CP angle 360°6-6-20167.07 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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getting more & more information

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Approaches to the brainstem –Rhoton

https://www.youtube.com/watch?v=K-42KXujh0o

Posterior view of CP angle

MINIMALLY INVASIVE RETROSIGMOIDAPPROACH (MIRA) - Port of entry to Endoscopic Lateral Skull Base

Superior anatomical view of the leftcerebellopontine angle (CPA): The CPA is definedas the angle formed in the horizontal section by thepons and the cerebellum in which the trigeminal (V)and acousticofacial nerve bundle (VIII) are located.The angle is bordered laterally and anteriorly by theposterior face of the petrous temporal bone. Thetip of the endoscope (4 mm diameter) is facing theacousticofacial nerve bundle which is the referencelevel, crossing the middle of the CPA from thebrainstem to the internal auditory meatus (IAM), andseparating it into two anatomical areas. Superiorly andanteriorly, the trigeminal area is usually inspected forthe management of trigeminal neuralgia. Inferiorly, thelower cranial nerve area is inspected for treatment ofhemifacial spasm and glossopharyngeal neuralgia.aica indicates anterior-inferior cerebellar artery;m, malleus; i, incus.

Posterior view of CP angle 1. level 1 = Trigeminal area

2. Level 2 = AFB area3. Level 3 = Lower cranial nerve area 4. Level 4 = Foramen magnum area

The petrosal or anterior surface of the cerebellum faces the posterior surface of the temporal bone and the brain stem. The neurovascular bundles define four levels from superior to inferior:

trigeminal, acousticofacial, lower cranial, and foramen magnum.

Right retrosigmoid approach under the operating

microscope. The acousticofacial nerve bundle crosses the middle

of the cerebellopontine angle (CPA). Its entrance into the

porus acusticus provides an unquestionable identification.

The flocculus overlies the root entry zone of the

cochleovestibular and facial nerves. Superiorly, the trigeminal nerve exits the pons and travels obliquely in an anterosuperior

direction toward the petrous apex. Interiorly, the posterior

inferior cerebellar artery and the glossopharyngeal nerve are

seen.

Right retrosigmoid approach under the operatingmicroscope. The acousticofacial nerve bundle crosses the middleof the cerebellopontine angle (CPA). Its entrance into theporus acusticus provides an unquestionable identification.The flocculus overlies the root entry zone of thecochleovestibular and facial nerves. Superiorly, the trigeminalnerve exits the pons and travels obliquely in an anterosuperiordirection toward the petrous apex. Interiorly, the posteriorinferior cerebellar artery and the glossopharyngeal nerve areseen.

Posterior view of the left CPA with a 30° angledendoscope gives a view of CPA contents and permitsobservation of the blind spots by “looking around the corner.” V indicates trigeminal nerve; VI, abducens nerve; IV, trochlear nerve; VII,

facial nerve anteriorly hidden by VIII; VIII, vestibulocochlear nerve; IX, glossopharyngeal nerve; X, vagusnerve; XI, spinal accessory nerve; XII, hypoglossal nerve; aica, anterior-inferior cerebellar artery; DV, Dandy’s vein or superior petrosal vein; SPS, superior petrosal sinus; Tent, tentorium.

Level 1 = Trigeminal area

The trigeminal nerve from the poms to the Meckelcavity (trigeminal cavity). Posterior to the trigeminal nerve liesthe superior petrosal vein (Dandy vein). Superior to thetrigeminal nerve the superior cerebellar artery. In the backgroundand inferiorly, the abducent nerve and basilar arteryare seen. In the background and superiorly, the free border ofthe tentorium and the mesencephalic area are seen.

The entrance of the trigeminal nerve into theMeckel cavity. The superior petrosalvein prior to its entranceinto the superior petrosal sinus is seen.

Closer view of the superior area of the left CPA:tip of the 30° endoscope is above the acousticofacial nerve

bundle (VIII-VII) and its entrance in the internal auditorymeatus (IAM). The trigeminal nerve (V) runs obliquely upward

from the lateral part of the pons toward the petrous apex. It exits the posterior fossa to enter the middle fossa by passingbeneath the tentorial attachment to enter Meckel’s cave.

Posterior to the trigeminal nerve lies the superior petrosal vein or Dandy’s vein (DV) entering the superior petrosal sinus.The trochlear nerve (IV) is seen in the background passing

underneath the tentorium.

Here, the tip of the endoscope is positioned at

the level of the posterior margin of the trigeminal nerve in

order to carry out an inspection above it, visualizing the rostral

and cranial branches of the superior cerebellar artery and

the trochlear nerve. The trochlear nerve disappears under the

free margin of the tentorium. The point of entrance is just

before the cavernous sinus. In the background, the oculomotor

nerve and the posterior cerebral artery, are seen, as well as the free border of the tentorium and the uncus of the

temporal lobe.

