Orbit 360°21-9-2016

2.02 pm

Great teachers – All this is their work . I am just the reader of their books .

Prof. Paolo castelnuovo

Prof. Aldo Stamm Prof. Mario Sanna

Prof. Magnan

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Orbital fascia = Periorbita

Bulbar fascia includes

1. Tenon’s capsule 2. Tubular sheat for each orbital muscle 3. medial & lateral check ligament 4. suspensory ligament of lockwood

Medial Orbital

Approach-Periorbitaelevated

from bone

Superior oblique tendon goes underneath the superior rectus where are inferior oblique muscle goes below the inferior rectus

Anterior wall of Cavernous sinus , SOF , Orbital apex in continnum

Anterior wall of Cavernous sinus , SOF , Orbital apex in continnum

[ SOF = ALSC + Orbital apex]

For detailed understanding of ALSC see “ SOF 360° ” presentation in

website : Click

http://www.slideshare.net/muralichandnallamothu/superior-orbital-

fissure-360

The term cavernous sinus addresses only the venous aspect, neglecting the neural and soft tissue components. A more comprehensive and rational term is lateral sellar

compartment (Parkinson 1990 ) .

• Lateral sellar compartment ( = Cavernous sinus ) is in continuation with SOF & Orbit

• SOF devided into [ SOF = ALSC + Orbital apex]

1. ALSC = Anterior lateral sellarcompartment – Located anterior to the anterior loop of the cavernous portion of the internal carotid artery.

2. Orbital apex

Anterior lateral sellar compartment [ ALSC ][ SOF = ALSC + Orbital apex]

Parts of ALSC ( Anterior lateral sellarcompartment )

1. Superior Part – Nervous compartment

a. Lateral Group of nerves - from lateral to medial - LFT[ Liver functional tests ] Menumonic – Lacrimal N., Frontal N.,TrochlearN.

b. Middle Group of nerves - 3rd , 6th , Nasocilliary N.

2. Inferior part – Venous compartment - Inferior Opthalmic vein – The inferior venous compartment is given by the confluence of the superior ophthalmic vein ( SOV ) and inferior ophthalmic vein ( IOV ), which drain into the cavernous sinus (Froelich et al. 2009 ) .

ORBITAL APEX [ SOF = ALSC + Orbital apex]

Orbital apex is divided into the

1. intraconal compartment

2. extraconal compartments - passed by the lacrimal, trochlear, and frontal nerves. The frontal and trochlear nerves ascend above the Levator muscle & superior rectus muscle.

Within the intraconal space, the

1. superomedialforamen - optic nerve and the ophthalmic artery pass.

2. superolateralforamen - oculomotor, nasociliary, and abducens nerves pass.

1. 3rd nerve supplies to the muscles from medially – so when you are doing principle of divergence [ to separate the ocular muscles ] to remove the intraconal tumors , don’t stretch

too much , chances of nerve avulsion from the muscle is there sothat muscle palsy 2. SO4 LR6 – all muscles by 3rd nerve , super oblique by 4th nerve , lateral rectus by 6th nerve 3. MG = medial group of nerves – 3rd, 6rth , nasociliary ; LG = lateral group of nerves – LFT [

mneumonic = Lacrimal , frontal , trochlear ]

Orbital apex

[ SOF = ALSC + Orbital apex]

Orbital apex & Medial wall

Parts of Orbital Apex

Orbital apex is divided into the – intraconal compartment– extraconal compartments - passed by the lacrimal,

trochlear, and frontal nerves. The frontal and trochlear nerves ascend above the Levator muscle & superior rectus muscle.

Within the intraconal space, the 1. superomedial foramen - optic nerve and the

ophthalmic artery pass.

2. superolateral foramen - oculomotor, nasociliary, and abducens nerves pass.

Anterior wall of Cavernous sinus , SOF , Orbital apex in continnum

[ SOF = ALSC + Orbital apex]

ORBITAL APEX [ SOF = ALSC + Orbital apex]

Orbital apex is divided into the

1. intraconal compartment

2. extraconal compartments - passed by the lacrimal, trochlear, and frontal nerves. The frontal and trochlear nerves ascend above the Levator muscle & superior rectus muscle.

Within the intraconal space, the

1. superomedialforamen - optic nerve and the ophthalmic artery pass.

2. superolateralforamen - oculomotor, nasociliary, and abducens nerves pass.

