L-OCR & M-OCR 360°11-8-20168.15 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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L-OCR & M-OCR 1. baby eyes are L-OCR

2. baby eyebrows are optic nerves3. baby mouth is sellar ( Pituitary )

4. baby cheaks are parasellar carotid

Outside the sphenoid owl eyes as sphenoid osteumwhereas inside sphenoid baby eyes as L-OCRs

1. Sphenoid sinus2. Sphenoethmoidal cell or onodi cell

Spneoethoidal cell superior lat to sphenoid

L-OCR

L-OCR – Triangle 1. Upper boarder – Optic nerve & Opthalmic artery

2. Posterior boarder – Clinoidal carotid 3. Lower boarder – 3rd N. [ COM – Carotico-Occulomotor

membrane seperates 3rd N from Clinoidal carotid ] [ 6th N. & 4th N. & V1 present inferior to 3rd N. ]

L-OCR – Triangle 1. Upper boarder – Optic nerve & Opthalmic artery

2. Posterior boarder – Clinoidal carotid 3. Lower boarder – 3rd N. [ COM – Carotico-Occulomotor

membrane seperates 3rd N from Clinoidal carotid ] [ 6th N. & 4th N. & V1 present inferior to 3rd N. ]

In civil engineering , term of strut mean object carry the load in inclined way & column means load carrying in vertical way ....so optic strut carry the weight of ACP

in inclined position ,

....from this point in clinoidectomy to remove the ACP you must destabilize it by drilling the strut before elevation of cone bone " shark tooth “ the strut obliquely

separate the optic foramen from occulomotor foramen

Strut Column

1. SOF present between two structs [ OS – optic strut & MS – maxillary strut ] 2. OS [ optic struct separates optic canal from SOF ]

....from this point in clinoidectomy to remove the ACP you must destabilize it by drilling the strut before elevation of cone bone " shark tooth “ the strut

obliquely separate the optic foramen from occulomotor foramen

Red ring – Pneumatization in Optic strut – which is nothing but L-OCR

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

The optic strut has two neural-facing surfaces( yellow dotted lines) and one vascular-facing surface (red dotted line).

[ COM – Carotico-Occulomotormembrane seperates 3rd N from Clinoidal carotid ]

If we look from laterally ACP is going posteriorly from OS whereas LWS going anteriorly

ACP anterior clinoid process, ALSC anterior lateral sellarcompartment, FR foramen rotundum, GWS greater wing of the sphenoid, ICAc cavernous portion of the internal carotid artery, ICT inferior common tendon, LWS lesser wing of the sphenoid, MM muscle of Muller, OA ophthalmic artery, ON optic nerve, OS optic strut, SOF superior orbital fi ssure, SS sphenoid sinus, V2 second branch of the trigeminal nerve, IIIcnoculomotor nerve, VIcn abducens nerve, black circle frontal nerve, black arrowhead nasociliary nerve

Through pterional approach

The bone of the anterior clinoid (AC) process has been left in place, positioned within the lateral opticocarotid recess.

L-ocr is the space in Optic strut - not the space in Anterior clinoid process

ICAcl clinoidal portion of the internal carotid artery , The clinoidalsegment of the internal carotid artery faces the posterior aspect of the optic

strut [L-OCR ]

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

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

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

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 .

1. Various types of Opthalmic artery2. Various types of Optic nerve

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

L-ocr is the space in Optic strut - not the space in Anterior clinoid process

Note Optic strutNote Optic strut- Right Optic nerve Anterio-superior view

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].

In type III & type IV there is pneumatisation of ACP [ anteiror clinoidprocess ] • 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 – in type III & type IV there is pneumatisation of ACP [ anteiror clinoid

process ]

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 - in type III & type IV there is pneumatisation of ACP [ anteiror clinoid process ]

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

Different variants of L-OCRs – In pituitary or any sphenoid surgery first try to identify the prominent landmark L-OCRs sothat you will not injure the parasellar carotid & you can use Doppler to identify parasellar carodtid

Different variants of L-OCRs – In pituitary or any sphenoid surgery first try to identify the prominent landmark L-OCRs sothat you will not

injure the parasellar carotid & you can use Doppler to identify parasellar carodtid

M-OCR

Sagittal sections and superior views of the sellar region showing the optic nerve and chiasm, and carotid artery. The prefixed chiasm is located above the tuberculum. The

normal chiasm is located above the diaphragma. The postfixed chiasm is situated above the dorsum.