The endoscope is positioned between the trigeminal

nerve and the tentorium. The superior cerebellar artery

encircles the brain stem above the trigeminal nerve and below

the trochlear nerve. The superior cerebellar artery, arising as a

single trunk, bifurcates into rostral and caudal trunks. The pontomesencephalic incisure, with the third cranial nerve, lies between the uncus and the trochlear nerve. The posterior

cerebral artery and a branch passing to the mesencephalon

are seen.

Arterial relationships around the oculomotor nerve.The superior cerebellar artery lies interiorly, and the posteriorcerebral artery superiorly. The exit zone of the third cranialnerve between the superior cerebellar artery and the posteriorcerebral artery is seen.

Left side. The trigeminal nerve and Dandy vein are

seen entering the superior petrosal sinus.

Left side. The trigeminal nerve and Dandy vein are

seen entering the superior petrosal sinus.

using the 30° angled endoscope, the Meckel cavity and the intradural course of the abducent nerve are seen delimiting the petrociival area. After piercing the inner layer of the duramater, the nerve changes direction and courses medially toward the petrous apex.

The upper major sensory fibres& lower less motor fibres

Level 2 = AFB area

From Clinical anatomy book

From CP angle book – see other photos – fig 9

Left side. The acousticofacial nerve bundle runs

obliquely from the pons to the internal acoustic meatus in asuperolateral direction. Its length between the entry zone of the nerves and the porus of the internal acoustic meatus varies from 8 mm to 14 mm. A groove or raphe on the posterior surface of the cochleovestibular nerves indicates the division of the cochlear segment interiorly and the vestibular segment superiorly. A labyrinthine artery arises from the loop of the anterior inferior cerebellar artery. The fifth nerve lies in

the background.

Left side. The acousticofacial nerve bundle runs

obliquely from the pons to the internal acoustic meatus in a

superolateral direction. Its length between the entry zone of

the nerves and the porus of the internal acoustic meatus

varies from 8 mm to 14 mm. A groove or raphe on the posterior surface of the cochleovestibular nerves indicates the division of the cochlear segment interiorly and the vestibular segment superiorly. A labyrinthine artery arises from the loop of the anterior inferior cerebellar artery. The fifth nerve lies in the background.

FN & SVN converge as they pass toward the fundus , while the CN & IVN can be seen diverging from each other as they pass laterally to the fundus - ---

Basal turn of cochlea pushing away IVN from CN

See the cochlea in below photo

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

Add other slides of Retrosigmoid & retrolabyrinthine approach

Posterior semicircular canal is aligned with axis of petrous bone

Add middle cranial fossa photos

Fig. 5.30 A simple middle cranial fossa approach has been established,and the internal auditory canal dura has been opened. A Anterior, B Bill’sbar, FN Facial nerve, P Posterior, SSC Superior semicircular canal,SV Superior vestibular nerve

The acousticofacial bundle components have been separated.Both the facial nerve (FN) cochlear nerve (CN) can now be seen.AICA Anterior inferior cerebellar artery

Keep sashidhar tatavarthy post vertigo MRI pictures & mario sanna facial nerve or vestibular schawannoma book -- crossing of vestibular & cochlear

nerves as we go from medial to lateral direction

Left Ménière disease: In around 40% of cases,the anterior inferior cerebellar artery (aica) forms a vascularloop running toward the porus acusticus, usually inferior to thevestibulocochlear nerve bundle. Within the vestibulocochlear nerve,the vestibular fibers (Ve) are more superior (rostral) and close to thetrigeminal nerve, and the cochlear nerve (Co) is inferior (caudal)and close to the lower cranial nerves (LCN).

Left Ménière disease: A small dissector is insertedinto the inter-vestibulocochlearcleavage plane to divide thevestibulocochlear nerve into its two parts.

Mneumonic is Circle inspector of Police [ CI ] – Cochlear nerve is inferior

In cisternal AFB cochlear nerve is inferior to vestibular nerve

In IAC cochlear nerve is anterio-inferior quadrant

At the end of tumor removal, the most lateral fundus part of the internal auditory meatus is checked with an endoscope. Often there is residual tumor (T) in the fundus. Fn indicates facial nerve; Cn, cochlear nerve; Vn, residual vestibular nerve.

Vestibular neurotomy is progressively performed with

microsurgical scissors.

Left endoscopic vestibular neurotomy is complete.The facial nerve located anteroinferior to the vestibular nerve is nowvisible.

Left microsurgical vestibular neurotomy with terminalfibers being dissected by blunt probe. co indicates the cochlear

nerve; ve, sectioned vestibular nerve; aica, anterior inferiorcerebellar artery.

Anterior to the Acoustico facial Nerve Bundle

The abducent nerve. In the background, the vertebraland basilar arteries are first visualized. The origin of the

anterior inferior cerebellar artery is clearly seen.

Inferior to the Acousticofacial NerveBundle

A closer view of the CPA from the porus acusticus.

The root exit zones of the facial nerve and the abducentnerve

are seen. Note the relationships between the loop of the

anterior inferior cerebellar artery and the acousticofacialnerve

bundle. The lower cranial nerves are seen in the background.

A deeper view, showing the relationships betweenthe vertebral artery and the lower clivus; the flocculus lobeand the anterior inferior cerebellar artery are seen.

