Endoscopic lateral skull base

Endoscopic lateral skull
base
16-4-2017
11.23 pm

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Some of these slides belongs to ENT
proper so Neurosurgeons please
skip those slides & concentrate on
skull base slides

Great teacher Dr. Sree Ram Murthy MS (ENT) FRCS ; INDIA –
so many photos in this presentation are his work -
https://www.facebook.com/sreeram.murthy.52

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

• DEAR SURGEONS
FACIAL RECESS, other side of coin if you see the facial recess from
ear side it is facial sinus you can observe the sius how big it is tha
course of vertical facial nerve and all other structures we have
taken the pic in reverse sitting position it is for residents only for
understanding retro tympanum FN decompression is easy in this
position
1) I S joint
2) pyramidal tip
3) ponticulus
4) facial sinus
5) sinus tympani
6) chordal crest
7) fossula of Grivot
Red dotted lines vertical FN

Some thing different..
can we do wonders
edoscopically with reverse
position?
Answer is yes...
Endoscopic ear surgeons try
stapideoplasty in this position
and see how easy the surgery
is..

1) I S joint
2) pyramidal tip
3) ponticulus
4) facial sinus
5) sinus tympani
6) chordal crest
Red dotted lines
vertical FN

This is how we see
1) I S joint
2) pyramidal tip
3) ponticulus
4) facial sinus
5) sinus tympani
6) chordal crest
Red dotted lines
vertical FN

Here sinus tympani is
actually facial recess .
The point which I want to
highlight in this diagram is
- lower point of henles
spine is exactly in line with
2nd genu - so when you
are going deeper and
deeper in cortical don't
drill below/ nearer to
lower point of henles spine
, you may hit the 2nd genu
. Always drill above henles
spine . This is very useful in
1. Children 2. Contracted
antrum

Encounterd an interesting abnormality of the facial nerve while doing cortical
mastoidectomy...... the facial nerve was exposed in its 2nd genu with hump formation
which was blocking the ventilation pathway in the attic region.....the bony ridge that is
seen was cleard and the attic widened to establish the ventilation pathway.... sorry for
the poor picture quality.....
https://www.facebook.com/photo.php?fbid=528275190567736&set=gm.4663452667
81574&type=3&theater

geniculate crest
• Dear ent surgeons it is a geniculate crest a sharp bony crest
between 1st and 2nd part if facial nerve A rare picture we did it
endoscopic cadaveric dissection It is one of the 10 commandments
of Fisch you know other nine
• Geniculate crest continue downwards and forms Bils bar we lifted f
n to show crest Traumatic f n palsies occur at pergeniculate areas
because the crest so sharp like knife and ganglion is fixed between 3
points 1 deep labyrinthine part 2 deep gutter like pre cochleariform
part if h f n 3 at foramen of Henli U can observe geniculate crest
clearily in microscopic t b dissection we cannot see crest clearly u
can observe poramen of Henli clearly here facial nerve
decompressions concentrate onthis crest during decompression
Dear residents u ask t b dissection surgeons to show this structure
during dissection course it is useful

10 mm RULES
Dear surgeons there are 1 to 10 mm rules
in temporal bone surgery If surgeon follows
those rules the ear surgery is easy and
methodical. In temporal bone no structure
is more than 10 mm in length.

10 MM RULES and 5 COLLARS OF
BONE
• 10 MM RULES and 5 COLLARS OF BONE
Dear Otologists..
There are 5 collars (colour) of bone and 10 mm Rules (1mm, 2mm,
3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm,10mm) present in ear
and temporal bone surgery
-There is thin bony collar surrounding the important structures of
the ear like the collar of the neck, with particular different colours.
after visualising the color of the bone the surgeon can identify the
structure deep to the collar
the collars are..
1) Red spongotic collar - Jugular bulb
2) Pink collar - Dura
3) Blue collar - Sigmoid sinus
4) Yellow collar - Internal Auditory Canal
5) White ivory collar - Bony labyrinth

• 1 mm rule
In posterior part of attic, tegmen is high where
as in anterior part of attic tegmen slops down to
join tensor canal Here the rule of "1" is
applicable.

1) Incus. 2)
Malleus. 3) Superio
incudo malleolar
ligament.
4) Cog . 5) Medial
attic. 6) lateral
attic. 7) Surface line
for internal squamo
petrosal suture.
8) Posterior incudal
lig.

"1" MM RULE IN TEMPORAL BONE
SURGERY
THREE POINT TRIANLE
1. From tip of short process of incus to nearest point of dome of LSC It is 1.25
mm
2. From dome of LSC to facial nerve It is 1.77 mm.
3. From tip of short process of incus to facial nerve It is 2.36 mm.
The distance of 3 point triangle are important for otologist in
1) facian nerve decompression through trans mastoidally
2) facial recess approach
3) in intact incus trans mastoid geniculate ganglion decompression aftre
removal of incus butterss
4) in tranns mastoid supra labyrinthine approach
Here the minimum distance between 3 points is 1.25 mm and the maximum
distance is 2.36 mm Hence at working in this 3 tier comportant. it is better to
use 1 mm bur to avoid injury to these structures

1 Tip of short process of incus 2 Dome of LSC
3 From dome of LSC to nearest point of facial nerve

1 Tip of short process
of incus
2 Dome of LSC
3 From dome of LSC to
nearest point of facial
nerve

• Rule of 3 is applicable, which means anterior
to posterior end of oval window is 3mm,
from posterior end of oval window to anterior
border of second genu of Facial Nerve is 3mm,
from anterior border of second genu of Facial
Nerve to apex of Arnold Triangle is 3mm.

• RULE OF 4 IN TEMPORAL BONE SURGERY
Rule of 4 in temporal bone surgery is applicable to the bony labyrinth
The semicircular canals bear very constant relationship to one other
The transverse diameter of horizontal semicircular is 4 mm
3) The half length of Lateral semicircular canal (from tip of incus to
posterior end of LSC)is 4 mm
4) The diameter of bony PSC is 4mm
5) The half length of PSC is 4mm
6 The diameter of bony SSC is 4 mm
7) The half length of bony SSC is 4 mm
8) The arch of SSC is roughly 4 mm
9 ) so 4 mm is constant landmark in bony labyrinth
10) This knowledge enables surgeon to locate each canal particularly the
posterior at operation using 4 mm burr as a handy measuring device

• 11) 4mm half distance of LSC 2 mm gap+4mm diameter of bony PSC total 10 mm
Hence surgeon wants to skeletonise the labyrinth with out injuring the labyrinth
he has to stay 10 mm away from the tip of incus along Donaldsons line
downwards
11) If the surgeon drills the bone with in 10 mm of tip of incus along donoldsons
line will destroy the posterior canal in sac decompression surgeries
12) Hard angles and hard triangles are based on rule of 4 in temporal surgeries
12) so surgeons use of 4 mm burr in labyrinthine surgery is handy and safe
14) In Temporal bone dissection subarcuate endoscopy to internal auditory canal is
latest exercise The inner diameter of SSC arch is roughly 4 mm hence using 2.8 mm
endoscope and following antrocerebellar canal of Chatellier surgeon can directly
visualise ICA
14) It is useful for surgeon to try subarcuate endoscopy, in bone dissection It is
based up on rule of 4.
My special thanks to prof Livio presuitti, prof Daniele Marchioni and prof Jao Flavio
Nogueira who taught me this Anatomy.

• RULE OF 5
Vestibule is has an anteroposterior diameter
of 5 mm and superioinferior length is 5 mm
hence 5 mm is reliable length in middle ear
During cochlear drilling in posterior area it is
advisable to use below 5 mm burr.

a, b Left ear. View of the oval window after stapes removal. Drawing showing the position of the saccule and
the utricle with respect to the oval window. The saccule is occupying the major anterior portion visible
through the oval window, from a lateral to medial view.
Ss: sinus subtympanicus; rw: round window; f: finiculus; su: subiculum; pr: promontory; psc: posterior
semicircular canal.

