Endoscopic Supraorbital Surgery: Chapter 8


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Endoscopic Skull Base Surgery
Chapter 8: The Fully Endoscopic Supraorbital Approach
By Hrayr K. Shahinian, M.D., FACS

Abstract

This chapter discusses the application of the supraorbital endoscopic keyhole approach to surgery of the anterior and middle skull base. Through a strategically placed keyhole craniotomy, the endoscopic supraorbital approach allows for thorough visualization of critical structures at the median and paramedian skull base without the need for frontal or bifrontal osteotomies, brain retraction, or potentially disfiguring skin incisions. In our experience, we found that the adaptation of rigid endoscopy to the supraorbital approach has broadened the possible surgical exposure with virtually no brain retraction. It minimizes the risk of injury to brain tissue, cranial nerves, and vascular structures and facilitates complete tumor resection due to superior visibility. Other advantages include a more cosmetic, hidden skin incision, within the hair of the eyebrow, and a faster, smoother, and more pleasant postoperative course for the patient. The chapter provides a thorough description of the fully endoscopic supraorbital approach, including indications, operating room setup, patient positioning, operative technique, illustrative cases, potential complications, and ways to avoid these complications (in the author's experience).

1. Introduction

The application of endoscopic approaches to surgery of the anterior and middle skull base, as well as the parasellar region, can eliminate the need for traditional open craniotomies without compromising surgical success. Wide surgical exposures often come at the expense of a significant degree of brain retraction and craniofacial dissection, often resulting in undesirable perioperative morbidity. Through a strategically placed keyhole craniotomy, the endoscopic supraorbital approach has allowed for thorough visualization of critical structures at the median and paramedian skull base without the need for frontal or bifrontal osteotomies, brain retraction, or potentially disfiguring skin incisions. Furthermore, the frontal branch of the facial nerve and the temporalis muscle are not involved in the surgical approach, thus avoiding their injury and allowing for a more cosmetic, hidden, skin incision, within the hair of the eyebrow, and a faster, smoother, and more pleasant postoperative course for the patient.

In our experience, we found that the adaptation of rigid endoscopy to the supraorbital approach has broadened the possible surgical exposure without the introduction of additional dissection or retraction. Endoscopes with varying angles of view have provided a panoramic perspective of the relevant surgical anatomy and allowed for thorough evaluation of the extent of intracranial disease. The maneuverability of the endoscope allows it to be positioned directly at the level of dissection, effectively reducing the viewing and operating distances. Endoscopic imaging thereby facilitates complete tumor resection due to the superior visibility via a minimally invasive technique. We believe that access to the anterior and middle skull base with virtually no brain retraction minimizes the risk of injury to brain tissue, cranial nerves, and vascular structures. The fully endoscopic supraorbital approach has provided extended access to all lesions of the skull base that traditionally have required subfrontal, bilateral subfrontal, transbasal, or pterional approaches.

2. Indications

The fully endoscopic supraorbital approach provides minimally invasive surgical access to lesions of the midline anterior skull base, such as olfactory groove or planum sphenoidale meningiomas, esthesioneuroblastomas, and transcranial extensions of orbital and paranasal sinus tumors; lesions of the middle skull base, such as medial sphenoid wing meningiomas, schwannomas, neurofibromas, and middle cranial fossa arachnoid cysts; and lesions of the parasellar region, such as anterior clinoid or suprasellar meningiomas, craniopharyngiomas, anterior communicating artery (ACoA) aneurysms, and pituitary macroadenomas with supra- and parasellar extensions.

3. Instrumentation

The instruments needed to successfully execute this procedure include an endoscopic tower containing a high-definition digital camera, a xenon or halogen light source, digital recording devices, 0- and 30-degree rigid endoscopes, two endoscope holding arms, endoscope irrigation sheaths and pumps, and precision microinstruments.