The vertebral artery joins its fellow on the oppositeside and gives off several perforating arteries to the spinalcord.

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.

Microvascular Decompression (MVD) Surgery for Unilateral Disabling Tinnitus

Subarcuate artery (red arrow) causing compressionof the cochlear nerve.

Subarcuate artery is gently displaced from the

cochlear nerve and coagulated. The demyelinized zone on the cochlear nerve is visible as a grayish discoloration and narrowing of the nerve in contact area (yellow arrow).

The AICA forms collateral branches along its path, in padicular in the area of its loop. Recurrent arteries for the cerebral trunk and the origin of the facial nerve, the internal auditory artery and

the subarcual artery, the purpose of which is vascularization of the inner ear (Fig. 3).

Anatomy of the AICA branches1. Labyrinthine artery

2. Subarcual artery3. Recurrent artery for the cerebral trunk

Level 3 = Lower cranial nerve area

Right side. The acousticofacial nerve bundle, posteriorinferior cerebellar artery, and lower cranial nerves are seenin the lower part. The inferior cerebellar vein (not constant)enters the jugular bulb. As the posterior fossa is approachedfrom behind the sigmoid sinus, the jugular dural fold appearsas a white linear structure overlying the lower cranial nerves.

Right side. The acousticofacial nerve bundle, posteriorinferior cerebellar artery, and lower cranial nerves are seenin the lower part. The inferior cerebellar vein (not constant)enters the jugular bulb. As the posterior fossa is approachedfrom behind the sigmoid sinus, the jugular dural fold appearsas a white linear structure overlying the lower cranial nerves.

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 duralporus of the tenth cranial nerve. The vagus and the accessorynerve exit the posterior fossa together in a sleeve of durathrough the jugular foramen.

Closer view of the inferior area of the left CPA, with

the tip of the endoscope just over the flocculus. The vagus nerve

(X) and spinal accessory nerve (XI) arise as a widely separatedseries of rootlets that originate from the lower medulla and from theupper cervical cord. The rootlets of the hypoglossal nerve (XII) runhorizontally and are displaced and stretched by the curved vertebral

artery (VA). The posterior-inferior cerebellar artery (PICA) arisesfrom the vertebral artery and forms a vascular loop inferior to the

root exit /entry zone of the acoustic-facial nerve bundle (VII/ VIII).

Level 4 = Foramen magnum area

The right side of the bulbomedullary junction. It is the lowermost and narrowest part of the posterior fossa. This area requires special dissection prior to endoscopic investigation between the pontomedullarystem and the jugular foramen.

Right side. The root fibers of the hypoglossalnerve (12) collect in two bundles, which pierce the dura intwo dural pori. The hypoglossal nerve is situated more anteriorlyand medially than the root fibers of the lower cranialnerves. The arterial relationship is the vertebral artery, withperforating arteries to the brain stem. The curved vertebralartery displaces and stretches the hypoglossal nerve fibers.

10 Vagus nerve

11 Accessory nerve

12 Hypoglossal nerve

PICA Posterior inferior cerebellar artery

Vert. A Vertebral artery

The posterior inferior cerebellar artery travelsthrough the nerve fiber roots of the accessory nerve andencircles the brain stem. The course of the vertebral artery isinferior and anterior to the lower cranial nerves and thehypoglossal nerve. Fibrous tissue surrounds the entrance ofthe vertebral artery into the CPA.

9 Glossopharyngeal nerve10 Vagus nerve11 Accessory nerve12 Hypoglossal nervePICA Posterior inferior cerebellar arteryVert. A Vertebral artery

Left side. The lower cranial nerves, with the poste-riorinferior cerebellar artery arising from the vertebral artery in the background.

Neurovascular relationships between the exit zone of the root fiber bundles of the eleventh and twelfth nerves, the posterior inferior cerebellar and vertebral arteries. Fibrous tissue is seen around the vertebral artery.

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

A 30° endoscope provides an overview of the medullary canal,

Two cerebellar lobes and the medullary stem. Theposterior inferior cerebellar artery encircles the medullarystem. The opposite vertebral artery exits from the dural porusand raises the hypoglossal nerve.

The pontomedullary junction. The vertebral arteryjunction is at the level of the junction of the inferior and midclivus.The basilar artery runs in a straight line on the surfaceof the pons. The exit zones of the hypoglossal and abducentnerves are at the same level. The abducent nerve exits fromthe pontomedullary junction, and ascends in a rostral and lateraldirection toward the clivus.

A closer view of the anterior border of the pontomedullarystem and the vertebral artery junction and originof the basilar artery. Perforating arteries arise from the vertebraland basilar arteries.

The endoscope is focusing on the hypoglossal nervearea. The posterior inferior cerebellar artery arises from thevertebral artery in the background, and runs between the twobundles of the hypoglossal nerve.

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

The endoscope is focusing on the hypoglossal nerve area. The posterior inferior cerebellar artery arises from thevertebral artery in the background, and runs between the two bundles of the hypoglossal nerve.

