Endoscopic Skull Base Surgery Chap. 6: Endonasal Endonasal or Transnasal Approach


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Endoscopic Skull Base Surgery
Chapter 6: Endoscopic Endonasal or Transnasal Approach
By Hrayr K. Shahinian, M.D., FACS

Abstract

This chapter describes the fully endoscopic endonasal, also called transnasal, approach. The advantages of the endoscopic endonasal approach include a more thorough tumor resection, fewer surgical complications, elimination of unnecessary steps, and reductions in operative and hospitalization times. These advantages have rendered the fully endoscopic endonasal approach the "gold standard" in pituitary surgery. In our practice, the fully endoscopic endonasal approach has improved our ability to achieve complete resection of pituitary and other sellar tumors. The chapter provides a thorough description of the fully endoscopic endonasal approach, including indications, operating room setup, patient positioning, operative technique, state-of-the-art illustrative cases (including a clinical background on the most important pathologies in this area), potential complications, and ways to avoid these complications (in the author's experience).

1. Introduction

Over the past few decades surgical access to the pituitary gland and other tumors of the sellar region has, for the most part, been limited to the traditional transseptal transsphenoidal approach. Larger tumors have often required a conventional craniotomy for optimal decompression. More recently, the introduction of the endoscopic endonasal approach has offered a less invasive alternative to access the pituitary gland, providing superior intraoperative imaging by virtue of angled lenses that allow panoramic views of the regional anatomy. This has allowed for more thorough tumor resection and fewer surgical complications. Because the entire surgery is performed through a nostril without the need for any incisions, the need for transseptal dissection, metallic transsphenoidal retractors, and postoperative nasal packing has been eliminated, thus minimizing patient discomfort and postoperative pain. In our practice, the fully endoscopic endonasal approach has improved our ability to achieve complete tumor resection. The elimination of unnecessary steps and reductions in complications and recovery times have rendered the fully endoscopic endonasal approach the "gold standard" in pituitary surgery. Most of our patients are able to go home the day after surgery.

2. Indications

The fully endoscopic endonasal approach provides minimally invasive access to the anterior, middle, and posterior cranial base. It is indicated for the surgical management of pituitary tumors, including secretory and nonsecretory pituitary adenomas with or without suprasellar extension, Rathke's cleft cysts, clival chordomas, craniopharyngiomas, some meningiomas, and optic nerve gliomas, and it is useful in the repair of anterior cerebrospinal fluid (CSF) fistulas; these indications expand those for the traditional transseptal transsphenoidal microsurgical technique. Because this minimally invasive technique provides a distinct advantage in terms of operative time, perioperative morbidity, and faster overall recovery, the use of an endoscopic endonasal approach is particularly suited to pediatric patients, elderly patients, and patients with significant medical comorbidities.

3. Instrumentation

The instruments needed to successfully execute this technique include an endoscopic tower containing a three-chip high-definition digital camera, a xenon or halogen light source, 0- and 30-degree rigid endoscopes, a dedicated endoscope holding arm, an endoscope irrigation sheath, and precision microinstruments.

4. Operating Room Setup (Figure 1)

Once the patient is anesthetized, the operating room table is turned so that the head of the patient is rotated 180 degrees away from the anesthesiologist. Corrugated extension tubing is used to bridge the distance from airway to anesthesia machine; there are no adverse effects from adding this amount of dead space to the airway circuit. The next step is to position the imaging hardware: the C-arm fluoroscopy image intensifier is brought to the head of the table and rotated so that the trajectory of the beam yields centrally positioned sphenoid and sella contours on the fluoroscopy monitor, which is placed over the patient's right shoulder. The endoscopic tower is placed over the patient's left shoulder, directly in the line of vision of the surgeon, who stands on the patient's right side. The endoscope holding arm is affixed to the bed on the side opposite the surgeon and wrapped in a sterile drape. The arm reaches over the patient's upper body and the grasping end rests above the patient's nose; its orientation can be adjusted to alter the position of the endoscope as necessary.

This setup provides the surgeon with an unobstructed view of the monitor displaying the endoscopic image as well as ready access to continuous and still fluoroscopic imaging. Because the surgeon is not looking down into the eyepieces of a microscope, and instead directly forward at the video screen, proper alignment of these components is essential to keeping the surgeon oriented to a surgical plane that is perpendicular to the sphenoid rostrum.