4. Operating Room Setup (Figure 1)

The patient is placed supine on the operating room table. Following the induction of general anesthesia, the airway circuit is extended with corrugated tubing and the head is rotated 180 degrees away from the anesthesiologist who stands at the foot of the table. The endoscopic tower is placed caudad to the patient's head directly facing the surgeon who stands cephalad to the patient's head. The scrub nurse stands to the side of the surgeon ipsilateral to the approach. Two separate pneumatically-powered holding arms are affixed to the table, one on each side of the patient, and wrapped in sterile drapes. One holding arm is dedicated to holding the endoscope and the other is used to hold other endoscopic instruments or soft silicone spatulas.

5. Patient Positioning (Figure 2)

The patient is placed supine on the operating room table and the head of the bed is slightly raised to improve venous drainage. Following the induction of general anesthesia, the patient's neck is extended approximately 30 degrees so that the frontal and temporal lobes relax and retract away from the orbital roof and the floor of the skull base once cerebrospinal fluid (CSF) is drained. The patient's head is maintained at 0-degree rotation. The head is fixed in place using a Mayfield three-pin clamp. This position enhances surgical access to the anterior and middle cranial fossa from an anterior subfrontal trajectory.

6. Operative Technique

Following general anesthesia, the frontal and paranasal areas are cleansed with an aqueous antiseptic solution and then draped. A standard skin incision is placed within the hair of the eyebrow a few millimeters above the orbital rim. The skin, soft tissue, and pericranium are incised down to the level of the cranium and small hooks are used to retract these layers superiorly and inferiorly (Figures 3 (A), (B), and (C)). The position of the incision will vary slightly according to each patient's individual skull shape. A small burr hole is then placed laterally and inferiorly within the frontal bone, and a 1.5 cm supraorbital craniotomy is performed with its lower end flush with the skull base (Figures 4 (A) - (D)). The dura is then incised curvilinear along the frontal pole and reflected downwards, and CSF is slowly drained (Figures 5 (A) and (B)). A combination of mild hyperventilation, positioning, and CSF drainage opens a path for the endoscope as the frontal lobe "relaxes" away from the anterior cranial base. The endoscope is introduced through the keyhole craniotomy and advanced between the frontal lobe and the floor of the anterior cranial base (Figures 6 (A) - (C)).

From this point, surgery will vary according to the type of pathology being addressed. For lesions of the middle cranial fossa the endoscope is further advanced over the orbital roof and the lesser wing of the sphenoid bone all the way to the middle cranial fossa. For lesions of the parasellar region or the mid-anterior skull base the endoscope is advanced towards the frontal midline; the olfactory and optic nerves provide useful landmarks when accessing this region.

Using a combination of custom-designed bipolar electrocoagulation, a microCUSA, microinstruments, and microdissection techniques, the tumor is gradually internally decompressed, followed by sharp resection of the capsule. Once the resection is completed, the 0-degree endoscope is withdrawn and a 30-degree endoscope is introduced and rotated along its longitudinal axis, clockwise and anticlockwise, to survey the entire region for any residual tumor out of the straight view of the 0-degree endoscope. Any tumor remnants are further resected to assure total tumor excision. In middle cranial fossa tumors, the sphenoid ridge and/or the superior orbital roof could be drilled away, to give either a better basal view or better access to the tumor.

Following tumor removal, the whole area is copiously irrigated and hemostasis is secured. The dura is then closed watertight and covered with a layer of collagen dural substitute membrane and a dural sealant to prevent any CSF leak (Figures 7 (A), (B), and (C)). The keyhole bone flap is then repositioned and secured in place using absorbable microplates and screws, and an injectable hydroxyapatite bone substitute is used to fill the bone defect around the keyhole bone flap (Figures 8 (A) and (B)). The pericranium, soft tissue, and skin incision are then sutured in layers with careful attention to the aesthetic repair. Steri-strips and a small adhesive bandage dressing are then applied to the suture line (Figures 9 (A) - (C)). If the frontal sinus has been opened during the bony work, its mucosa is stripped away and the nasofrontal duct is obliterated and the sinus is cranialized.

The majority of patients undergoing this procedure are monitored in either the intensive care unit (ICU) or a step-down unit overnight and thereafter transferred to the ward until discharged home, typically 48 hours after the operation.