•
6 mm Rule - The anterioposterior length of Incus
bone from IM joint to tip of the Incus is 6 mm, The
distance between the tip of Incus to the tegmen is 6
mm,
Surgeon while removing the bone above the tip of
the incus in posterior epitympanotomy should not
use more than 5 mm burr or else injury to incus or
tegmen occurs with bigger burr.
My special thanks to prof Livio presuitti, prof Daniele
Marchioni and prof Jao Flavio Nogueira who taught
me this Anatomy.

7 mm Rule
- The distance between the anterior commissure of oval
window to vertical ICA is 7 mm in normal cellular bone.
- The length of vertical ICA is 7 mm.
- ICA is present anterior and inferior to oval window Hence in
endoscopic transmeatal approaches to clival
tumours transcochlear approaches and combained
approaches to posterior fossa it is better to use below 6 mm
burr and drill the bone from posterior to anterior direction
and take the control of ICA If bigger burs are used in narrow
anterior space surgeon may directly hit ICA.
- Remember the best landmark for identification of vertical
carotid is anterior commissure of oval window in normal
cellular bone the distance between these two structures is 7
m mm.
- The length of vertical ICA from carotid foramen to bulge
of genu of ICA is 7 mm
- My special thanks to prof Livio presuitti, prof Daniele
Marchioni and prof Jao Flavio Nogueira who taught me this
Anatomy.

FACIAL NERVE BLOOD SUPPLY
Dear surgeons facial nerve is supplied by two arterial system
1 Labyrinthine artery branch of Iaca inturn a branch of basilar artery(vertibral
systum)
2 superficial petosal artery branch of middle meningeal artery inturnbranch
of e c a
3 stylomastod artery abranch of post auricular artery inturn abranch of eca
So vertibral external carotid arterial junction in present at facial nerve at
labyrinthine segment proximal to geniculate ganglion At that point vascular
supply is weak and it is called"weak spot“
At the second genu superficial petrosal and stylomastoid arteries anastomose
with rich vascular supply hence it is called "Rich area“
Extrinsic vascular net work the above 3 arteries present with their venae
comitantes present between periosteum and epineurium so here the
stylomastoid artery along with vertical fn runs in deep bone may not be
visible

Superficial petrosal artery runs along hfn at its upper
border is visible clearly surgeons if u drill abone at second
genu area once u reach fn area there is spouting of
sentinel bleeding That is called LIGHT HOUSE SIGN
Vertibral system is not as robust at iac and labyrinthine
part of fn
The intrisic vascular network present with in epineural
sheath of nerve consists of small arterioles capillaries and
venules Lymph vessels have not been identified in neural
compartment
The extrensic and intrensic vascular system support the fn
such that even one of the major vessel canbe ligated or
nerve can be lifted from canal with out effect on fn

1 Long process of incus 2 superficial petrosal artery 3 H f n
4 pyramidal process 5 chorda 6 junction point between s p a
and stylomastoid artery 7 L s s 8 Antrum 9 Stylo mastoid
artery

• Dear surgeons
Tympanic diaphragm divides the attic from mesotympanum Microscopically the
diaphragm may not be visible Endoscopically tympanic diaphragm and
ventilatory routes to attic are important fot functional ear surgery
There are 3 main ventilatory routes to attic
1) supra tubal recess
2) Isthmus anticus
3) Isthmus posticus
Supratubal recess is main ventilatory pathway to anterior attic Above STS anterior
epitympanic recess is present tensor tympani fold seperates these two in 30% of
cases there is 2nd door between these two So anterior attic directly ventilated from
ET to through main door and 2nd door to anterio attic space in 70% cases the
second is closed then ventilation to anterior attic space comes from isthmus anticus
Surgical importance
1) in every tympanoplasty surgery surgeon should visualize these spaces any
obstruction is present remove that
2) it prevents selective disventilation syndrome
3) These anatomical details and removal of obstruction in these pathways prevents
unnecessory mastoidectomies

1) Supra tubal recess 2) Isthmus anticus 3) Isthmus posticus 4) Long process
of incus 5) Malleus 6) GATE 1 (from anterior to posterior) 7) Horizontal
tensor fold 8) Anterior attic space 9) Ventilatory route 10) Supra tensor
recess 11) Tensor canal 12) Tip of malleus 13) Tegmen 14) Eustachian
tube 15) Bend of ICA

SECOND ventilatory pathway to
attic..

• SECOND ventilatory pathway to attic..
It is situated between cochleariform process to long process of incus,
Cog vertical tensor folds are seen anteriorly in 50% of cases, circular
hole present in vertical tensor fold so ventilation passes through the
mesotympanum isthmus anticus then anterior attic. Then the ear is
safe ear
This space is mainly occupied by body of incus (biggest ossicle u can
observe incus), this space is anterior part of posterior attic, the block
ofthis gate causes retraction body of incus is also main obstruction.
you can visualize roof of attic clearly
• Surgical importance:
1) Some surgeons say it is clearence route of attic and if is blocked,
edema and granulations may be present in that area.
2) Cog is surface land mark for geniculate ganglion.
3) In case of attic retraction pockets surgeon can visualize this space
and see the obstruction including tensor folds surgeon can excise tha
fold completely
4) surgeon can test the mobility of incudo malleolar joint by pressing
the medial surface of incus.

1) Handle of malleus 2) Cochleariform process 3) Tensor
tendon 4) Cog 5) Vertical tensor lig fold 6) Medial surface of
body of incus 7) Incus 8) Tegmen tympani 9) Horizontal Facial
Nerve

• THIRD VENTILATORY GATE:
Third vetilatory gate to attic is biggest gate lot of
dynamic changes occur at this gate. It is present behind
long process of incus and medial to posterosuperior
part of TM, This gate ventilates posterior attic, auditus,
antrum and mastoid. The critical structures like
pyramidal process, posterior tympanic sinus, are
present at the entrance of gate Gas exchange and
buffering actions take place through the gate. This gate
also ventilates the medial attic.
1) Blockage of this gate by edema granulations leads to
retraction pockets.
2) Removal of squamosal cap is important to visualize
this gate completely in functional ear surgery.
3) Mastoidectomy on demand starts at this area.
4) This is main area of ventilation.
5) All cells of mastoid are ventilated through this gate.

1) Long process of incus 2) Stapes 3) Stapes tendon 4) Horizontal FN 5)
Lateral semicircular canal 6) Chordal crest 7) Pyramidal eminence 8)
Pyramidal crest 9) Facial sinus 10) Ponticulus 11) Posterior tympanic sinus
inferior 12) Posrerior tympanic sinus superior 13) Sinus tympani 14)
Auditus 15) Antrum

1) Long process of
incus 2) Stapes 3)
Stapes tendon 4)
Horizontal FN 5)
Lateral semicircular
canal 6) Chordal
crest 7) Pyramidal
eminence 8)
Pyramidal crest 9)
Facial sinus 10)
Ponticulus 11)
Posterior tympanic
sinus inferior 12)
Posrerior tympanic
sinus superior 13)
Sinus tympani 14)
Auditus 15) Antrum

• TYMPANOPLASTY
Dear surgeons, If you are doing tympanoplasty
in this type of ears then your results are very
good, both functionally and in controling the
discharge. Here the ventilatory pathways to
attic and mastoid are very patent Please
before attempting mastoids in this type of
ears please look for attic ventilation. Dont do
unnecessory mastoidectomies here, simply
close the perforation even if the ears are wet.

