Usefulness of the Three-step Simple Binostril Approach in Endoscopic Endonasal Transsphenoidal Surgery

Abstract

We describe a three-step, simple binostril approach to endoscopic endonasal transsphenoidal surgery in cases of sellar/parasellar lesions. In the first step, the mucosa of the lower third of the ethmoid bulla on the outside was coagulated with monopolar microdissection needle and opened to create space on the outside of the middle turbinate. The middle turbinate was moved outward using this space, and the natural ostium of the sphenoid sinus could be confirmed easily. In the second step, a less than 10 mm incision was made from the right natural ostium of the sphenoid sinus to the right nasal septal mucosa. The anterior wall of the sphenoid sinus was removed to free the sphenoid sinus. In the third step, the instrument was inserted through the left nostril using a hole connected to the natural ostium of the sphenoid sinus to reach the sellar floor via both nostrils. It took longer for the trainee than for the instructor to reach the sellar floor in the first four cases. However, there was no significant difference in the approach time after the fifth case. Approach-related postoperative complications were observed in 52 cases of sellar/parasellar lesions performed. This approach was considered to provide sufficient space and was simple and less burdensome to the patient.

Introduction

Endoscopic endonasal transsphenoidal surgery (ETSS) has recently become mainstream for lesions in the sellar and parasellar areas. Compared to microscopic transsphenoidal surgery, ETSS allows for a wider view of the sella turcica and surrounding area and produces better surgical results with fewer complications due to less damage to the mucosa in the nasal cavity.^1-3) However, it requires operating in a confined workspace and mastering techniques to avoid interference of instruments in the nasal cavity while maintaining intraoperative clarity of vision.⁴⁾ There are two approaches to reaching the sellar floor with ETSS: the binostril and mononostril approaches. Both approaches are effective and safe, but the binostril approach is considered useful for large tumors and tumors that invade the parasellar region or cavernous sinus.⁵⁾ The binostril approach is easy, even for beginners, because of its large operating space, but the mucosal incision is complex. Furthermore, because of the wide incision in the nasal mucosa, postoperative patient satisfaction has been reportedly lower than that with the unilateral nasal method.⁶⁾ Conversely, the mononostril approach is less invasive to the patient than the binostril approach because the sellar floor can be reached in a shorter time while maintaining the nasal mucosa on one side. The operation is limited, however, by the narrow surgical space and interference between instruments. This method is particularly difficult to manipulate when surgery requires ipsilateral enlargement around the sellar floor.⁵⁾ When one of the authors performed two cases of ETSS for the first time in January 2019 using the conventional binostril approach, they had difficulty obtaining a clear field of view and manipulating the instruments in the narrow space within the nasal cavity. Therefore, a three-step simple binostril approach was developed, which was proven simple and easy to operate in the nasal cavity. Using this approach, we report that the technique can be easily learned by a beginner in a short period and can be performed safely.

Case Report

This study was performed in accordance with the Declaration of Helsinki and was approved by the ethics committee of our hospital (approval number: 2020028). Written informed consent was obtained from all participants. Study data were retrospectively evaluated from 52 cases of sellar/parasellar lesions treated with a three-step simple binostril approach performed by trainees at Fukuoka Neurosurgical Hospital from January 2019 to December 2021. Of these, 36 cases treated from January 2019 to December 2020 were compared by measuring the approach time between operators with different experience levels during the same period. Approach time was defined as the time from the start of surgery to just before the start of the opening of the sellar floor. Patients were observed for at least 6 months postoperatively. Statistical analysis was performed using IBM SPSS analysis 24 (IBM Corp., Armonk, NY, USA). The Kruskal-Wallis test was used to compare the approach times of the three groups of surgeons. Comparisons between groups were calculated using the Dunn test and modified using the Bonferroni method. P < 0.05 was considered statistically significant.

Surgical procedures(three-step simple binostril approach)

The endoscope system used involved a VISERA 4K UHD (Olympus, Tokyo, Japan) rigid speculum with a 4 mm outer diameter and 0° or 30° viewing angle. An EndoArm (Olympus, Tokyo, Japan) was used as the endoscope-holding device. The endoscope was fixed to the EndoArm, and an assistant helped with endoscope manipulation, as needed. A nasal speculum was not used in all cases. Under general anesthesia, the patient's upper body was raised by 20°, and the head was tilted 20° toward the left shoulder in a circular seat with the right rotation unfixed.

