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CP angle 360°
6-6-2016
7.07 pm
Great teachers – All this is their work .
I am just the reader of their books .
Prof. Paolo castelnuovo
Prof. Aldo Stamm P...
For Other powerpoint presentatioins
of
“ Skull base 360° ”
I will update continuosly with date tag at the end as I am
gett...
Approaches to the brainstem –
Rhoton
https://www.youtube.com/watch?v=
K-42KXujh0o
Posterior view of CP angle
MINIMALLY INVASIVE RETROSIGMOID
APPROACH (MIRA) - Port of entry to Endoscopic Lateral Skull Base
Superior anatomical view of the left
cerebellopontine angle (CPA): The CPA is defined
as the angle formed in the horizonta...
Posterior view of CP angle
1. level 1 = Trigeminal area
2. Level 2 = AFB area
3. Level 3 = Lower cranial nerve area
4. Lev...
The petrosal or anterior surface of the cerebellum faces the posterior surface of the temporal
bone and the brain stem. Th...
Right retrosigmoid approach under the operating
microscope. The acousticofacial nerve bundle crosses the
middle
of the cer...
Posterior view of the left CPA with a 30° angled
endoscope gives a view of CPA contents and permitsobservation of the blin...
Level 1 = Trigeminal area
The trigeminal nerve from the poms to the Meckel
cavity (trigeminal cavity). Posterior to the trigeminal
nerve lies
the su...
Closer view of the superior area of the left CPA:
tip of the 30° endoscope is above the acousticofacial nerve
bundle (VIII...
Here, the tip of the endoscope is positioned at
the level of the posterior margin of the trigeminal nerve in
order to carr...
The endoscope is positioned between the trigeminal
nerve and the tentorium. The superior cerebellar
artery
encircles the b...
Left side. The trigeminal nerve
and Dandy vein are
seen entering the superior
petrosal sinus.
Left side. The trigeminal ne...
using the 30° angled endoscope, the
Meckel cavity and the intradural course
of the abducent nerve are seen
delimiting the ...
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...
FN & SVN converge as they pass toward the fundus , while the CN & IVN can
be seen diverging from each other as they pass l...
7up- 7th is above
Coca 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 au...
The acousticofacial bundle components have been separated.
Both the facial nerve (FN) cochlear nerve (CN) can now be seen....
Keep sashidhar tatavarthy post vertigo MRI pictures & mario sanna facial
nerve or vestibular schawannoma book -- crossing ...
Left Ménière disease: In around 40% of cases,
the anterior inferior cerebellar artery (aica)
forms a vascular
loop running...
Mneumonic is Circle inspector of Police [ CI ] – Cochlear nerve is inferior
In cisternal AFB cochlear nerve is
inferior to...
Vestibular neurotomy is
progressively performed with
microsurgical scissors.
Left endoscopic vestibular
neurotomy is compl...
Left microsurgical vestibular neurotomy with terminal
fibers being dissected by blunt probe. co indicates the cochlear
ner...
Anterior to the Acoustico facial Nerve
Bundle
The abducent nerve. In the background, the vertebral
and basilar arteries are first visualized. The origin of the
anterior...
Inferior to the Acousticofacial Nerve
BundleA closer view of the CPA from the porus acusticus.
The root exit zones of the ...
The vertebral artery joins its fellow on the
opposite
side and gives off several perforating
arteries to the spinal
cord.
...
Microvascular Decompression (MVD) Surgery for Unilateral
Disabling Tinnitus
Subarcuate artery (red arrow)
causing compress...
The AICA forms collateral branches along its path, in padicular in the area of its loop. Recurrent
arteries for the cerebr...
Level 3 = Lower cranial nerve
area
Right side. The acousticofacial nerve
bundle, posterior
inferior cerebellar artery, and lower cranial
nerves are seen
in t...
A closer view of the pars nervosa of
the jugular foramen. The
glossopharyngeal nerve has its own
dural porus, which is sit...
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
re...
Right side. The root fibers of the hypoglossal
nerve (12) collect in two bundles, which pierce
the dura in
two dural pori....
The posterior inferior cerebellar artery travels
through the nerve fiber roots of the accessory
nerve and
encircles the br...
Left side. The lower cranial
nerves, with the poste-rior
inferior cerebellar artery
arising from the vertebral
artery in t...
The root fibers of the spinal
accessory nerve and the fibers of C1
and C2. The entrance of the vertebral
artery is the bou...
Two cerebellar lobes and the
medullary stem. The
posterior inferior cerebellar artery
encircles the medullary
stem. The op...
A closer view of the anterior border
of the pontomedullary
stem and the vertebral artery
junction and origin
of the basila...
PICA passes between two bundles of 12th nerve &
between two roots of 11th nerve
The endoscope is focusing on the
hypogloss...
Closer view of the inferior area of the left CPA, with
tip of the endoscope between the acousticofacial nerve bundle and l...
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 periosteum
have 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...