1) cochleariform process 2) malleus 3) incus 4)
cog 5) vertical tensor fold 6) supra tensor space 7)
Eustachian tube

COG
• COG -
cog.. cog.. cog.., it is familiar name for temporal bone surgeon
Microscopically it may be or may not be visible clearly But endoscopically
it is clear structure, a bony septum that detaches from the tegmen
tympani cranially, coming down vertically towards the cochleariform
process.
The surgical implications of this cog are
1) It is medial projection of transverse crest
2) This transverse crest due to its various positions can alter the anterior
attic
3) If the cog is fully formed it is a constant land mark for geniculate
ganglion during endoscopic approach to attic
4) Cog is considered to be junction between saccus anticus and saccus
medius
5 ) It represent the border between anterior epitympam and posterior
epitympanum both have completely different ventilatory pathways

• 6) In 70% cases the vertical tensor fold attaches to cog sometimes the vertical
tensor fold is complete or it may be partial, If the vertical tensor fold and
horizontal tensor folds are complete then there is complete ventilation block for
anterior attic space.
6)In above cases surgeon should completely remove cog along with tensor fold for
ventilation and to prevent selective disventilation syndrome.
7) In some cases vertical tensor fold attaches in front of cog not to the cog, There
is small space between cog and above ligament, that small place in front of cog is
Lurking space for cholesteatomas in those cases surgeon has to look for the space
for clearance of disease.
8) Supralabyrinthine space is situated between superior semicircular canal
posteriorly, facial nerve anteroinferiorly and tegmen superiorly. Cog divides this
space into two.
In supralabyrinthine space cholesteatomas cog has to be drilled completely for
removal of the disease.
9) cog is roughly indicates the Fisch plane(meatal plane).
10) Cog is rough land mark for IAC on medial side.

ANTERIOR PART OF POSTERIOR
ATTIC - ROOT ENTRY FOR PETROUS
APEX

ANTERIOR PART OF POSTERIOR ATTIC ROOT ENTRY FOR
PETROUS APEX
• Anterior part of posterior medial attic is a surgical space, it
has a important surgical implication. it is bounded
superiorly by tegmen
anteriorly by cog
inferiorly by isthmus anticus
medially by supralabyrinthine space
laterally by ossicular heads
posteriorly it is freely communicates with posterior medial
attic
The latero medial diameter is 1.8 mm and antero posterior
lengh is 4mm
Microscopically it is not visible through the ear unless surgeon
performs atticotomy and removal of ossicles With 45 degree
endoscope visualising through isthmus anticus this space is
clearly seen.

The surgical implications of this space are
• 1 for complete removal of cholesteatomas in attic
space
2 for drilling of cog
3 for the perforation of vertical tensor folds in
selective disventilation syndromes
4 for supra labyrinhine approach to petrous apex
5 for decompression of geniculate ganglion
6 for transmeatal exposure of mid fossaà
7 Rarely for cutting tensor tendon in clik tinnitus
8 For excison of malleolar head
9 In tubotomies and tuboplasties

Endoscopic ear surgeons should look in to this
space routinely to get more details of attic
Microscopically this space is not visible, Clear
visualisation of this space endoscopically leads to
new approaches in future in functional endoscopic
ear surgery
• 1 tegmen
2 cog
3 vertical tensor fold
4 tensòr tendon
5 prussaks space
6 handle of malleus
7 supratubal space

• It is unfortunately most neglected portion for ENT and skull base
surgeons.
Hypotympanum is a part of tympanum below the floor of external
auditory canal, extending anteriorly from Carotid canal to styloid
apparatus posteriorly,
the floor is dome shaped with concavity facing downwards
The depth of Hypotympanum is variable from 1 mm to 6 mm The
anteroposterior distance is 10mm and mediolaterally it is 4 mm.
The surgical implications of Hypotympanum are
1) Though it is root entry for major vessels it is neglected part
2) It is more variable in depth, surgeon should be careful while
entering this cavity
3) Normally Hypotympanum is occupied by trabeculi of variable
heights usually they are 7 to 9mm, the anterior long one is called
trabeculi longa where as posterior long one is called trabeculi
profunda.
4) Some times in Hypotympanum the whole trabeculi are absent.
The floor or jugular wall or pavementum pyramidalis raises up to
cochlear capsule.

• 5) The nature of Hypotympanum tells the surgeon the
type of temporal bone.
6) After opening the Hypotympanum if the trabeculi
present surgeon is safe because the jugular dome is 6
mm in deep and sigmoid sinus is posterior.
7) High jugular bulb is associated with anteriorly placed
sigmoid sinus where translabyrinthine and intact
fallopian bridge techniques are very difficult.
8) With high jugular bulb touching cochlear capsule
infra cochlear approach to petrous apex is impossible
• 9) The pneumatic cells opens into Hypotympanum
extends into infratubal pneumatic track towards apex
of pyramid in the disease process surgeon has to
carefully follow the track to remove disease
completely.
10) In 24% cases bony cavity or anterior hypotympanic
sinus is present in front of the Hypotympanum at the
junction of inner and outer walls

• 11) Anterior hypotympanic sinus common area of Lurking
cholesteatomas With endoscopic approach surgeon can
remove the disease.
12) Finiculus or sustantaculum is a bony crest connecting
the postis anticus (anterior lip ) of round window to
hypotympanum. It is an important land mark.
13) Under the cochlear capsule and finiculus there is deep
tunnel passes under the ICA to reach petrous apex it is
called sub cochlear tunnel (tunnel of promontory). usually
it is present common pathway for extension of
cholesteatoma is through this tunnel Microscopically this
tunnel is not visible endoscopically we can remove the
disease from this tunnel.
14) in 16% cases the bony jugular wall is dehiscent surgeon
should be very careful while elevating or removing the
disease
15) Jugulo carotid septum present between ICA and jugular
bulb present in hypotympanum. Erosion of crotch is
characteristic sign of glomus jugulare tumours.

• 16) "Artery of trouble", inferior tympanic artery a branch of
ascending pharyngeal artery along with Jacobson's nerve passes
through the crotch. The Ascending pharyngeal artery is smallest
branch of external carotid in glomus it is the main arterial blood
supply gives lot of trouble to surgeon hence Henly named it "Artery
of trouble"
17) Finiculus is rough surface land mark for Jacobson's nerve and
inferior tympanic artery in Hypotympanum.
18) Brackmans triangle is present in hypotympanum The base of
the triangle is formed by base of cochlear capsule the anterior limb
is formed by ICA the posterior limb is by jugular bulb, It is common
route of infracochlear approach for petrous apex.
19) Endoscopically subtympanic sinus is divided from
hypotympanum by finiculus.
20) Erosion of outer tympanic wall of hypotympanum leaving
annulus intact occur in keratosiscalled "Hanging rope sign"
So surgeons Hypotympanum is such important structure during
temporal bone dissections we do not dissect this part routinely but
endoscopically we can observe clear anatomy of this part.
My special thanks to prof Livio presuitti, prof Daniele Marchioni and
prof Jao Flavio Nogueira who taught me this Anatomy.

SUPRATUBAL RECESS
ANTERIOR ATTIC SPACE

SUPRATUBAL RECESS
ANTERIOR ATTIC SPACE
Supratubal space and anterior attic space are commonly heard spaces in
cholesteatoma surgery Microscopically these spaces may not be clearly
visible. These two places are very important for functional otological surgeon
Supratubal space is upper part of protympanum Anterior attic space is space
above the supratubal space in front of malleus These two spaces develop
from saccus anticus and posterior attic space space develop from saccus
medius
SURGICAL IMPLICATIONS
1) Endoscopic functional otological surgeon should know detailed anatomy of
these spaces in order to perform complete functional surgery
2) Ligaments are connective tissue bands and ligamental mucosal folds are
two approximated mucosal surfaces with space connective tissue fibres LML,
AML, PML and PIL are ligaments where as tensor folds and lateral incudo
malleolar folds are ligamental mucosal folds
3) horizontal tensor fold separates the supra tubal space to anterior attic
space In 70% of cases it totally separates STS to anterior attic space In this
type the ventilation of anterior attic is from isthmus anticus

• 4) In 30%of cases the horizontal tensor fold has
perforation through which supratubal space
communicates with anterior attic space
5) Vertical tensor space is attaches to cog or some
times anterior to it separates anterior attic space
to posterior attic space
6) If any granulations edema or cholesteatoma
blocks the isthmi or air pathways in tensor folds
that will lead to retractions dis ventilation finally
cholesteatomas
7) The size and position of supratubal space and
anterior attic space is variable and depends up on
the horizontal tensor fold if the fold is horizontal
the supratubal space is shallow and if the
horizontal tensor fold is oblique the supratubal
space is deep

• 8 ) Vertical tensor fold may be complete or partial
9) The common places of presence of
cholesteatoma in middle ear cleft are sinus
tympani anterior attic recess and hypotympanic
sinus
10) Anterior atticotomy is a surgical procedure in
which opening of anterior attic space to remove
the cholesteatoma with microscope
11) with an endoscope endoscopic surgeon
should remove the disease and Re-establish the
ventilation of these places, It is functional
otologic surgery
12) supratubal space and anterior attic have
smooth walls where as posterior attic is having
bony excretions That is differentiating point.

