Microscopic and Endoscopic Transsphenoidal Surgery

To the Editor:

In every part of the world, transsphenoidal surgery performed with a sublabial or a transnasal approach is the procedure of choice for treating the majority of sellar lesions (10). Its importance in the management of lesions of the sellar area, as well as the continuing interest in this approach, is emphasized by the technical and conceptual experience gained during the past century as well the advent, during the past decade, of a new procedure—pituitary endoscopy, an operation that is performed with an endoscope from beginning to end without the use of an operating microscope or a transsphenoidal retractor (5, 9, 13).

In addition, the great efficacy and minimal invasiveness of the transsphenoidal technique reach their utmost use in experienced hands and in specialized centers. Evidence that experienced hands obtain superior results is provided by a number of classic reports that clearly indicated that better outcomes for patients and a significant decrease in complications were correlated with the surgical experience of the surgeon (1, 7, 8). Specialized centers are defined as those with a team that is dedicated specifically to performing pituitary surgery and includes a neurosurgeon, a neuroradiologist, a pituitary endocrinologist, a neuro-ophthalmologist, a neuropathologist, and a radiotherapist, as well as, if possible, an otolaryngologist with endoscopic experience and a basic research group to study the pathological material and the molecular biology of pituitary disease. These two conditions—experienced hands and specialized centers—offer the patient the greatest opportunity for successful long-term management.

Today there are two different surgical options for performing the transsphenoidal procedure: the microsurgical and endoscopic approaches, supported by their differing respective underlying philosophies. Microsurgery is currently performed with the use of a sublabial, transnasal, or endonasal approach with the aim of reaching the pathology within the sella and avoiding the need for a craniotomy and/or brain retraction. The operating microscope is the visualizing instrument, providing illumination and magnification of the surgical field and stereoscopic vision at a constrained focal distance from the target. Transsphenoidal microsurgery is a well-established procedure offering excellent-quality optical images and good depth of field. Furthermore, the surgical corridor created by the spreading of the transsphenoidal retractor allows comfortable working access, with a specific skill set that is naturally acquired and easier to learn than that required to perform the endoscopic procedure. At the same time, it involves a degree of additional surgical trauma, and there is a limitation on the width of the visible surgical field, mainly in the sphenoid sinus, where important anatomic landmarks may be hidden from direct view.

The endoscopic approach is performed with a rigid endoscope inserted into one nostril through the endonasal route. The endoscope currently used is a visualizing instrument without a working channel, and the instruments are introduced adjacent to it, usually through the same nostril. The endoscope lens is placed inside the sphenoid sinus after enlargement of the sphenoid ostium, and there is no need to use a nasal speculum to create a surgical corridor inside the nostril. The use of this approach results in less intraoperative trauma, with no nasal or sublabial incision; reduced postoperative complications caused by the approach; no postoperative packing; improved upper-airway function; and reduced postoperative discomfort. A decreased incidence of complications after the use of the endoscopic procedure was recently reported (6). The endoscope offers the possibility of thorough inspection of the anatomy near the site of surgery (19), with closer and wider visualization of the endo-, supra-, and parasellar structures and no visual restriction because of the nasal speculum. At the same time, to work without the open access provided by the transsphenoidal retractor requires specific endoscopic skills that are attained only after traversing a steep learning curve. This explains the longer operative time often required the first few times the surgeon uses this procedure. Furthermore, the currently available endoscopes offer only a two-dimensional view, without a true sense of depth, even though the true depth can be approximated by moving the endoscope in and out to distinguish the same anatomic landmarks at different depths and perspectives. Another concern related to the endoscopic approach is that profuse bleeding can be a serious obstacle to vision, especially for the beginner. Endoscopy, because of the renewed anatomic interest that is essential to the comprehension and improvement of the approach itself, has the great merit of contributing to superior and more contemporary knowledge of the possibilities of the transsphenoidal approach to the anterior cranial base. Because of the increased visual scope it affords, it has encouraged anatomic studies (2, 3) and enhanced a variety of procedures (11, 14–">18), both microscopic and endoscopic. It has the great merit of having stimulated applications of a relatively static surgical technique.

Midway between these two different strategies for accomplishing the same transsphenoidal approach, the endoscope-assisted microsurgical procedure represents a useful compromise. The endoscope can be used to perform only the nasal aspect of the procedure and to allow a minimally traumatic insertion of the transsphenoidal retractor, with the major part of the operation being performed with the aid of the operating microscope. Alternatively, the endoscope can be used as a final complement to the microsurgical procedure to ensure thorough sellar-suprasellar exploration after removal of the lesion with the use of its intriguing insight into the anatomy.