1. M-OCR is nothing but Middle Clinoid Process [ indicated by Green Button in both photos ]

2. M-OCR is the junction point of clinoidal carotid & Supra-clinoidal carotid ( = 1st part intracranial carotid )

The optic chiasm is referred to as prefixed when it is located above the

tuberculum sellae and as a postfixed chiasm when it is situated

superior to the dorsum sellae

Parasagittal cadaveric specimen with a postfixed chiasm. Note the more inclined pituitary stalk (stalk). For reference, note the left and right optic

nerves

Parasagittal cadaveric specimen with a normally positioned opticchiasm. For reference, note the right optic nerve (II)

Subfrontal cadaveric dissection in a specimen found to have aprefixed chiasm. Note the anterior location of the pituitary stalk (arrow).

For reference, note the optic nerves (II) and left internal carotid artery(ICA)

Middle clinoid process forming clinocarotid foramen.

The mOCR is located just medial tothe paraclinoidal-supraclinoidal ICA transition and inferior to the distal cisternal segment of the ON(Labib et al. 2013 ).

Cl clivus, ICAc cavernous portion of the internal carotid artery, ON optic nerve, PG pituitary gland, PS planum sphenoidale, TS tuberculum sellae, yellow asterisks upper dural ring, blue arrowheads lower dural ring, white asterisk lateral optico-

carotid recess, white circle medial optico-carotid recess, white arrow ophthalmic artery, black arrows middle clinoidprocess, red arrows lateral tubercular crest, yellow arrows endocranial region corresponding to MCP

1. The mOCR is placed at the confluence of the sella, tuberculum sellae, carotid protuberance, optic canal and planum sphenoidale. The mOCR corresponds to the

lateral extent of the tuberculum sellae. ---- white asterisk lateral opticocarotid recess, white circle medial opticocarotid recess ---

2. The mOCR is located just medial to the paraclinoidal-supraclinoidal ICA transition and inferior to the distal cisternal segment of the ON (Labib et al. 2013 ).

Infrachiasmatic cistern is occupied by first part of intra-cranial carotid

In the lateral border of the chiasmatic cistern the first part ofthe ICAi is visible.

Note the first part of ICAi in chiasmatic cistern in bifrontalcraniotomy approach & note the optico-carotid recess on both sides .

Endoscopic anterior skull base approach

Pituitary stalk [ yellow arrow ] in Subtemporal approach ; ON = Optic nerve ; PC = Posterior clinoid ; SCA = Superior

cerebellar artery

IATROGENIC CAROTID INJURE AREAS -

1. Upper & Lower point of C-shape of parasellarcarotid - mnemonic

2. Upper point is m-OCR ( optico - carotid recess ) -junction of para seller & intra-cerebral carotid

3. Lower point is posterior genu - junction of paraclival & parasellar carotid

Two potential iatrogenic carotid injury areas

We have to very careful at m-OCR in transtubercular & transplanum drilling because praclinoidal & supraclinoidaljunction is exactly m-OCR

Posterior genu is the most common area of iatrogenic injury of carotid

1. The mOCR is placed at the confluence of the sella, tuberculum sellae, carotid protuberance, optic canal and planum sphenoidale. The mOCR corresponds to the

lateral extent of the tuberculum sellae. ---- white asterisk lateral opticocarotid recess, white circle medial opticocarotid recess ---

2. The mOCR is located just medial to the paraclinoidal-supraclinoidal ICA transition and inferior to the distal cisternal segment of the ON (Labib et al. 2013 ).

Limits of the bone resection – Inner ring in below photo- we have to be very careful while removing the m-ocr bone in Trans-tubercular approach because mOCR is

located just medial to the paraclinoidal-supraclinoidal ICA transition

• Posterior ethmoidal arteries• Medial OCRs

KISSING CAROTIDS - we have to observe in CECT scan to ruleoutwhether the two m-ocr’s come together .

1. http://radiopaedia.org/articles/kissing-carotids2. http://www.ncbi.nlm.nih.gov/pubmed/17607445

• The term kissing carotids refers to tortuous and elongated vessels which touch in the midline. They can be befound in:

• retropharynx 2

• intra-sphenoid 1

– within the pituitary fossa

– within sphenoid sinuses

– within sphenoid bones

• The significance of kissing carotids is two-fold:

– may mimic intra-sellar pathology

– catastrophic if unknown or unreported before transsphenoidal / retropharyngeal surgery

• The significance of kissing carotids is two-fold:

–may mimic intra-sellar pathology

–catastrophic if unknown or unreported before transsphenoidal / retropharyngeal surgery

M-OCR drilling

SIS & IIS

Pituitary present between “ four blues” SIS – superior intercavernous sinus &

IIS – inferior intercavernous sinus

1. Note ASIS & PSIS2. Note Subarachnoid space at antero-superior area , which is the potential

CSF leak area in pituitary surgery .

Usually the DS originates few millimeters below the TS.

PSIS – Posterior superior intercavernous sinus ASIS & PSIS together called CIRCULAR SINUS

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