Accepted Manuscript
“The Extended Lateral Supraorbital Approach and Extradural Anterior Clinoidectomy
through a Fronto-pterio-orbital Window: Technical Note and Pilot Surgical Series”
Hugo Andrade-Barazarte, M.D, Ph.D, Max Jägersberg, M.D, Sirajeddin Belkhair,
M.D, Rachel Tymianski, M.B, Mazda K. Turel, M.D, Karl Schaller, M.D, Juha A.
Hernesniemi, M.D., Ph.D, Michael Tymianski, M.D, Ph.D, Ivan Radovanovic, M.D.,
Ph.D
PII:

S1878-8750(16)31402-4

DOI:

10.1016/j.wneu.2016.12.087

Reference:

WNEU 5048

To appear in:

World Neurosurgery

Received Date: 25 September 2016
Revised Date:

19 December 2016

Accepted Date: 20 December 2016

Please cite this article as: Andrade-Barazarte H, Jägersberg M, Belkhair S, Tymianski R, Turel MK,
Schaller K, Hernesniemi JA, Tymianski M, Radovanovic I, “The Extended Lateral Supraorbital Approach
and Extradural Anterior Clinoidectomy through a Fronto-pterio-orbital Window: Technical Note and Pilot
Surgical Series”, World Neurosurgery (2017), doi: 10.1016/j.wneu.2016.12.087.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
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ACCEPTED MANUSCRIPT

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“The Extended Lateral Supraorbital Approach and Extradural Anterior Clinoidectomy
through a Fronto-pterio-orbital Window: Technical Note and Pilot Surgical Series”.
1,3
2
Hugo Andrade-Barazarte
M.D., Ph.D., Max Jägersberg M.D., Sirajeddin
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Belkhair M.D., Rachel Tymianski M.B., Mazda K, Turel M.D., Karl Schaller
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M.D., Juha A. Hernesniemi M.D., Ph.D., Michael Tymianski M.D., Ph.D., Ivan
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Radovanovic M.D., Ph.D.

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Division of Neurosurgery, Toronto Western Hospital, University Health
Network and Department of Surgery, University of Toronto, ON, Canada.

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Division of Neurosurgery, Geneva University Hospitals and University of
Geneva, Geneva, Switzerland
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Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland

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Disclosure:

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The authors have no personal, financial, or institutional interest in the published
materials.

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M.D. (corresponding author)

Division of Neurosurgery, Toronto Western Hospital, University Health
Network and Department of Surgery, University of Toronto, ON, Canada.
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Hugo Andrade-Barazarte

Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland

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Phone:

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Email:

+16475156604

hugoandrade2@yahoo.es

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ACCEPTED MANUSCRIPT
Title: The Extended Lateral Supraorbital Approach and Extradural Anterior

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Clinoidectomy through a Fronto-pterio-orbital Window: Technical Note and Pilot

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Surgical Series

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Background: Lateral approaches to treat anterior cranial fossa lesions have evolved since the

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first frontotemporal approach described by Dandy in 1918

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Objective: To describe a less invasive approach to perform an extradural anterior

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clinoidectomy (EAC) through a lateral supraorbital approach (LSO) for anterior circulation

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aneurysms and antero-lateral skull base lesions

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Methods: The extended LSO involves performing a standard lateral supraorbital craniotomy,

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followed by drilling of the sphenoid wing and the lateral wall of the orbit through the frontal

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bony opening of the LSO without any temporal extension of the craniotomy. This creates a

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fronto-pterio-orbital window exposing the periorbita, the superior, medial and anterior aspect

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of the temporal dura as well as the superior orbital fissure (SOF). After unroofing the SOF,

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the meningo-orbital fold is cut and the temporal dura is peeled from the lateral wall of the

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cavernous sinus to expose the anterior clinoid process allowing a standard opening of the

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optic canal and anterior clinoidectomy.

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Results: The extended LSO and EAC allowed access to: 4 sphenoid wing/anterior clinoidal

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meningiomas, 5 anterior circulation aneurysms, 2 temporomesial lesions, and 1

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orbital/cavernous sinus abscess. Postoperatively, 2 patients had a transient hemiparesis, 2

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patients had a transient third nerve palsy, 1 patient had minimal visual field deterioration. All

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patients had mRS ≤ 1 at 8 weeks follow-up.