• 13) At the entrance of supra tubal recess tensor canal is
protruding landmark
14) some times supratubal recess is communicated with
peri carotid and peri tubal cells Surgeon should be careful
while removing disease at that area.
15) Rarely 1st genu of ICA reaches upto supratubal recess
surgeon should be very careful at these situations
16) The relation between CAL (chorda tympani, anterior
tympanic artery and anterior malleolar ligament) and
supratubal recess should be familiar to surgeon while doing
anterior tympanotomy of Morimutsue
During microscopic temporal bone dissection courses no
surgeon showed me these spaces. Endoscopically
everything is shown clearly. Hence for cholesteatoma
surgeons these spaces are very important to better
understanding of ventilation and disease and its removal.
My special thanks to prof Livio presuitti, prof Daniele
Marchioni and prof Jao Flavio Nogueira who taught me this
Anatomy.

• This is endoscopic view of upper retrotympanum, here elevations and depressions
are present, sometimes absent or may be partially present.
- Like the Cochleariform process in mesotympanum, Finiculus in Hypotympanum,
here in the Retrotympanum, the Piramidal eminence is the reference point.
- The Pyramidal eminence , chordal eminence and styloid eminence are the
important eminences.
1) Pyramidal eminence - from this three crests arise which divide the upper
retrotympanum into 4 compartments.
2) Chordal eminence - it is the prominence from which the chorda comes out from
posterior wall.
3) Styloid eminence - A bony prominence of posterior wall at the level of
sibiculum.
4) Chordal crest - It is vertical crest connecting chordal eminence to Pyramidal
eminences
5) Pyramidal crest - crest between Pyramidal eminence and styloid eminence
6) Ponticulus - It is present between Pyramidal eminence and posterior part of
promontory
7) Sibiculum - present between postis posticus of round window and
Retrotympanum.
• LATERAL COMPARTMENT
It is present between chorda tympani and FN
A) Facial sinus - is between chorda and FN above chordal crest
B) Fossula of Grivot - is between Pyramidal eminence and chorda below chordal
crest.

• MEDIAL COMPARTMENT
A) Sinus Tympani- It is present between Ponticulus and Sibiculum.
B) Posterior Tympanic Sinus of Proctor- It is present between Facial
Nerve and Ponticulus and it is divided into Posterior Tympanic Sinus
Inferior and Superior by Stapedial Tendon.
C) Subpyramidal Sinus- It is present under the Pyramidal
Eminence.Cholesteatoma present in Sinus Tympani extends to
Posterior Tympanic Sinus through Subpyramidal Sinus into Isthumus
Posticus finally Aditus, Antrum and Mastoid.
These compartments are important for endoscopic cholesteatoma
surgeon Majority of these compartments can be visualized with 45
degree endoscope sitting in front of the patient

• Dear surgeons appreciate the above surgical anatomy to appreciate the following surgical
implications
1) Sinus Tympani is common site of Cholesteatoma Type A ,Type B, which is approachable
through endoscope,Type C is approached through Arnold Triangle.
2) Fossule of Grivot is present in 50 percent cases, it is nidus for Cholesteatoma, it is 1 mm
in diameter.
3) Rules of 1,2,3,4,5,6,7,8,9,10 mm are applicable for temporal bone dissection.
4) Rule of 3 is applicable, which means anterior to posterior end of oval window is 3mm,
from posterior end of oval window to anterior border of second genu of Facial Nerve is
3mm, from anterior border of second genu of Facial Nerve to apex of Arnold Triangle is
3mm.
5) Common site of Lurking Cholesteatoma is Sinus Tympani and Subpyramidal Sinus
6) FN passes posterio lateral to Pyramidal eminence, too deep drilling is dangerous at this
region
7) Stapes muscle is 7mm in length and it originates from Pyramidal ridge not Pyramidal
eminence
8) Gentle curettage of posterior meatal wall is necessary to visualise retrotympanum
properly
9) Fustis is resistant to cholesteatoma destruction, hence it does not allow cholesteatoma
to go down.
10) We can see "muscle of musician" (The Stapedius) here Facial nerve supplies this muscle
passes underneath the muscle

• 11) ampulla of posterior semicircular canal is present at the floor of sinus tympani
hence deep curettage leads to injury it, leading to SN hearing loss.
12) while removing cholesteatoma here the direction of movements of
instruments is posterior to anterior to prevent subluxation of stapes.
13) Anterior tympanum is meso and protympanum mainly compared to nose
serves cleaning where as posterior tympanum as attic antrum and mastoid
compared as a lung serves as gas exchange and buffering action.
14) Isthmus posticus situated between long process of incus and posterior incudal
ligament mainly serves as a ventilation to key area, Isthmus posticus serves mainly
as a clearing area.
15) sibiculum divides retro tympanum in to upper and lower compartments.
16) lower retrotympanum acts as prechamber for sound out flow.
Every cholesteatoma surgeon should be familiar with this anatomy Microscopically
we may not see these, For residents this anatomy with excellent pictures are very
useful.
My special thanks to prof presuitti, prof Marchioni and prof Jao Flavio Nogueira
who taught me all these things.

it is endoscopy with 45 degrees through posterior
isthmus with intact incus 1 . Horizontal f n 2. l s s 3
.auditus 4. antrum 5. long process of incus

SUB PYRAMIDAL SINUS AN
IGNORED SPACE :

• SUB PYRAMIDAL SINUS AN IGNORED SPACE :
Subpyramidal space unknown, but very important space in retro tympanum it is
present under the pyramidal space
It is bounded:
Larerally by pyramidal process
Medially by vestibule
Inferiorly by ponticulus
Superiorly leading in to posterior tympanic sinus superiaris of Proctor.
Posteriorly by 2nd turn of FN
Anteriorly by posterior tympanic sinus inferior
Microscopically this space ia not visible clearly
Surgical importance
1) in 8 % of sinus cholesteatomas this space is involved
2) sinus cholesteatoma is extended to antrum through space and posterior
tympanic sinus to enter antrum it passes medial to body of incus
3) attic cholesteatoma extends to antrum through posterio pouch of von troltch
passes lareral to incus
4) second genu of FN is 3.5 mm posterior to pyramidal tip while curetting pyramid
to enter the space for removal of cholesteatoma surgeon should not curette too
posterior and prevent damage to FN
5) In transcanal labyrinthectomy the posterio part of vestibule is entered through
this space
6) sinus tympani sub pyramidal sinus posterior tympanic sinus are present in a row
in retro tympanum
To prevent recurrence surgeon should know thouroughly these spaces in
cholesteatoma surgery
7) some times pyramidal bridge present between pyramid and superior gives
subpyramidal sinus pathway.

1 pyramidal process 2 stapes tendon
3 stapes 4 ponticulus 5 sibiculumm 6 sinus tympani
7 sub pyramidal sinus 8 round window

• COCHLEARIFORM PROCESS
Dear sirs,
It is spoon shaped bony process present over medial wall of middle
ear Its surgical implications are
1) it is most resistant part for cholesteatoma bony erosion, hence it
is visible even in massive erosion by disease, a land mark
2) Tensor muscle hooks round it to form tendon and forms anterior
boundary of isthmus anticus
3) from here tensor muscle passes anteriorly to eustachian tube,
hence forms land mark in tubotomy
4) from here FN takes "7" degree up to form pre cochleariform part
5) Jocobson nerve passes vertically down wards it is useful in
Jocobson's neurectomy
6) COG or transverse crest is roughly present at this level

• 7) vertical tensor fold attaches to this its perforation is necessory in
selective dis ventilation syndrome
7) At this level basal turn of cochlea ends and second turn starts
8) 4 to 5 mm below this cochlear nerve from IAC enters modiolus, a
good land mark for trans cochlear surgery
9) Bills bar exactly situated at fundus of IAC at this level on medial
side, a good land mark in inner ear surgery
10) plesters 3 rd window is made 1 .5 mm below its posterior edge
as cochleatomy and piston insertion in cases of obliterative
otosclerosis with unidentifiable windows
11) From its posterior edge BAST crest arises attaches to facial canal
it is remnant of stapedial artery gives support to facial canal
12) It is approximate level of anterior wall of vestibule so 1st part of
FN passes anterior to it.