5. Patient Positioning (Figure 2)

The patient is placed supine on the operating room table with the head of the bed raised 45 degrees. The neck is slightly extended, and the head is rotated to the right and fixed in position with a carbon horseshoe three-pin clamp. The surgeon operates through the patient's right nostril, which provides a natural axis along which the long, slender endoscopes and surgical instruments can be passed posteriorly. In patients with a significantly deviated nasal septum that effectively obliterates the working space through the right nostril, or in those with histories of right-sided sinus surgeries or other structural abnormalities of the right nasopharynx, an approach through the left nostril should be considered.

6. Operative Technique

The face, nares, and abdomen are prepared with antibacterial surgical scrub. Intranasal epinephrine or cocaine-soaked sponges are not used. Sterile towels are used to cover the face, leaving only the nose exposed during surgery (Figure 3).

The first step of the operation is performed with a 0-degree endoscope with either a 2.7 or 4 mm diameter, depending on the volume of the nasal passage. Intranasal retractors and speculums are not required during the procedure. The endoscope is attached to the grasping end of the endoscope holder, advanced into the nostril, and used to conduct a brief survey of the anterior nasal vestibule. The anteroinferior border of the middle turbinate and the architecture of the nasal septum are identified (Figures 4 (A) and (B)). An elevator is placed flatly against the surface of the nasal septum and firm, sustained, medial pressure is applied, displacing the septal mucosa and underlying cartilage. The elevator is then intranasally rotated and a similar force is applied laterally to displace the middle turbinate. The middle turbinate may fracture, but out-fracturing is not explicitly necessary to provide adequate exposure. Once the anterior nasal passage is widened, the holding arm is released and the endoscope is advanced further posteriorly. The same maneuvers are then repeated along the entire face of the septum and turbinate until a passage wide enough to accommodate the endoscope and the accompanying microinstruments is created. Intranasal dissection should be performed meticulously and atraumatically, as bleeding from traumatized mucosa anteriorly can obscure the vision posteriorly (Figures 5 (A) and (B)).

The posterior nasopharyngeal wall and sphenoid ostium mark the deepest extent of the intranasal dissection. Because the sphenoid ostium is often difficult to detect due to its diminutive size or mucosal inflammation, confirmation of appropriate positioning is obtained before proceeding by passing a long metallic suction cannula into the posterior nasopharynx and fluoroscopically identifying that its tip is abutting the anterior wall of the sphenoid sinus.

The mucosa overlying the anterior wall of the sphenoid sinus is cauterized using a combination suction-cautery instrument. Subperiosteal dissection with an elevator is then carried out to expose the entire anterior sphenoid; limits of dissection are the cribriform plate superiorly, the vomer inferiorly, and beyond both sphenoid ostia laterally. Fluoroscopy may again be used to confirm these anatomic limits. The perpendicular plate of the ethmoid bone, Rostrum "keel" of sphenoid bone, as well as the vomer may be removed with a rongeur to more completely expose the anterior and inferior surface of the sphenoid sinus (Figures 6 (A) - (E)).

Once the sphenoid sinus is completely exposed, its mucosal lining is dissected free, grasped with a rongeur, and removed to minimize the risk of a postoperative mucocele. Any septae within the sphenoid sinus are also removed. The intersphenoidal septum is commonly bent to one or the other side and is also removed using a rongeur. The posterior wall of the sinus, which makes up the floor of the sella turcica, and the bilateral carotid prominences are immediately recognizable. The floor of the sella is usually intact; however, it may be thinned, fractured, or even completely obliterated by an expanding tumor. If the sella is intact, its floor must be removed to provide access to the tumor. As with the anterior wall of the sphenoid sinus, this is accomplished in a piecemeal fashion with the use of a fine chisel and angled rongeurs; limits of bone removal are the cavernous sinuses laterally, the planum sphenoidale superiorly, and the top of the clivus inferiorly. Maximal exposure of the tumor is achievable only with adequate removal of bone; however, serious consideration must be given to the surrounding neurovascular structures, including the carotid arteries and cavernous sinuses laterally and the optic nerves and chiasm superiorly (Figures 7 (A) - (C)).