The Fukushima middle cranial fossa retractor has
been applied to maintain the elevated dura.
Three-quarters of the canal c...
The different areas of access for the middle fossa approaches.
a Classic middle fossa approach to the internal auditory ca...
The landmarks for the internal
auditory canal (arrow) in middle
fossa approach. AE, arcuate
eminence; gspn, greater
superf...
An anatomical dissection carried out
through the middle fossa,
illustrating the relationships between
the various structur...
The posterior rhomboidal area
(Q) of the anterior petrous apex.
The anterior triangular area
has been uncovered by
section...
The amount of circumferential
exposure of the internal auditory
canal near the fundus is only 180°.
Kawase approach
The qu...
the anterior petrosectomy with preoperative embolization of the inferior
petrosal sinus is a time-conserving approach givi...
Videos of kawase approach or
Anterior Transpetrosal approach
– click
http://aiimsnets.org/AnteriorTranspe
trosalapproach.a...
The whole length of the horizontal
portion of the internal carotid artery
(ICA) is exposed up to the anterior
foramen lace...
Surgical Anatomy after Opening of the Dura
The middle fossa transpetrous approach.
The anterior inferior cerebellar
artery is seen looping around the
acousticofacial bundle (AFB).
At a higher magnification...
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.
Open...
A closer view at the level of the fundus of
the internal
auditory canal. The facial nerve lies
anteriorly and superiorly. ...
A closer view at the level of the porus acusticus. The anterior inferior cerebellar artery forms a
vascular loop and gives...
The root exit zone of the facial nerve
is anterior to the root of the cochlear
nerve and superior to the rootlets of
the l...
The pontobulbar junction and the roots of the
lower cranial nerves are visualized. The loop of the posterior
inferior cere...
Right enlarged middle fossa approach. The internal
auditory canal has been opened, revealing the acousticofacial
Perve bun...
Lateral view of CP angle
Various Transpetrous approaches to get lateral view of CP angle
( = to reach Lateral part of Posterior cranial fossa dura ...
Photograph of a cadaveric dissection showing an overview of the temporal bone and depicting the posterior
surface of the p...
Middle cranial fossa Transpetrous approach - the anterior
petrosectomy with preoperative embolization of the inferior petr...
Retrolabyrinthine Transpetrous (
= Transapical )
Retrolabyrinthine Transpetrous ( =
Transapical ) &
Translabyrinthine Transpetrous ( =
Transapical ) &
Transcochlear Transp...
COMBINED APPROACHES
Retrolabyrinthine Transpetrous ( = Transapical
)Subtemporal Approach
Retrolabyrinthine Transpetrous ( ...
A view of the cerebellopontine angle
through the retrolabyrinthine
approach Note the narrow field and
limited control.
Pos...
The middle fossa dura has
been cut. The oculomotor
nerve (III) is clearly seen.
With more retraction of the
temporal lobe ...
Retrolabyrinthine Subtemporal Transapical
(Transpetrous Apex) Approach
Schematic drawing showing the
incision to be perfor...
The dura of the middle fossa is
detached from the superior surface of
the temporal bone from posterior to
anterior.
With f...
The middle meningeal artery (MMA)
and the three branches
(V1, V2, V3) of the trigeminal nerve
are identified.
View after c...
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 ...
Panoramic view showing the
structures after opening of the
posterior fossa dura.
At higher magnification, the anterior
inf...
Tilting the microscope downward,
the lower cranial nerves
are well seen.
Retrolabyrinthine Subtemporal
Transtentorial Approach
The retrolabyrinthine craniotomy
has been performed. The petrous
ape...
The tentorium (*) is cut, taking care not to injure the
trochlear nerve.
The tentorium is further cut until
the tentorial ...
Branches of the trigeminal nerve (V1, V2, V3) at the level of
the lateral wall of the cavernous sinus.
Endoscopic Retrolabyrinthine
approach – from Prof. Magnan book
Translabyrinthine Transpetrous (
= Transapical )
Retrolabyrinthine Transpetrous ( =
Transapical ) &
Translabyrinthine Transpetrous ( =
Transapical ) &
Transcochlear Transp...
The Enlarged Translabyrinthine Approach with Transpetrous ( =
Transapical ) Extension
Schematic drawings showing the amoun...
Drilling inferior to the right
internal auditory canal (IAC).
Further extensive drilling inferior to the internal auditory...
Extensive bone removal inferior and
superior to the internal auditory
canal (IAC). Bone superior to the
canal (*) is still...
The whole contents of the canal are
displaced inferiorly to show the extent
of bone removal. The anterior wall of
the cana...
Schematic drawing showing the technique and extent of bone removal in the type I
(green line) and type II (red line) trans...
General view of the structures in the
cerebellopontine angle
after opening the dura. Note the enhanced
exposure of the ang...
With more traction of the tentorium, a panoramic view of the
structures in the angle is available. The trochlear nerve (IV...