PRE COCHLEARIFORM PART OF
HORIZONTAL FACIAL NERVE (HFN)

PRE COCHLEARIFORM PART OF HORIZONTAL
FACIAL NERVE (HFN)
• Surgical Implications -
• 1) It is present between geniculate ganglion up to cochleariform process usually 3
to 5 mm in length
It is separated from 1st part by geniculate gutter, this part of nerve passes through
deep gutter Laterally it is covered by supralabyrinthine and perigeniculate cells of
3 to 5 mm thickness. cochleariform process is useful landmark 5 mm of bone
separates between it and 1st part
2) Anterior epitympanic recess is useful landmark for identification of this part of
nerve.
3) Removal of malleus is necessary for skeletonising this part of nerve
4)The continuity of direction of this part anteriorly is greater superficial petrosal
nerve through foramen of Henli.
5) Excessive curetting of bone and deep drilling of bone in anterior attic space
endangers this nerve damage in cholesteatoma surgery.
6) Supra labyrinthine space is situated between it anteroinferiorly and SSC
posteriorly tegmen at roof a common route for supralabyrinthine approach to
petrous apex.
7)The angle between this part and labyrinthine part is 70 degrees Once surgeon
looks at this laterally these two parts are superimposed.

• 8) GENICULATE GANGLION
-It is bluish pink in colour because of its rich blood supply
-It is usually covered by fairly thick segment of bone, sometimes it may be covered
by thin sheath or sometimes this sheath may also be absent
-It lacks bony covering in 15% of cases so it is vulnerable to injuries during surgery
especially in Mid fossa approach
-The arachnoid piamater extends up to Geniculate ganglion so this area of Facial
nerve is primary site for cholesteatoma, vascular malformations, meningiomas and
schwannomas.
-The proximal (pre Cochleariform ) segment is 3 to 5 mm in length
• 9) FISH IN POND APPEARANCE
At the mastoid part the Facial nerve is deep in the bone like a fish in pond, at the
post Cochleariform of Horizontal Facial Nerve the fish comes to the surface of
water and the Facial nerve appears as a prominent structure
The fish again goes deep into the pond where the Facial nerve deep inside the
fallopian canal at the 1'st part and at the IAC.
• 10) "1 MM RULE" IN TEMPORAL BONE
usually 1mm of bone separates between Horizontal facial nerve and foot plate
facial nerve and lateral semi circular canal and facial nerve and vestibule at the
anterior part of foot plate. Hence facial nerve passes through narrow space
surrounded by important structures thus prolapse of nerve occurs laterally
towards middle ear side Here the diameter of FN is 1.5 to 2 mm here at mid
horizontal FN, but the available space is 1 mm (1mm rule), so nerve prolapse
occurs at this part so rule of 1 applicable to facial nerve here.

POST COCHLEARIFORM SEGMENT
OF HORIZONTAL FACIAL NERVE

POST COCHLEARIFORM SEGMENT OF
HORIZONTAL FACIAL NERVE
• 1) It is often clearly visible paricularly after removal of incus to Otosurgeon
2) It is 6 mm in length and 1.75 mm in diameter, Here often there is dehiscence of fallopian
canal and often the nerve prolapse towards oval window
3) According to Fisch and Yanagihara there are two areas of marked narrowing of facial canal
in adults
A) at meatal foramen
B) at mid tympanic region
Remember if the narrowing above the oval window it is not pathological
4) This segment is situated between BAST crest and pyramidal crest These two crests holds
the nerve firmly
5) Gurriors Line of 3 ridges The lower border line this part of FN corresponds to vestibular
crest of medial wall of vestibule and in turn corresponds to transverse crest of fundus of IAC,
All three are at same level This is good land mark for surgeon in transmeatal opening of IAC
6) Anterior ends of LSC and FN are parellel 1 mm seperates between two where as at
posterior end of foot plate FN is little far away from LSC 2 mm of bone seperates between
two
7) At anterior end of foot plate FN is close to vestibule 1 mm of bone seperates between two
where as at posterior end of footplate vestibule directs medially and 2.5 mm of bone
seperates between these two

8) Rule of 3 The distance between anterior and posterior ends of foot plate is 3 mm, The distance
between posterior commissure of foot plate and the anterior border of 2nd genu of FN is 3mm
finally the distance between 2nd genu to apex of Arnold triangle is 3 mm.
9) Barber poling drilling important for FN decompression vertical FN should be drilled from
posterior side of nerve at 2nd genu on lateral side where as on tympanic side it is drilled from
inferior side of nerve to decompress FN
10) At 2nd genu area the FN is vulnerable to injury during mastoid surgery
11) In middle portion the HFN runs over the oval window forming the roof of the posterior
tympanic sinus of Proctor this is common area of injury in cholesteatoma.
12) The second segment of FN is linked to mastoid part not by angle but by curve Fossa incudis is
present superior to this. Inferiorly inferior Schwalbe sinus present
13) From distal part of HFN the nerve enters the wall of GALLE
14) The distance between the 2nd genu to LSC is 1.77 mm the distance between tip of incus to
LSC is 1.25 mm, where as the tip of incus to 2nd genu is 2.36mm. These three points forms facial
triangle while drilling bone near the 2 genu these measurements are important for safe drilling.
15) Pyramidal Triangle - It is the small triangular bone between distal horizontal facial nerve and
Pyramid, the base of the triangle is formed by fallopian crest The apex is situated towards
posterior The length of triangle is 3 mm Hence at the apex of the triangle at 3 mm posterior to
pyramidal process the FN turns to become 2nd genu It is surgically important, while endoscopic
transmeatal decompression of the nerve.
My special thanks to prof Livio presuitti, prof Daniele Marchioni and prof Jao Flavio Nogueira who
taught me this Anatomy.

STYLOID COMPLEX IS IT
NEGLECTED?
Especially for - intact fallopian bridge
technique for glomous jugulare
surgery

• STYLOID COMPLEX IS IT NEGLECTED?
• Styloid complex bone is present between tympanic and
labyrinthine walls of inferior retro tympanum.
Microscopically this region is not clearly visible, styloid
complex is of 2nd arch origin including facial nerve
Styloid complex is composed of
1) styloid eminence from retro tympanum towards
sibiculum
2) styloid peg it is tympanic part of styloid process
3) styloid button- round button medial to styloid
eminence may be present or may not be, If it is present
it indicates good retro facial cellular tract.
Vertical facial nerve is present behind styloid complex
jugular bulb is always medial to it may be very close or
1.2 cm apart to this Observe these pics the cross point
of styloid ridge and pyramidal ridge from the point
vertical FN is 5 mm posterior.

endoscopic endomeatal skull base surgeon should be
thoroughly familier with styloid complex area
1)Idetification ofstyloid complex facilitate the faster
and safer exposure of FN endoscopic endomeatally
2) styloid button indicates presence of good retro facial
cell tract
3) styloid peg is tympanic portion of styloid process In
tranmeatal skull Base surgery it is good land mark
4) In intact fallopian bridge technique for glomous
jugulare surgery identification of FN and drilling of
styloid complex is most important
5) Above the styloid complex middle retro tympanum
is hosting chamber for cholesteatomas.
Hence dear endoscopic ear surgeons please visualise
this neglected but very important part routenely while
you are performing EES In future it may give important
endoscopic route to skullBase surgery