At present, the microscope offers excellent-quality three-dimensional visualization and comfortable surgical access, and the endoscope permits a wider and closer view of the target and a better postoperative course for the patients. The following are some questions to consider:

• Why do some surgeons use the microscope and others use the endoscope to treat the same pathology?

• Why have many practicing neurosurgeons chosen not to use endoscopy?

• Which method should be taught to beginners in transsphenoidal surgery: the microscopic or the endoscopic technique?

A neurosurgeon who is already trained in the transsphenoidal technique can become confident in using the endoscope in a step-by-step fashion. He or she can first explore the surgical site with the use of an endoscope after performing a traditional transsphenoidal microsurgical approach to detect whether tumor remnants are present in the lateral or upper corners of the resection cavity. In this way, the surgeon starts acquiring confidence by mastering the peculiarities of endoscopic vision and begins to learn specific endoscopic dexterity, which may take time and repeated practice. He or she will progressively obtain the skills needed to manage any situation by using the endoscope as the sole visualizing tool. Some adventurous surgeons who have had prior experience in performing traditional transsphenoidal microsurgery—we among them—have followed this course.

Just as it was difficult for many neurosurgeons in the premicrosurgical era to abandon magnifying lenses for the intraoperative microscope, it is difficult at present for the experienced surgeon to abandon the microscope for the endoscope. Such surgeons must acquire a new, specific skill with the endoscope, which can be very unpleasant, because they already know how to work rapidly, comfortably, and safely with the microscope and have difficulty in beginning again to acquire dexterity with the use of the endoscope, which has a steep learning curve. Only if better overall results, a lower complication rate, and better compliance on the part of patients with the endoscopic approach are demonstrated and reported will the experienced surgeon eagerly make the change to performing transsphenoidal endoscopic surgery. As a matter of fact, it is unusual to find a neurosurgeon with experience in performing 1000 or more transsphenoidal operations who has switched to the use of the endoscope.

The young neurosurgeon has the difficulties of the beginner in both cases—microscopy and endoscopy—and must learn only how to perform the operation correctly with an experienced neurosurgeon watching over his or her shoulders. He or she can easily start directly with the endoscope as the sole visualizing tool throughout the operation, provided that:

• Preliminary, accurate theoretical studies have been performed;

• Dissection studies have been performed on cadavers;

• Some practical or observational study of nasal and paranasal sinus endoscopic surgery has been conducted;

• The surgeon fully understands that pituitary surgery is a specific field of neurosurgery that requires well-coordinated teamwork; and

• It is understood that one need not abandon the operating microscope or consider it outmoded.

Since 1997 at Federico II University of Naples, both the passage from microsurgery to endoscopy by an experienced neurosurgeon and a recently trained neurosurgeon and the preliminary acquisition of skill in performing pituitary endoscopy by residents were accomplished without any serious difficulties. We think that a young neurosurgeon should know how to perform both procedures, because there are situations that could be managed better with one rather than with the other. For example, in the presence of a very small sella, the surgical instruments and the endoscope converge at the target. The difficulty in maneuvering the endoscope and the instruments in such a small space, as well as the wide anatomic vision coupled with the relatively small image of the sella being disproportionate to the surgical requirements, is a drawback of the use of the endoscope. The capability of zooming the microscope onto the surgical area without interfering with the instruments makes the use of the microscope especially favorable in such a case. Similarly, in the setting of a conch-type sphenoid sinus, movement of the endoscope can be difficult, and, moreover, the advantages of minimal invasiveness are partially lost because it is necessary to remove the posterior part of the nasal septum to have more room in which to work. Conversely, the endoscopic procedure is advantageous when an overview is required, as in the setting of a parasellar lesion extension and in patients who already have undergone surgery with a transsphenoidal approach (4). Because of the endonasal introduction of the endoscope into the previously enlarged sphenoid ostium and because the approach to the target is obscured by scars and adhesions, endoscopic surgery can be performed with the benefit of wider anatomic vision, thus minimizing the risks that reoperation often entails.

We are convinced that the major objective should be the ability of the surgeon to work comfortably with two hands in the surgical field, a condition that is sufficient and necessary for a confident, safe, and reliable approach. The indications for surgery are the same with microscopic and endoscopic procedures (9, 12). The objective differences between the two procedures in terms of results will become evident after the analysis of large series of endoscopic operations, which will obviously require several years of follow-up. It is difficult to be dogmatic regarding whether the ideal transsphenoidal pituitary operation should be performed with the use of microscopy or endoscopy. Both methods are excellent, provided that:

• The pathology can be identified and managed effectively;

• The surgeon can work in a condition of utmost effectiveness and safety; and

• The surgeon is familiar with the options and/or can choose one or the other as necessary.

