertebral artery, withperforating arteries to the brain stem. The curved vertebralartery 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

SCG = Supracondylar groove

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,

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

Vertebral artery

Robbins level II. 1 Sternocleidomastoid muscle, 2 posterior belly of digastric muscle, 3spinal accessory nerve (common trunk), 4 internal jugular vein, 5 splenius capitis muscle, 6 levatorscapulae muscle, 7 anterior scalene muscle, 8 transverse process of atlas, 9 hypoglossal nerve, 10carotid 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 connectedin front by a short anterior arch and posteriorly

by a longer curved posterior arch. 1, anterior archof 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

Fibrous tissue surrounds the entrance ofthe vertebral artery into the CPA.

Left side. Combined transsigmoid, suboccipitaland extreme lateral approaches provide an overview off the craniocervical junction, the foramen magnum area, and the surrounding structures of the medullary stem.

In transcochlear approach

Anterior cranial fossa

Anterior & Posterior perforated substance

Anterior perforated substance & olfactory track relation

Fronto-polar artery

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

Cisterns

Oculomotor cistern

Oculomotor cistern Cranial nerve III enters the roof included in its own cistern

(oculomotor cistern).

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

Chiasmatic cistern

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

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

Retrosellar

Interpeduncular cistern[ = basal cistern ]

Interpeduncular 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 bodiesWithout removing the DS , Subchiasmatic view downwards After removing the DS & midclivus

Craniopharyngioma

https://www.facebook.com/groups/405175366256295/permalink/552393251534505/?stream_ref=2

Hypothalamus & 3rd ventricle relation diagram

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/preview.html

Optic pathway

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

Recurrent artery of Heubner

Recurrent artery of Anterior cerebral artery = Recurrent artery of Heubner

The recurrent artery of Heubner usually origins from the post-communicating segment of the anteriorcerebral 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 basalsurface 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

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

Intradural Anatomy

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

1st & 2nd cervical vertebrae

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

the dura .

HADAD FLAP ---1, areaof origin of the nasoseptal flap (dotted line); 1b, area of origin of the

extended nasoseptal flap, including the floor of the nasal fossa, and ifnecessary, the mucosa of the inferior meatus; 2, position of the nasoseptal

flap used for repair of the anterior and posterior ethmoid roof andcribriform plate; when bilateral flaps are taken, the anterior skull basecan 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 nasoseptalflap used for repair of the region of the clivus; the arrows indicate

the different ways in which the nasoseptal flap (HBF) can be rotatedfrom the nasal septum for repair of different zones of the cranial base.

anterolateral endonasal flap.

Pituitary surgery

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.

Cavernous Sinus MRI anatomy

Liliequist membrane [LM]

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

APPROACHES

DRAF III

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

Trans-ptyregoid approach

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

Accessories

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

Deep temporal artery

Trigeminal area at Cerebello Pontine Angle – along with my voice

Click http://www.youtube.com/watch?v=YBqk4Jdnxic

CAROTID COURSE

Clickhttp://www.youtube.com/watch?v=JlNmSI3tS8Q

PETROCLIVAL MENINGIOMA DECISION MAKING

•Clickhttp://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

Clickhttp://www.youtube.com/watch?v=2rhafq3Ur0s

Hemifacial spasm

Video-1http://www.youtube.com/watch?v=-zlymD2LYsMVideo-2http://www.youtube.com/watch?v=gGyQFh3PqPg

Subfrontal craniotomy.

Subfrontal craniotomy.

Mandibulotomy [ Mental nerve bilaterally ]

AFB area

Fig. 74a, b The reference level is the acousticofacial nervebundle. The anterior inferior cerebellar artery, lying between

the auditory and facial nerves, is found in 38% of cases.

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

CBI- Cochlear nerve- Inferior

SKULL BASE 360° Above presentation is

SKULL BASE 360°-Part 2For

SKULL BASE 360°-Part 1Please click or copy/paste in URL or weblink area

http://www.slideshare.net/muralichandnallamothu/edit_my_uploads

[ Dated: 19-4-14 ] I will update continuosly with date tag at the end as I am getting more

& more information