1) styloid eminence 2) pyramidal process 3) pyramidal eminence 4)
jugular bulb 5) styloid peg 6) otosclerotic triangle ( fossula anti
fenestrae) 7) posterior malleolar ligament 8) styloid ridge 9)
pyramidal ridge 10) styloid button

1) styloid eminence 2) pyramidal process 3) pyramidal
eminence 4) jugular bulb 5) styloid peg 6) otosclerotic triangle
( fossula anti fenestrae) 7) posterior malleolar ligament 8)
styloid ridge 9) pyramidal ridge 10) styloid button

FURGUSON'S SQUARE
This is superiorly formed by facial nerve inferiorly formed by stapes
tendon posterior boundary is upper lip of pyramidal process and
anterior boundary is long process of incus
Its content is posterior crus of stapes Microscopically it may not be
much appreciable, But endoscopically it is clearly seen Now a days we
are doing endoscopic reverse position stapes surgery that means we
sit in front of patient and do surgery by Victor Goodhil method, most
of the ear pathologies are present in posterior part of tympanum If u
sit anteriorly u r target is straight in front of u then the surgery is easy.
Furgusons square is clearly visible in reverse position The advantages
of this position are
1) we can visualise posterior part of foot plate with out much bone
curette and without removing posterior crus and stapes tendon
2) we can see pathology in retrotympanum with "0" degree scope
3) we can visualise posterior tympanic sinus of proctor for
cholesteatomas

• 4) endoscopic trans meatal facial nerve decompression
5) mainly to see posterior stapedio vestibular ligament in
otosclerosis (now a days the degree of deafness in otosclerosisis
due amount of fixation of that lig)
6) posterior meatal wall, stepes tendon and posterior crus do not
come in to way during stapes surgery.
Microscopically surgeon sits infront of patient and do operation is
difficult but endoscopically it is easy, keep in mind our target area is
straight in front of us rather than in our stomach surgeons please
try and see how easy the stapes surgery is..
7) with this Plesters antrotomy and antral control to check and type
1 2 3 atticotomies procedures are easy
8) Removal of squomosal cap of Isthmus posticus and follow the
disease towards auditus and antrum without extensive
mastiodectomies is possible..

POSTERIOR EPITYMPANOTOMY
(ATTICO TYMPANATOMY) SURGICAL
IMPLICATIONS

• POSTERIOR EPITYMPANOTOMY (ATTICO TYMPANATOMY)
SURGICAL IMPLICATIONS
• Dear surgeons, posterior epitympanotomy is 2nd excerise
in temporal bone dissection lot of clinical implications are
attributed to this space
1) Rule of "6" - The distance between the tip of incus to
tegmen is 6 mm, Hence surgeon should not use bigger burs
than 6 mm while drilling this area The drilling should be
medial to lateral direction
2) Rule of "7" - The length of incus from tip of incus to
lncudo malleolar lig is 7 mm. It is useful measurement
while performing mini sub temporal approach
3) The lateral attic is situated between ossicles and scutum
of Leidy is narrow space measuring about 0.6 mm, Hence it
is not advisable to probe in this space with bigger probes.
4) Upper part of lateral attic, superior attic, and medial attic
is called superior attic This space is clear in this approach
5) Axis of rotation of ossicles passes from posterior incudal
lig to anterior malleolar lig, Hence subluxation of incus
causes up to 25 db hearing loss as occurs in stapedectomy.

• 6) Supratubal recess and anterior attic space is
not seen through procedure with intact
ossicles. hence surgeon should search for
above spaces through endomeatal route with
intact ossicles.
7) Superior lncudo malleolar ligament is
clearily seen through this procedure is land
mark for internal squamo tympanic suture, a
good land mark in mid fossa surgery.
8) Internal petro squamosal venous sinus or
LAKE OF LUSCA runs along the above suture
which connects sigmoid sinus to middle
meningeal vein, some times in adults it
persists because of profuse bleeding while
seperating dura from tegmen in mid fossa.

• 9) Vein of ENGLISH is a vein connects lake of lusca to
sigmoid sinus in majority cases. If vein of english is
present, it opens into sigmoid sinus above vein of
Santorini. surgeons should not confuse it for Labbes
vein as it opens in to transverse sinus posteriorly, if
vein of English is present it looks like a bluish thread
through intact thin tegmen in this procedure.
10) In posterior part of attic, tegmen is high where as
in anterior part of attic tegmen slops down to join
tensor canal . Here the rule of "1" is applicable.
11) Supra labyrinthine space present between superior
semicircular canal and HFN lies anterior to incus, it is
good route for petrus apex.
• Hence residents, while performing posterior
epitympanotomy please observe above points to get
good knowledge of temporal bone

1) Incus. 2) Malleus. 3) Superio incudo malleolar ligament.
4) Cog . 5) Medial attic. 6) lateral attic. 7) Surface line for
internal squamo petrosal suture.
8) Posterior incudal lig.

FUSTIS
•
it is fustis a solid bony column connecting the retrotympanum to round
window niche. So far this structure is neglected Microscopically it may
not be clearly visible, but endoscopically it is seen clearly The surgical
implications of this structure are
1) its origin is pylogenically different from other parts of that area
hence it behaves differently
2) It contains enzymes which are resistant to cholesteatoma
destruction
3) it prevents sinus cholesteatoma extending downwards..
4) This structure is directed towards round window, in narrow round
window niche by following its upper border, we can identify the round
window membrane
5) It divides upper part of subtympanic sinus, concomerata into
medialis and lateralis. C medialis is site for posterior ampullary nerve
section.
6) Fustis regulates smooth out flow of sound waves from round
window membrane.

• 7) It helps in creation of pressure difference between round and oval windows
encourages acoustic coupling.
8) It gives support round window niche because both postis anticus and postis
posticus contains cochlea and subcochlear portion that are hollow structures.
9) This structure modulates according to round window niche i. e, "V" shaped,
square shaped, triangular gothic shaped, like that, to have a relation with RW
10) In absent sibiculum, the fustis gives support.
11) Fustis narrows the round window niche there by protects the round window
membrane (rupture)normally.
12) embryologically fustis develops between periosteal layer of the labyrinthine
capsule and the thin smooth plate of Pavementum Pyramidalis and it is
ontogenically important structure.
So surgeons, fustis is very important structure at outflow gate of sound in middle
ear.
In 1968 Bruce Proctor mentioned, Recently prof Presutti, Prof Marchioni and Prof
Joao F Nogueira described this part.
so surgeons please look this important but poor part while performing surgeries
because it is present in all middle ears..

• So far round window is neglected part in
middle ear Now a days it is gaining popularity
For type4 and 5 t plasties sono inversion
techniques viroplasties gentamycin and other
chemical perfusions cochlear implant
insertions corticosteroid perfusions in s n d
skullbase approaches round window is
important There are so many verieties of
shapes of r w s I have previously discussed 4
types of r w s

" High arched" round window
• Dear surgeons it is" High arched" round window it is
present 1-3%of cases you can compare this window to
normal r w which is shown here The arched round
window associated with
1 compressed cochlear capsule in caratico facial angle
2 Deep hypotympanum
3 long trabiculae including trabicula longa
4 wide concomerata lateralis and absent concomireta
medialis
Wide postis posticus with subcochlear tunnel
5 wide sinus tympani

"PARABOLIC" round window
• Dear surgeons it is "PARABOLIC" round
window in shape present 1% of cases
characterised by
1 two vertical limbs longer than tegmen
2 wide niche
3 Third limb is formed by styloid complex
4 s shaped cochlea including sub vestibular
portion
5 wide finiculus with high pavementum
pyramidalis
6 deep carotid recess
7 3rd part of facial nerve is nearer to middle ear

• Surgical implications
1 wide angle cochlea hence cochlear implant electrode
insertion is easy
2 narrow vestbular window stapes surgery is difficult
3 endoscopic endomeatal f n decompression is easy in
these cases
4 vibroplasty is easy
5 infracochlear approach to petrous apex is not
possible in this type of round windows
6 endoscopic endomeatal approach to IAC is easy in
this type of cases
7 s shaped cochlea here allows wide transcochlear
approach to clivus