Transcochlear Transpetrous ( =
Transapical )
Retrolabyrinthine Transpetrous ( =
Transapical ) &
Translabyrinthine Transpetrous ( =
Transapical ) &
Transcochlear Transp...
Various types of Modified
transcochlear approach
Don't give too much
importance to the jargon
of approaches .
Approaches d...
An extended mastoidectomy,
labyrinthectomy, identification
of the internal auditory canal, and
drilling of the cochlea has...
Using a diamond burr to uncover
the labyrinthine segment of
the facial nerve (FN).
The facial nerve (FN) is completely unc...
Identification of the greater
superficial petrosal nerve (gspn).
The greater superficial petrosal
nerve is (gspn) cut.
The geniculate ganglion (GG) and
the labyrinthine portion of
the facial nerve (FN) are elevated.
The tympanic segment is f...
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 t...
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...
View after complete performance of
the approach. The
dashed lines represent the dural
incision.
View after opening the dur...
Tilting the microscope downward,
both the ipsilateral (VA)
and contralateral (VAc) vertebral
arteries come into view.
With...
Lilliquits membrane present over the
basillar artery & 3rd N. origin area
Mild retraction of the tentorium (Ten)
provides a good view of
the oculomotor nerve (III) and its relation
to the superior...
The Type C Modified Transcochlear
Approach – after cutting the
tentorium
With mild retraction of the temporal lobe, the bi...
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 musculoperiosteal
flap 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 overlying
the genu from the latera...
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 dural
incis...
The dura has been opened and
the tumor (T) can be seen.
Closure of the dura. The remaining
defect (white arrowheads), toge...
Surgical Anatomy after Opening the
posterior cranial fossa dura
General view of the structures that can
be visualized afte...
The facial nerve can be clearly seen
in the middle part of the approach
after retracting the posteriorly lying
cochlear ne...
At the inferior part of the
approach the lower cranial nerves
can be appreciated.
The relation between the inferior
petros...
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),
lon...
Subperiosteal separation of the suboccipital
muscles identifies the vertebral artery (VA).
The foramen transversarium has
...
Dissection of the right side. The
sternomastoid muscle (StM) has
been retracted anteriorly. The
levator scapulae (LS) and ...
The transverse process of the atlas (TPC1)
forms an important landmark in this region.
Course of the vertebral artery
(VA)...
At a higher magnification, the C2 nerve root
is seen crossing the vertebral artery (VA).
The point where the vertebral
art...
A presigmoid craniotomy has been partially
performed, ex- posing the sigmoid sinus
(SS). A suboccipital craniotomy (*)
ext...
Opening the dura posterior and
parallel to the sigmoid sinus.
Surgical Anatomy after Opening the Dura
A general view showing the different structures exposed after opening the dura. A ...
At a higher magnification, the nerves
IX−XI are seen coursing toward the
jugular foramen. The two bundles of
the hypogloss...
intra operative photograph through operating microscope during removal of posterior
fossa arachnoid cyst -showing medulla ...
The posterior inferior cerebellar artery travels
through the nerve fiber roots of the accessory
nerve and
encircles the br...
Left side. The lower cranial
nerves, with the poste-rior
inferior cerebellar artery
arising from the vertebral
artery in t...
The root fibers of the spinal
accessory nerve and the fibers of C1
and C2. The entrance of the vertebral
artery is the bou...
Two cerebellar lobes and the
medullary stem. The
posterior inferior cerebellar artery
encircles the medullary
stem. The op...
Pontomedullary junction = Vertebro-basillar junction =
Junction of Mid clivus & Lower clivus = foramen lacerum area
The po...
Lower half of paraclival carotid - caudal part, the lacerum segment of
the paraclival carotid
”The unsolved surgical probl...
A closer view of the anterior border
of the pontomedullary
stem and the vertebral artery
junction and origin
of the basila...
PICA passes between two bundles of 12th nerve &
between two roots of 11th nerve
The endoscope is focusing on the
hypogloss...
PICA passes between two bundles of 12th nerve &
between two roots of 11th nerve
Cadaveric dissection image demonstrating t...
With a more downward angulation of the microscope, the upper part of the
spinal cord (SpC) is well controlled. The posteri...
Endoscopic transcochlear
approach
DEAR SURGEONS these are pictures of C PAngle
It is transmeatal endoscopic cadaveric dissection of c p angle
45 70 degrees ...
Vcn ) Vestibulocochlear nerve
6th) 6th cranial nerve
Dc) Durello canal
P) Pons
Ica) Internal carotid artery
Iac) Anterior ...
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, visuali...
The basilar artery (BA) can be seen
very tortuous.
Cadaveric dissection of the middle third of the clivus with removal of the basilar
plexus and exposing the dura. The abduc...
Gulfar segment of 6th nerve (GS in left picture ) ( gVIcn in right picture ) - The
gulfar segment can be identified at the...
1. 6th N. crossing carotid at Petro-clival junction when viewing in lateral skull base - The
lateral aspect of the parasel...
