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 » Objectives
 » Procedure
 » Discussion
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Table of Contents    
VIDEO SECTION-OPERATIVE NUANCES: STEP BY STEP
Year : 2021  |  Volume : 69  |  Issue : 4  |  Page : 829-832

Treading Toward Anterolateral Skull Base by Unlocking the Frontotemporal Dural Fold Along with Extradural Clinoidectomy: Translation from A Cadaver to Clinical Scenario


1 Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
2 Department of Neurosurgery, AIIMS, New Delhi, India

Date of Submission17-Mar-2021
Date of Acceptance30-Jul-2021
Date of Web Publication2-Sep-2021

Correspondence Address:
Dr. Arun K Srivastava
Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.325332

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 » Abstract 


Background and Introduction: Unlocking of the frontotemporal dural fold (FTDF) and extradural removal of the anterior clinoid process (EACP) are challenging but mandatory skills for micro-neurosurgeons. Despite the presence of an extensive body of literature on this subject, the translation of this cadaveric and 3D simulation to a real patient turns out to be a very demanding and difficult task.
Objective: This video is aimed to address the surgical nuances and major adjustments necessary in the unlocking of the FTDF and extradural ACP removal in an actual case for an early-career neurosurgeon.
Surgical Technique: A 40-year lady presented with features of acromegaly with radiological evidence of significant component of the tumor in the right cavernous sinus along with sellar suprasellar component. To achieve a good hormonal control, a complete tumor excision was required, which was achieved with FTDF and EACP removal. The cavernous sinus was approached through the Parkinson's triangle.
Results: The patient had uneventful recovery and good hormonal control at the 3-month follow-up.
Conclusion: FTDF unlocking and EACP are elegant procedures and need to be learned by all neurosurgeons. This article will provide excellent teaching material for young neurosurgeons.


Keywords: Cadaveric, extradural clinoidectomy, FTDF, skull base, unlocking
Key Message: The Fronto-temporal dural fold (FTDF) cutting, separation of the Dural duplication and the Extra dural anterior clenoid process (EACP) drilling is mandatory for treading in the area of the Anterolateral skull base.


How to cite this article:
Srivastava AK, Mishra S, Kumar A, Nangarwal B, Das KK, Bhaisora KS, Verma P, Jaiswal AK, Behari S. Treading Toward Anterolateral Skull Base by Unlocking the Frontotemporal Dural Fold Along with Extradural Clinoidectomy: Translation from A Cadaver to Clinical Scenario. Neurol India 2021;69:829-32

How to cite this URL:
Srivastava AK, Mishra S, Kumar A, Nangarwal B, Das KK, Bhaisora KS, Verma P, Jaiswal AK, Behari S. Treading Toward Anterolateral Skull Base by Unlocking the Frontotemporal Dural Fold Along with Extradural Clinoidectomy: Translation from A Cadaver to Clinical Scenario. Neurol India [serial online] 2021 [cited 2021 Oct 18];69:829-32. Available from: https://www.neurologyindia.com/text.asp?2021/69/4/829/325332




The FTDF is a two-layered meningeal (dura mater) band; its outer layer is formed by the extension of the temporal dura (TD), and the inner layer is the extension of the superior surface dura of the ACP covered by the basal frontal dura mater.[1] The unlocking of FTDF is like unleashing the door chain, and extradural anterior clinoidectomy (EADC) is akin to twisting the doorknob to open the obscure areas of the anterolateral skull base. The history of anterior clinoidectomy has traveled from Drake to Dolenc—while the former introduced intradural clinoidectomy, Dolenc is credited with extradural clinoidectomy.[2],[3],[4]


 » Objectives Top


Transition from cadaveric dissection to a real patient scenario is technically difficult and demanding as far as FTDF and EADC removal is concerned. In our experience, the biggest challenges are bleeding, brain bulge, and distorted anatomy in the presence of pathology. In this video, we highlight the key steps to overcome these challenges.