Once the sella is adequately exposed, the overlying dura is incised in a cruciate fashion with a modified No. 11 scalpel. The ventral surface of the pituitary gland in microadenomas or the tumor in macroadenomas is exposed and any tumor is then removed using suction and ring curettes of varying diameters and orientations. The extent of intrasellar dissection must incorporate information from preoperative imaging regarding the displacement of the normal gland by the tumor. The Valsalva maneuver, rather than saline injection through a lumbar catheter, is used to deliver suprasellar extensions of tumor into the sella (Figures 8 (A) - (C)).

Until this point of the procedure, the 0-degree endoscope provides all of the imaging; its optics allow near complete exposure of the sella turcica and a partial view of the suprasellar structures including the optic chiasm and the arachnoid membrane investing the median eminence. However, the extent of visualization under the 0-degree endoscope is limited by its optical capabilities. Therefore, once tumor resection under the 0-degree endoscope is deemed complete, it is replaced with the 30-degree endoscope. By advancing the 30-degree endoscope into the sella turcica and then rotating it in a clockwise and counterclockwise direction along its longitudinal axis, the right and left parasellar and suprasellar areas are thoroughly visualized and any hidden tumor remnants are removed.

A fat graft is harvested from the abdomen to seal the intrasellar contents, and it is secured in place with 2 cc of dural sealant or fibrin glue. Postoperative nasal packings are not used. A small gauze sponge fastened beneath the nose (a "mustache" dressing) serves to collect minimal oozing for 24 hours postoperatively. Patients are monitored in a step-down unit overnight following surgery, and in almost all cases are discharged home the following day (Figures 9 (A) and (B)).

7. Illustrative Cases

7. 1. Pituitary Microadenoma

7. 1.1. Background

Pituitary tumors less than 10 mm in diameter (microadenomas) may be secretory or nonsecretory and may be discovered only incidentally or at autopsy. Of the secretory adenomas, the most common are prolactinomas. Other secretory tumors may secrete adrenocorticotropic hormone (ACTH), causing Cushing's disease; growth hormone, causing acromegaly; gonadotropins, causing disturbance in the level of sex hormones; or, rarely, thyroid-stimulating hormone (TSH), causing hyperthyroidism. In most cases, magnetic resonance imaging (MRI) can be used to locate the microadenoma, and treatment options are based on the location and symptoms that a microadenoma is causing. Although some microadenomas can be treated with medication, many require surgery.

7.1.2. Approach

After the sphenoid sinus is opened and its septae and mucosa are removed, the sellar floor is identified and a small quadrangle of bone overlying the microadenoma is outlined and in-fractured with a chisel and then removed with the pituitary rongeur. The opening is enlarged as needed and the underlying dura is electrocoagulated and opened and the microadenoma within the pituitary gland is identified. Using the curved pituitary microscissors, a plane is created between the microadenoma and the normal pituitary gland, after which the microadenoma is resected. A 1 mm margin is also resected circumferentially around the tumor bed to prevent recurrence.

7.1.3. Cases

7.1.3.1. Microadenomectomy for a left pituitary microadenoma: Figures 10 (A) - (J)

7.1.3.2. Microadenomectomy for a pituitary microadenoma: Figures 11 (A) - (H)

7.1.3.3. Left one-third hypophysectomy for a pituitary microadenoma: Figures 12 (A) - (K)

7.2. Pituitary Macroadenoma (Figure 13)

7.2.1. Background

Pituitary tumors exceeding 10 mm in diameter (macroadenomas) are usually nonsecretory tumors that present with mass effect causing visual disturbances, such as bitemporal hemianopsia from compression of the optic chiasm, headache from direct stretching of the dura, hydrocephalus from obstruction of the foramen of Monro, or hypopituitarism from compression of the pituitary gland itself. Some macroadenomas may be asymptomatic, while others are secretory and may produce distinct clinical syndromes as a result of hormonal overproduction, such as acromegaly, Cushing's disease, or hyperprolactinemia. The latter can also be caused by direct pituitary stalk compression by an enlarging macroadenoma regardless of hormone activity.

Panhypopituitarism may present with a deficiency of all the pituitary hormones, but often some are spared. The larger the macroadenoma, the more likely it is to affect pituitary hormones. Pituitary apoplexy, a medical emergency, may result from infarction or sudden hemorrhage within the tumor; this complication tends to occur with macroadenomas but not with microadenomas. MRI studies can be used to define the boundaries of a pituitary macroadenoma and depict any partial descent of the adenoma into the sphenoid sinus.