Level 2 = AFB area
Cadaveric dissection image taken with a 70-degree endoscope. The right internal
auditory canal (IAC) can be clearly visual...
Cadaveric dissection image on the right side with retraction inferiorly of the
glossopharyngeal and vagus nerves to reveal...
Level 3 = Lower cranial nerve
area
Cadaveric dissection with image taken just above the skeletonized hypoglossal canal
(HC) at the cerebellopontine angle. Th...
Cadaveric dissection image taken following dissection of the right lower third of the
clivus. As the posterior inferior ce...
PICA passes between two bundles of 12th nerve &
between two roots of 11th nerve
Cadaveric dissection image demonstrating t...
Level 4 = Foramen magnum area
Cadaveric dissection image showing the hypoglossal nerve
exiting the hypoglossal foramen with its corresponding vein that
...
Note
1. Basillar artery is kinky , not always straight
2. observe bilateral hypoglossal canals
Cadaveric dissection follow...
For Other powerpoint presentatioins
of
“ Skull base 360° ”
I will update continuosly with date tag at the end as I am
gett...
CP angle 360°
CP angle 360°
CP angle 360°
CP angle 360°
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CP angle 360°
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CP angle 360°
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CP angle 360°
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CP angle 360°

  1. 1. CP angle 360° 6-6-2016 7.07 pm
  2. 2. Great teachers – All this is their work . I am just the reader of their books . Prof. Paolo castelnuovo Prof. Aldo Stamm Prof. Mario Sanna Prof. Magnan
  3. 3. For Other powerpoint presentatioins of “ Skull base 360° ” I will update continuosly with date tag at the end as I am getting more & more information click www.skullbase360.in - you have to login to slideshare.net with Facebook account after clicking www.skullbase360.in
  4. 4. Approaches to the brainstem – Rhoton https://www.youtube.com/watch?v= K-42KXujh0o
  5. 5. Posterior view of CP angle
  6. 6. MINIMALLY INVASIVE RETROSIGMOID APPROACH (MIRA) - Port of entry to Endoscopic Lateral Skull Base
  7. 7. Superior anatomical view of the left cerebellopontine angle (CPA): The CPA is defined as the angle formed in the horizontal section by the pons and the cerebellum in which the trigeminal (V) and acousticofacial nerve bundle (VIII) are located. The angle is bordered laterally and anteriorly by the posterior face of the petrous temporal bone. The tip of the endoscope (4 mm diameter) is facing the acousticofacial nerve bundle which is the reference level, crossing the middle of the CPA from the brainstem to the internal auditory meatus (IAM), and separating it into two anatomical areas. Superiorly and anteriorly, the trigeminal area is usually inspected for the management of trigeminal neuralgia. Inferiorly, the lower cranial nerve area is inspected for treatment of hemifacial spasm and glossopharyngeal neuralgia. aica indicates anterior-inferior cerebellar artery; m, malleus; i, incus.
  8. 8. Posterior view of CP angle 1. level 1 = Trigeminal area 2. Level 2 = AFB area 3. Level 3 = Lower cranial nerve area 4. Level 4 = Foramen magnum area
  9. 9. 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.
  10. 10. 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 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.
  11. 11. Posterior view of the left CPA with a 30° angled endoscope 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.
  12. 12. Level 1 = Trigeminal area
  13. 13. The trigeminal nerve from the poms to the Meckel cavity (trigeminal cavity). Posterior to the trigeminal nerve lies the superior petrosal vein (Dandy vein). Superior to the trigeminal nerve the superior cerebellar artery. In the background and inferiorly, the abducent nerve and basilar artery are seen. In the background and superiorly, the free border of the tentorium and the mesencephalic area are seen. The entrance of the trigeminal nerve into the Meckel cavity. The superior petrosal vein prior to its entrance into the superior petrosal sinus is seen.
  14. 14. 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 auditory meatus (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 passing beneath 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.
  15. 15. 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.
  16. 16. 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 posterior cerebral artery superiorly. The exit zone of the third cranial nerve between the superior cerebellar artery and the posterior cerebral artery is seen.
  17. 17. 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.
  18. 18. 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 dura mater, the nerve changes direction and courses medially toward the petrous apex. The upper major sensory fibres & lower less motor fibres
  19. 19. Level 2 = AFB area
  20. 20. From Clinical anatomy book
  21. 21. From CP angle book – see other photos – fig 9
  22. 22. 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.