 » Procedure Top


The patient was in supine position, with malar prominence at the top, with the head extended about 15 degrees with an axial head rotation by 30 degrees contralaterally [Figure 1]. The skin incision and the skin flap were raised along with the galeal layer as described by Prof. Yasargil [Figure 1].[5] The temporalis muscle was detached by the Oikawa technique [Figure 2].[6] A free bone flap gave unhindered lateral access. We used the technique of deepening or reshaping the orbito-zygomatic groove, allowing us to avoid an orbito-zygotomy.[7]
Figure 1: Supine with malar prominence being the highest point. The incision line should be planned in such a way that McCarty's point should fall within one cm of the line joining the two ends of the incision

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Figure 2: Oikawa Technique: The temporalis muscle is easily separated with the help of a sharp periosteum at its inferior part shown by the No-3 sharp Penfield elevator. Further, temporalis separation is done from the inferior to superior direction. Utmost care is taken not to use monopolar cautery. The real patient (a) image is compared with a cadaveric (b) image

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The foramen of spinosum was identified and widened to delineate the MMA. It was coagulated and cut. Then, foramen ovale was widened and V3 mobilized. Next, the exposure and division of the orbito meningeal artery (OMA) were done. The orbital roof was drilled anteromedially and anterolaterally to the entrance of the OMA [Figure 3]a. The OMA was sharply divided [Figure 3]b, followed by the removal of this inferior part of the foramen to deroof the h-SOF harboring the FTDF [Figure 4]. Unlocking of the FTDF was done by cutting it with the surgical knife. The EACP removal was achieved by the bony and the dural/ligamentous detachment [Figure 5], [Figure 6], [Figure 7].
Figure 3: (a) Blue arrow showing the OMA in its foramen. (b) The OMA is coagulated and sharply cut in its foramen. The drilling of the lower part of the bony foramen will open the h-SOF. PO: Peri-Orbital; TD: Temporal Duramater

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Figure 4: (a) After the division of the OMA (blue arrow), the h-SOF is exposed harboring the FTDF (black arrow). The FTDF lies over the lateral free edge of the ACP (green arrow) while the triangular bone overhang at the v-SOF. (b) The black line depicts the FTDF and it is cut in the direction of the black line and the further sharp division of the dural duplication of the cavernous dura and temporal dura (TD) is done in the direction of the dural groove shown by the orange line

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Figure 5: Cadaveric skull showing the relation and attachment of the ACP. 1-Base with the lesser wing of sphenoid (black arrow); 2-Anterior root forming the roof of the optic canal (orange arrow); 3-Posterior root is formed by the optic strut (OS, green arrow). The sequence of the clinoidectomy is detachment in the sequence 1-2-3. # h-SOF: horizontal segment of the superior orbital fissure. # v-SOF: vertical segment of the superior orbital fissure

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Figure 6: The second boney connection (the anterior root, AR) of the ACP forming the roof of the optic canal to be drilled

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Figure 7: The base and anterior root of the ACP has already been drilled and now the ACP is having only one remaining bony attachment, the optic strut (OS) shown by the blue arrow. The drilling of the OS should be done from the optic nerve side while protecting the internal carotid artery (ICA)

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Video link: https://youtu.be/WPoeL7nJA2E

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Video timeline with audio transcript