The three-step simple binostril approach

In the first step, an endoscope was inserted into the right nasal cavity, the right middle turbinate was moved inward, and the mucosa of the lower third of the ethmoid bulla on the outside was coagulated with monopolar and opened to create space on the outside of the middle turbinate. The middle turbinate was moved outward using this space, and the lower end of the upper turbinate was visible. Then, the location of the natural ostium of the sphenoid sinus could be confirmed at the medial lower end of the superior turbinate (Fig. 1A-D). In the second step, a less than 10 mm C-shaped incision was made with a monopolar from the right natural ostium of the sphenoid sinus to the right nasal septal mucosa. At that time, the lower end of the superior turbinate, which is outside the right natural ostium of the sphenoid sinus, was continuously dissected. The incised mucosa was flipped to the pharyngeal side, and the bilateral sphenoid natural ostium was contiguous without any incision at all in the left nasal septal mucosa. The anterior wall of the sphenoid sinus and ethmoid perpendicular plate were removed to free the sphenoid sinus (Fig. 1E-H). In the third step, relying on the light from the endoscope inserted into the right nasal cavity, the instrument was inserted using a hole in the mucosa continuous with the left sphenoid natural ostium via the left nostril. Normally, the left nasal septal mucosa was not incised (Fig. 1I, J). If there was no hole to the natural ostium in the mucosa of the anterior wall of the sphenoid sinus continuous with the left nasal septal mucosa or if the depth of the sphenoid sinus was less, a vertical incision (roughly measuring 10 mm) was made on the side of the right nasal septal mucosa exposed in front of the incision, and the instrument was inserted through the left nostril (Fig. 1K, L). The instrument was inserted through both nostrils to remove the septum in the sphenoid sinus and reach the sellar floor. These three steps provided the same visibility and maneuverability as the conventional binostril approach technique and allowed the resection of the sella turcica and surrounding lesions (Fig. 1M-T).

Fig. 1.

Step 1

The natural ostium of the medial inferior end of the superior nasal turbinate cannot be seen through the narrow right nasal cavity (A). The middle turbinate can be easily moved medially, and the ethmoid bulla can be seen on its outer side (B). When the mucosa of the lower third of the ethmoid bulla is coagulated with monopolar and opened, a space is created outside the middle turbinate (C). Moving the middle turbinate outward, the lower end of the superior turbinate can be seen, and the sphenoid ostium on the medial side can be identified (D).

Step 2

A less than 10 mm C-shaped incision was made with a monopolar from the right natural ostium of the sphenoid sinus to the right nasal septal mucosa (E, F). The C-shaped right nasal septal mucosa and the lower edge of the superior turbinate on the outside of the right sphenoid ostium are continuously transected (G). The ethmoid perpendicular plate and the anterior wall of the sphenoid sinus were removed without any incision in the left nasal septal mucosa (H).

Step 3

Relying on the light from the endoscope inserted into the right nasal cavity, the instrument is inserted through a hole in the mucosa continuous with the left sphenoid natural mouth via the left nostril (I). Instrument inserted via the left sphenoid natural ostium (J). In some cases, a vertical incision of approximately 10 mm was made in the right and left nasal septal mucosa (K). Instrument inserted via a vertical incision made in the left nasal septal mucosa (L).

Instrument inserted via the left sphenoid natural ostium, lateral to the left nasal septal mucosa (M). An instrument inserted via a vertical incision made in the left nasal septal mucosa moves the left nasal septal mucosa outward (N). In most cases, deep manipulation is possible with instruments inserted via the left sphenoid natural ostium (O). The left nasal septal mucosa, which is completely preserved after tumor removal, and the right nasal septal mucosa, which is mostly preserved, can be observed from the right nasal cavity (P, Q). There is little or no mucosal damage in the left nasal cavity (R). T1-weighted magnetic resonance imaging with contrast of a representative case preoperatively (S) and 6 months postoperatively (T) shows that the tumor has been gross totally resected.

