Clivus 360°

Clivus 360°21-12-201610.51 pm

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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Sphenoid osteum

Sphenoid osteum present at the juction of upper 2/3rd

& lower 1/3rd junction of Superior turbinate – this became very useful to me in extensive fungal sinusitis

with polyposis & bleeding.

Three sequential indentations are made with the blunt end of the 4-mm microdebrider blade starting at the medial upper limit of

the posterior bony choana and moving directly superiorly medial to the cut edge of the superior turbinate.

Basi occiput & basi sphenoid

Both clivus & petrous bone devidedinto three 1/3rds

Clivus

1. Upper Clivus

2. Mid Clivus

3. Lower Clivus

One neurosurgeon classified into 4 quadrants like this

The “Ventral” Rule of Three - 3 turbinates codes to upper,middle, lower Clivus ...

Pneumatization of the sphenoid sinus

In conchal sphenoid surgical landmarks –

1. posterior end of vomer or keel of sphenoid tells about the position of pituitary

2. lateral boarder of posterior choana [ or MPP ]tells about paraclival carotid & sellar carotid C-SHAPE convex is lateral to this line

3. posterior lower boarder of vomer is at the junction of middle & lower 1/3rd clivus & it is exactly at foramen lacerum –my understanding

Upper Clivus

Accoding to literature of lateral skull base - by Prof. Mario sanna -1. Upper clivus – Upto 6th nerve entry dorello’s canal (petro-clival junction)

2. Middle clivus – from 6th nerve to jugular foramen 3. Lower clivus – from jugular foramen to foramen magnum

Lateral skull base Anterior skull base

According to literature of anterior skull base –The middle third clivus (M. 1/3rd) begins at the sella floor (SF) and extends to

the floor of the sphenoid sinus (SSF), and the lower third (L. 1/3rd) extends from the floor of the sphenoid sinus to the foramen magnum (FM).

Lateral skull base Anterior skull base

Mid clivus is from “Floor of sella to Floor of sphenoid” – best Mneumonic – is nothing but clivus between paraclival carotids

Cadaveric dissection demonstrating that instrumentation without adequate removal of the floor of the sphenoid sinus results in a straight instrument being driven high into the middle third of the clivus beneath the pituitary fossa. Removal of the floor of the sphenoid sinus (SS) will allow

access to the junction of the posterior sphenoid floor and adjacent clivus.

Cadaveric dissection in the plane between the periosteal layer of dura and the meningeal layer of dura (MD) covering the right side of the pituitary gland. The pituitary dentate ligaments (DL) can be clearly visualized. CS,

cavernous sinus.

Pituitary Translocation for Access to the Upper Third of the Clivus

Cadaveric dissection of the sphenoid sinus demonstrating the removal of bone over the anterior genu of the intracavernouscarotid arteries, sella, tuberculum sella, and the posterior half of the planum sphenoidale (PS). CCA, anterior genu of the intracavernouscarotid artery; IIS, inferior intercavernous sinus; SIS, superior intercavernous sinus; P, pituitary gland.

Fig. 19.23 Cadaveric dissection demonstrating the osteotomies at the base of the posterior clinoids (PC) for separation with the body ofthe dorsum sella (DS). P. CCA , posterior genu of the intracavernous carotid artery; PCA, paraclival carotid artery; ICCA, intracranialcarotid artery; BA, basilar artery; PL, posterior lobe of the pituitary gland; AL, anterior lobe of the pituitary gland.

Cadaveric dissection demonstrating the osteotomies at the base of the posterior clinoids (PC) for separation with the body of the dorsum sella (DS). P. CCA , posterior

genu of the intracavernous carotid artery; PCA, paraclival carotid artery; ICCA, intracranial carotid artery; BA, basilar artery; PL, posterior lobe of the pituitary gland;

AL, anterior lobe of the pituitary gland.

Cadaveric dissection image demonstrating the close anatomical relationship of the posterior clinoid (PC) with both the intracranial carotid artery (ICCA)

and the posterior genu of the intracavernous carotid artery (P. CCA). AL, anterior lobe of the pituitary gland; PL, posterior lobe of the pituitary gland;

BA, basilar artery.

green dotted triangle area for entry of the endoscope into the interpeduncular fossa

Normal pituitary YELLOW in color

• Anterior & posterior lobe of pituitary

ICAc cavernous portion of the internal carotid artery, IPS inferior petrosal sinus,

PAp petrous apex, SPCG sphenopetroclivalgulf, 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 ).