  23. 23. 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
  24. 24. 7up- 7th is above Coca cola – cochlear n. is cola[=lower]
  25. 25. Add other slides of Retrosigmoid & retrolabyrinthine approach
  26. 26. Posterior semicircular canal is aligned with axis of petrous bone
  27. 27. 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’s bar, FN Facial nerve, P Posterior, SSC Superior semicircular canal, SV Superior vestibular nerve
  28. 28. The acousticofacial bundle components have been separated. Both the facial nerve (FN) cochlear nerve (CN) can now be seen. AICA Anterior inferior cerebellar artery
  29. 29. 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
  30. 30. Left Ménière disease: In around 40% of cases, the anterior inferior cerebellar artery (aica) forms a vascular loop running toward the porus acusticus, usually inferior to the vestibulocochlear nerve bundle. Within the vestibulocochlear nerve, the vestibular fibers (Ve) are more superior (rostral) and close to the trigeminal nerve, and the cochlear nerve (Co) is inferior (caudal) and close to the lower cranial nerves (LCN). Left Ménière disease: A small dissector is inserted into the inter-vestibulocochlear cleavage plane to divide the vestibulocochlear nerve into its two parts.
  31. 31. 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.
  32. 32. Vestibular neurotomy is progressively performed with microsurgical scissors. Left endoscopic vestibular neurotomy is complete. The facial nerve located anteroinferior to the vestibular nerve is now visible.
  33. 33. Left microsurgical vestibular neurotomy with terminal fibers being dissected by blunt probe. co indicates the cochlear nerve; ve, sectioned vestibular nerve; aica, anterior inferior cerebellar artery.
  34. 34. Anterior to the Acoustico facial Nerve Bundle
  35. 35. The abducent nerve. In the background, the vertebral and basilar arteries are first visualized. The origin of the anterior inferior cerebellar artery is clearly seen.
  36. 36. Inferior to the Acousticofacial Nerve BundleA closer view of the CPA from the porus acusticus. The root exit zones of the facial nerve and the abducent nerve are seen. Note the relationships between the loop of the anterior inferior cerebellar artery and the acousticofacial nerve bundle. The lower cranial nerves are seen in the background. A deeper view, showing the relationships between the vertebral artery and the lower clivus; the flocculus lobe and the anterior inferior cerebellar artery are seen.
  37. 37. The vertebral artery joins its fellow on the opposite side and gives off several perforating arteries to the spinal cord. 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.
  38. 38. Microvascular Decompression (MVD) Surgery for Unilateral Disabling Tinnitus Subarcuate artery (red arrow) causing compression of 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).
  39. 39. 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 branches 1. Labyrinthine artery 2. Subarcual artery 3. Recurrent artery for the cerebral trunk
  40. 40. Level 3 = Lower cranial nerve area
  41. 41. Right side. The acousticofacial nerve bundle, posterior inferior cerebellar artery, and lower cranial nerves are seen in the lower part. The inferior cerebellar vein (not constant) enters the jugular bulb. As the posterior fossa is approached from behind the sigmoid sinus, the jugular dural fold appears as a white linear structure overlying the lower cranial nerves. Right side. The acousticofacial nerve bundle, posterior inferior cerebellar artery, and lower cranial nerves are seen in the lower part. The inferior cerebellar vein (not constant) enters the jugular bulb. As the posterior fossa is approached from behind the sigmoid sinus, the jugular dural fold appears as a white linear structure overlying the lower cranial nerves.
  42. 42. A closer view of the pars nervosa of the jugular foramen. The glossopharyngeal nerve has its own dural porus, which is situated 0-3 mm upwards from the dural porus of the tenth cranial nerve. The vagus and the accessory nerve exit the posterior fossa together in a sleeve of dura through the jugular foramen. 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).
  43. 43. Level 4 = Foramen magnum area
  44. 44. 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 pontomedullary stem and the jugular foramen.
  45. 45. Right side. The root fibers of the hypoglossal nerve (12) collect in two bundles, which pierce the dura in two dural pori. The hypoglossal nerve is situated more anteriorly and medially than the root fibers of the lower cranial nerves. The arterial relationship is the vertebral artery, with perforating arteries to the brain stem. The curved vertebral artery displaces and stretches the hypoglossal nerve fibers. 10 Vagus nerve 11 Accessory nerve 12 Hypoglossal nerve PICA Posterior inferior cerebellar artery Vert. A Vertebral artery
  46. 46. The posterior inferior cerebellar artery travels through the nerve fiber roots of the accessory nerve and encircles the brain stem. The course of the vertebral artery is inferior and anterior to the lower cranial nerves and the hypoglossal nerve. Fibrous tissue surrounds the entrance of the vertebral artery into the CPA. 9 Glossopharyngeal nerve 10 Vagus nerve 11 Accessory nerve 12 Hypoglossal nerve PICA Posterior inferior cerebellar artery Vert. A Vertebral artery
  47. 47. Left side. The lower cranial nerves, with the poste-rior inferior 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.
  48. 48. 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,
  49. 49. Two cerebellar lobes and the medullary stem. The posterior inferior cerebellar artery encircles the medullary stem. The opposite vertebral artery exits from the dural porus and raises the hypoglossal nerve. 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.
  50. 50. A closer view of the anterior border of the pontomedullary stem and the vertebral artery junction and origin of the basilar artery. Perforating arteries arise from the vertebral and basilar arteries. The endoscope is focusing on the hypoglossal nerve area. The posterior inferior cerebellar artery arises from the vertebral artery in the background, and runs between the two bundles of the hypoglossal nerve.