The posterior inferior cerebellar artery travels through the nerve fiber roots of the accessory nerve

Closer view of the inferior area of the left CPA, withtip of the endoscope between the acousticofacial nerve bundle and lower cranial nerves. PICA

originating from the vertebral arterycan be seen forming a loop near the REZ of the facial nerve. AICA arises from the more medial basilar artery and traverses under the acousticofacial nerve

bundle to supply the anterior surface of cerebellum. Abducens nerve (VI) is occasionally formed by two different nerve bundles as seen here.

Superior view of CP angle

Middle cranial fossa Transpetrous ( = Transapical )

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

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

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

The temporalis muscle and periosteumhave been elevated as one flap.

The craniotomy has been performed using a small drill.

The craniotomy flap has been elevated and the middle fossa (MFD) can be seen.

The branches of the trigeminal nerve (V1, V2, V3) can beidentified at the anterior part of the approach.

The Fukushima middle cranial fossa retractor has been applied to maintain the elevated dura.

Three-quarters of the canal circumference is skeletonized, leaving a thin shell of bone over it.

The different areas of access for the middle fossa approaches.a Classic middle fossa approach to the internal auditory canal.

b Enlarged middle fossa approach for tumor removal. c−e The middlefossa transpetrous approach.

The landmarks for the internal auditory canal (arrow) in middle fossa approach. AE, arcuateeminence; gspn, greater superficial petrosal nerve; MMA, middle meningeal artery.

A schematic representation of the position of the internal audi tory canal in middle cranial fossa approach. EAC, external auditory canal; IAC, internal auditory canal; SSC, superior semicircular canal; SPS, superior petrosalsinus.

An anatomical dissection carried out through the middle fossa,illustrating the relationships between the various structures in this area.

A closer view of the lateral end of the internal auditory canal.

The posterior rhomboidal area (Q) of the anterior petrous apex.

The anterior triangular area has been uncovered by sectioning the mandibular nerve (V3) and reflecting the gasserian ganglion.

The amount of circumferential exposure of the internal auditory canal near the fundus is only 180°.

Kawase approachThe quadrangular area of the petrous apex anterior to the internalauditory canal is drilled and the horizontal segment of the internalcarotid artery (ICA) is exposed.

the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and

preserving hearing.http://www.worldneurosurgery.org/article/S0090-3019(00)00271-8/fulltext

Videos of kawase approach or Anterior Transpetrosal approach

– click

http://aiimsnets.org/AnteriorTranspetrosalapproach.asp#

The whole length of the horizontal portion of the internal carotid artery (ICA) is exposed up to the anterior foramen lacerum (AFL).

The dura is opened by creating an inferiorly based flap, the dashed lines.

Surgical Anatomy after Opening of the DuraThe middle fossa transpetrous approach.

The anterior inferior cerebellar artery is seen looping around the acousticofacial bundle (AFB).

At a higher magnification a prominent flocculus (Fl) is observed.

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

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

After removing the remaining bone of the petrous apex, the basilar artery (BA) can be seen in the prepontine cistern.

Opening the dura of the middle cranial fossa exposes the third nerve (III) and intracavernous portion of the internal carotid artery (ICA).

A closer view at the level of the fundus of the internal

auditory canal. The facial nerve lies anteriorly and superiorly. The vestibular nerve posteriorly is separated from the

facial nerve by a plane of cleavage. The cochlear nerve is

located inferior to the facial nerve.

The cochlear nerve travels along an inferior coursein the internal auditory canal. Inferior to the vestibular nerveat the porus acusticus, it becomes inferior to the facial nerveat the lateral end of the internal auditory canal. There is alabyrinthine artery coursing between the cochlear and facialnerves.

A closer view at the level of the porus acusticus. The anterior inferior cerebellar artery forms a vascular loop and gives off labyrinthine arteries, which fix the contact between the artery and

the inferior surface of the acousticofacial nerve bundle at the inferior lip of the meatus.

The root exit zone of the facial nerve is anterior to the root of the cochlear nerve and superior to the rootlets of the lower cranial nerves.

7 Facial nerve8 Vestibulocochlear nerve9 Glossopharyngeal nerve10 Vagus nerveAICA Anterior inferior cerebellar arteryIAC Internal auditory canalPICA Posterior inferior cerebellar artery

The pontobulbar junction and the roots of thelower cranial nerves are visualized. The loop of the posterior

inferior cerebellar artery is seen in the background.

Right enlarged middle fossa approach. The internalauditory canal has been opened, revealing the acousticofacial

Perve bundle contained within it. The facial nerve runs anteriorly,and the superior vestibular nerve lies posteriorly. The

loop of the anterior inferior cerebellar artery runs near theMeatus, below the acousticofacial nerve bundle.