0.00–0.28 min: I'm going to share a technique of frontotemporal dural fold unlocking and extradural clinoidectomy in a case of giant growth hormone-secreting pituitary adenoma with an extensive component in the right cavernous sinus. The positioning is supine, malar up, suture line planned in such a way that McCarty's point is within 1 cm of the suture line. 0.28–1.15 min: Classical Zygotomy was avoided and Zygoma lowering was performed. Oikawa technique to separate temporalis muscle from bone. Flushing of the skull base is required to avoid undue traction over the brain and dura mater. As we are planning to have exposure from the second cranial nerve right up to the V3 cranial nerve, we have started our procedure with the dilation of the foramen spinosum to control the middle meningeal artery inside the foramina. 01:34–2.16 min: The artery has to be coagulated and sharply cut inside the foramina. Now, our next aim is to drill the bone over the foramen ovale and deroofing of foramen ovale to have V3. We can mobilize this V3 laterally to have a good view of the lateral wall of the cavernous sinus. 2.16–03:11 min: Foramen ovale has been deroofed. Now, the V3 can be mobilized. We have to identify this orbito meningeal artery entering into the orbit. The orbital apex which is formed by the Lesser and greater wing of sphenoid is to be drilled papery thin around the entrance of orbito-meningeal artery (OMA). The very idea is to see and follow the orbito meningeal artery going into the orbit. 03:11–04:11 min: In some cases, this orbito meningeal artery directly passes through the horizontal segment of the superior orbital fissure. But in this case, it is passing through a foramen. So, that is how it is seen. Now, we are drilling medial and lateral to the orbito meningeal artery. Coagulation and sharp division of the orbito-meningeal is done to avoid retraction of the uncoagulated artery inside the globe and later leading to the hematoma formation in the globe. This can lead to a hematoma. Now we understand that if we take out the bone, forming the floor of the foramen to the OMA, will open the horizontal segment of the superior orbital fissure. The black arrow is showing the frontotemporal dural fold. This is the triangle bone overhanging over the vertical segment of the superior orbital fissure. 04:11–05:20 min: The removal of this triangular bone will show us the dural groove. So, blue is cavernous sinus dura, white is temporary dura, and the line between them is the dural groove. Some unnamed venous channels must be coagulated and cut with low current bipolar. Now we are going to cut the frontotemporal dural fold keeping the knife perpendicular based on the lateral surface of the free edge of the anterior clinoid process. This minor bleeding can be easily controlled with coagulation. The exploitation of the right plane is very important. So, this is the initial opening of the dural duplication. 05:20–06:33 min: A right technique will be rewarded with a beautiful separation of the dural duplication. Now we are going to disconnect the second bony connection of the anterior clinoid process that is the anterior root forming the roof of the optic canal. The optic nerve is secured with a dissector and the anterior root is drilled to open the optic canal. Now the third bony connection is the optic strut shown by the blue arrow. Now we are drilling the optic strut securing the internal carotid artery laterally with the help of a dissector and medially we have to take care of the optic nerve. Now, the clinoid is free from all its three bony connections, and just having one ligamentous attachment with the falciform ligament. Sharp dissection is required to make it free from all the ligamentous attachments. 06:33–06:51 min: Now the further separation of the dural duplication requires a lax brain and that we are going to achieve with the opening of the Sylvian fissure. 06:51–8.00 min: CSF is coming under pressure, but the goal will be achieved if we are able to open the Sylvian fissure cistern in high magnification. I think in this case, we are supposed to go intradural to remove the seller and supra seller parts. This can be converted into a dural flat. Now the sharp dissection to exploit this dural duplication. Now, we are aiming to peel the temporal dura up to the V3 segment. So, a bit lax brain and with the pathology inside the cavernous sinus, this can be easily achieved. 8.00–9:15 min: Second cranial nerve, the further retraction of the temporal dura can be done with the help of tucking it with the multiple sutures and retracting it back. Separation of the dural duplication just at the medial edge of the V3 nerve. Now, CSF is coming from Meckel's cave. Now we can expose the second cranial nerve up to V3. Here in this picture, we are showing up to V1. After the micro neurosurgical technique, we were able to take out the tumor gross total. And this is showing the preserve ocular movement. Thank you.

Outcome

The postoperative period was uneventful. Complete tumor excision was achieved with improvement in hormonal control. All the ocular movements were preserved.