Upper clivus – Upto 6th nerve entry dorello’s canal (petro-clival junction)

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 ).

Pregnant of upper clivus is Sella

Endoscopic view of the fl oor of the third ventricle. The dorsum sellae and the upper premesencephalic (mammillary bodies) region are evident.

DS dorsum sellae, IR infundibular region (infundibulum), MBs mammillary bodies, PS pituitary stalk, ThV fl fl oor of the third ventricle

0° endoscope. In the next pictures the retrosellar area is presented when an endoscope is inserted behind the pituitary stalk and orientated downwards (arrows). The dorsum sellae is

outlined with a dotted line. - From Atlas of Endoscopic Anatomy for Endonasal lntracranial Surgery ; Paolo Cappabianca

30° endoscope. After the introduction of a downward orientated endoscope behind the dorsum sellae the basilar tip is visualized.

PCoA = posterior communicating artery, SCA = superior cerebellar artery, P1-P2 = posterior cerebral artery.

30° endoscope. Right side. closer view. PCoA = posterior communicating artery. SCA = superior cerebellar artery. P1 = posterior cerebral artery.

30° endoscope. Left side. closer view. SCA = superior cerebellar artery. P1-P2 = posterior cerebral artery.

PCoA = posterior communicating artery.

ENDOSCOPIC ENDONASAL PITUITARY TRANSPOSITION APPROACH TO THE SUPERIOR CLIVUS - Rare basilar or PCA aneurysms could be accessed as well , though this requires significant experience and very careful patient selection.

A. Preoperative CTA showing a three-dimensional reconstruction view of a large PCA aneurysm causing an oculomotor nerve palsy. B. Intraoperative view of the aneurysm before clipping. C. Intraoperative view of the aneurysm after clipping. Intraoperative angiogram showing complete obliteration of the aneurysm and patency of normal basilar apex branches.

A. Preoperative CTA showing a three-dimensional reconstruction view of a largePCA aneurysm causing an oculomotor nerve palsy. B. Intraoperative view of the aneurysm beforeclipping. C. Intraoperative view of the aneurysm after clipping. Intraoperative angiogram showing

complete obliteration of the aneurysm and patency of normal basilar apex branches.

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.

Pituitary transposition (Upper clivus): Take special care to identify and preserve thesuperior hypophyseal arteries. (SHA)

Extradural:Dissect the pituitary gland from the remainingsellar floor and posterior wall.Lift the pituitary gland, expose and drill out theposterior clinoids.

Intradural:Open the sellar dura anteriorly and dissect the dura from the tunica.Transect the ligaments that join these two layers and the inferior hypophyseal arteries. Divide the diahragm exposing the stalk of the pituitary.Transpose the gland superiorly over the chiasm.

Endoscopic view with 45º lens after pituitary transposition. MB:mammillary bodies; PCA: posterior cerebral artery; PCoA: posterior communicatingartery; SCA: superior cerebellar artery; VA: vertebral artery; III: third cranial nerve

Mid Clivus

Mid clivus is from “Floor of sella to Floor of sphenoid” – best Mneumonic – is nothing but clivus between paraclival carotids

Lower half of paraclival carotid - caudal part, the lacerum segment of the paraclival carotid

”The unsolved surgical problem remains the medial wall of the ICA at the level of the anterior foramen lacerum, until now unreachable with the available surgical

approaches." - In lateral skull base by Prof. Mario sanna – this unreachable is Carotid-Clival window which is accessable in Anterior skull base

Infrapetrous Approach

Carotid-Clival window – Mid clivusa. Petrosal face

b.Clival face

1. Mid clivus – from floor of sella to floor of sphenoid sinus 2. From carotid-clival window we can reach petrous apex by infra-petrous approach

3. Mid clivus is in between paraclival carotids

1. Mid clivus – from floor of sella to floor of sphenoid sinus 2. From carotid-clival window we can reach petrous apex by infra-petrous approach

3. Mid clivus is in between paraclival carotids

1. Mid clivus – from floor of sella to floor of sphenoid sinus 2. From carotid-clival window we can reach petrous apex by infra-petrous approach

3. Mid clivus is in between paraclival carotids

JT = jugular tubercle separates the hypoglossal canal from Jugular foramen

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

The foramen lacerum (FL) is located lateral to the floor of the sphenoid sinus at the level of the spheno-petro-clival confuence.