1. 3rd nerve supplies to the muscles from medially – so when you are doing principle of divergence [ to separate the ocular muscles ] to remove the intraconal tumors , don’t stretch

too much , chances of nerve avulsion from the muscle is there sothat muscle palsy 2. SO4 LR6 – all muscles by 3rd nerve , super oblique by 4th nerve , lateral rectus by 6th nerve 3. MG = medial group of nerves – 3rd, 6rth , nasociliary ; LG = lateral group of nerves – LFT [

mneumonic = Lacrimal , frontal , trochlear ]

Orbital apex

[ SOF = ALSC + Orbital apex]

Parts of Orbital Apex

Zonule of zinn - inserts on the infraoptic tubercle, which is often found as a canal located beneath the optic strut .

The four rectus muscles insert posteriorly, through the Inferior common tendon ( ICT ) , on the infraoptic tubercle, a small

depression below the optic strut.

More anteriorly, the Inferior common tendon ( ICT ) splits into a superior and inferior tendon. From the inferior tendon originate the medial, inferior, and lateral rectus

muscles, and from the superior originates the superior rectus muscle.

Inferior common tendon ( ICT ) MG medial group of nerve(oculomotor, nasociliary, abducens),

black arrow - lateral group of nerves (frontal,lacrimal, trochlear)

Greater wing of sphenoid – at posterior end of orbit – Through orbit if we breach greater wing of sphenoid we go to the middle cranial fossa

Clinoid has three roots of attachment 1. Anteriror root = Anterior Clinoid process attachemnt to planum

2. Posterior root = Optic struct = L-OCR 3. 3rd root = Anterior Clinoid process attachment to Lesser wing of sphenoid

Clinoid has three roots of attachment 1. Anteriror root = Anterior Clinoid process attachemnt to planum

2. Posterior root = Optic struct = L-OCR 3. 3rd root = Anterior Clinoid process attachment to Lesser wing of sphenoid

Three surgical attachments of the right anterior clinoid process. (a, sphenoid ridge; b, roof of optic canal; c, optic strut.)

Anterior clinoid drilling videos in FTOZ [ neurosurgery skull base ]

1. https://www.youtube.com/watch?v=wO2cWHiOdO0

2. https://www.youtube.com/watch?v=4dkQY3zxJHU

3. https://www.youtube.com/watch?v=vd4_lPVIUvE

4. https://www.youtube.com/watch?v=_dvYB1InGMc

5. https://www.youtube.com/watch?v=83_VuKHXOmQ

6. https://www.youtube.com/watch?v=0KwBhTqNXA4

7. https://www.youtube.com/watch?v=pCURjQ83HzU

8. https://www.youtube.com/watch?v=DNIy0L3oFgY

9. https://www.youtube.com/watch?v=GT4eBB2x58Q

10. https://www.youtube.com/watch?v=OS4Mc0X8tlU

11. https://www.youtube.com/watch?v=_xq9e3p1cc4

1. SOF present between two structs2. OS [ optic struct separates optic canal from SOF ]

1. SOF present between two structs2. OS [ optic struct separates optic canal from SOF ]

SOF & IOF are in C-shape when you see through orbit /maxilla/nose

Anterior clinoid process [ ACP ] has 3 roots of attachements :

1. Anterior root – ACP attachment to sphenoid planum medial to falciform ligament

2. posterior root = OS = L-OCR3. 3rd root to lesser wing of sphenoid

Optic strut [ OS ] = L-OCR [ Pneumatisationof OS ] =

Posterior root of Anterior clinoidprocess [ ACP ]

OS = L-OCR = posterior root of ACP

1. Surpa-optic pneumatisation starts from anterior root of ACP & goes to ACP , infra-optic pneumatization starts in posterior root of ACP [ = OS = L-OCR ] &

may goes into ACP 2. In ACP drilling if there is pneumatization we will directly open into sphenoid

so we have to plug with fat after ACP drilling in neurosurgical skull base

Surpa-optic pneumatisation starts from anterior root of ACP & goes to ACP , infra-optic pneumatization starts in posterior root of ACP [ = OS

= L-OCR ] & may goes into ACP

Various types of Optic nerve

• Type I: The most common type, it occurs in 76% of patients. Here, the nerve courses immediately adjacent to the sphenoid sinus, without indentation of the wall or contact with the posterior ethmoid air cell [Figure 11].

• Type II: The nerve courses adjacent to the sphenoid sinus, causing an indentation of the sinus wall, but without contact with the posterior ethmoid air cell [Figure 12].