  51. 51. 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 the vertebral 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
  52. 52. Closer view of the inferior area of the left CPA, with tip of the endoscope between the acousticofacial nerve bundle and lower cranial nerves. PICA originating from the vertebral arterycan be seen forming a loop near the REZ of the facial nerve. AICA arises from the more medial basilar artery and traverses under the acousticofacial nerve bundle to supply the anterior surface of cerebellum. Abducens nerve (VI) is occasionally formed by two different nerve bundles as seen here.
  53. 53. Superior view of CP angle
  54. 54. Middle cranial fossa Transpetrous ( = Transapical )
  55. 55. A right-sided skin incision for the middle cranial fossa approach.
  56. 56. The skin and subcutaneous tissues have been elevated as one flap.
  57. 57. The temporalis fascia has been harvested and the temporalis muscle cut using monopolar diathermy.
  58. 58. The temporalis muscle and periosteum have been elevated as one flap.
  59. 59. The craniotomy has been performed using a small drill.
  60. 60. The craniotomy flap has been elevated and the middle fossa (MFD) can be seen. The branches of the trigeminal nerve (V1, V2, V3) can be identified at the anterior part of the approach.
  61. 61. 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.
  62. 62. 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 middle fossa transpetrous approach.
  63. 63. The landmarks for the internal auditory canal (arrow) in middle fossa approach. AE, arcuate eminence; 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 petrosal sinus.
  64. 64. 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.
  65. 65. 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.
  66. 66. The amount of circumferential exposure of the internal auditory canal near the fundus is only 180°. Kawase approach The quadrangular area of the petrous apex anterior to the internal auditory canal is drilled and the horizontal segment of the internal carotid artery (ICA) is exposed.
  67. 67. 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
  68. 68. Videos of kawase approach or Anterior Transpetrosal approach – click http://aiimsnets.org/AnteriorTranspe trosalapproach.asp#
  69. 69. 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.
  70. 70. Surgical Anatomy after Opening of the Dura The middle fossa transpetrous approach.
  71. 71. The anterior inferior cerebellar artery is seen looping around the acousticofacial bundle (AFB). At a higher magnification a prominent flocculus (Fl) is observed.
  72. 72. The distal part of the vertebral artery (VA) can be seen. The distal part of the vertebral artery (VA) can be seen.
  73. 73. 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).
  74. 74. 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 course in the internal auditory canal. Inferior to the vestibular nerve at the porus acusticus, it becomes inferior to the facial nerve at the lateral end of the internal auditory canal. There is a labyrinthine artery coursing between the cochlear and facial nerves.
  75. 75. 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.
  76. 76. 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 nerve 8 Vestibulocochlear nerve 9 Glossopharyngeal nerve 10 Vagus nerve AICA Anterior inferior cerebellar artery IAC Internal auditory canal PICA Posterior inferior cerebellar artery
  77. 77. The pontobulbar junction and the roots of the lower cranial nerves are visualized. The loop of the posterior inferior cerebellar artery is seen in the background.
  78. 78. Right enlarged middle fossa approach. The internal auditory 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 the Meatus, below the acousticofacial nerve bundle.
  79. 79. Lateral view of CP angle
  80. 80. 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
  81. 81. 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 transpetrosal approaches 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.
  82. 82. 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
  83. 83. Retrolabyrinthine Transpetrous ( = Transapical )
  84. 84. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area
  85. 85. COMBINED APPROACHES Retrolabyrinthine Transpetrous ( = Transapical )Subtemporal Approach Retrolabyrinthine Transpetrous ( = Transapical )Subtemporal Transtentorial Approach Retrolabyrinthine Subtemporal Transapical Approach Retrolabyrinthine Subtemporal Transtentorial Approach
  86. 86. A view of the cerebellopontine angle through the retrolabyrinthine approach Note the narrow field and limited control. Posterior fossa dura (PFD) structures exposed through the standard retrolabyrinthine approach. A view of the posterior fossa dura through the combined retrolabyrinthine subtemporal transapical approach.
  87. 87. The middle fossa dura has been cut. The oculomotor nerve (III) is clearly seen. With more retraction of the temporal lobe and the tentorium (*), the optic nerve (II) is seen.
  88. 88. Retrolabyrinthine Subtemporal Transapical (Transpetrous Apex) Approach Schematic drawing showing the incision to be performed. A retrolabyrinthine approach is performed.
  89. 89. 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.
  90. 90. The middle meningeal artery (MMA) and the three branches (V1, V2, V3) of the trigeminal nerve are identified. View after cutting the middle meningeal artery (MMA) and the mandibular branch of the trigeminal nerve (V).
  91. 91. The internal auditory canal (IAC) is identified. A large diamond burr is used to drill the petrous apex.
  92. 92. The petrous apex has been drilled. The internal carotid artery (ICA) is identified. At higher magnification, the abducent nerve (VI) is identified at the level of the tip of the petrous apex (PA).