JT jugular tubercle, HC hypoglossal canal –

addFig 3.78 also

Pontomedullary junction = Vertebro-basillar junction = Junction of Mid clivus & Lower clivus = foramen lacerum area The pontomedullary junction. The vertebral artery junction is at the level of the

junction of the inferior and midclivus. The basilar artery runs in a straight line on the surface of the pons. The exit zones of the hypoglossal and abducent nerves are at the same level. The abducent nerve exits from the pontomedullary junction, and ascends

in a rostral and lateral direction toward the clivus.

Very rare specimen..The vbj is far inferior to floor of sphenoid sinus

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.

Clival recess

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

understanding

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

Anterior cranial fossa dura Posterior cranial fossa dura

Lower Clivus

Groove for medulla on Lower Clivus [ = Basi Occiput ]

1. 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,

2. The SCG [Supracondylar groove] represents a reliable landmark for hypoglossal canal (HC) identification (red arrow) (Morera et al. 2010 ) .

The tubercular compartment corresponds to the Jugular tubercle ( JT )

Line along the lateral pharyngeal tubercle [ LPT ] passes through Jugular tubercle [ JT ] – so when you are drilling LPT in anterior skull

base you will land up on JT .

LPT lateral pharyngeal tubercle, OC occipital condyle, PT pharyngeal tubercle, SCG supracondylar groove

Jugular tubercle ( JT )

Line along the lateral pharyngeal tubercle [ LPT ] passes through Jugular tubercle [ JT ] – so when you are drilling LPT in anterior skull base you will land up on JT .

Red rings = hypoglossal canals , yellow ring = pharyngeal tubercle [ PT ] , blue rings = lateral pharyngeal tubercle [ LPT]

Line along the lateral pharyngeal tubercle [ LPT ] passes through Jugular tubercle [ JT ] – so when you are drilling LPT in anterior skull base you will

land up on JT . yellow ring = pharyngeal tubercle [ PT ] , blue rings = lateral pharyngeal

tubercle [ LPT] , green ring = Jugular tubercle

Hypoglossal canals

From front – through nose From back

Lower clivus devided into 1. tubercular compartment [ Above red line ]2. condylar compartment [ Below red line ]

Hypoglossal canal present at the junction of anterior 1/3rd & posterior 2/3rd

Lower clivus + petrous bone [ base ]

Petrous bone

devidedinto three

1/3rds

Lower clivus + petrous bone [ base ] + Zygomatic bone

Petrous bone devidedinto three 1/3rds

Lateral skull base view – observe the petrous apex

Lower clivus + petrous apex in anterior skull base

1. observe the petrous apex in both views2. hypoglossal canal medial to parapharyngeal carotid & jugular fossa

ICA Vertebro-basillar

1. 3th nerve between PCA & SCA 2. 4th nerve coming from dorsal brain stem passes above SCA [ some times SCA has two branches] 3. 6th nerve originates at VBJ [ Vertebro-basillar junction ] . 6th

nerve may have two rootlets of origin , one above & one below the AICA 4. In 30 % of cases AICA passes in between 7th & 8th nerves 5. PICA passes between two bundles of 12th nerve & between two roots of 11th nerve [ 11c = 11th cervical , 11s = 11th spinal root ] 6. The exit zones of the 6th and 12th

nerves are at the same level [ same vertical line when view from Transclival approah ( through lower clivus ) ]7. 11th nerve behind left vertebral artery at cervico-medullary junction . 11th is closely related to the vertebral artery (VA) at the point of dural entrance