• Type III: The nerve courses through the sphenoid sinus with at least 50% of the nerve being surrounded by air [Figure 13].

• Type IV: The nerve course lies immediately adjacent to the sphenoid and posterior ethmoid sinus [Figure 14] and [Figure 15].

Figure 11: Coronal CT showing type I optic nerve (arrows) the nerve is seen to course immediately adjacent to the sphenoid sinus, without contact with the posterior

ethmoid air cell

Figure 12: Coronal CT showing type II optic nerve (curved arrows) causing an indentation of the sinus wall, but without contact with the posterior ethmoid air cell

Figure 13: Coronal CT shows type III optic nerve (arrows) where more than 50% of the nerve is surrounded by air

Figure 14: Coronal CT showing type IV optic nerve on the right (arrow) -The nerve course lies immediately adjacent to the sphenoid and posterior ethmoid sinus. O:

Onodi cell; S: Sphenoid sinus

Figure 15: Coronal CT showing type IV optic nerve bilaterally (arrows). O: Onodi cell; S: Sphenoid sinus

Delano, et al., found that 85% of optic nerves associated with a pneumatized anterior clinoid process were of type II or type III configuration, and of these, 77% showed dehiscence [Figure 16], indicating the vulnerability of the optic nerve during FESS.

Figure 16: Coronal CT shows pneumatisation of anterior clinoid process (stars) with type III optic nerve (stars) with bony canal dehiscence bilaterally

Pneumatization of anterior clinoid process – in various planes + onodi cell on both sides of sphenoid [ when transverse septum present in sphenoid it is

onodi cell ] + sphenoid recess on left side between V2 & VN .

The same cadaver photo what you are seeing in CT scan above – Note the supraopticpneumatisation [ present in anterior clinoid process ] in an onodi cell .

The sphenoid sinus septa may be attached to the bony canal of the optic nerve, predisposing the nerve to injury during surgery .

Figure 17: Coronal CT showing sphenoid septa (arrow) attached to the bony walls of type III optic nerve bilaterally (stars)

The muller’s muscle extends for the whole length of the inferior orbital fissure, passes above the maxillary strut and enters the

superior orbital fissure.

Cadaveric dissection demonstrating the anatomy of the right orbital apex followingremoval of the lamina papyracea, periorbita, and orbital fat. (OA, ophthalmic artery; MR, medial

rectus; ON, optic nerve; IR, inferior rectus; MM, Muller muscle; V2, second branch of thetrigeminal nerve.)

An important vein travelling the SOF is quite constant. It is immediately under the periorbit, outside the muscular cone, and reaches the cavernous venous compartment. This vein can be a

limiting factor for drilling the SOF area (Dallan et al. 2013 ).

CS cavernous sinus, IRM inferior rectus muscle, lOCR lateral optico-carotid recess, MM Muller’s muscle, MRM medial rectus muscle, ON optic nerve, pwMS posterior wall of the maxillary sinus, VN vidian nerve, V2 second branch of the trigeminal nerve, white asterisk indicates lateral optico-carotid recess, black asterisks indicate the nasal part of the superior orbital fi ssure, black arrow indicates the division of the oculomotor nerve, red arrow indicates ophthalmic artery, yellow arrow indicates maxillary strut

By dividing IRM and MRM tendons it is possible to identify the 2 main branches of the oculomotor nerve, and laterally to it, the first segment of the

ophthalmic artery (Dallan et al. 2013 ).

By dividing IRM and MRM tendons it is possible to identify the 2 main branches of the oculomotor nerve, and laterally to it, the first segment of the

ophthalmic artery (Dallan et al. 2013 ).

Orbital Apex

FN frontal nerve, IRM inferior rectus muscle, LaN lacrimal nerve, LRM lateral rectus muscle, LWS lesser wing of the sphenoid, MRM medial rectus muscle, NCN nasociliary nerve, ON optic

nerve, SRM superior rectus muscle, SS sphenoid sinus, V2 second branch of the trigeminal nerve, IIIcn oculomotor nerve, red asterisk trochlear nerve, red arrowhead abducens nerve, red

circle ophthalmic artery

Thicker inferior division of 3rd N. & thinner superior division of 3rd N . 2. Nasociliary N passes between divisions of 3rd N.

3. In the annulus, the nasociliary nerve passes medially, and it is located between the two divisions of the oculomotor nerve; the abducens nerve runs

superiorly and laterally to reach the lateral rectus muscle.