  93. 93. 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.
  94. 94. Tilting the microscope downward, the lower cranial nerves are well seen.
  95. 95. Retrolabyrinthine Subtemporal Transtentorial Approach The retrolabyrinthine craniotomy has been performed. The petrous apex has been partially drilled. The middle fossa dura (*) is incised.
  96. 96. The tentorium (*) is cut, taking care not to injure the trochlear nerve. The tentorium is further cut until the tentorial notch is reached. With retraction of the temporal lobe the optic (II), oculomotor (III) and contralateral oculomotor (IIIc) nerves are seen.
  97. 97. Branches of the trigeminal nerve (V1, V2, V3) at the level of the lateral wall of the cavernous sinus.
  98. 98. Endoscopic Retrolabyrinthine approach – from Prof. Magnan book
  99. 99. Translabyrinthine Transpetrous ( = Transapical )
  100. 100. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area
  101. 101. The Enlarged Translabyrinthine Approach with Transpetrous ( = Transapical ) Extension Schematic drawings showing the amount of bone removal around the internal auditory canal in the different variants of the translabyrinthine approach. Note that in the transapical modification the exposure 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.
  102. 102. Drilling inferior to the right internal auditory canal (IAC). Further extensive drilling inferior to the internal auditory canal (IAC) toward the petrous apex.
  103. 103. 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.
  104. 104. 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) transapical extension. F, facial nerve; C, cochlear nerve; Vs, superior vestibular nerve; Vi, inferior vestibular nerve.
  105. 105. 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.
  106. 106. General view of the structures in the cerebellopontine angle after opening the dura. Note the enhanced exposure of the angle and the excellent exposure of the trigeminal nerve (V). The trigeminal nerve (V) is pushed superiorly. The basilar artery (BA) in the prepontine cistern can be seen well.
  107. 107. With more traction of the tentorium, a panoramic view of the structures in the angle is available. The trochlear nerve (IV) is seen before piercing the tentorium to gain access to the middle fossa.
  108. 108. Transcochlear Transpetrous ( = Transapical )
  109. 109. Retrolabyrinthine Transpetrous ( = Transapical ) & Translabyrinthine Transpetrous ( = Transapical ) & Transcochlear Transpetrous ( = Transapical ) predominently to reach Level 1 = Trigeminal nerve area & Level 2 = AFB area
  110. 110. 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 anat omy. Automatically you can individualize the approach for the tumor .
  111. 111. 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.
  112. 112. Using a diamond burr to uncover the labyrinthine segment of the 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 the level of the fundus of the internal auditory canal.
  113. 113. Identification of the greater superficial petrosal nerve (gspn). The greater superficial petrosal nerve is (gspn) cut.
  114. 114. The geniculate ganglion (GG) and the labyrinthine portion of the facial nerve (FN) are elevated. The tympanic segment is freed.
  115. 115. A beaver knife is used to free the mastoid segment. The superior vestibular nerve (SVN) is detached from its attachment.
  116. 116. 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
  117. 117. Removal of the fallopian canal with a rongeur.
  118. 118. Surgical Anatomy after Opening the posterior cranial fossa dura Drilling of the cochlea (Co). Drilling of the petrous apex (PA).
  119. 119. View after complete performance of the approach. The dashed lines represent the dural incision. View after opening the dura, showing excellent control of the basilar artery (BA) and prepontine cistern.
  120. 120. 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 of the superior cerebellar artery at the basilar artery (BA) can be seen. Note the excellent control of the trigeminal nerve (V).
  121. 121. Lilliquits membrane present over the basillar artery & 3rd N. origin area
  122. 122. Mild retraction of the tentorium (Ten) provides a good view of the oculomotor nerve (III) and its relation to the superior cerebellar artery (SCA) lying inferiorly and the posterior cerebral artery (PCA) lying superiorly. The trochlear nerve (IV) is seen running on the undersurface of the tentorium. Meckel’s cave (MC) can be opened when necessary.
  123. 123. The Type C Modified Transcochlear Approach – after cutting the tentorium With mild retraction of the temporal lobe, the bifurcation of the internal carotid artery (ICA) into the anterior (ACA) and middle cerebral (MCA) arteries is seen. The ipsilateral (ON) and contralateral (ONc) optic nerves are seen. The oculomotor nerve (III) is embraced by the posterior cerebral artery (PCA) superiorly and the superior cerebellar artery (SCA) inferiorly
  124. 124. POTS = Petro-Occipital Trans- sigmoid approach
  125. 125. POTS = Petro-Occipital Trans-sigmoid approach predominently to reach Level 3 = Lower cranial nerve area
  126. 126. The C-shaped skin incision. A skin flap is raised.
  127. 127. A U-shaped musculoperiosteal flap is outlined.
  128. 128. Bone exposure. Note that no retractors are used. The internal jugular vein (IJV) is identified.