1. 3th nerve between PCA & SCA 2. 4th nerve coming from dorsal brain stem passes above SCA [ some times SCA has two branches] 3. 6th nerve originates at VBJ [ Vertebro-basillar junction ] . 6th nerve may have two rootlets of origin , one above & one below the AICA 4. In 30 % of cases AICA passes in between 7th & 8th nerves 5. PICA passes between two bundles of 12th nerve & between two roots of 11th

nerve [ 11c = 11th cervical , 11s = 11th

spinal root ] 6. The exit zones of the 6th and 12th nerves are at the same level [ same vertical line when view from Transclival approah ( through lower clivus ) ]7. 11th nerve behind left vertebral artery at cervico-medullary junction . 11th is closely related to the vertebral artery (VA) at the point of dural entrance

1. 3th nerve between PCA & SCA 2. 4th nerve coming from dorsal brain stem passes above SCA [ some times SCA has two branches]

3. 6th nerve originates at VBJ [ Vertebro-basillar junction ] . 6th nerve may have two rootlets of origin , one above & one below the AICA 4. In 30 % of cases AICA passes in between 7th & 8th nerves

5. PICA passes between two bundles of 12th nerve & between two roots of 11th nerve [ 11c = 11th cervical , 11s = 11th spinal root ] 6. The exit zones of the 6th and 12th nerves are at the same level [ same vertical line when view from Transclival approah ( through lower

clivus ) ]7. 11th nerve behind left vertebral artery at cervico-medullary junction . 11th is closely related to the vertebral artery (VA) at the point of dural

entrance

1. Laceral carotid & jugular tubercle & lower cranial nerves 9th ,10th ,11th are in the same line .

2. hypoglossal canal present between occipital condyle/foramen magnum & jugular tubercle

1. Laceral carotid & jugular tubercle & lower cranial nerves 9th ,10th ,11th are in the same saggital line .

2. hypoglossal canal present between occipital condyle/foramen magnum & jugular tubercle3. PICA passes between two bundles of 12th nerve & between two roots of 11th nerve [ 11c =

11th cervical , 11s = 11th spinal root ] & encirlces lower cranial nerves 9th ,10th ,11th

Trans clival trans odontoid trans tubercular view of brainstem and cranial nerves....note sharp oblique course of 6 nerve and two trunks of 12 nerve

which joins to form single trunk in hypoglossal canal...a dorsal clival branch of meningohypophyseal trunk is seen along six nerve close to dorello

canal...AICA is seen going towards IAM.

Coronal cut – hypoglossal canal

Inferior clival line (Fernandez-Miranda et al. 2012 ) The longus capitis and rectus capitis anterior muscle attach on the inferior surface of the clivus. Below the RCAM the occipito-cervical joint capsule lies. The area of attachement of the RCAM

has been named inferior clival line (Fernandez-Miranda et al. 2012 ) and correspond to the SCG [supracondylar groove ] (that is a landmark for the hypoglossal canal).

AAAM anterior atlanto-axial membrane, AAOM anterior atlanto-occipital membrane, AIM anterior intertrasversarius muscle, Cl clivus, C1 atlas, C1TP transverse process of C1, C2 axis, ET eustachian tube, JF jugular foramen, JT jugular tubercle, HC hypoglossal canal, ICAc cavernous portion of the internal carotid artery, LCapM longus capitis muscle, LColM longus colli muscle, PG pituitary gland, RCAM rectus capitis

anterior muscle, RCLM rectus capitis lateralis muscle, blue-sky arrow apical ligament, green arrow external ori fi ce of the hypoglossal canal, black arrow lateral atlanto-occipital ligament, black asterisk foramen

lacerum

The area of attachement of the RCAM has been named inferior clival line (Fernandez-Miranda et al. 2012 ) and correspond to the SCG [supracondylar

groove ] (that is a landmark for the hypoglossal canal).

SCG = Supracondylar groove – is an important landmark to hypoglossal canal

When we are drilling lower clivus – lateral to hypoglossal canal we get Jugular fossa

Jugular fossa is just lateral to hypoglossal canal

Cadaveric dissection image demonstrating structures seen following dissection of the lower third of the clivus. Note how

the basilar arteries and vertebral arteries can be extremely tortuous in their course.

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.