Accessing intraconal lesions endonasally requires manipulation of the extraocularmuscles. The nerve branches that supply the oculomotor muscles run in the medial

surface of the muscles. Thus, try to avoid excessive retraction of the extraocularmuscles to avoid inadvertent muscle paresis.

The pterygopalatine fossa presents an extension within the superior orbital fissure ( SOF ), inferior to the lateral sellar compartment and Muller’s muscle. It is composed of

fat, small veins, and nerve fibres associated with the pterygopalatine ganglion (PPG) (Weninger and Prahmas 2000 ) .

Cadaveric dissection demonstrating the anatomy of the right orbital apex following removal of the lamina papyracea, periorbita, and orbital fat. (OA, ophthalmic artery;

MR, medial rectus; ON, optic nerve; IR, inferior rectus; MM, Muller muscle; V2, second branch of the trigeminal nerve.)

a–c Contents of the orbita. (a) Reconstruction of the medial aspect of the orbit. (b) Right orbit, endoscopic view of the upper part of the anterior medial intraconal space. (c) Right orbit, endoscopic view of the medial intraconal space. AEA,

anterior ethmoidal artery; CAs, ciliary arteries; DNA, dorsal nasal artery; IRM, inferior rectus muscle; IRMb, branch for the inferior rectus muscle; ITN, infratrochlear nerve; IVcn, trochlear nerve; LCN, long ciliary nerve; MRM, medial rectus muscle;

NCN, nasociliary nerve; OA, ophthalmic artery; ON, optic nerve; PEA, posterior ethmoidal artery; SB, skull base; SOA, supraorbital artery; SOM, superioroblique muscle; SON, supraorbital nerve; SOV, superior ophthalmic vein; STA,

supratrochlear artery; STN, supratrochlear nerve. Black circles, periorbit.

Left orbit, macroscopic vision of the medial intraconalspace. EB, eyeball; IIIcn, oculomotor nerve; IOA, infraorbital artery; IRM, inferior rectus muscle; IRMb, branch

for the inferior rectus muscle; MRM, medial rectus muscle; NCN, nasociliary nerve;OA, ophthalmic artery; ON, optic nerve; PEA, posterior

ethmoidal artery; SOM, superior oblique muscle; SOV, superiorophthalmic vein. Stars, long ciliary nerves.

The medial and inferior rectus muscles arise from the portion of the anular tendon situated medial to and below the optic canal. Tributaries of the inferior ophthalmic vein pass downward on the medial side of the

anular tendon and cross below the inferior rectus muscle to join the main trunk of the vein where it exits the intraconal area by passing between the heads of the lateral and inferior rectus muscles to enter the anterior-

inferior part of the cavernous sinus.

1. Note 3rd nerve on medial surface of medial rectus muscle 2. The medial rectus muscle has been divided near the globe and reflected posteriorly. In this

case, the ophthalmic artery courses below the optic nerve to reach the medial part of the orbit.

Central retinal artery origin from Ophthalmic artery – the only artery which can’t be mobilized in skull base surgery is Ophthalmic artery because central retinal artery is torn

The ophthalmic artery has been elevated to expose the ciliary ganglion on the lateral aide of the optic nerve. The motor (parasympathetic) root of the ciliary ganglion arises from the branch of the inferior division of the oculomotor nerve to the inferior oblique muscle. The sympathetic

root of the ciliary ganglion arises from the carotid sympathetic plexus.

“ PEA based Hadad “ flap – useful in where sphenopalatine artery sacrificed.

Orbit from superiorly

Branches of V 1

Lateral part- from lateral to medial - LFT[ Liver functional tests ]

Menumonic – Lacrimal N., Frontal N.,Trochlear N.

Immediately after removing the periorbita

1. Lateral part- LFT [ Liver functional tests ] Menumonic – Lacrimal N., Frontal N.,TrochlearN. & Superior Opthalmic Vein.

2. The frontal and trochlear nerves ascend above the Levator muscle & superior rectus muscle.

Frontal N. devides into Sup.Troch.N. & Supraorb.N. – NOTE Fal.Lig

1. Thicker inferior division of 3rd N. & thinner superior division of 3rd N . 2. Nasociliary N passes between divisions of 3rd N.

3. In the annulus, the nasociliary nerve passes medially, and it is located between the two divisions of the oculomotor nerve; the abducens nerve runs superiorly and laterally to reach the

lateral rectus muscle.