7. Illustrative Cases

7.1. Anterior Cranial Fossa Tumors

7.1.1. Background (Figure 10)

Midline or paramedian anterior skull base lesions, such as olfactory groove or planum sphenoidale meningiomas, esthesioneuroblastomas, and transcranial extensions of orbital or paranasal sinus tumors, have traditionally been approached through "craniofacial" unifrontal or bifrontal craniotomies with elevation of one or both frontal lobes and significant brain retraction; the most common surgical approaches being variants of either the standard subfrontal or pterional approaches.

In our experience, despite the small size of the supraorbital keyhole craniotomy, the exploration followed by slow CSF drainage has proven to be large enough for safe intracranial microsurgical interventions, while the integrity of as much normal tissue as possible is preserved and unnecessary manipulation or brain retraction is not required. The endoscopic supraorbital approach has allowed us excellent visualization of anterior cranial fossa tumors and vascular and neural structures in this region, while avoiding the deleterious effects of frontal lobe retraction without sacrificing exposure or final outcome.

7.1.2. Approach (Figure 11)

Under general anesthesia, after positioning, prepping, draping, and skin incision, a 1.5 cm supraorbital keyhole craniotomy is performed, the dura is incised open and CSF is slowly drained. After adequate relaxation of the frontal lobe, a 0-degree endoscope is introduced and advanced along the floor of the anterior cranial fossa.

The operation then proceeds according to the exact pathology being addressed. For mid-frontal skull base lesions, including meningiomas and esthesioneuroblastomas, following the initial exposure of the tumor, a small area of the surface is electrocoagulated and a biopsy obtained for intraoperative frozen section confirmation of the pathology. Dissection then proceeds along the floor of the anterior cranial fossa, and small feeding arteries from below are electrocoagulated and divided to devascularize the tumor. The tumor is then internally decompressed using a combination of a microCUSA, bipolar electrocautery, microinstruments, and microdissection techniques. Following internal debulking, the tumor capsule is identified and a plane of dissection with the normal frontal lobes is started. The capsule is then gradually and circumferentially resected without undue pressure on the frontal lobes. In olfactory groove meningiomas (OGMs), the tumor is resected off the floor of the anterior cranial fossa and from both olfactory bulbs; the ipsilateral olfactory bulb is often circumferentially infiltrated by tumor while the contralateral one may occasionally be preserved. The last portion of the tumor to be dealt with is typically the inferior posterior portion abutting the suprasellar area and the optic nerves and chiasm. Dissection off the optic nerves, chiasm, and anterior cerebral artery (ACA) complex is carried out using sharp dissection techniques.

Once the tumor is completely resected, hemostasis is secured and the whole area is copiously irrigated. At this point, the endoscope is gradually withdrawn and a second survey of the entire region is conducted using an angled endoscope to identify and remove any tumor remnants. The dura is then reapproximated and cranioplasty is carried out followed by layered suturing of the subcutaneous tissues and skin.

7.1.3. Cases

7.1.3.1. Olfactory groove meningioma: Figures 12 (A) - (I)

7.1.3.2. Planum sphenoidale meningioma: Figures 13 (A) - (T)

7.2. Middle Cranial Fossa Tumors

7.2.1. Background

Access to tumors of the middle cranial fossa has traditionally required aggressive transcranial approaches via open craniotomies, such as the frontotemporal, pterional, and extended orbitozygomatic approaches. These wide exposures, however, often involve significant frontal and/or temporal lobe brain retraction, unnecessary surgical dissection, and potentially disfiguring skin incisions, thus resulting in undesirable perioperative morbidity.

While routinely using the endoscopic supraorbital approach to access tumors of the anterior cranial base, we found that the adaptation of rigid endoscopy to the supraorbital approach broadens the available surgical exposure, thus providing, in addition, extended access to the middle cranial fossa without the need for additional dissection or retraction. Utilizing the fully endoscopic supraorbital approach to access the middle cranial fossa and the sylvian fissure area, we have enhanced our ability to appreciate the anatomy of this area due to superior visibility and to perform a more complete resection of middle cranial base tumors, including meningiomas, archacnoid cysts, and other lesions.