Lateral view of CP angle

Various Transpetrous approaches to get lateral view of CP angle ( = to reach Lateral part of Posterior cranial fossa dura )

predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area

1. Retrolabyrinthine Transpetrous ( = Transapical )

2. Translabyrinthine Transpetrous ( = Transapical )

3. Transcochlear Transpetrous ( = Transapical )

predominently to reach Level 3 = Lower cranial nerve area

4. POTS = Petro-Occipital Trans-Sigmoid approach

5. Infralabyrinthine Transpetrous ( = Transapical ) -- which is nothing but IFTA-A , PONS , IFTA-B Transpetrous approach

[ IFTA-A,B = Infratemporal fossa approach A , B / PONS = petro-occipital trans-sigmoid approach ]

predominently to reach Level 4 = Foramen magnum area

6. Exrtreme lateral or Far lateral or Transcondylar approach

Photograph of a cadaveric dissection showing an overview of the temporal bone and depicting the posterior surface of the petrous part. The sphenoid bone, which articulates anteriorly with the petrous and squamous

temporal bone, has been removed in this specimen. The pyramidal petrous part, located between the sphenoid and occipital bones, has a base, apex, and three surfaces. The sigmoid sinus descends along the posterior surface of the mastoid part and turns anteriorly toward the jugular foramen. The posterior transpetrosalapproaches involve progressive degrees of resection of the petrous temporal bone. The retrolabyrinthine

(green outline) dissection exposes the area between the superior petrosal sinus, the sigmoid sinus, and the posterior semicircular canal. The translabyrinthine approach (pink outline) extends more anteriorly to remove

all three semicircular canals and to expose the anterior wall of the IAC. The transcochlear (blue outline) dissection extends even more anteriorly to the petrous apex, resulting in an almost complete petrosectomy

with the widest and most direct exposure of all the posterior transpetrosal approaches. PET. = petrous/petrosal; POST. = posterior; RETROLAB = retrolabyrinthine; S.C. = semicircular canal; SIG. = sigmoid;

SUP. = superior; TRANSLAB = translabyrinthine.

Middle cranial fossa Transpetrous approach - the anterior

petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing.http://www.worldneurosurgery.org/article/S0090-3019(00)00271-8/fulltext

Retrolabyrinthine Transpetrous ( = Transapical )

Retrolabyrinthine Transpetrous ( = Transapical ) &

Translabyrinthine Transpetrous ( = Transapical ) &

Transcochlear Transpetrous ( = Transapical )

predominently to reach

Level 1 = Trigeminal nerve area & Level 2 = AFB area

COMBINED APPROACHES Retrolabyrinthine Transpetrous ( = Transapical

)Subtemporal ApproachRetrolabyrinthine Transpetrous ( = Transapical

)Subtemporal Transtentorial Approach

Retrolabyrinthine SubtemporalTransapical Approach

Retrolabyrinthine SubtemporalTranstentorial Approach

A view of the cerebellopontine angle through the retrolabyrinthineapproach Note the narrow field and limited control.

Posterior fossa dura (PFD) structures exposed through the standard retrolabyrinthine approach.

A view of the posterior fossa durathrough the combined retrolabyrinthine subtemporaltransapical approach.

The middle fossa dura has been cut. The oculomotornerve (III) is clearly seen.

With more retraction of the temporal lobe and the tentorium

(*), the optic nerve (II) is seen.

Retrolabyrinthine Subtemporal Transapical(Transpetrous Apex) Approach

Schematic drawing showing the incision to be performed.

A retrolabyrinthine approach is performed.

The dura of the middle fossa is detached from the superior surface of the temporal bone from posterior to anterior.

With further detachment of the dura, the middle meningeal (MMA) artery is clearly identified.

The middle meningeal artery (MMA) and the three branches(V1, V2, V3) of the trigeminal nerve are identified.

View after cutting the middle meningeal artery (MMA) andthe mandibular branch of the trigeminal nerve (V).

The internal auditory canal (IAC) is identified.

A large diamond burr is used to drill the petrous apex.

The petrous apex has been drilled. The internal carotid artery(ICA) is identified.

At higher magnification, the abducent nerve (VI) is identifiedat the level of the tip of the petrous apex (PA).

Panoramic view showing the structures after opening of the

posterior fossa dura.

At higher magnification, the anterior inferior cerebellar artery (AICA)is seen stemming from the basilar artery (BA) at the prepontine cistern. The artery is crossed by the abducent nerve (VI). Note the good control of the prepontine cistern through this approach.

Tilting the microscope downward, the lower cranial nerves

are well seen.

Retrolabyrinthine SubtemporalTranstentorial Approach

The retrolabyrinthine craniotomy has been performed. The petrous apex has been partially drilled.

The middle fossa dura (*) is incised.

The tentorium (*) is cut, taking care not to injure thetrochlear nerve.

The tentorium is further cut until the tentorial notch isreached. With retraction of the temporal lobe the optic (II), oculomotor(III) and contralateral oculomotor(IIIc) nerves are seen.