A segment of the orbital portion of the optic nerve has been removed. This exposes the branch of the inferior division of the oculomotor nerve, which passes below the optic nerve and enters the medial rectus muscle.

When you are approaching endoscopically the upper most one is Sup.Orb.M superiorly & Medial rectus

inferiorly

Medial approachis directed through the interval between the superior oblique

and the levator muscles.

Lateral approach

Nasociliary N. [ 3rd branch of V1 ] devides into AEN & PEN

Anterior limit of Transplanum approach is PEA – when we are removing a triangular piece of bone in

Transplanum approach , the base of traingle is PEA

PEA roughtly corresponds with Optic tubercle continuation above

Orbit from Inferiorly

Orbit from inferiorlyInferior orbital muscle is complete muscle , whereas Sup.Obl.M is muscular & tendinous

Orbit from inferiorly after cutting the Inferior rectus muscle

Orbit from inferiorly after cutting the Inferior rectus muscle

OPTIC NERVE DECOMPRESSION

Optic nerve decompression:

Remove the bone (by drilling) over the orbital apex and

identify the optic foramen and optic nerve canal:

a) superior and medial aspect of the orbital apex

b) 4-6 mm posterior to the posterior ethmoidal artery

c) at a level that grossly corresponds with the level of the

rostrum of the sphenoid (coronal axis).

Use the drill to thin the bone of the optic nerve canal.

Remove the remaining bone using dissecting instruments

or 1mm Kerrison’s rongeurs.

Most commonly, the optic canal decompression extends

posteriorly to the level of the lateral optic carotid recess

(LOCR).

LOCR corresponds to the pneumatization of the optic strut.

The anterior clinoids are at the superior aspect of the

optic canal just above the LOCR; therefore, it is at this level

that the optic nerve enters its canal after it intradural

course (i.e. it is not surrounded by bone).

Optic tubercle

In 83% the OA passes around the lateral aspect of the optic nerve (b, left); in the remaining cases the OA stays medial to the

optic nerve, 17% - this point important in optic nerve decompression

One artery in the head which we can’t move – is OA – Central retinal artery is avulsed

Relation of PEA & ONAnterior limit of Transplanum approach is PEA – when we are removing a triangular piece of bone in Transplanum approach , the base of traingle is PEA

Anterior limit of Transplanum approach is PEA – when we are removing a triangular piece of bone in

Transplanum approach , the base of traingle is PEA

PEA roughtly corresponds with Optic tubercle continuation above

The sphenoid ostium (SO) is first opened inferiorly (black arrow, 1) then laterally (black arrow, 2). This should afford a

clear view into the sphenoid sinus and the remaining anterior face of the sphenoid can be removed up toward the optic tubercle (OT) but

usually stopping short of the tubercle to lessen the potential risk to the optic nerve.

Opthalmic artery – Retrograde branch of Intracranial carotid

Branches of the cavernous internalcarotid artery ( ICA ), a rare variation: ophthalmicartery passing through the superiororbital fissure

classification of the ophthalmic artery typeshttp://www.springerimages.com/Images/MedicineAndPublicHealth/1-

10.1007_s10143-006-0028-6-1a = intradural type,

b = extradural supra-optic strut type [ Optic strut = L-OCR ]c = extradural trans-optic strut type

on optic nerve, pr proximal ring, cdr carotid duralring= upper dural ring , ica internal carotid artery

I think this variation is type c

In both type a = intradural type,b = extradural supra-optic strut types Opthalmic

foramen is in Optic canal

In Type c = extradural trans-optic strut type , the Opthalmicforamen in Optic strut

http://www.nature.com/eye/journal/v20/n10/fig_tab/6702377f3.html#figure-title

The upper diagram is Type a or b Opthalmic artery , the lower diagram is Type c Opthalmic artery

Dup OC = Duplicate Opthalmiccanal

Origin and intracranial and intracanalicular course of the ophthalmic artery and its subdivisions, as seen on opening the optic canal (reproduced from Hayreh67).

Both from one specimen. (a) The extraduralorigin of the right ophthalmic artery, so that no ophthalmic artery is seen even on opening theoptic canal; a thinning of the dural sheath is seen at 'X', indicating the position of the artery. (b) The ophthalmic artery is seen after removing the duralsheath covering it (reproduced from Hayrehand Dass2).