• Hi, this is human cochlea, I did it in Fortaliza, Brazil with help of prof Jao
flavio Nogueria, 3 years back
it is endoscopic dissected specimen Its base is situated between two
windows,
- Remember its apex is directed towards carotid facial angle you should
know the course of horizontal FN and greater petrosal nerve which passes
through facial hiatus (Henli's foramen)
- The internal carotid artery is usually situated 7.5 mm anterior to anterior
end of foot plate, if you want it drill cochlea anterior to foot plate please
use 5 mm bur not more than that in trans cochlear approach
- geniculate ganglion situated over apex of cochlea.
- labyrinthine part of facial nerve passes over the roof of 2nd and basal
turns in parisier's triangle.
- The thickness of cochlear wall is 1 mm to 1.5 mm over promontory
Hence it is advisable not to use monopolar cautery over promontory.
- In sclerotic mastoids the cochlea close hug the ICA But in cellular
mastoids there is gap between ICA and cochlea hence in endoscopic
transcochlear approach to clivus it is better to leave anterior turn of
cochlea particularly in sclerotic mastoids.
- cochlea is under tensor tympani muscle in tubotomy procedure after
removal of tensor muscle
- please do not drill the medial wall of tensor canal wall as there is 1 mm
bone separates it from cochlea.
These arer few anatomy and surgical implications of cochlea Any more
advise me..

• VESTIBULE
Vestibule is central part of labyrinth measuring about 5×5
mm anterio posterior and superio inferior. The depth of
cavity is 2 mm at periphery and 3 mm at centre and below
surgical implications.
1) The deepest portion of cavity is at its centre and below
3mm hence piston should be inserted at this level
2) LINE OF 3 RIDGES OF GURRIER
The lower border of HFN is at level of vestibular crest and
it turn corresponds to level of transverse crest on fundus
level It is important land mark in endoscopic transmeatal
opening of IAC.
3) Anteriorly saccule is closure to lateral surface
perilymphatic fibres attaches between saccule and foot
plate here piston should not be placed here

• 4) Utricle is horizontally placed structure
where as saccule is vertically placed on medial
wall
5 ) utricle is placed at the level of HFN hence
in transfoot plate cochlea destruction angled
hook is used.
6) Vestibular pyramid is small bony projection
present on anterior part of vestibular crest
contains terminal fibres of utricular nerve
7) Posterior recess is deep recess present
posteriorly in vestibule in which crus
commune and ampulla of PSC opens in to.

• 8) Cochlear recess is a small recess present
behind vertical vestibular crest, inferiorly it lodges
beginning of ductus cochlearis.
9) RIECHERTS SPOT - small cribriform area
present at inferior part of cochlear recess though
nerve filaments go to initial portion of vestibular
portion cochlea these are nerve filaments of
BECHTEREW it has to be destructed in
labyrinthectomy.
8) At floor of vestibule origin of osseous spiral
lamina and vestibulo tympanic fissures present,
these parts are important for cochlear implant
surgeon
9) Mouth of scala vestibuli is present at the
antero inferior part of oval window In total
stapectomy surgeon should not disturb this area.

• 10) Sulciform gutter a small groove present behind utricular recess
in which the endolymphatic duct opens in to vestibule During
labyrinthine surgeries this area should be safeguarded.
11) The inferior level of vestibule present 1 mm below oval window
anterior level is at anterior level of oval window superior level of
vestibule is at ampulla of LSC where as the posterior level of
vestibule present 3mm posterior to oval window hence 3 mm hook
is necessary to destruct labyrinth through oval window.
RULE OF 5
Vestibule is has an anteroposterior diameter of 5 mm and
superioinferior length is 5 mm hence 5 mm is reliable length in
middle ear
During cochlear drilling in posterior area it is advisable to use below
5 mm burr.
prof Jao Flavio Nogueira who taught me this Anatomy.

PARISIER'S TRIANGLE
(DANGEROUS TRIANGLE)

PARISIER'S TRIANGLE
(DANGEROUS TRIANGLE)
Perisier's triangle is very important triangle in endoscopic ear surgery
1) Superior limb is formed by inferior part of HFN
2) The apex is formed by the geniculate ganglion
3) The base is formed by the anterior commissure (end) of oval window
4) Inferior limb is formed by tunning point of jocobson's nerve to the the
geniculate ganglion.

• The surgical implications are
1) This triangle contains labyrinthine part of FN.
2) During transotic or transcochlear approaches surgeon should respect this triangle and drill carefully
to avoid injury to FN.
3) Clinically labyrinthine part consists of two segments a meatal segment of nerve, labyrinthine part of
nerve. total length of this nerve is 3 to 5 mm. Anteriorly we can see these parts clearly through this
triangle.
4) 1st part of FN passes close to lower border of precochlear HFN towards anterior end of oval window
in this triangle.
5) Irregular drilling of cochlea in this triangle damages FN That is why it is called DANGERS TRIANGLE.
6) During trans meatal endoscopic dissection of IAC, this triangle important for identification of nerves
7) Translabyrinthine approach visualises posterior surface of 1st part of FN, in transcochlear approaches
the anterior surface of the nerve is exposed. In transottic approaches 270 to 320 degrees of 1 st part of
FN is exposed.
8)Observe closely the labyrinthine part of FN there is a constriction of labyrinthine segment and meatal
segment.
Facial nerve key points
1) Facial nerve changes direction 5 times during its course from brain stem to styloid foramen.
2) No other nerve in body covers such a long distance in bony canal
3) facial nerve contains 10000 axons that are responsible for the innervation of the face musculature
and also for the communications with other nerves human body
4) work with injured facial nerve requires lot of patience.

• RULE OF 2 IN TEMPORAL BONES
1) The diameter of geniculate fossa is 2 mm
2) The distance between between geniculate fossa to anterior wall
of vestibule is 2 mm
3) The thickness of geniculate crest is 2 mm
4 ) The diameter of horizontal facial nerve in that area is 2 mm
Hence while drilling the bone or curetting the bone at
perigeniculate area it is not advisable to use bigger burs more than
2mm diameter
5) The meatal segment of facial nerve is usually 2 mm anterior and
superior to superior vestibular nerve.
prof Jao Flavio Nogueira who taught me this Anatomy

SURFACE MARKING OF INTERNAL AUDITORY CANAL ON
MEDIAL WALL OF MIDDLE EAR
Dear surgeons it is dissected dry temporal bone
showing the surface landmark for fundus of iac .
The land mark is BENZWHEEL You can observe
three wings of Benz wheel So iac is present
anterior to oval window

1 oval window 2 round window 3 ponticulus 4 sibiculum
A Basal turn of cochlea B middle turn C apical turn

Surgical implications
1 every resident should be familier with this picture to do further
transmeatal skull base surgery
2 surgeon should respect antero superior part of this
wheel(labyrinthine part of f n travels)while doing transcochlear
approach or modified transcochlear approaches endoscopically
through the meatus
3 in performing cochleactomies
4 for endoscopic endomeatal rerouting of fn from iac to stylo mastoid
foramen
5 for removal of clival skullbase tumours
7 It is front gate to extended endoscopic approaches
8 For decompression of labyrinthine fn in cases of transverse fractures

• Dear surgeons it is BENZ wheel in ear
1. Superiorly it is bounded oval window
2. anteriorly by cochlea and
3. inferiorly by scala of basalturn of cochlea
The cochlear nerve from i a c entering to modiolus through
the center of the wheel c in picture is cochlear nerve This
is first surgical land mark for endoscopic endomeatal
approach to i a c
Note the relations between vestibular window modiolus and
basal turn of cochlea
1) endoscopic cochlear neurectomy
2) endoscopic approach to i a c
3) Trans cochlear approaches to skull base
4) c i surgery
5) vestibular nerve sections

11) FN in IAC
12) cochlear nerve

Endoscopic transcochlear
approach

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
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 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

endomeatal endoscopic dissection
for internal auditory canal

• Dear surgeons
This is endomeatal endoscopic dissection for internal auditory canal
Under the horizontal facial nerve infront of Round Window
including anterior part of oval window is surface land mark for ICA
The steps follows:
1) Posterior cochleactomy, Identification of base of modiolus
2) Creation of benz wheel. Benz wheel divides promontory
a) below the RW
b) anteroinferiorly cochlea
c) antero superiorly internal auditory canal including paresiers
triangle.
3) opening of posterior wall of Internal auditury canal identifying
vestibular nerves.
4) Anteriorly once removal of vestibular nerves cochlear and facial
nerves are visible.
5) The direction of these nerves are important relation once this
excerise is well known endoscopic endomeatal exposure of clive
and transcochlear approaches are easy
Microscopically trancochlear approach is described by pro
portmann but it is not clear.
Dear microscopic temporal bone surgeons you combine your
microscopic bone excerise with endoscopes to give maximum
benifit to residents.