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

Endoscopic Retrolabyrinthineapproach – from Prof. Magnan book

Translabyrinthine Transpetrous ( = Transapical )

Retrolabyrinthine Transpetrous ( = Transapical ) &

Translabyrinthine Transpetrous ( = Transapical ) &

Transcochlear Transpetrous ( = Transapical )

predominently to reach

Level 1 = Trigeminal nerve area & Level 2 = AFB area

The Enlarged Translabyrinthine Approach with Transpetrous ( = Transapical ) Extension

Schematic drawings showing the amount of bone removalaround the internal auditory canal in the different variants of the

translabyrinthine approach. Note that in the transapical modification theexposure is 320° and about 360° in types I and II, respectively. Abbreviations

as in Fig. 5.1. cn, cranial nerve; CN, cochlear nerve; FN, facial nerve;IV, inferior vestibular nerve; SV, superior vestibular nerve.

Drilling inferior to the right internal auditory canal (IAC).

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

Extensive bone removal inferior and superior to the internal auditory canal (IAC). Bone superior to the canal (*) is still to be removed.

The whole contents of the internal auditory canal (IAC) are pushed inferiorly to allow removal of the remaining bone (*) superior to the canal.

The whole contents of the canal are displaced inferiorly to show the extent of bone removal. The anterior wall of the canal can also be drilled if needed.

Schematic drawing showing the technique and extent of bone removal in the type I (green line) and type II (red line) transapicalextension. F, facial nerve; C, cochlear nerve; Vs, superior vestibular nerve; Vi, inferior vestibular nerve.

Schematic drawing showing the technique and extent of bone removal in the type I (green line) and type II (red line) transapical extension. F, facial nerve; C, cochlear

nerve; Vs, superior vestibular nerve; Vi, inferior vestibular nerve.

General view of the structures in the cerebellopontine angleafter opening the dura. Note the enhanced exposure of the angle andthe excellent exposure of the trigeminal nerve (V).

The trigeminal nerve (V) is pushed superiorly. The basilarartery (BA) in the prepontinecistern can be seen well.

With more traction of the tentorium, a panoramic view of thestructures in the angle is available. The trochlear nerve (IV) is

seen before piercing the tentorium to gain access to the middle fossa.

Transcochlear Transpetrous ( = Transapical )

Retrolabyrinthine Transpetrous ( = Transapical ) &

Translabyrinthine Transpetrous ( = Transapical ) &

Transcochlear Transpetrous ( = Transapical )

predominently to reach

Level 1 = Trigeminal nerve area & Level 2 = AFB area

Various types of Modified transcochlear approach

Don't give too much importance to the jargon of approaches . Approaches developed from anatomy . Anatomy not developed from approaches. Know the www.skullbase360.in anatomy. Automatically you can individualize the approach for the tumor .

An extended mastoidectomy, labyrinthectomy, identification

of the internal auditory canal, and drilling of the cochlea has been performed.

The facial nerve (FN) has been skeletonized.

The facial nerve (FN) has been skeletonized.

Using a diamond burr to uncover the labyrinthine segment ofthe facial nerve (FN).

The facial nerve (FN) is completely uncovered. Note Bill’s bar(BB) separating the nerve from the superior vestibular nerve (SVN) at thelevel of the fundus of the internal auditory canal.

Identification of the greater superficial petrosal nerve (gspn).

The greater superficial petrosalnerve is (gspn) cut.

The geniculate ganglion (GG) and the labyrinthine portion ofthe facial nerve (FN) are elevated.

The tympanic segment is freed.

A beaver knife is used to free the mastoid segment.

The superior vestibular nerve (SVN) is detached from its attachment.

The whole contents of the internal auditory canal are transposed posteriorly with the facial nerve (FN).

New position of the facial nerve (FN) after posterior rerouting

Removal of the fallopian canal with a rongeur.

Surgical Anatomy after Opening the posterior cranial fossa dura

Drilling of the cochlea (Co). Drilling of the petrous apex (PA).

View after complete performance of the approach. Thedashed lines represent the duralincision.

View after opening the dura, showing excellent control of thebasilar artery (BA) and prepontine cistern.

Tilting the microscope downward, both the ipsilateral (VA)and contralateral (VAc) vertebral arteries come into view.

With a slight retraction of the middle fossa dura, the origin ofthe superior cerebellar artery at the basilar artery (BA) can be seen. Notethe excellent control of the trigeminal nerve (V).

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

Mild retraction of the tentorium (Ten) provides a good view ofthe oculomotor nerve (III) and its relation to the superior cerebellarartery (SCA) lying inferiorly and the posterior cerebral artery (PCA) lyingsuperiorly. The trochlear nerve (IV) is seen running on the undersurfaceof the tentorium.

Meckel’s cave (MC) can be opened when necessary.

The Type C Modified TranscochlearApproach – after cutting the

tentoriumWith mild retraction of the temporal lobe, the bifurcation of the internal carotid artery (ICA) into the anterior (ACA) and middle cerebral (MCA) arteries is seen. The ipsilateral (ON) and contralateral (ONc) optic nerves are seen. The oculomotor nerve (III) is embraced by the posterior cerebral artery (PCA) superiorly and the superior cerebellar artery (SCA) inferiorly

POTS = Petro-Occipital Trans-sigmoid approach

POTS = Petro-Occipital Trans-sigmoid approach predominently to reach Level 3 = Lower cranial nerve area

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

A U-shaped musculoperiostealflap is outlined.