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Conclusion: The extended LSO opens a new route (fronto-pterio-orbital window) to perform

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safely an EAC, and increases the surgical exposure, angles and operability of a less invasive

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keyhole craniotomy (LSO) to treat anterior cranial fossa lesions

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Keywords

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Anterior cranial fossa; Extradural anterior clinoidectomy; Intracranial aneurysm; Lateral

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supraorbital approach; Tumor.

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Running Title

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The Extended Lateral Supraorbital Approach

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Anterior choroidal artery

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ACP,

Anterior clinoid process

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CN,

Cranial nerve

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CT,

Computed tomography;

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CTA,

Computed tomographic angiography;

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DSA,

Digital substraction angiography

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EAC,

Extradural anterior clinoidectomy

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IAC,

Intradural anterior clinoidectomy

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IAs,

Intracranial aneurysms;

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ICA,

Internal carotid artery;

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ICAbif,

Internal carotid artery bifurcation

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ICG,

Indocyanine green videoangiography

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LSO,

Lateral supraorbital approach

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MCA,

Middle cerebral artery;

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MOF,

Meningo-orbital fold;

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MRI,

Magnetic resonance imaging;

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mRS,

Modified Rankin Scale;

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SAH,

Subarachnoid hemorrhage;

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SOF,

Superior orbital fissure

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ACCEPTED MANUSCRIPT
INTRODUCTION

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The lateral supraorbital approach (LSO) emerged as a less invasive and faster modification of

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the pterional approach to provide access to a variety of vascular or tumoral lesions of the

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anterior skull base.1-4 An expansion of this approach includes performing an intradural

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anterior clinoidectomy (IAC) mainly for paraophtalmic aneurysms and anterior clinoidal

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meningiomas3. However, wide extradural access to the orbit and the cavernous sinus remains

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restricted and this approach limits an intradural pretemporal route to the temporomesial

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structures and access to the posterior fossa lateral to the clinoid and supraclinoid carotid

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artery. The extradural anterior clinoidectomy (EAC) described and later refined by Dolenc5, 6

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is a well-established technique to enhance surgical access to the skull base, and to control

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critical neurovascular structures such as the optic nerve, clinoidal internal carotid artery (ICA)

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and the contents of the cavernous sinus5, 7-13. It follows standardized steps and requires

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performing a pterional or an orbitozygomatic craniotomy.5, 14, 15 In this study, we present a

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modification and extension of the standard LSO including a full removal of the sphenoid

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wing, opening of lateral wall of the orbit and an EAC. This opens a fronto-pterio-orbital

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window without any temporal extension of the craniotomy to improve the access to internal

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carotid artery aneurysms and anterior skull base lesions, including those in the cavernous

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sinus and in the temporomesial region.

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METHODS

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Study cohort

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From January 2012 to April 2016, we retrospectively identified 12 patients who underwent an

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extended LSO and EAC by the senior author (IR) for the treatment of anterior circulation

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aneurysms and neoplastic or infectious lesions of the anterior skull base. The study population

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comprised of 12 patients (9 women and 3 men) with a median age at diagnosis of 56 years

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(range 21-77 years). We categorized preoperative and postoperative neurological status at

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discharge and at 8-week follow-up according to the modified Rankin scale (mRS), immediate

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morbidity, and surgical complications. Table 1 summarizes patients’ characteristics.

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Surgical Technique: Extended LSO and Extradural anterior clinoidectomy

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After performing a standard LSO craniotomy (Figure 1A).2 Under the operating microscope,

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the dura is detached from the orbital roof and the sphenoid wing. (Figure 1B) Then, the

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orbital roof and the sphenoid wing are thinned off using a 5 mm diamond drill, exposing the

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superior, medial and anterior temporal dura, the superior orbital fissure (SOF) and the

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meningo-orbital fold (Figure 1C). All the bone drilling is performed through the frontal bony

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opening of the regular LSO, without any temporal extension of the craniotomy. This

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additional bony resection increase the extradural exposure and develops a flat trajectory from

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the subfrontal region towards the anterior skull base, the orbit and the temporal pole. Thus

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opening a “fronto-pterio-orbital” window, exposing the periorbita, and the superior, medial

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and anterior aspect of the temporal lobe extradurally. Then, the SOF is unroofed, and the

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meningo-orbital fold is cut allowing stripping off the temporal dura from the ACP and the

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lateral wall of the cavernous sinus (Figure 1D). After this, the ACP is resected extradurally

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following a standard technique.6, 13 First the optic canal is identified extradurally, and opened

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with a 2 mm diamond drill, followed by drilling off the ACP using a 3 and 2 mm diamond

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drills, then the optic strut is detached and the remaining ACP is removed.6, 13 The dura is

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opened in a longitudinal manner along the Sylvian fissure towards the optic nerve sheath, and

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the distal dural ring (Figure 1E). An additional curvilinear cut is performed under the frontal

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lobe, and then multiple tack-up sutures are placed over the craniotomy edges, allowing a

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complete exposure of the anterior cranial fossa and the surrounding neurovascular structures

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(Figure 1F).