Cadaveric dissection with image taken just above the skeletonized hypoglossal canal (HC) at the cerebellopontine angle. The anterior inferior cerebellar artery (AICA) can be seen intimately associated with the vestibulocochlear nerve (CN VIII), facial nerve

(CN VII), and the nervus intermedius (NI). The posterior inferior cerebellar artery (PICA) can be seen running between the vagus (CN X) and spinal and cranial portions

of the accessory nerves (CN XI – S, CN XI – C).

Cadaveric dissection image taken following dissection of the right lower third of the clivus. As the posterior inferior cerebellar artery (PICA) courses from the vertebral

artery (VA) it frequently runs through the rootlets that make up the hypoglossal nerve (CN XII). It may tent these rootlets as it courses to the cerebellomedullary fissure to

run intimately with the cranial nerves IX – XI. CN X, vagus nerve; HC, hypoglossal canal; IPS, inferior petrosal sinus; BA, basilar artery; FM, foramen magnum; A. AOM, anterior

atlanto-occipital membrane.

The hypoglossal nerve do not exit with VA. It can have maximum 3 outlets. On the contrary, C1 roots exit with the VA.

Through endoscopic lateral skull base - The curved vertebral artery displaces and stretchesthe hypoglossal nerve fibers.

Through anterior skull base

HC = hypoglossal canal , JT= Jugular Tubercle

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

Hypoglossal is just behind the upper end of parapharyngel carotid – very easy way to

identify 12th nerve in paraphayrngeal space – Dr.Satish jain

FCB & JT & LCNs are at same level from anterior to posterior

FCB = Fibrocartilago basalis , JT = Jugular tubercle , LCNs Lower cranial nerves ( = 9th , 10th, 11th )

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

Posterior cranial fossa (jugular and hypoglossal areas); vision obtained with a 45° endoscopethrough a clival window

AICA anteroinferior cerebellar artery, BA basilar artery, IO inferior olive, LA labyrinthine artery, PCA posterior cerebral artery, PcomAposterior communicating artery, PICA posteroinferior cerebellar artery, POV preolivary vein, RPA recurrent perforating artery, SCA

superior cerebellar artery, SPV superior petrosal vein, VA vertebral artery, IIIcn oculomotor nerve, Vcn trigeminal nerve, VIcn abducensnerve, VIIcn facial nerve, VIIIcn vestiboloacoustic (statoacoustic) nerve, IXcn glossopharyngeal nerve, Xcn vagus nerve, XIIcn hypoglossal

nerveThe LA usually originates from the AICA, rarely directly from the BA. It feeds the inner ear. AICA and SCA course through the

cerebellopontine cistern. AICA enters the lower part of cerebellopontine cistern and it usually bifurcates into its rostral and caudal trunks within the cistern. PICA origins from the VA, near the inferior olive, and passes posteriorly around the medulla. It could pass rostral, caudal or even between the rootlets of the hypoglossal nerve. RPA(s) are arteries that present a recurrent course and reach the root entry zone of

the VII and VIII cns. They send branches to these nerves and to the brainsterm around the root entry zone.

Intracranial hypoglossal region. Anterior endoscopic transnasal-transclival vision is compared with a posterior retrosigmoid endoscopic one

JF jugular foramen, JT jugular tubercle, IO inferior olive, PICA posteroinferior cerebellar artery, VA vertebral artery, IXcnglossopharygeal nerve, Xcn vagus nerve, XIcnCR cervical roots of accessory nerve, XIcnSR spinal roots of accessory nerve,

XIIcn hypoglossal nerveCranial nerves IX and X present a close relationship with the fi rst portion of the PICA. They are protected by the arachnoid

membrane (Roche et al. 2008 ) . The roots of cranial nerve XIcn from the spine pass through the foramen magnum posterior to the vertebral artery. Within the hypoglossal canal, XIIcn is surrounded by a venous plexus and dural and arachnoid

sheets. Branches of the ascending pharyngeal artery coursing through the hypoglossal canal are seen in about 50 % of cases (Lang 1995 ) . Also branches from the posterior meningeal artery have been described (Janfaza and Nadol 2001 ). The

transcisternal vein to the area of the JF can be seen. Also, veins to the hypoglossal canal can be present. The hypoglossal nerve do not exit with VA. It can have maximum 3 outlets. On the contrary, C1 roots exit with the VA.