Bone exposure. Note that no retractors are used.

The internal jugular vein (IJV) is identified.

The internal jugular vein is liberated.

An extended mastoidectomy has been performed.

A wide retrosigmoid craniotomy.The sigmoid sinus (SS) is uncovered. Note that the bone overlyingthe genu from the lateral to the sigmoid sinus is intact (arrowhead).

The dura is separated from the overlying bone.

The dura is separated from the overlying bone.

The endolymphatic sac (ELS) is identified.

Further separation of dura from the overlying bone.

Placement of aluminum to protect the dura from injury.

The cochlear aqueduct (CAq)is identified.

Complete drilling of the retrofacial air cells.

The approach has been completed. The dotted line representsthe duralincision.

The dura has been opened and the tumor (T) can be seen.

Closure of the dura. The remaining defect (white arrowheads), together with the operative cavity, is obliterated with abdominal fat.

Surgical Anatomy after Opening the posterior cranial fossa dura

General view of the structures that can be visualized after opening the dura. At the superior aspect of the approach,

the fourth (IV) and fifth (V) cranial nerves can be appreciated.

The facial nerve can be clearly seen in the middle part of the approach after retracting the posteriorly lying cochlear nerve. Separation of the glossopharyngeal nerve (IX) from the vagus (X) and accessory (XI) nerves at the medial aspect of the jugular foramen.

Further inferiorly, the ninth (IX), tenth (X), and eleventh (XI) cranial nerves can be seen exiting the skull through the jugular foramen

At the inferior part of the approach the lower cranial nerves can be appreciated.

The relation between the inferior petrosal sinus (ips) and the lower cranial nerves.

The origin of the hypoglossal nerve (XII).

.

The drilled occipital condyle (OC) and the hypoglossal canal (HC).

Exrtreme lateral or Far lateral or Transcondylar approach

Exrtreme lateral or Far lateral or Transcondylar approach predominently to reach

Level 4 = Foramen magnum area

Patient placed in the lateral decubitus position.

The incision.

The levator scapulae (LS) and the splenius capitis (SpC)muscles are identified.

Detaching the splenius capitis (SpC), longissimus capitis (LC) and levatorscapulae muscles reveals the inferior and superior oblique muscles. More posteriorly, the semispinalis capitis muscle (SsC) can beseen.

Subperiosteal separation of the suboccipitalmuscles identifies the vertebral artery (VA).

The foramen transversarium has been opened to better expose the vertebral artery (VA).

Dissection of the right side. The sternomastoid muscle (StM) has been retracted anteriorly. The levator scapulae (LS) and the splenius capitis (SpC) muscles can be identified at a superficial level.

Reflecting the splenius capitis(SpC) muscle together with the slender, deeply attached longissimus capitis (LC) muscle reveals the deep inferior (IO) and superior (SO) oblique muscles.

The transverse process of the atlas (TPC1) forms an important landmark in this region.

Course of the vertebral artery (VA) after leaving the transverse process of the axis. The foramen transversarium of the atlas (hatched lines) has been opened. Pa, posterior arch of the atlas.

At a higher magnification, the C2 nerve root is seen crossing the vertebral artery (VA).

The point where the vertebral artery (VA) pierces the dura.

A presigmoid craniotomy has been partially performed, ex- posing the sigmoid sinus (SS). A suboccipital craniotomy (*) extending caudal to the level of the foramen magnum is performed.

The occipital condyle (OC) is partially drilled.

Opening the dura posterior and parallel to the sigmoid sinus.

Surgical Anatomy after Opening the DuraA general view showing the different structures exposed after opening the dura. A cuff of

adherent dura is left attached to the vertebral artery (VA). Note the close proximity of the spinal accessory nerve (XIs) to the artery and the dura at this level. The lower cranial nerves in relation to the posterior inferior cerebellar artery are appreciated. The cerebellum is gently retracted to

expose the different structures at the cerebellopontine angle.

The accessory nerve (XI) is closely related to the vertebral artery (VA) at the point of dural entrance. Note the dura attached to the artery at this level.

At a higher magnification, the nerves IX−XI are seen coursing toward the jugular foramen. The two bundles of the hypoglossal nerve (XII) are closely related to the vertebral artery (VA) before they unite to course in the hypoglossal canal in the partially drilled occipital condyle (OC). XIs, spinal accessory nerve.

Changing the tilt of the microscope, the two vertebral arteries

and the vertebrobasilar junction (VBJ) are exposed. Note the control

of the ventrolateral surface of the medulla (Med). VA, vertebral artery;

VAc, contralateral vertebral artery.

intra operative photograph through operating microscope during removal of posterior fossa arachnoid cyst -showing medulla oblnagata-cervical spinal cord -cerebellar

tonsils-vertebral artery-hypoglossal nerve -accessory nerve -1st cervical nerve root -PICA loope,after removal of cyst wall

The posterior inferior cerebellar artery travelsthrough the nerve fiber roots of the accessory nerve andencircles the brain stem. The course of the vertebral artery isinferior and anterior to the lower cranial nerves and thehypoglossal nerve. Fibrous tissue surrounds the entrance ofthe vertebral artery into the CPA.