7.2.2. Approach (Figure 14)

The bone of the sellar floor is removed in a piecemeal fashion to expose the dura overlying the pituitary gland. A cruciate incision is used to open the sellar dura. The dura is freed from the underlying tumor capsule and pituitary gland using the curved dissector; the pituitary gland and tumor are thus exposed. A biopsy from the tumor is initially obtained to confirm the diagnosis, and then the tumor is internally debulked using ring curettes and gentle suction. Tumor is carefully dissected laterally from the medial walls of the cavernous sinuses and internal carotid arteries under direct endoscopic visualization. Using a blunt ring curette, any tumor from the area of the tuberculum sellae that is hidden from direct view is then removed. The Valsalva maneuver can be used if necessary to force the suprasellar component of the tumor into the operative field. The 0-degree endoscope is then withdrawn and the 30-degree endoscope is inserted to survey for any residual tumor, superiorly, inferiorly, or laterally.

7.2.3. Cases

7.2.3.1. Pituitary macroadenoma: Figures 15 (A) - (P)

7.2.3.2. Pituitary macroadenoma: Figures 16 (A) - (N)

7.2.3.3. Pituitary macroadenoma: Figures 15 (A) - (X)

7.3. PeriClival Tumors

7.3.1 Background

A variety of lesions occur in and around the clival region including the anterior foramen magnum. Meningiomas, chordomas and neurofibromas are the most common tumors. ,Other pathologies include chondrosarcomas, tuberculomas, epidermoids, and others. These tumors whether extra or intradural occur in a critical area of the skull base, and may pose unique diagnostic and management challenges. The progressive growth of such tumors often results in compression and invasion of important neighboring structures. Associated symptoms are typically non-specific and may persist chronically before acute or focal neurological findings develop. Tumors such as clival chordomas may invade the surrounding cranial nerves causing clinical signs including headache and cranial nerve deficits. The cranial nerve involved most often is the CN VI (Abducent), other signs may include dysphagia, facial pain, facial paresis, visual loss, hearing loss, and ataxia.

Many operative techniques approaches have been utilized in the surgical management of periclival tumors; the choice among different approaches usually depends on the location and extent of the tumor. Nevertheless, the clivus along with the posterior surface of the petrous bone constitutes the most anatomically complex area of the skull base and the most difficult to access surgically. A plethora of transfacial approaches including the transbasal, transnasal and transoral approaches along with several transcranial approaches such as the suboccipital, subtemporal and transcondylar approaches,have provided a vast experience in the treatment of these previously unresectable tumors. The individual case, whether using a single or staged approach or whether using endoscopic minimally invasive techniques or more traditional open microsurgical techniques, is offered, based on the specifics of each individual situation. No single technique can provide an exposure adequate enough for thorough resection of all clival and periclival lesions but all procedures are geared toward as complete a resection as possible.

7.3.2. Approach

The endoscopic endonasal approach offers a minimally invasive, anatomically direct route for resection of clival and retroclival tumors that obviates the need for brain retraction. To approach the clivus or the retroclival region, the endoscope is advanced towards the sphenoid sinus and its mucosa and any septae are removed in the usual manner. Upon entering the sphenoid sinus the tumor may be immediately visualized in some cases such as in chordomas of the upper third of clivus. In these cases the clivus typically has a diseased "moth-eaten" appearance; and is resected as thoroughly as possible. In retroclival tumors, a transclival approach is performed whereby the entire length of the clivus can be drilled using cutting and diamond burrs to obtain direct access to the prepontine region. For intradural prepontine lesions, the dura is sharply incised taking great care to avoid any injury to the Basilar artery immediately posterior and the underlying tumor is first identified and subsequently resected..

The surgical principles that are followed include obtaining a frozen section analysis of the tumor to confirm the histopathologic diagnosis and resecting the tumor piecemeal using a combination of dissecting microinstruments, microCUSA and microbipolar. Resection of any tumor extensions into the sphenoid sinus, the sella turcica or the anterior clivus is performed. Following the resection, the 0° endoscope is slowly withdrawn from the surgical field and a 30° endoscope is placed to confirm gross removal of all tumor remnants. A small Teflon-coated pledget is then placed in the region of the clivus to mark the limits of surgical resection if a second-stage procedure is planned. Small dural defects should be avoided at all cost in case of extradural lesions . If the dura is incised open to access an intradural prepontine lesion, it is closed with a double layer of fat graft and a collagen dural substitute followed by application of fibrin or dural sealant. The clival defect is obliterated with a Hydroxyapatite bone substitute.