a: right inferior turbinate; b: right middle turbinate; c: right nasal septal mucosa; d: right ethmoid bulla; e: right superior turbinate; f: nasal septum; g: anterior wall of the sphenoid sinus; h: left nasal septal mucosa; i: vomer; j: instrument inserted through the left sphenoidal natural ostium; k: instrument inserted via a vertical incision made in the left nasal septum; l: tumor; m: arachnoid hanging down from the cranial side; n: tumor removal cavity

arrow: ostium of the right sphenoid sinus

dotted arrow: incision line of the right nasal septal mucosa

dashed arrow: vertical incision made in the left nasal septal mucosa

Results

From January 2019 to December 2021, 52 ETSSs were performed by a trainee using the three-step simple binostril approach, including 28 pituitary adenomas, 18 Rathke's cleft cysts, 3 meningiomas of the tuberculum sellae, 1 meningioma of the cavernous sinus, 1 arachnoid cyst, and 1 nasopharyngeal cancer. Among 28 cases of pituitary adenoma, 13 (46.4%) were Knosp grade 1, 7 (25.0%) were grade 2, 7 (25.0%) were grade 3, 1 was (3.6%) grade 4, and 0 were grade 0; 22 (78.6%) cases were nonfunctioning pituitary adenomas, and 6 (21.4%) were functional adenomas. The functional adenomas included three GH-producing tumors, two ACTH-producing adenomas, and one PRL-producing adenoma. Gross total resection (GTR) was achieved in 25 patients (89.3%), with 1 Knosp grade 4 and 2 Knosp grade 3 patients having subtotal resection (STR). In Knosp grades 0-2, GTR was achieved in all 20 patients (100%), and in Knosp grades 3-4, 5 of 8 patients (62.5%) had GTR. In addition, one of six patients (16.7%) with functional pituitary adenoma had a residual tumor and underwent reoperation later. All (100%) of the 14 patients with preoperative visual abnormalities had normalized or improved visual function, and none had postoperative worsening of visual function. There was one case (3.6%) of permanent diabetes insipidus after surgery. There were no cases of postoperative cerebrospinal fluid (CSF) leak, meningitis, postoperative bleeding requiring surgery, or postoperative arterial intranasal hemorrhage. All Rathke's cleft cysts were treated by opening the cyst and cleaning the inside of the cyst. No cases of postoperative CSF leak, DI, meningitis, hemorrhage, or epistaxis were observed, and no cases required reoperation. Meningiomas in the tuberculum sellae were GTR in all three cases, and a meningioma in the cavernous sinus and a nasopharyngeal carcinoma were partial resections. All 52 patients did not complain of an abnormal sense of smell or nasal discomfort 1 month after surgery. Figure 2 shows the approach time per surgeon for 49 consecutive cases (Case no. 1-49) performed using the three-step simple binostril approach. The same surgeon was in charge from the beginning to the end of the surgery. All surgeons were neurosurgeons. A trainee who was a beginner in ETSS performed 36 cases, 8 were performed by an instructor who had performed approximately 1000 ETSS cases, and 5 were performed by 2 residents who were beginners in ETSS. The average approach time was 34.6 min (SD, 15.4 min; range, 18-100 min) for the trainee, 27.8 min (SD, 9.3 min; range, 9-37 min) for the instructor, and 56.4 min (SD, 13.5 min; range, 41-68 min) for the residents. An experienced ETSS instructor had shorter approach times immediately after introducing the three-step simple binostril approach. A trainee physician had significantly longer approach times in the first four cases (mean, 66.5 min; SD, 20.2 min; range, 47-100 min; p = 0.018), but there was no significant difference after the fifth case (mean, 30.6 min; SD, 8.6 min; range, 18-48 min; p = 1). Trainees' approach times after the fifth case were significantly shorter than those of the initial four cases (p = 0.006) (Fig. 3). After the trainees' fifth case, three cases (no. 21, 24, and 29) were slightly outside the range of the instructor's approach time (the gray area in Fig. 2). Cases 21 and 29 were anatomically complex, with many septa in the sphenoid sinus. In case 24, the tumor had spread to the anterior cranial base, so the expansion technique was used. The approach times for the first two cases performed by a trainee using the conventional binostril approach before introducing the three-step simple binostril approach were 65 and 92 min.

Fig. 2.

The figure shows 49 consecutive approaches of approach time by one trainee, one instructor, and two residents.

Fig. 3.

Group A shows the approach time of eight cases by one instructor. Group B shows the approach time of the initial four cases by one trainee. Group C shows the approach time of 32 late cases by one trainee.

The trainee took longer to reach the sellar floor in the first four cases compared with the supervisor (mean, 66.5 min; SD, 20.2 min; range, 47–100 min; p = 0.018), but there was no significant difference after the fifth case (mean, 30.6 min; SD, 8.6 min; range, 18–48 min; p = 1). The approach time was significantly shorter than the initial four cases (p = 0.006).