Schematic drawing origin (a medial, b central, c lateral) and exit(d lateral, emedial) of superior wall of the ophthalmic artery

A diagrammatic representation of variations in origin and intraorbital course of ophthalmic artery. (a) Normal pattern. (b–e) The ophthalmic artery arises from the internal carotid artery as usual,

but the major contribution comes from the middle meningeal artery. (f and g) The only source of blood supply to the ophthalmic artery is the middle meningeal artery, as the connection with the internal carotid artery is either absent (f) or obliterated (g) (reproduced from Hayreh and Dass3).

Note central retinal artery - book name “ The Orbit and Sellar Region

Microsurgical Anatomy and Operative Approaches “ – author Rhoton

Origin, course, and branches of the ophthalmic artery in two adult specimens. Segment Y disappeared in (a) and segment Z disappeared in (b), resulting in the ophthalmic artery crossing under the optic nerve in both. In (b) an anastomosis is seen in lateral wall of the cavernous sinus between the part of the internal carotid artery lying in proximal part of the cavernous sinus and a branch from the ophthalmic artery passing through the superior orbital fissure (reproduced from

Hayreh67).

Various relations of OA [ Opthalmic artery ] to ON

left figure when it crosses under the optic nerve (in 17.4%) and right figure when it crosses over the optic nerve (in 82.6%).

http://streaming.osu.edu/player/?f=Medicine/Orbit_for_Distribution_OT

TO.mp4

Endoscopic Endonasal Orbital Approach

http://streaming.osu.edu/player/?f=Medicine/Orbit_for_Distribution_OTTO.mp4

below photo from above video - A = anterior ethmoidal artery M= middle ethmoidal artery especially on right side P = Posterior

ethmoidal artery

endoscopic endonasal cadavericORBITAL TRANSPOSITION

Sree Ram Murthy Dr : Dear surgeons it is a endoscopic endonasalcadaveric ORBITAL TRANSPOSITION technique

The steps follows

1 complete exposure of anterior skull base2 identification of septal branch of a e a and 1st olfactory fibre3 removal of lamina papyracea4 identification of aea and pea5 cutting of both arteries and release the globe6 gentle lateralization globe along with periorbita up to mid pupillary point7 complete exposure of medial orbital roof and further according to pathology

Murali Chand Nallamothu: What are indications of orbital transposition.

Sree Ram Murthy Dr Vizak ENT: Now a days it is important part the indications 1. removal of infections lateral to mid pupillary level 2. lateral osteomas of frontal sinuses 3. trans orbital approaches to middle cranial tumours4. exposure of cavernous sinus trans orbitally

I think 1 & 2 indications can be done by external approaches by brow or bicoronal incisions

1 septal branch of a e a

2 orbital roof4 posterior ethmoidal groove

3 first olfactory fibre

Cavernous haemangioma of orbit

rbital cavernous haemangioma via transconjectival +Lat canthotomyincision ( Ant Orbitotomy) yesterday. Transconjectival is a nice approach

to infra orbatal rim or to inferior orbit! – Dr.P.K.Banerjee [ +919407983485 ]

Cavernoma orbit

Intraconal endoscopic anatomy

Two papers – click

Transnasal Approach to the Medial IntraconalSpace: Anatomic Study and Clinical Considerations – click - http://sci-hub.cc/10.1055/s-0030-1263106

Compartmental endoscopic surgical anatomy of the medial intraconal orbital space

http://onlinelibrary.wiley.com.sci-hub.cc/doi/10.1002/alr.21320/abstract

To get any paper of any journal free click www.sci-hub.bz or www.sci-hub.cc

How to get FREE journal papers in www.sci-hub.bz or www.sci-hub.cc

1. When same paper published in different journals , the same paper has different DOIs -- so we have to try with different DOIs in www.sci-hub.bz orwww.sci-hub.cc if one of the DOI is not working.

2. If the paper has no DOI , copy & paste URL of that paper from the main journal website . If you can't get from one journal URL try with different journal URL when the author publishes in different journals .

3. Usually all new papers have DOIs . Old papers don't have DOIs . Then search in www.Google.com . Old papers are usually kept them free in Google by somebody . Sometimes the Old papers which are re-published will have DOIs. Then keep this DOI in www.sci-hub.bz or www.sci-hub.cc

4. Add " .pdf " to title of the paper & search in www.Google.com if not found in www.sci-hub.bz or www.sci-hub.cc

For Other powerpoint presentatioinsof

“ Skull base 360° ”I will update continuosly with date tag at the end as I am

getting more & more information

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www.skullbase360.in- you have to login to slideshare.net with Facebook

account for downloading.