7.3.3. Cases

7.3.3.1. Prepontine Epidermoid Tumor: Figures 16 (A) - (Z)

8. Potential Complications

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

Bleeding, infection, cerebrovascular accident, and death (These are also potential complications associated with traditional transcranial and transspheoidal approaches to the pituitary gland.)
Endocrine complications include anterior pituitary insufficiency (this is typically detected postoperatively, and may involve one or more of the pituitary axes) and posterior pituitary insufficiency leading to complications such as transient or persistent diabetes insipidus (DI).
CSF leak, meningitis
Direct neurovascular injuries can occur to the optic apparatus, cranial nerves, carotid artery, hypothalamus, or brain.
Early or delayed postoperative epistaxis, resulting from rupture of a small septal vessel or mucosal branch of the sphenopalatine artery
Sphenoid sinus complications include sphenoid sinusitis or mucocele (symptomatic or asymptomatic).
Direct injuries during the approach may include nasal septal perforations, anosmia resulting from mucosal trauma or dissection, and accidental bone fractures (hard palate, orbital wall, cribriform plate).
Severe frontal headaches, tension pneumocephalus

9. Avoiding Complications in Author's Experience

Improved endoscopic visualization allows the surgeon to recognize and avoid injuring the normal pituitary gland, optic apparatus, carotid prominences, cavernous sinuses, and hypothalamus. Thus, many catastrophic complications that were once associated with limited visibility or blind dissection, such as anterior and posterior pituitary insufficiencies, blindness, cranial nerve deficits, and CNS injury, are generally avoidable. Transient DI is probably the most common cause of prolonged hospital stay, but rarely does it persist permanently. Generally, all complications occur less frequently than with the traditional transsphenoidal approach.

The completely endonasal approach eliminates the need for extensive mucosal dissection, the use of nasal speculums, and postoperative nasal packing. Therefore, approach-related complications, such as septal perforations or bony injuries, are completely avoidable. A postoperative sphenoid sinus mucocele, as well as sphenoid sinusitis, are rare occurrences with the endoscopic approach. Delayed epistaxis is rare; when significant, it is managed with either posterior packing or neuroradiologic embolization.

The anatomy of the sphenoid sinus depends on the age of the patient and the pathology encountered. It may be nonaerated in pediatric patients, multiseptated, completely filled with tumor that has invaded through the floor of the sella, or, as in the case of a clival chordoma, protruding from the clivus. Preoperative MRI studies provide useful information on the individual sphenoid anatomy. Additionally, it is recommended to revisit the patient's imaging studies during the initial exposure of the sellar areas to keep orientation to the midline, and avoid complications that may result from a deviated trajectory.

Violation of the arachnoid membrane during surgery may result in CSF leak, pneumocephalus, or even bacterial meningitis. Our principle surgical rule is to avoid penetrating the arachnoid membrane, as this significantly increases the possibility of serious morbidity and can result in injury to the optic nerves and chiasm, carotid artery and its branches, and the hypothalamus and, by definition, will result in an intraoperative CSF leak creating the possibility of meningitis, subarachnoid hemorrhage, vasospasm, and tension pneumocephalus.

If too much of the pituitary gland is resected during surgery, the patient may need to be placed on hormonal replacement indefinitely. Therefore, these tumors should be resected with minimal trauma to the underlying normal pituitary gland. Total tumor resection is the ultimate goal of surgery. Large macroadenomas with supra or parasellar extension that is beyond the limits of the endonasal approach should undergo a second-stage endoscopic supraorbital or transglabellar approach.

Tumor resection is considered complete only after a final survey with the angled endoscopes is completed, confirming absence of all tumor. A 70-degree endoscope may also be used in this examination; however, in most cases, the information obtained by the 30-degree lens is sufficient to identify any tumor remnants. Tumor remnants in these areas, constituting the potential sources of recurrence, are effectively removed with a superb visual appreciation of the critical surrounding structures. Inadequate repair of clival dural defects remains the greatest potential complication in clival and transclival tumor resection and a double layered closure technique as described is recommended. Lumbar drains are no longer used.