7.2.2. Approach

Under general anesthesia, after positioning, prepping, draping, and an eyebrow skin incision, a 1.5 cm keyhole supraorbital craniotomy is performed, the dura is opened, and CSF is slowly drained until adequate relaxation of the frontal lobe is obtained. A 0-degree endoscope is then introduced and advanced subfrontally along the floor of the anterior cranial fossa . The endoscope is then advanced either all the way to the middle cranial fossa (for medial sphenoid wing/cavernous sinus meningiomas and other middle cranial fossa tumors) or toward the sellar region (for parasellar region tumors or tumor extensions).

For middle cranial fossa tumors, including medial sphenoid wing/cavernous sinus meningiomas or schwannomas, a small area of the tumor surface is electrocoagulated and a piece of the tumor is sent for frozen section confirmation of the diagnosis. Following that and using a combination of custom-designed bipolar electrocautery, a microCUSA, microinstruments, and microdissecting techniques, the tumor is centrally decompressed and gradually resected. Attention is then shifted to the lateral and inferior aspects of the tumor, which usually extend down to the floor of the middle cranial fossa. Therefore, the superior orbital roof and/or the sphenoid ridge are drilled off for better access to the floor of the middle cranial fossa. Once this step is completed, excellent visualization of the floor of the middle cranial fossa is achieved and the inferior-most aspect of the tumor is resected. The remaining tumor capsule is then dissected circumferentially and gradually resected off of the medial temporal and frontal lobes. The medial/inferior aspect of the tumor is usually the most hazardous to resect, as it is closely related to the ipsilateral carotid artery and cavernous sinus; therefore, it is dealt with last. Using a combination of a bipolar electrocautery and sharp dissection with angled microscissors, this final portion of the tumor is gradually shaved off the internal cerebral artery (ICA) and lateral cavernous sinus from anterior to posterior starting with the most medial anterior and inferior aspect of the tumor until the ICA is cleared.

For parasellar region tumors or tumor extensions, such as in giant pituitary macroadenomas, the tumor is first exposed and a biopsy is obtained and sent for frozen section confirmation. Following that and using a combination of custom-designed bipolar electrocautery, a microCUSA, microinstruments, and microdissection techniques, the tumor is gradually internally decompressed and resected. The parts of the tumor closest to the carotid artery, the cavernous sinuses, and the optic nerves and chiasm are dealt with last. Again using microdissection techniques and microinstruments, the medial and inferior portions of the tumor are gradually shaved off the critical neurovascular structures in this area using sharp dissection techniques. For suprasellar extensions of giant sellar lesions, a Teflon sponge may be left in the suprasellar cistern as a marker of the extent of suprasellar tumor resection if a second stage operation is being planned.

After tumor resection is achieved, the 0-degree endoscope is slowly withdrawn and a 30-degree or 70-degree endoscope is used to conduct a second survey of the entire region; any remaining tumor is further dissected and removed. Following that, hemostasis is secured and the entire region is copiously irrigated. The dura is then closed, followed by cranioplasty and layered suturing of the subcutaneous tissue and skin.

7.2.3. Cases

7.2.3.1. Medial sphenoid wing meningioma (right sided): Figures 14 (A) - (O)

7.2.3.2. Suprasellar epidermoid (left sided): Figures 15 (A) - (L)

8. Potential Complications

Potential complications of the fully endoscopic supraorbital approach include the following:

Bleeding, infection, meningitis, cerebrovascular accident, CSF leak, and death, as well as the potential risk for endocrinological morbidity, vascular complications, neuropsychological and behavioral disorders, and neurocognitive disorders (These are also potential complications associated with open approaches with more extensive dissection.)
Postoperative severe headaches, lethargy, confusion, or slow mentation can occur due to pneumocephalus.
A long postoperative course of recovery or a generally obtunded patient with no focal signs of neurological deficit is probably due to postoperative frontal lobe edema or contusion.
CSF rhinorrhea can occur via an internal fistula through an occult frontal sinus opening.
Transient or permanent anesthesia of the frontal scalp may occur due to stretching or sectioning of the supraorbital and supratrochlear nerves during the eyebrow incision.
Transient swelling and/or cellulitis of the periobital area may occur.
Transient frontalis muscle palsy due to transmitted stretch on the frontal branch of the facial nerve
Orbital complications may be due to direct injuries such as globe perforation; postoperative diplopia is usually caused by extensive dissection, cerebral edema, or extensive removal of the orbital walls; enophthalmos may result from expansion of the volume of the orbital cavity due to resection of the orbital walls; pulsatile exophthalmos may result from extensive drilling of the orbital roof.
Direct injuries to neural and/or vascular structures include direct cavernous sinus, cranial nerve, or carotid artery injuries (especially in patients with ICA encasement or displacement by the tumor or with tumor extending into the cavernous sinuses), which present with symptoms such as opthalmoplegia or cerebrovascular stroke (CVS); unilateral or bilateral loss of vision from injury to the optic nerves or their blood supply; loss of the sense of smell (anosmia), from damage to the olfactory nerves; endocrinopathies such as temporary or permanent diabetes insipidus (DI) or various degrees of hypopituitarism, resulting from direct injury to the pituitary stalk or gland, respectively.

9. Avoiding Complications in Author's Experience

To avoid these complications, the keyhole craniotomy should be far enough from the frontal sinus, the nasofrontal ducts should be obliterated, and the sinus cranialized in case of accidental opening. The medial limit of the incision should always be kept lateral to the supraorbital notch, bearing in mind that palsy of the supraorbital and supratrochlear nerves may be avoided. Pneumocephalus resulting in severe postoperative headache, as well as meningitis, CSF leak, and osteomyelitis are usually complications of inadequate separation of the cranial cavity from the sinonasal tract during cranioplasty. Postoperative frontal edema or contusion is usually the result of prolonged traction; this is not required with the supraorbital approach and should be avoided. The frontal branch of the facial nerve virtually never crosses in this area when the eyebrow skin incision is performed correctly; therefore it is not likely to be directly injured. However, overstretching of the skin is unnecessary and should be avoided as transient palsy of the frontalis muscle may occur due to transmitted stretch from the skin. As with open approaches, direct neurovascular injuries are avoided with careful use of microinstruments. Orbital complications, such as postoperative diplopia, are self limited, but they may last for a few weeks and are managed conservatively. Enophthalmos and pulsatile exophthalmos are prevented by avoiding extensive removal of the superior orbital wall (not more than one-half of the superior orbital roof should be drilled ); however, reconstructing the orbital walls with autogenous bone or titanium mesh is another option in case of extensive orbital roof drilling. Diabetes insipidus is an infrequent occurrence and is usually temporary.

In planning the operation, it is important to consider the individual characteristics of each of the anterior cranial fossa tumors. For instance, in OGMs the blood supply comes into the tumor through the bone in the midline of the anterior fossa from branches of the ethmoidal, middle meningeal, and ophthalmic arteries, and the posterior capsule of the tumor may be densely attached to the optic nerves, chiasm, and anterior cerebral arteries. There may be small feeding vessels from the ACoA complex and from the A2 segments of the ACAs; although these small feeding vessels can be sacrificed, it is critical to follow them carefully to ensure they are not perforating vessels. Preservation of these perforators, which supply the optic nerve, chiasm, and hypothalamus, is vital. If dissection of the tumor off of these perforators is difficult, or if the tumor has infiltrated the optic nerves, it is better to leave a small amount of tumor behind rather than create major deficits due to operative injury. Following complete tumor excision, the dural attachment of the tumor is totally excised and any bone hyperostosis is removed. The region of the cribriform plate is covered with a graft of pericranial tissue and Gelfoam to prevent a CSF leak.