Pearl and pitfalls

  1. The brain bulge in the background of a real pathology is to be addressed adequately. The method adopted by us is as follows:


    1. Opening of the Sylvian fissure/cistern
    2. Tapping the ventricle through any one of the various described entry points
    3. Opening and releasing the CSF from the Meckel's cave
    4. Cutting of the inferior part of the dura on the medial stem of the Sylvian fissure for early control and drainage of CSF from the carotioco-optic cistern


  2. Bleeding from the cut edge of the FTDF can be coagulated and then cut with the help of scissors.
  3. Bleeding from the lateral wall of the cavernous sinus: shredded gel foam can be filled in the cavernous sinus rent. The second option is the glue or flowable hemostatic material.
  4. Cleavage plane/Dural groove: Dividing the FTDF along the edges of the SOF reveals a cleavage plane between the temporal fossa dura and the lateral wall of the cavernous sinus [Figure 4]. The peeling of meningeal layers through this cleavage plane opens the v-SOF. The 4th nerve is identified first as the 3rd nerve remains hidden below the anterior root of the ACP. This cleavage plane is further demarcated by the color difference during the actual surgery, not appreciated in the cadaveric model [Figure 4].



 » Discussion Top


The management of paraclinoid aneurysms requires complete drilling of the OS. It requires a sharp division of the PDR to have a proximal vascular control in the clinoidal segment of the ICA [Figure 8]. The CS lesions like cavernous hemangioma are approached purely from the extradural approach. This requires the 3rd nerve to be preserved carefully at the anteromedial part of the CS. The pituitary adenoma with suprasellar and parasellar (CS) extension is very well managed by this approach. The FTDF cutting and ACP removal unlocks the brain in all three planes, beautifully described by Iype Cherian et al. in a cadaveric model.[8]
Figure 8: Left-sided craniotomy with left carotid triangle cadaveric (a) is compared with the real (b) patient. A good operative technique will lead to a bloodless field

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 » Conclusion Top


The present video focuses on the basic techniques and tricks to unlock the FTDF and applied anatomy of boney attachment of the ACP.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

1.
Yoon BH, Kim HK, Park MS, Kim SM, Chung SY, Lanzino G. Meningeal layers around anterior clinoid process as a delicate area in extradural anterior clinoidectomy: Anatomical and clinical study. J Korean Neurosurg Soc 2012;52:391-5.  Back to cited text no. 1
    
2.
Drake C, Vanderlinden R, Amacher A. Carotid-ophthalmic aneurysms. J Neurosurg 1968;29:24-31.  Back to cited text no. 2
    
3.
Dolenc V. Direct microsurgical repair of intracavernous vascular lesions. J Neurosurg 1983;58:824-31.  Back to cited text no. 3
    
4.
Dolenc V, Pregelj R, Kocijančč I. Evolution from the classical pterional to the contemporary approach to the central skull base. In: Cavernous Sinus. Springer; 2009. p. 61-74.  Back to cited text no. 4
    
5.
Yaşargil MG, Reichman MV, Kubik S. Preservation of the frontotemporal branch of the facial nerve using the interfascial temporalis flap for pterional craniotomy: Technical article. J Neurosurg 1987;67:463-6.  Back to cited text no. 5
    
6.
Oikawa S, Mizuno M, Muraoka S, Kobayashi S. Retrograde dissection of the temporalis muscle preventing muscle atrophy for pterional craniotomy. J Neurosurg 1996;84:297-9.  Back to cited text no. 6
    
7.
Mishra S, Srivastava A, Kumar H, Sharma B. Reshaping the zygomatic complex: A “small step” in frontotemporal craniotomy and a “big leap” in exposure. Neurol India 2015;63:723-6.  Back to cited text no. 7
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8.
Cherian I, Burhan H. “Unlocking the brain”-key concepts to accessing the anterolateral skull base made simple. Indones J Neurosurg 2020;3. doi: 1015562ijnv3i3103.  Back to cited text no. 8
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]



 

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