• 1) Surface marking for IAC
2) Vestibule
3) Modiolus
4) Spherical recess
5) Horizontal FN
6) Round window
7) Modiolus
8) Posterior part of vesribule
9) RW niche
10) Medial wall of vestibule
10) Superior and inferior vestibular nerves
11) FN in IAC
12) cochlear nerve

• IAC 360 DEGREES :
• Surgeons it is cadaveric endoscopic
dissection of IAC 360 degrees.
• The dissection steps are
1) Simple mastoidectomy
2) Intact fallopian bridge technique
3) Trans labyrinthine approach to IAC
4) Trans meatal cochlectomy
5) Identification of ICA
6) 360 degree exposure of IAC

• Surgical implications
It is basic exercise of mastoidectomy intact fallopian bridge
technique tranmeatal exposure of IAC and finally transotic
approach
For transotic removal of acoustic tumours.
Here surgeon can know the relation between IAC Facial nerve
and ICA
It is a combination of trans labyrinthine approach to IAC to
expose its posterior surface transmeatal approach to expose
anterior surface of IAC finally intact fallopian bridge technique
for under surface exposure of IAC. It is done fully
endoscopically.
Dear temporal bone surgeons practice this exercise you know
360 degrees of IAC and the relations with the surround
structures.

1) ICA 2) Eustachian tube 3) Eochleactomy (endomeatal transcochlear
route 4) IAC (360 degrees) 5) Horizontal Facial Nerve 6) Crotch 7)
Jugular bulb 8) Translab approach to IAC 9) labyrinthine Facial
Nerve 10) Vestibular nerves

posterior ampullary nerve
(singular nerve)

E N T surgeons it is rare video of exposure and visualising of posterior ampullary
nerve (singular nerve).
It arises from inferior vestibular nerve and passes through the singular foramen
which is situated 1 mm medial to fundus of IAC, then it passes posteriorly towards
sinus tympani.
At the floor of the sinus tympani ampulla of posterior semicircular canal is present.
The singular nerve supplies to the ampulla of posterior semicircular canal
The surgical landmark for this nerve is concomerata medialis and posterior lip of
round window, hereby drilling posterior to Round window exposes the singular
nerve,
In the above video we can see
- IAC
- Inferior vestibular nerve
- A white structure, thread like, passing from IVN in IAC, towards sinus tympani is
clearly seen.
The indications for this exposure are
- Identification of IAC in which it guides ur towards posterior wall of IAC
- Nerve section in BPPV
Sometimes due to its variational course we may not be able to visualise this nerve.
Prof Richard R Gacek described this procedure for BPPV (Gacek's Neurectomy).
https://www.facebook.com/groups/1618442198418497/permalink/1676666562596
060/

See video
https://www.facebook.com/groups/1
618442198418497/permalink/16766
66562596060/

Fully Endoscopic Subtemporal
Approach

INDICATIONS
.
The fully endoscopic subtemporal approach provides minimally
invasive surgical access to the
1. ipsilateral petroclival,
2. Suprasellar and parasellar, cavernous sinus, and
3. medial sphenoid wing regions.
Pathologies in these areas may include
1. Hypothalamic gliomas;
2. craniopharyngiomas, especially with a prefixed-optic
chiasm;
3. trigeminal schwannomas or neurofibromas;
4. petroclival, sphenoid wing, and cavernous sinus meningiomas;
5. arachnoid cysts of the middle cranial fossa;
6. pituitary macro adenomas with major lateral extensions;
7. chordomas of the middle and upper clivus;
8. carcinomas; rhabdomyosarcomas; and other benign and
malignant lesions extending to or through the middle skull base,
with or without invasion of the cavernous sinus

COMPLICATIONS
During the skin incision, the frontotemporal branch of
the facial nerve is the most likely motor branch to be injured
because it is vulnerable in its superficial path as it penetrates
just below the zygomatic arch close to the
temporomandibular joint and traverses an oblique course
superiorly over and above the zygomatic arch. This is avoided
by carefully elevating the lateral periosteum of the arch to
protect the nerve and not extending the skin incision below
the lower border of the zygomatic root. The course of the
nerve over the zygomatic arch can be estimated by a line
connecting a point 0.5 cm inferior to the tragus to a point 1.5
cm lateral to the superior brow.

The auriculotemporal nerve, a sensory branch of
the mandibular division of the trigeminal nerve, lies
posterior to the superficial temporal artery within
the temporoparietal fascia (the surgeon may often
encounter an anterior branch of the artery during
the skin incision), and therefore elevation anterior
to the frontal branch of the superficial temporal
artery should proceed with caution to avoid injuring
this nerve. Whenever

MECKEL'S CAVE THROUGH
ENDOSCOPIC SUBTEMPORAL APPROACH
• Today I have done Radio frequency gangliolysis of Gassarian
ganglion for severe Trigeminal neuralgia through fully
endoscopic subtemporal fossa extra dural approach.
'C' shaped, 2 cm preauricular incision, mini craniotomy separation
of mid fossa dura from Temporal bone, middle menengial artery
coagulation, Identification and following the GSPN, foramen ovale,
mandibular nerve, Extradural Isolation of Gassarian Ganglion
by KAWASE method and radio frequency lysis of ganglion are the
steps.
Through this fully endoscopic approach, Merkel's cave and
Gassarian Ganglion are visualised.
For a better understanding, Cadaveric dissection of middle cranial
fossa is posted here..
Patient was having severe neuralgia prior to this surgery, now the
the pain is temporarily subsided.. Long term results are awaited.

The Fully Endoscopic Retrosigmoid
Approach = MIRA
MIRA = Minimally invasive
retrosigmoid approach

subarcuate artery
• Dear surgeons drVetrivel showed us subarcuate artery
usually it is eaither branch of labyrinth artery or from
aica asit passes through iac it sends branch to petrous
apex and its branches to posterior meningeal artery
and superficial petrosal artery then it passesthrough
the petromastiod orantro cerebellar canal of Chatellier
and comes to antrm under the.arch.of ssc to supply
medial wall of antrum The surgical implications are
1 it is surgical land mark for a light house sign b to
guide to subsrcuate endoscopy to internal auditory
canal c to follow the vein of Els worth Luscas lake The
rule of 4 is applicable here

SSC dehiscence = Superior semi
circular canal dehiscence

Video of endoscopic SCCD
https://youtu.be/yTiF_OGrbEo

Microscopic repair of SCCD
• MCV Clinics #012
GIDDINESS...Corrected by simple surgery
• Surgically correctable causes of giddiness include Superior
SCCDehiscence (congenital), Lateral
SCC Dehiscence (cholesteatoma/ Iatrogenic), etc.
All inner ear diseases – accurate diagnosis is more critical than the
management.
Only HRCT is useful and Plain CT Brain will not pick it up. Caloric
responses may be variable.
• Case of a 67yr.old with recurrent vertigo lasting 2-3hrs for 5
months, triggered by bending down and getting up.
Our patient had a Transmastoid exposure of labyrinth, thinning of
tegmen antri, followed by exposure of Superior SCC Arch under GA.
Oncedehiscence was exposed it was plugged with periosteum.
• — with Anand Veluswamy.

Endoscopic lateral skull base

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