In some cases, massive nonfunctioning pituitary macroadenomas may enlarge to completely occupy the suprasellar cistern and the third ventricle up to the level of the foramen of Monroe or even beyond. They may also extend laterally through the medial wall of the cavernous sinus, lateral to the carotid artery and into the middle cranial fossa or anteriorly onto the planum sphenoidale and anterior skull base. These are frequent causes of the inability to completely resect these tumors from an endonasal approach.Therefore, in our practice we have adopted two-stage endoscopic approaches and found them ideal for complete resection of massive pituitary macroadenomas. The two-stage surgical approach involves an endoscopic endonasal approach for resection of the intrasellar/suprasellar components of the tumor, followed by a supraorbital (or transglabellar) resection of the extrasellar/parasellar components. This can be done either simultaneously or as two separate procedures. The approach (supraorbital versus transglabellar) is tailored depending on the extension and configuration of the tumor.

Legends

Figure 1: Operating Room Setup Figure 2: Patient Positioning Figures 3 (A), (B), and (C): Draping and Skin Incision Figures 4 (A) - (D): Burrhole and Keyhole Craniotomy Lower Case Figures 4 (A): a. Burrhole Lower Case Figures 4 (B): a. Keyhole Bone Flap Lower Case Figures 4 (C): a. Frontal Dura Lower Case Figures 4 (D): a. Frontal Dura b. Orbital Roof After Partial Drilling Improve the Exposure Figures 5 (A) and (B): Dural Opening Lower Case Figures 5 (b): a. Reflected Dura b. Lower Surface of Frontal Lobe Figures 6 (A) - (D): Regional endoscopic anatomy of the anterior cranial fossa Lower Case Figure 6 (C): a. Left Optic Nerve Figures 7 (A), (B), and (C): Closure of the Dura Lower Case Figure 7 (B): a. Collagen Dural Substitute (Onlay Graft) Lower Case Figure 7 (C): a. Fibrin Glue Figures 8 (A) and (B): Cranioplasty Lower Case Figure 8 (A): a. Absorbable Microplate and Screws Lower Case Figure 8 (B): a. Hydroxyapatite Bone Substitute Figures 9 (A) - (C): Skin Closure Lower Case Figure 9 (B): a. Close up View of the Eyebrow after Complete Skin Closure Figure 10: NO LEGEND Figure 11: NO LEGEND Figures 12: (A) Contrast-enhanced, T1-weighted coronal MRI showing an OGM. (B) Intraoperative endoscopic view showing the initial exposure of an OGM Lower Case Figure 12 (B): a. Olfactory Groove Meningioma (OGM) b. Cribriform plate and Olfactory Groove Area c. Lower Surface of Frontal Lobe (C) - (G) Intraoperative endoscopic view showing the Gradual Resection of an Olfactory Groove Meningioma (OGM) Lower Case Figure 12 (D): a. Gradual Debulking of an Olfactory Groove Meningioma (OGM) b. Lower Case Figure 12 (F): a. Posterior Capsule of Olfactory Groove Meningioma (OGM) Lower Case Figure 12 (G): a. Posterior Capsule of Olfactory Groove Meningioma (OGM) Being Removed (I) Intraoperative endoscopic view following complete tumor removal Lower Case Figure 12 (H): a. Gelfoam with Dural Graft Underneath Covering Cribriform Plate (I) Postoperative contrast-enhanced, T1-weighted coronal MRI Figures 13: (A) Contrast-enhanced, T1-weighted saggital MRI showing a planum sphenoidale meningioma (B) Contrast-enhanced, T1-weighted coronal MRI showing a planum sphenoidale meningioma (C) and (D) Intraoperative endoscopic view showing the initial exposure of a planum sphenoidale meningioma Lower Case Figure 13 (C): a. Meningioma b. Planum Sphenoidale (E) - (P) Intraoperative endoscopic view showing the decompression of a planum sphenoidale meningioma using a combination of blunt and sharp dissection Lower Case Figure 13 (H): a. Close up View During Gradual Decompression of Meningioma Lower Case Figure 13 (K): a. First Appearance of Ipsilateral