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Ethics

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This study has the approval of the Research Ethics Board. We conducted a retrospective

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analysis of the patients treated by the senior author (I.R.) through an extended LSO.

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RESULTS

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Table 1 shows surgical procedure, results and postoperative outcome. We performed an

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extended LSO with partial or total extradural anterior clinoidectomy according to the need of

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skull base exposure and mobilization of neurovascular structures.

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Illustrative Cases

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Case 1 (Video 1)

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A 25-year-old woman presented with sudden onset of occipital headaches. A brain CT

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showed Fisher grade 1 subarachnoid hemorrhage (SAH), distributed in the gyri of the

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convexity but no blood in the basal cisterns (Figure 2A). A CTA and a DSA revealed an 8

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mm saccular aneurysm in the transition zone of the left supraclinoid ICA, between the

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clinoidal segment and the ophthalmic segment, projecting ventrally and not involving the

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origin of the left ophthalmic artery (Figure 2B, 2C). After a multidisciplinary discussion, this

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aneurysm was not considered the source of the bleeding. However, due to the gender and age

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of the patient, and some uncertainty about the source of bleeding, we offered microsurgical

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treatment of the aneurysm after the patient recovered from the acute SAH. The patient

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underwent a left extended LSO and total EAC as described above. The left ICA, the left optic

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nerve and the anterior choroidal artery (AchA) were identified. A small infundibulum was

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visualized at the origin of the AchA. Then, the distal and proximal dural rings were opened to

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obtain proximal control of the clinoidal ICA and to expose the aneurysm dome (Figure 2D).

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This aneurysm dome had a very thin wall, but without signs of previous rupture. The

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aneurysm neck was exposed and clipped using a curved 5.2 mm clip, and a second curved

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mini clip was applied to secure a small neck remnant (Figure 2E). Indocyanine green

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videoangiography (ICG) showed patency of the parent vessel and exclusion of the aneurysm.

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At discharge, the patient had a left III cranial nerve palsy, which completely resolved at the 8-

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weeks

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(https://www.dropbox.com/s/hrpepsv3y3nwswi/Case1Video.mp4?dl=0)

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Case 2 (Video 2)

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A 21-year-old woman presented with a two months history of visual disturbances, related to a

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right homonymous hemianopia. A brain MRI showed a 4 cm intra-axial lesion with bright

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heterogeneous gadolinium enhancement in the left amygdala and hippocampus, extending in

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the temporal horn of the left lateral ventricle, the ambient and perimesencephalic cisterns, and

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compressing the midbrain (Figure 3A and 3B). MRI Flow voids revealed that the tumor

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encased the left AchA and left posterior cerebral artery (3C). The patient underwent a left

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extended LSO and partial EAC to allow mobilization of the neurovascular structures and to

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obtain a wide surgical view of the temporomesial structures through a transsylvian and

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pretemporal route (Figure 3D). An intraoperative fresh-sample biopsy reported a pilocytic

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astrocytoma grade I prompting a maximal safe resection strategy. The lesion was approached

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through the left limen insulae as described by Yasargil16 and a transylvian/pretemporal

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approach (Figure 3E), achieving a subtotal resection and successful decompression of the

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midbrain with preservation of the encase AChA and PCA (Figure 3F). Postoperatively, the

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patient suffered a right hemiparesis that progressively improved, 5 days later she was

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discharged for rehab and neuroncological assessment. At 8-week follow-up the patient was

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able

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(https://www.dropbox.com/s/qc1v7cn0it204s7/Case2video.mp4?dl=0)

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Case 3 (Video 3)

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A 33-years-old man presented with headaches, left retroocular pain, and vomiting during two

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days. CT and MRI images demonstrated a left sided (Figure 4A, 4B, 4C) medial sphenoid

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wing and anterior clinoidal meningioma measuring 4.5 cm in diameter and causing significant

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mass effect on the frontal and temporal lobes with perilesional edema. The patient underwent