Nerves and vessels of the posterior cranial fossa. (a) Basilar tip region, endoscopic view (b) Right cerebellopontine angle, endoscopic view from anterior. (c) Right laterobulbar region, endoscopic intracranial view. (d) Three-dimensional reconstruction of the posterior cranial fossa. AICA,

anteroinferior cerebellar artery; BA, basilar artery; DV, Dandy’s vein; Fl, flocculus; IIIcn (CS), intracavernous portion of the oculomotor nerve; IIIcn, oculomotor nerve; IO, inferior olive; IXcn, glossopharyngeal nerve; IX–X, glossopharyngeal and vagus nerves; LA, labyrinthic artery; LPMVN,

lateropontomesencephalic vein network; P1, posterior cerebral artery (first segment); P2, posterior cerebral artery (second segment); PcomA, posterior communicating artery; PICA, posteroinferior cerebellar artery; POV, preolivary vein; PV, peduncular vein; RPA, recurrent perforating artery; SCA, superior cerebellar artery; SPV, superior petrosal vein; TGAs, thalamogeniculate arteries; TPAs, thalamoperforating arteries; VA,

vertebral artery; Vcn, trigeminal nerve; VIcn, abducens nerve;VII–VIIIcn, facial nerve and vestibuloacoustic nerve; VIIcn, facial nerve; VIIIcn, vestibuloacoustic nerve; X/XIcn, vagus and accessory nerves; XIcn,

accessory nerve; XIIcn, hypoglossal nerve.

TPV & LAPMVs , PMedSV unite to form SPV AICA anteroinferior cerebellar artery, BA basilar artery, LPMVN lateropontomesencephalic venous network, PBs pontine branches, PcomA posterior communicating artery, PICA posteroinferior cerebellar artery, PMedSVpontomedullary sulcus vein, SCA superior cerebellar artery, SPV superior petrosalvein, TPAs talamoperforating arteries, TPV transverse pontine vein, IIIcn oculomotornerve, Vcn trigeminal nerve, VIcn abducens nerve, VIIcn facial nerve, VIIIcn vestibulo-cochlear (statoacoustic) nerve

PICA passes between two bundles of 12th nerve 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.

PICA can be seen running between the vagus (CN X)

PICA can be seen running between spinal and cranial portions of the accessory nerves (CN XI – S, CN XI – C).

Endoscopic lateral skull base

Endoscopic anterior skull base

Lateral skull base – far lateral approach

PICA passes between two bundles of 12th nerve & between two roots of 11th nerve

Cadaveric dissection image demonstrating the posterior inferior cerebellar artery (PICA) running between the vagus (CN X) and the cranial accessory nerve rootlets (CN XI-C) at the position where

the nerves exit the brainstem. CN VII, facial nerve; CN VIII, vestibulocochlear nerve; NI, nervusintermedius; CN IX, glossopharyngeal nerve; CN XI-S, spinal accessory nerve

The tip of the endoscope lies between the acousticofacial nerve bundle and the anterior inferior cerebellar artery. The posterior inferior cerebellar artery arises from the vertebral artery, runs between the root fibers of the hypoglossal nerve, and forms a loop below the roots of the lower cranial nerves, before coursing in a posterior direction.

Transcochlear approach leads to Mid clivus above foramen lacerum [ FL ] & lower clivus below foramen lacerum [ FL ]

AAAM anterior atlanto-axial membrane, AAOM anterior atlanto-occipital membrane, AIM anterior intertrasversarius muscle, Cl clivus, C1 atlas, C1TP transverse process of C1, C2 axis, ET eustachian tube, JF jugular foramen, JT jugular tubercle, HC hypoglossal canal, ICAc cavernous

portion of the internal carotid artery, LCapM longus capitis muscle, LColM longus colli muscle, PG pituitary gland, RCAM rectus capitisanterior muscle, RCLM rectus capitis lateralis muscle, blue-sky arrow apical ligament, green arrow external ori fi ce of the hypoglossal canal,

black arrow lateral atlanto-occipital ligament, black asterisk foramen lacerum

Note CL [ Mid clivus above FL & lower clivus below FL ] in these photos after drilling of cochlea