Legends:

Figure 1: Operating Room Setup
Figure 2: Patient Positioning
Figure 3: Draping
Figures 4 (A) and (B): Endoscopic Anatomy of the Nose

Lower Case: Figure 4 (A)
1. Middle Turbinate
Lower Case Figure 4 (B)
1. Anterior Inferior Border of the Middle turbinate

Figures 5 (A) and (B): Posterior Septoplasty

Lower Case Figure 5 (A)
1. Mucosa Overlying Face of Sphenoid Sinus
2. Mucoperichondrium Overlying Cartilaginous Nasal Septum
Lower Case Figure 5 (B)

Right Sphenoid Ostium
Face of Sphenoid Sinus
Ethmoidal Crest (Articulates with Perpendicular Plate of Ethmoid Bone)
Rostrum "keel" of Sphenoid Bone (Articulates with Alae of Vomer)

Figures 6 (A) - (E): Opening of Sphenoid Sinus

Lower Case Figure 6 (B)
1. Right Sphenoid Ostium
2. Left Sphenoid Ostium
3. Rostrum "keel" of Sphenoid Bone

Figures 7 (A) - (C): Sellar Exposure

Lower Case Figure 7 (A):
1. Mucosal Lining of Sphenoid Sinus
Lower Case Figure 7 (B):
1. Intersphenoidal Septum

Figures 8 (A) - (C): Sellar Opening

Lower Case Figure 8 (A)
1. Carotid Protruberences
2. Sellar Floor
Lower Case Figure 8 (B)
1. Sellar Dura
Lower Case Figure 8 (C)
1. Sellar Dura
2. Arachnoid Membrane Junction
3. Planum Sphenoidale
4. Upper Clivus

Figures 9 (A) and (B): Closure

Lower Case Figure 9 (A)
1. Fat Graft
Lower Case Figure 9 (B)
1. Dural Sealant

Figures 10:

(A) T1-weighted coronal contrasted MRIs showing a pituitary microadenoma
(B) and (C) Opening of the dura and initial exposure of pituitary microadenoma
Lower Case Figure 10 (C)
1. Adenoma
(D) - (F) Intraoperative endoscopic view showing microadenomectomy
Lower Case Figure 10 (D)
1. Adenoma
2. Ring Curette
(G) - (I) Intraoperative Endoscopic view after complete resection removal of a pituitary microadenoma
Lower Case Figure 10 (H)
1. Adenoma Cavity
2. Normal Pituitary
3. Arachnoid Membrane Junction
4. Planum Sphenoidale
Lower Case Figure 10 (I)
1. Fat Graft
(J) Postoperative contrast-enhanced coronal MRIs

Figures 11:

(A) T1-weighted coronal contrasted MRI showing pituitary microadenoma
(B) and (C) Opening of the dura for Resection of pituitary microadenoma
Lower Case Figure 11 (B)
1. Sellar Dura Cauterized
2. Planum Sphenoidale
3. Clivus
4. Right Carotid Protruberence
5. Left Carotid Protruberence
Lower Case Figure 11 (C)
1. Adenoma Bulge
2. Sharp Dissection of Adenoma
(D) - (F) Intraoperative endoscopic view showing microadenomectomy and fat graft placement
Lower Case Figure 11 (D)
1. Adenoma b. Ring Curette
Lower Case Figure 11 (E)
1. Adenoma Cavity After Compete Resection
2. Normal Pituitary
Lower Case Figure 11 (F)
1. Fat Graft
Lower Case Figure 11 (G)
1. Dural Sealant
(H) Postoperative contrast-enhanced coronal MRI

Figures 12:

(A) T1-weighted coronal contrasted Dynamic MRI showing a pituitary microadenoma
(B) Intraoperative endoscopic view showing one-third left Pituitary Hypophysectomy and fat graft placement
Lower Case Figure 12 (B)
1. Pituitary
2. Clivus
3. Right Carotid Protuberance
4. Planum Sphenoidale
5. Left Carotid Protuberance
Lower Case Figure 12 (C)
1. Straight Microscissors
Lower Case Figure 12 (F)
1. Microadenoma
2. Remaining NormalPituitary
Lower Case Figure 12 (G)
1. Medial Wall of Left Cavernous Sinus
2. Remaining Normal Pituitary
Lower Case Figure 12 (J)
1. Fat Graft
Lower Case Figure 12 (K)
1. Dural Sealant