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a left extended LSO, left sphenoid wing resection, extradural optic nerve decompression with

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partial EAC to reduce the risk of optic nerve manipulation and devascularize the tumor

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extradurally. The dura was opened in a curvilinear fashion, and the meningioma disconnected

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of the base (Figure 4D). We performed a near total resection of the tumor (Figure 4E) as we

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left a small residual adherent to a large middle cerebral artery (MCA) perforator encased by

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the tumor. Pathology report came back as a WHO grade 2 meningioma. The patient was

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discharged home one week after surgery and underwent radiation therapy assessment. Patient

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did not experience any postoperative complications. At 8-weeks follow-up, he was

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completely asymptomatic.

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(https://www.dropbox.com/s/s8qcsm8ogtha5bj/Case3video.mp4?dl=0)

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Complications and Outcomes

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Two (17%) patients suffered transient III cranial nerve (CN) palsy, secondary to manipulation

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of the III CN during the microsurgical clipping and dissection of the dural attachments, and 2

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(17%) patients experienced transient hemiparesis related to ischemia in the territory of the

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AChA. One patient had a minimal deterioration of a pre-existing quandranopsia. All patient

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had an mRS ≤ 1 at 8 week follow-up.

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DISCUSSION

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General considerations

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Lateral approaches to lesions of the anterior cranial fossa have evolved since the first

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macrosurgical frontotemporal approach described by Dandy17 in 1918, and achieved maturity

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with the microsurgical pterional approach described by Yasargil while maintaining the same,

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shortest, antero-lateral route to the central skull base and anterior circulation.18, 19 Key

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elements of the pterional approach, including the resection of the sphenoid wing and

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microsurgical cisternal dissection principles are in fact techniques to reduce surgical

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invasiveness to the brain. Further evolution of variants of the pterional approach, either by its

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skull base extensions (orbitozygomatic osteotomy and anterior clinoidectomy) or by its

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reduction to keyhole bony openings, follow a similar logic of reduced invasiveness to the

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brain, soft tissues or both.

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The lateral supraorbital approach is a fast, simple, targeted yet versatile variant of the

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pterional craniotomy, which allows treating a wide variety of anterior circulation and skull

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base lesions while decreasing skin and temporalis muscle trauma as well as unnecessary brain

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exposure. However, it does not allow extradural access to the central skull base and its

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intradural exposure is limited by the sphenoid ridge and the ACP, hampering comfortable

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access to the temporal opercula in the Sylvian fissure, the temporomesial structures and the

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posterior fossa lateral to the supraclinoid carotid through a pretemporal route and along the

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tentorial ridge.

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In this report, we present a technical modification of the lateral supraorbital approach and its

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combination with a skull base technique (EAC) through the opening of a fronto-pterio-orbital

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window, allowing an enhanced access to those structures not optimally exposed through a

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standard LSO. In essence, the extended LSO with EAC represent a combination of two

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previously established techniques, the LSO of Hernesniemi and the EAC of Dolenc by adding

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their respective benefits in terms of breadth of exposure and limited invasiveness.2, 6

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Surgical cases

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In our series, the extended LSO provided adequate and comfortable surgical trajectory,

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exposure and field of view similar to the standard pterional approach. A limitation of the

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previously described LSO is the anterior surgical trajectory compared to the lateral trajectory

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of the pterional approach.20 However, this limitation of the trajectory is not present while

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performing the extended LSO, due to the inside drilling of the sphenoid wing through the

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inner frontal region providing both surgical angles (lateral and anterior). Therefore, compared

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to the classical LSO, the extended LSO provides a wider range of surgical exposure, allowing

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complete exposure of the Sylvian fissure and access to lesions involving superior temporal

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gyrus, mesial temporal region, cavernous sinus, interpeduncular region and retrosellar area as

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is illustrated by our surgical cases.

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Among keyhole approaches, the minipterional craniotomy (MPT)21 is a good alternative to

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the LSO and has been used successfully for similar indications. In our practice, we have used

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the MPT approach for some MCA aneurysms where we think it has an advantage over the

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LSO such as a long M1 segment or an aneurysm pointing inferiorly and embedded in the

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temporal opercula. Nevertheless, as the craniotomy is centered on the pterion with the

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superior temporal line as a superior limit, the frontal exposure is smaller than in the LSO.