  129. 129. The internal jugular vein is liberated. An extended mastoidectomy has been performed.
  130. 130. A wide retrosigmoid craniotomy. The sigmoid sinus (SS) is uncovered. Note that the bone overlying the genu from the lateral to the sigmoid sinus is intact (arrowhead).
  131. 131. The dura is separated from the overlying bone. The dura is separated from the overlying bone.
  132. 132. The endolymphatic sac (ELS) is identified. Further separation of dura from the overlying bone.
  133. 133. Placement of aluminum to protect the dura from injury. The cochlear aqueduct (CAq)is identified.
  134. 134. Complete drilling of the retrofacial air cells. The approach has been completed. The dotted line representsthe dural incision.
  135. 135. 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.
  136. 136. 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.
  137. 137. 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
  138. 138. 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.
  139. 139. The origin of the hypoglossal nerve (XII). . The drilled occipital condyle (OC) and the hypoglossal canal (HC).
  140. 140. Exrtreme lateral or Far lateral or Transcondylar approach
  141. 141. Exrtreme lateral or Far lateral or Transcondylar approach predominently to reach Level 4 = Foramen magnum area
  142. 142. Patient placed in the lateral decubitus position.
  143. 143. The incision.
  144. 144. The levator scapulae (LS) and the splenius capitis (SpC) muscles are identified. Detaching the splenius capitis (SpC), longissimus capitis (LC) and levator scapulae muscles reveals the inferior and superior oblique muscles. More posteriorly, the semispinalis capitis muscle (SsC) can be seen.
  145. 145. Subperiosteal separation of the suboccipital muscles identifies the vertebral artery (VA). The foramen transversarium has been opened to better expose the vertebral artery (VA).
  146. 146. 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.
  147. 147. 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.
  148. 148. 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.
  149. 149. 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.
  150. 150. Opening the dura posterior and parallel to the sigmoid sinus.
  151. 151. Surgical Anatomy after Opening the Dura A 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.
  152. 152. 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.
  153. 153. 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
  154. 154. The posterior inferior cerebellar artery travels through the nerve fiber roots of the accessory nerve and encircles the brain stem. The course of the vertebral artery is inferior and anterior to the lower cranial nerves and the hypoglossal nerve. Fibrous tissue surrounds the entrance of the vertebral artery into the CPA. 9 Glossopharyngeal nerve 10 Vagus nerve 11 Accessory nerve 12 Hypoglossal nerve PICA Posterior inferior cerebellar artery Vert. A Vertebral artery
  155. 155. Left side. The lower cranial nerves, with the poste-rior inferior 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.
  156. 156. 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,
  157. 157. Two cerebellar lobes and the medullary stem. The posterior inferior cerebellar artery encircles the medullary stem. The opposite vertebral artery exits from the dural porus and raises the hypoglossal nerve. 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.
  158. 158. 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.
  159. 159. 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 clivus a. Petrosal face b.Clival face
  160. 160. A closer view of the anterior border of the pontomedullary stem and the vertebral artery junction and origin of the basilar artery. Perforating arteries arise from the vertebral and basilar arteries.
  161. 161. 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 the vertebral 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
  162. 162. 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, nervus intermedius; 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.
  163. 163. 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.
  164. 164. Endoscopic transcochlear approach
  165. 165. DEAR SURGEONS these are pictures of C PAngle 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
  166. 166. Vcn ) Vestibulocochlear nerve 6th) 6th cranial nerve Dc) Durello canal P) Pons Ica) Internal carotid artery Iac) Anterior wall of internal auditory canal Dv) Dandy vein Sca) Superior cerebellar vein Ten) Tentorium
  167. 167. Anterior view of CP angle
  168. 168. Level 1 = Trigeminal area
  169. 169. 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.
  170. 170. The basilar artery (BA) can be seen very tortuous.
  171. 171. 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.
  172. 172. Gulfar segment of 6th nerve (GS in left picture ) ( gVIcn in right picture ) - The gulfar segment can be identified at the intersection of the sellar floor and the proximal parasellar internal carotid artery (ICA) (Barges-Coll et al. 2010 ).
  173. 173. 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 ).
  174. 174. Level 2 = AFB area
  175. 175. 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.
  176. 176. 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.
  177. 177. Level 3 = Lower cranial nerve area
  178. 178. 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).
  179. 179. 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.
  180. 180. 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, nervus intermedius; CN IX, glossopharyngeal nerve; CN XI-S, spinal accessory nerve
  181. 181. Level 4 = Foramen magnum area
  182. 182. 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.
  183. 183. Note 1. Basillar artery is kinky , not always straight 2. observe bilateral hypoglossal canals Cadaveric dissection following the removal of the apical and alar ligaments, and the odontoid process has been drilled away (OP). This re veals the strong and thick transverse portion of the cruciform ligament (CL). Behind this is located the tectorial membrane (TM). ET, eustachian tube; SP, soft palate; HC, hypoglossal canal; VA, vertebral artery; BA, basilar artery.
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