Figure 13: No Legend
Figure 14: No Legend

Figures 15:

(A) T1-weighted saggital MRI showing a pituitary macroadenoma
(B) T1-weighted coronal contrast-enhnced MRI showing a pituitary macroadenoma
(C) and (D) Intraoperative endoscopic view showing initial exposure of pituitary macroadenoma
Lower Case Figure 15 (C)
1. Macroadenoma Bulge
2. Eroded Sellar Dura
3. Clivus
4. Planum Sphenoidale
Lower Case Figure 15 (D)
1. Close up View Showing Dural Erosion by Tumor
(E) - (I) Intraoperative endoscopic view showing gradual resection of pituitary macroadenoma
Lower Case Figure 15 (E)
1. Cauterized Sellar Dura
Lower Case Figure 15 (F)
1. Adenoma
Lower Case Figure 15 (G)
1. Adenoma
2. Ring Curette
Lower Case Figure 15 (I)
1. Final Portions of Adenoma
2. Ring Curette
(J) and (M) Intraoperative endoscopic view following complete resection of pituitary macroadenoma
Lower Case Figure 15 (J)
1. Close up View of Adenoma Cavity after Complete Tumor Removal
2. Pituitary
3. Medial Wall of Left Cavernous Sinus
Lower Case Figure 15 (K)
1. Close up View of Right Medial Cavernous Sinus Wall using 30-Degree Endoscope
Lower Case Figure 15 (L)
1. Close up View of Left Medial Cavernous Sinus Wall Using 30-Degree Endoscope
Lower Case Figure 15 (M)
1. Fat Graft
(O) Postoperative contrast-enhanced saggital MRI
(P) Postoperative contrast-enhanced coronal MRI

Figures 16:

(A) T1-weighted coronal contrast-enhanced MRIs showing a pituitary macroadenoma
(B) - (D) Intraoperative endoscopic view showing initial exposure for pituitary macroadenoma
Lower Case Figure 16 (B)
1. Cauterized Sellar Dura
2. Clivus
Lower Case Figure 16 (C)
1. Adenoma
Lower Case Figure 16 (D)
1. Close up View of Adenoma
(E) - (J) Intraoperative endoscopic view showing gradual resection of pituitary macroadenoma
Lower Case Figure 16 (E)
1. Adenoma
2. Ring Curette
Lower Case Figure 16 (G)
1. Adenoma
2. Normal Anterior Pituitary
Lower Case Figure 16 (H)
1. Residual Adenoma
Lower Case Figure 16 (I)

Adenoma
Ring Curette

Lower Case Figure 16 (J)
1. Final Remnants of Adenoma
(K) and (J) Intraoperative endoscopic view following complete resection of pituitary macroadenoma
Lower Case Figure 16 (K)
1. Close up View of Adenoma Cavity
2. Pituitary
Lower Case Figure 16 (L)
1. Close up View of Left Medial Cavernous Sinus Wall using 30-Degree Endoscope
Lower Case Figure 16 (M)
1. Fat Graft (N)
Postoperative contrast-enhanced coronal MRI

Figures 17:

(A) T1-weighted coronal contrast-enhanced MRI showing a pituitary macroadenoma
(B) - (F) Intraoperative endoscopic view showing initial exposure for pituitary macroadenoma
Lower Case Figure 17 (B)
1. Sellar Floor
2. Clivus
3. Planum Sphenoidale
Lower Case Figure 17 (C)
1. Sellar Dura
2. Right Carotid Protuberance
Lower Case Figure 17 (D)
1. Cauterized Sellar Dura
Lower Case Figure 17 (E)
- a. Adenoma
(G) - (R) Intraoperative endoscopic view showing gradual resection of pituitary macroadenoma
Lower Case Figure 17 (G)
- a. Adenoma
- b. Ring Curette
Lower Case Figure 17 (K)
- a. Adenoma
- b. Normal Anterior Pituitary
Lower Case Figure 17 (M)
- a. Adenoma
- b. Ring Curette
- c. Atraumatic Suction
Lower Case Figure 17 (Q)
- a. Final Portions of Adenoma
- b. Normal Anterior Pituitary
Lower Case Figure 17 (R)
- a. Close up View Showing Final Portions of Adenoma
- b. Normal Anterior Pituitary
- c. Arachnoid
(S) and (W) Intraoperative endoscopic view following complete resection of pituitary macroadenoma
Lower Case Figure 17 (S)
- a. Close up View of Adenoma Cavity
- b. Normal Anterior Pituitary
- c. Arachnoid
- d. Medial Wall of Left Cavernous Sinus
Lower Case Figure 17 (T)
- a. Close up View of Right Medial Cavernous Sinus Wall using 30-Degree Endoscope
- b. Arachnoid
Lower Case Figure 17 (U)
- a. Close up View toward Left Cavernous Sinus using 30-Degree Endoscope
- b. Arachnoid
Lower Case Figure 17 (V)
- a. Fat Graft
Lower Case Figure 17 (W)
- a. Dural Sealant
(X) Postoperative contrast-enhanced axial, saggital and coronal MRIs

Figures 18:

(A) T2-weighted axial and T1-weighted contrast-enhanced saggital MRIs showing a prepontine epidermoid tumor
(C) - (G) Intraoperative endoscopic view showing transclival exposure for removal of prepontine epidermoid tumor
Lower Case Figure 18 (B)
1. Clivus
2. Sella Turcica
3. Right Carotid Protuberance
Lower Case Figure 18 (C)
- a. Drilling Through Middle Third of Clivus (Cancellous Bone of Mid-Clivus)
Lower Case Figure 18 (D)
1. Dura
2. High-Speed Microdrill
3. Suction
Lower Case Figure 18 (D)
1. Dura
2. High-Speed Microdrill
3. Suction
Lower Case Figure 18 (E)
1. Dura Hook
2. Dura
3. Boundaries of Keyhole
4. Mid-Clival Bone
Lower Case Figure 18 (F)
1. Arachnoid
2. Right Curved MicroScissors
(H) - (P) Intraoperative endoscopic view showing gradual removal of prepontine epidermoid tumor
Lower Case Figure 18 (H)
1. Arachnoid
2. Pearly White Shadow of Epidermoid Tumor
3. Atraumatic Suction
Lower Case Figure 18 (I)
1. Epidermoid Tumor
2. Arachnoid
Lower Case Figure 18 (K)
1. Epidermoid Tumor
2. Left Superior Cerebellar Artery (SCA)
Lower Case Figure 18 (N)
1. Epidermoid Tumor
2. Left Superior Cerebellar Artery (SCA)
Lower Case Figure 18 (O)
1. Basilar Artery
2. Left Superior Cerebellar Artery (SCA)
3. Brainstem
4. Epidermoid Tumor
Lower Case Figure 18 (P)
1. Basilar Artery
2. Left Superior Cerebellar Artery (SCA)
3. Brainstem
4. Final Remnants of Epidermoid Tumor
(Q) - (S) Intraoperative endoscopic view after complete transclival removal of prepontine epidermoid tumor
Lower Case Figure 18 (Q)
1. Basilar Artery
2. Left Superior Cerebellar Artery (SCA)
3. Brainstem
4. Left Vertebral Artery
Lower Case Figure 18 (R)
1. Close-up View of Basilar Artery and Regional Anatomy of prepontine epidermoid tumor
Lower Case Figure 18 (S)
1. Basilar Artery
2. Left Superior Cerebellar Artery (SCA)
3. Brainstem
4. Left Vertebral Artery
5. Dura
(T) - (Y) Intraoperative endoscopic view showing closure after transclival removal of prepontine epidermoid tumor
Lower Case Figure 18 (T)
1. Fat Graft (First Closure Layer)
Lower Case Figure 18 (U)
1. Collagen Dural Onlay Graft (Second Closure Layer)
Lower Case Figure 18 (V)
1. Fat Graft (Third Closure Layer)
Lower Case Figure 18 (W)
1. Dural Sealant
2. Fat Graft
Lower Case Figure 18 (X)
1. Hydroxyapatite Bone Substitute
2. Dural Sealant
3. Fat Graft
Lower Case Figure 18 (Y)
1. Hydroxyapatite Bone Substitute
(Z) Postoperative contrast-enhanced T1-weighted axial and saggital MRIs