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This restricts the subfrontal route, the possibility of frontal lobe retraction (with retractors or

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dynamically with instruments) and finally the tangential angle along the fronto-lateral and

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fronto-basal surface. We therefore believe that like the LSO, the extended LSO provides a

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wider frontal exposure, while also offering a pterional route and allowing an EAC by opening

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the fronto-pterio-orbital window.

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Skull base drilling and tailored EAC

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Careful preoperative planning with 3D reconstructions images (CTA, MRI) and bony

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landmarks are essential while planning skull base drilling and anterior clinoidectomy. The

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degree of tailored EAC (partial or complete removal) depends on the amount of surgical

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exposure and mobilization required based on preoperative CT, 3D CT, 3D CTA and MRI.

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Typically, access to a paraophthalmic aneurysm or anterior clinoid meningioma would

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require a complete EAC, whereas a sphenoid wing meningioma or temporo-mesial mass

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would require a partial or minimal EAC.

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The additional deep bone resection, removal of the orbital roof and tailored anterior

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clinoidectomy opens and enhances the deep surgical exposure in the same way that it would

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work in a traditional pterional approach. The advantages are the same as those for the LSO

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over a full pterional craniotomy2, mainly a shorter fronto-temporal skin incision or an

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eyebrow incision, minimal trauma to the temporalis muscle, less brain exposure, and an

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increased surgical operability, manoeuvrability and surgical exposure.

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III Cranial Nerve Palsy and EAC

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Son et al22 published a rate of transient III CN palsy of 27% (6 of 22 cases) in patients treated

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through a standard pterional approach and EAC. Compare to our series, 17% (2 of 12 cases)

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experienced postoperative transient III CN palsy. The main reason for this transient palsy was

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PCom aneurysm dome dissection and mobilization away from the III CN in patient number 8

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and probably an anterior clinoid process drilling and removal in patient number 11 operated

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for a paraophthalmic aneurysm. This shows slightly better results while performing a

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minimally invasive technique and a skull base surgery tool as the EAC.

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Conclusion

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The extended LSO opens a new route (fronto-pterio-orbital window) to perform safely an

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EAC and increases the surgical exposure, angles and operability of a less invasive keyhole

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craniotomy (LSO) to treat anterior cranial fossa lesions.

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Yasargil MG, Antic J, Laciga R, Jain KK, Hodosh RM, Smith RD. Microsurgical
pterional approach to aneurysms of the basilar bifurcation. Surgical neurology. Aug
1976;6(2):83-91.
Yasargil MG, Fox JL. The microsurgical approach to intracranial aneurysms.
Surgical neurology. Jan 1975;3(1):7-14.
Salma A, Alkandari A, Sammet S, Ammirati M. Lateral supraorbital approach vs
pterional approach: an anatomic qualitative and quantitative evaluation.
Neurosurgery. Jun 2011;68(2 Suppl Operative):364-372; discussion 371-362.
Figueiredo EG, Deshmukh P, Nakaji P, et al. The minipterional craniotomy: technical
description and anatomic assessment. Neurosurgery. Nov 2007;61(5 Suppl 2):256264; discussion 264-255.
Son HE, Park MS, Kim SM, Jung SS, Park KS, Chung SY. The avoidance of
microsurgical complications in the extradural anterior clinoidectomy to paraclinoid
aneurysms. Journal of Korean Neurosurgical Society. Sep 2010;48(3):199-206.

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FIGURE LEGENDS

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Figure 1

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Intraoperative pictures and schematic drawings demonstrating the extended lateral

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supraorbital approach (LSO) and extradural clinoidectomy A) Planned craniotomy for a left

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classical LSO, B) Craniotomy of a left LSO, C and C’) Detachment of the left frontal dura

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from the lateral orbital wall, D and D’) Left Fronto-pterio-orbital window, demonstrating

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periorbita, meningo-orbital band and unroofting of the superior orbital fissure, E and E’)

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Surgical and schematic views after performing a complete extradural clinoidectomy, F and

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F’) Surgical and schematic views after dural opening and ipsilateral optic nerve exposure

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Figure 2

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A) 3-Dimensional digital subtraction angiography demonstrating an 8 mm left side clinoidal –

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ophthalmic segment aneurysm, B) 3-Dimensional computed tomographic angiography

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demonstrating an 8 mm left side clinoidal – ophthalmic segment aneurysm and relationship

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with left anterior clinoid process, C) Intraoperative picture after performing an extended

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lateral supraorbital approach, extradural clinoidectomy and opening of the distal dural ring,