Discussion

The binostril approach in ETSS provides wide operating space compared to the mononostril approach. The binostril approach is versatile, especially for lesions in the suprasellar and parasellar area.^3,7) Conversely, postoperative epistaxis, olfactory disturbances, and nasal discomfort are concerns due to the extent of mucosal damage in the nasal cavity. Furthermore, this procedure requires more time than the mononostril approach because of the complex mucosal incision.⁵⁾ The mononostril approach has the advantage of less mucosal damage to the nasal cavity and a shorter time to reach the sellar floor.^5,7) However, the target diseases are limited because of the small surgical space, and it is difficult to operate in-depth, especially for ETSS beginners. In other words, a beginner suffers from the narrow nasal operating space in the mononostril approach and the complicated mucous membrane incision in the binostril approach. When transitioning from microscopic surgery to endoscopic surgery, it has been reported that the patient mainly has difficulty with nasal manipulation in the early stages of the approach.^8,9) Therefore, we devised a three-step simple binostril approach, which is easier and more effective in learning to perform nasal manipulation even for ETSS beginners and is less invasive than the conventional binostril approach. In the first step of ETSS, an endoscope should be inserted into the nasal cavity to achieve the natural ostium of the sphenoid sinus, and we aim for the natural ostium of the sphenoid sinus after inserting the endoscope into the nasal cavity. The method reported by Yano et al.¹⁰⁾ requires packing epinephrine cotton between the middle turbinate and nasal septum to dislocate the middle turbinate outward. In this process, beginners have challenges because of the increased bleeding from the mucosa and obstruction of vision if pressure is forced, and the risk of going in the wrong direction if the orientation of the natural ostium is not obtained. Conversely, the ethmoid bulla on the outer side of the middle turbinate can be easily opened. Because the middle nasal turbinate can be moved significantly outward by this procedure, the natural ostium of the sphenoid sinus can be easily seen at the medial inferior end of the superior turbinate, allowing for a smooth procedure in the following steps (Fig. 1A-D). In other words, the opening of the ethmoid bulla in the first step is the most important step in the three-step simple binostril approach. Furthermore, although compression with epinephrine cotton may cause elevation of blood pressure¹¹⁾ and abrasion of the mucosa, our method does not require epinephrine cotton. The second step in our approach is characterized by a small incision of less than 10 mm in the right nasal septal mucosa without incising the left nasal septal mucosa and by the dissection of the inferior end of the superior turbinate in continuity with the nasal septal mucosa incision. The incision area of the nasal septal mucosa can be smaller than that in previous reports because the lower end of the superior nasal turbinate is separated, which increases the operating space.¹⁰⁾ Furthermore, it prevents damage to the sphenopalatine artery when the incised mucosa is flipped caudally (Fig. 1E-H). In our approach, the endoscope remains inserted in the right nasal cavity even in the third step and does not need to be inserted through the left nasal cavity. In our method, the deep left nasal septal mucosa is not dissected as reported by Yano et al.,¹⁰⁾ but the instrument is inserted through the left nostril using the foramen of the mucosa that is continuous with the left sphenoid natural ostium (Fig. 1I, J). If there is no hole in the mucosa leading to the natural ostium or if the depth of the sphenoid sinus is shallow, instruments can also be inserted through the left nostril by making a 10 mm vertical incision using a sickle-shaped scalpel in front of the left nasal septal mucosa exposed in the right nasal cavity. This approach is a modification of the one-and-a-half nostril approach reported by Wen et al.,¹²⁾ but our approach involves a smaller incision in the right nasal septum and is a simpler procedure (Fig. 1K, L). The instrument can be inserted through both nostrils to remove the septum of the sphenoid sinus and reach the sellar floor with the same field of view and maneuverability as a conventional bilateral nasal approach. We performed the three-step simple binostril approach without changing the extent of the mucosal incision or the procedure, regardless of the size of the lesion or the nasal cavity configuration, to enhance the learning effect. As a result, a trainee who was a beginner in ETSS was able to achieve the similar approach times as the instructor after the fifth case (Figs. 2 and 3). The surgical outcomes and complications of 28 pituitary adenomas performed by the trainee were similar to those reported in the previous literature.^12-28) The binostril approach has been reported to cause higher rates of postoperative epistaxis and olfactory disturbances than the mononostril approach.^7,14,29-31) In this series, there were no cases of postoperative arterial epistaxis or olfactory dysfunction 1 month after surgery, suggesting that the three-step simple binostril approach may be less invasive than the conventional bilateral nasal approach.

Conflicts of Interest Disclosure

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial or nonfinancial interest in the subject matter or materials discussed in this manuscript.