1.

Ahmed S, Elsheikh M, Stratton IM, Page RC, Adams CB, Wass JA: Outcome of transphenoidal surgery for acromegaly and its relationship to surgical experience. Clin Endocrinol (Oxf) 50: 561–567, 1999.

2.

Alfieri A, Jho HD: Endoscopic endonasal approaches to the cavernous sinus: Surgical approaches. Neurosurgery 49: 354–362, 2001.

3.

Alfieri A, Jho HD: Endoscopic endonasal cavernous sinus surgery: An anatomic study. Neurosurgery 48: 827–837, 2001.

4.

Cappabianca P, Alfieri A, Colao A, Cavallo LM, Fusco M, Peca C, Lombardi G, de Divitiis E: Endoscopic endonasal transsphenoidal surgery in recurrent and residual pituitary adenomas: Technical note. Minim Invasive Neurosurg 43: 38–43, 2000.

5.

Cappabianca P, Alfieri A, de Divitiis E: Endoscopic endonasal transsphenoidal approach to the sella: Towards functional endoscopic pituitary surgery (FEPS). Minim Invasive Neurosurg 41: 66–73, 1998.

6.

Cappabianca P, Cavallo LM, Colao A, de Divitiis E: Surgical complications associated with the endoscopic transsphenoidal approach for pituitary adenomas. J Neurosurg 97: 293–298, 2002.

7.

Ciric I, Ragin A, Baumgartner C, Pierce D: Complications of transsphenoidal surgery: Results of a national survey, review of the literature, and personal experience. Neurosurgery 40: 225–237, 1997.

8.

Clayton RN: How many surgeons to operate on acromegalic patients? Clin Endocrinol (Oxf) 50: 557–559, 1999.

9.

de Divitiis E, Cappabianca P: Endoscopic endonasal transsphenoidal surgery. Adv Tech Stand Neurosurg 27: 137–177, 2002.

10.

Elias WJ, Laws ER Jr: Transsphenoidal approaches to lesions of the sella, in Schmidek HH, Sweet WH, Schmidek and Sweet Operative Neurosurgical Techniques: Indications, Methods, and Results. Philadelphia, W.B. Saunders Co., 2000, vol 1, ed 4, pp 373–384.

11.

Frank G, Pasquini E, Calbucci F: Endoscopic approach to the cavernous sinus via an ethmoido-pterygo-sphenoidal route. Presented at the 5th European Skull Base Society Congress, Copenhagen, June 15–17, 2001 (abstr).

12.

Jho HD: Endoscopic transsphenoidal surgery, in Schmidek HH, Sweet WH, Schmidek and Sweet Operative Neurosurgical Techniques: Indications, Methods, and Results. Philadelphia, W.B. Saunders Co., 2000, ed 4, vol 1, pp 385–397.

13.

Jho HD, Carrau RL, Ko Y: Endoscopic pituitary surgery, in Rengachary SS, Wilkins RH (eds): Neurosurgical Operative Atlas. Park Ridge, AANS, 1996, vol 5, pp 1–12.

14.

Kaptain GJ, Vincent DA, Sheehan JP, Laws ER Jr: Transsphenoidal approaches for extracapsular resection of midline suprasellar and anterior cranial base lesions. Neurosurgery 49: 94–101, 2001.

15.

Kato T, Sawamura Y, Abe H, Nagashima M: Transsphenoidal-transtuberculum sellae approach for supradiaphragmatic tumours: Technical note. Acta Neurochir (Wien) 140: 715–719, 1998.

16.

Kim J, Choe I, Bak K, Kim C, Kim N, Jang Y: Transsphenoidal supradiaphragmatic intradural approach: Technical note. Minim Invasive Neurosurg 43: 33–37, 2000.

17.

Kouri JG, Chen MY, Watson JC, Oldfield EH: Resection of suprasellar tumors by using a modified transsphenoidal approach: Report of four cases. J Neurosurg 92: 1028–1035, 2000.

18.

Mason RB, Nieman LK, Doppman JL, Oldfield EH: Selective excision of adenomas originating in or extending into the pituitary stalk with preservation of pituitary function. J Neurosurg 87: 343–351, 1997.

19.

Perneczky A, Fries G: Endoscope-assisted brain surgery: Part 1—Evolution, basic concept, and current technique. Neurosurgery 42: 219–225, 1998.