Note CL [Mid clivus above FL & lower clivus below FL ] in these photos after drilling of cochlea

The clivus bone (CL) can be seen medial to the internal carotidartery (ICA). JB Jugular bulb

In the lower part of the approach, the glossopharyngeal nerve

(IX) can be seen. V Trigeminal nerve, VIII Cochlear nerve, AICA Anterior

inferior cerebellar artery, CL Clivus bone, DV Dandy’s vein, FN Facial

nerve, FN(m) Mastoid segment of the facial nerve, FN(t) Tympanic segment

of the facial nerve, GG Geniculate ganglion, ICA Internal carotid

artery, JB Jugular bulb, MFD Middle fossa dura, SCA Superior cerebellar

artery, SS Sigmoid sinus

Note CL [Mid clivus above FL & lower clivus below FL ] in these photos after

drilling of cochleaBT- basal turn of the cochlea Fig. 8.34 The bone medial to the

internal carotid artery (ICA) has beendrilled and the clivus bone (CL) has been reached. FN Facial nerve,JB Jugular bulb

Note CL [Mid clivus above FL & lower clivus below FL ] in these photos after

drilling of cochleaNote cochlear aqueduct [ CA ]

Here ICA is vertical part of carotid infrontto cochlea – this is not paraclival carotid

Note CL [Mid clivus above FL & lower clivus below FL ] in these photos after

drilling of cochlea

Note CL [Mid clivus above FL & lower clivus below FL ] in these photos after

drilling of cochleaNote the contralateral vertebral artery [ CVA ] in below photo

Mid clivus above FL & lower clivus [ CL ] below FL in Infratemporal fossa approach

ITFA with Transcondylar [ = TC ] Transtubercular [ = TT ] approach

Here Transcondylar is through Occipital Condyle ;Transtubercular is through Jugular tubercle &

lateral pharyngeal tubercle

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.)

Note 12th nerve in between JT ( Jugular tubercle ) & OC ( Occipital condyle ) in both lateral & anterior skull base

Lateral skull base Anterior skull base

Hypoglossal is just behind the upper end of parapharyngel carotid – very easy way to

identify 12th nerve in paraphayrngeal space – Dr.Satish jain

ITF-A + Transcondylar, transtubercular extension improves posteroinferolateral and medial exposure.

Comparison of classic ITFA (zone delimited by the red line) and ITFA with transcondylar–transtubercular extension (zone delimited by the blue line). * jugular

process of the occipital condyle , CF carotid foramen , DR digastric ridge , JF jugular foramen , MT mastoid tip . Note hypoglossal nerve at anterior 1/3rd & middle 1/3rd

junction .

Extreme lateral extension [ Far-lateral – Transcondylar ] approach

AFL anterior foramen lacerum , C1 atlas , CO cochlea , ICA internal carotid artery , IJV internal jugular vein , Lv vein of Labbé , M mandible , mma middle meningeal artery

OC occipital condyle , pc clinoid process , pp pterygoid plate , sph sphenoid sinus , sps superior petrosal sinus , TA transverse process of the atlas , TS transverse sinus , V2 maxillary branch of the trigeminal nerve , V3 mandibular branch of the trigeminal nerve , za zygomatic arch , VA vertebral artery , VII facial nerve , IX glossopharyngeal nerve , XI spinal accessory nerve , XII

hypoglossal nerve

Far-lateral approach further extends posteroinferolateral exposure

Schematic illustration of the extreme lateral approach (ELA)

For mid clivus – transcochlearapproah

& For lower clivus – far lateral / transcondylar approach OR

ITF-A + TC + TTFrom decision making of Mario sanna lateral

skull base book

The 6 linear landmarks of the PCF superimposed on a midsagittal T1-weighted MR

imaging from a patient with CMI: herniation (HR), McRae line (MC), clivus (CL), Twining

line (TW), cerebellum (CR), and supraocciput (SO).

http://www.ajnr.org/content/34/9/1758.figures-only?cited-by=yes&legid=ajnr;34/9/1758

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