9 Glossopharyngeal nerve10 Vagus nerve11 Accessory nerve12 Hypoglossal nervePICA Posterior inferior cerebellar arteryVert. A Vertebral artery

Left side. The lower cranial nerves, with the poste-riorinferior cerebellar artery arising from the vertebral artery in the background.

Neurovascular relationships between the exit zone of the root fiber bundles of the eleventh and twelfth nerves, the posterior inferior cerebellar and vertebral arteries. Fibrous tissue is seen around the vertebral artery.

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

A 30° endoscope provides an overview of the medullary canal,

Two cerebellar lobes and the medullary stem. Theposterior inferior cerebellar artery encircles the medullarystem. The opposite vertebral artery exits from the dural porusand raises the hypoglossal nerve.

The pontomedullary junction. The vertebral arteryjunction is at the level of the junction of the inferior and midclivus.The basilar artery runs in a straight line on the surfaceof the pons. The exit zones of the hypoglossal and abducentnerves are at the same level. The abducent nerve exits fromthe pontomedullary junction, and ascends in a rostral and lateraldirection toward the clivus.

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.

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

A closer view of the anterior border of the pontomedullarystem and the vertebral artery junction and originof the basilar artery. Perforating arteries arise from the vertebraland basilar arteries.

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

The endoscope is focusing on the hypoglossal nerve area. The posterior inferior cerebellar artery arises from thevertebral artery in the background, and runs between the two bundles of the hypoglossal nerve.

The posterior inferior cerebellar artery travels through the nerve fiber roots of the accessory nerve

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.

With a more downward angulation of the microscope, the upper part of the spinal cord (SpC) is well controlled. The posterior spinal artery (PSA) is also

seen.

Endoscopic transcochlearapproach

DEAR SURGEONS these are pictures of C P Angle

It is transmeatal endoscopic cadaveric dissection of c p angle

45 70 degrees of endoscopes are used through transmeatal transinternal

auditory canal route is used . We can see the anterior face of cp angle

here . All other procedures like retro sigmoid retrolab translab . We see

posterior face here infront of us 7th nerve comes first in other

procedures the vestibulo cochlear nerve bundle hides facial nerve

So here facial nerve is clearly vaisible from porus to pons

Surgical implications

1) endoscopic exposure to all pathological lesions of c p angle

2) Intra cranial grafting of facial nerve we are directly visualising the

intracranial portion of nerve

3) other pathologies of Meckles cave

4) No much bone drilling no brain retraction it is keyhole surgery for

future endoscopic lateral skull Base surgeons

5) The endoscopic otologist should be thorough with endoscopic

anatomy of this region before applying these type of procedures

Vcn ) Vestibulocochlear nerve6th) 6th cranial nerveDc) Durello canalP) PonsIca) Internal carotid arteryIac) Anterior wall of internal auditory canalDv) Dandy veinSca) Superior cerebellar veinTen) Tentorium

Anterior view of CP angle

Level 1 = Trigeminal area

Cadaveric dissection image taken with a 30-degree endoscope following removal of the superior third of the clivus, visualizing the small trochlear nerve seen running

along the tentorial membrane edge. BA, basilar artery; PCA, posterior cerebral artery; SCA, superior cerebellar artery; CN III, occulomotor nerve; CN IV, trochlear nerve; CN

V, trigeminal nerve; TM, tentorial membrane; PComA, posterior communicating artery; MB, mamillary body.

The basilar artery (BA) can be seenvery tortuous.

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.

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

Level 2 = AFB area

Cadaveric dissection image taken with a 70-degree endoscope. The right internal auditory canal (IAC) can be clearly visualized with the meatal segment of the anterior inferior cerebellar artery (AICA) entering the meatus. This vessel then loops between the facial (CN VII) and vestibulocochlear nerves. CN, cochlear nerve; CN V, trigeminal

nerve.

Cadaveric dissection image on the right side with retraction inferiorly of the glossopharyngeal and vagus nerves to reveal the choroid plexus (CP) as it spills out of the foramen of Luschka. The folliculus (F) can also be visualized laterally, just behind

the facial (CN VII) and vestibulocochlear nerves (CN VIII). AICA, anterior inferior cerebellar artery; PICA, posterior inferior cerebellar artery.

Level 3 = Lower cranial nerve area

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.

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

Level 4 = Foramen magnum area

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.

Note 1. Basillar artery is kinky , not always straight

2. observe bilateral hypoglossal canals

Cadaveric dissection following the removal of the apical and alar ligaments, and the odontoid process has been drilled away (OP). This re veals the strong and thick transverse portion of the

cruciform ligament (CL). Behind this is located the tectorial membrane (TM). ET, eustachiantube; SP, soft palate; HC, hypoglossal canal; VA, vertebral artery; BA, basilar artery.

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