Optic Nerve Behind Tumor Lower Case Figure 13 (L): a. Sharp Dissection of Last Remnants of Meningioma from Ipsilateral Optic Nerve Lower Case Figure 13 (N): a. Ipsilateral Optic Nerve (II) b. Contralateral Optic Nerve (II) Lower Case Figures 13 (P): a. Last remnant of Meningioma Adherent to Ipsilateral Optic Nerve (Q) and (R) Intraoperative endoscopic view following complete tumor removal and gradual withdrawal of the endoscope Lower Case Figures 13 (R): a. Gelfoam b. Clean Bone of Planum Sphenoidale (S) Postoperative contrast-enhanced MRI saggital (T) Postoperative contrast-enhanced MRI coronal Figures 14 (A) Contrast-enhanced, T1-weighted axial MRI showing a medial sphenoid wing meningioma (B) Contrast-enhanced, T1-weighted coronal MRI showing a medial sphenoid wing meningioma (C) and (D) Intraoperative endoscopic view showing the initial exposure of a medial sphenoid wing meningioma Lower Case Figure 14 (C): a. Ipsilateral Sphenoid Ridge b. Meningioma c. Lower Surface of ipsilateral Frontal Lobe Lower Case Figure 14 (D): a. Ipsilateral Sphenoid Ridge b. Meningioma c. Lower Surface of ipsilateral Frontal Lobe d. Arachnoid (E) - (K) Intraoperative endoscopic view showing the debulking of a medial sphenoid wing meningioma Lower Case Figure 14 (F): a. Meningioma b. Lower Surface of Ipsilateral Frontal Lobe c. Medial Surface of Ipsilateral Temporal Lobe Lower Case Figure 14 (K): a. Sphenoid Ridge is Partly Drilled For Better Exposure of the Middle Skull Base and its Floor (L) and (M) Intraoperative endoscopic view following complete tumor removal and gradual endoscope withdrawal Lower Case Figure 14 (L): a. Tumor Cavity following Complete Removal b. Dural Attachments are Cauterized and/or Resected Lower Case Figure 14 (M): a. Endoscopic view following complete tumor removal with Gelfoam in Cavity b. Outer Surface of Eyebrow (N) Postoperative contrast-enhanced, T1-weighted axial MRI (O) Postoperative contrast-enhanced, T1-weighted coronal MRI Figures 15: (A) Contrast-enhanced and non-contrasted, T1-weighted saggital MRIs showing a suprasellar epidermoid tumor (B) T2-weighted and Contrast-enhanced T1-weighted coronal MRIs showing a suprasellar epidermoid tumor (C) and (D) Intraoperative endoscopic view showing the initial exposure of a suprasellar epidermoid Lower Case Figure 15 (C) and (D): a. Epidermoid Tumor b. Ipsilateral Optic Nerve (II) c. Dura Overlying Ipsilateral Anterior Clinoid Process d. Planum Sphenoidale e. Lower Surface of Frontal Lobe f. Temporal Lobe g. Middle Cerebral Artery Bifurcation (E) and (F) Intraoperative endoscopic view showing the gradual resection of a suprasellar epidermoid Lower Case Figure 15 (E): a. Epidermoid Tumor Partially Debulked b. Ipsilateral Optic Nerve (II) c. Ipsilateral Internal Carotid Artery d. Middle Cerebral Artery Bifuracation Lower Case Figure 15 (E): a. Epidermoid Tumor Partially Debulked b. Ipsilateral Optic Nerve (II) c. Ipsilateral Internal Carotid Artery d. Middle Cerebral Artery Bifuracation Lower Case Figure 15 (F): a. Ipsilateral Internal Carotid Artery Bifurcation b. Ipsilateral Anterior Cerebral Artery c. Ipsilateral Internal Carotid Artery d. Ipsilateral Middle Cerebral Artery e. Middle Cerebral Artery Bifurcation f. Tumor Cavity g. Last Remnants of Epidermoid (G) - (J) Intraoperative endoscopic view and Close up views following complete tumor removal and endoscope withdrawal Lower Case Figure 15 (I): a. Ipsilateral Internal Carotid Artery Bifurcation b. Ipsilateral Anterior Cerebral Artery c. Ipsilateral Internal Carotid Artery d. Ipsilateral Middle Cerebral Artery e. Tumor Cavity following Completer Tumor Removal (K) Postoperative contrast-enhanced, T1-weighted saggital MRIs (L) Postoperative contrast-enhanced, T1-weighted coronal MRIs