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D) Clipping of the aneurysm, E) Postoperative 3-dimensional computed tomographic

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angiography demonstrating complete clipping of the aneurysm and patency of the parent

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vessel

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Figure 3

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Magnetic resonance with gadolinium (A, axial T2, B, sagittal, C, coronal) demonstrating an

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intra-axial lesion with bright heterogeneous enhancement compromising the left amygdala,

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hippocampus, extending into the temporal horn of the left lateral ventricle, the ambient and

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perimesencephalic cisterns, and compressing the midbrain, Intraoperative pictures (D, initial

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surgical exposure, E, opening of the left limen insulae), F) Postoperative magnetic resonance

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with gadolinium

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Figure 4

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Magnetic resonance with gadolinium (A, sagittal, B, axial, C, coronal) demonstrating a left

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side medial sphenoid wing and anterior clinoidal meningioma measuring 4.5 cm in diameter

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and causing significant mass effect on the frontal and temporal lobes with perilesional edema.

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Intraoperative picture (D, subfrontal exposure of the tumor), E) Postoperative magnetic

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resonance with gadolinium

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Anterior clinoid meningioma

2

Right Orbital/optic/cavernous
sinus abscess

Female

Case 4

77

Female

Diplopia, right side
decreased visual acuity

Case 7

Case 8

68

60

67

Female

Headache and
somnolence

Female

Left side visual field
defect

Female

Regrowth of previously
coiled aneurysm AcoA
aneurysm

1

Left sphenoid wing/anterior
clinoid meningioma

0

79

Case 6

1

Seizure

Case 3

23

Left Anterior clinoid/optic
canal meningioma

Male

Asymptomatic (MRI for
research purpose) slight
inferior visual field
defect right eye

Case 5

Approach

1

1

Vision improved

Simpson 4

3

1

Vision deteriorated

Complete

No

Abscess
drainage

1

1

Improved vision

1

1

Vision unchanged

No

1

Complete

No

Clipping

1

0

Normal vision

0

Previously coiled AcoA
Aneurysm and left Superior
hypohiseal aneurysm

Left Extended
LSO

Complete

No

Clipping

0

0

Normal vision

Complete

Transient right
hemiparesis, Left
III CN palsy

Clipping

3

1

Vision unchanged

0

0

Vision unchanged

1

1

Case 10

21

Female

Visual disturbances/
Left hemianopia

1
0

Incidental finding

Simpson 2

Partial

Conjunctivitis
Transient
postoperative
cognitive
impairment,
inferior field
defect right eye

Partial

2

Female

1

Left Extended
LSO

Male

52

1

Left Unruptured Carotidophthalmic aneurysm

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Case 12

Simpson 4

Complete (no
post op CT)

Left Extended
LSO

Case 9

Female

No

Complete

Left Extended
LSO

Left Mesiotemporal ruptured
cavernoma

Headaches, Nausea,
Vomiting

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Visual acuity

3

Diplopia, Left eye
ptosis

Case 11

mRs at 8weeks followup

Hematoma
evacuation
and resection

Female

Incidental finding/ Not
related SAH

Treatment

mRs at
discharge

Vision improved
(reported, no pre-op
exam available)

Left Extended
LSO

Right
Extended
LSO
Right
Extended
LSO

Complications

SC

Female

Conjunctival injection,
left side decreased
vision

Diagnosis

Extradural
Anterior
Clinoidectomy

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Presenting symptom

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Gender

Left PcoA Aneurysm and Left
AChoA

Left Extended
LSO

Left Sphenoid wing/anterior
clinoid meningioma
Left temporomesial intraaxial tumor (Pylocit
astrocytoma)

Left Extended
LSO

Partial

No

Simpson
grade 4

Left Extended
LSO

Partial

Transient right
hemiparesis

Subtotal
resection

3

1

vision unchanged

Left Ophthlamic segment Carotid Cave A

Left Extended
LSO
Left Extended
LSO

Complete

Transient Left III
CN palsy

Clipping

2

0

Normal vision

Partial

No

Clipping

1

0

Normal vision

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Case 1

Age

Preoperative
mRS

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Case
Number

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Left PcoA Aneurysm

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Surgical approaches are under constant evolution

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Minimally invasive microsurgical approaches and skull base techniques
increase surgical maneuverability and exposure

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Extradural anterior clinoidectomy is feasible through keyhole approaches

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The extended LSO opens a new route (fronto-pterio-orbital window) to
perform safely an EAC

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