Although presented over one hundred years ago, the transsphenoidal approach to pituitary adenoma is still the most suitable and safe route to pituitary adenoma, with a series of significant evolutional steps. The transsphenoidal approach to pituitary adenoma is still a non-universal approach used in different centers of different areas in our country. The transsphenoidal approach has a number of variations, including the endonasal rhinoseptoplastic, transnasal septal displacement, transnasal endoscopic, and sublabial transseptal approaches. Because of the bias inherent in neurosurgical training at different institutes and centers, the operative technique of transsphenoidal approach is not standardized.1-10 All of these options may confuse beginners.
In this article, we formulate the complete details of the transsphenoidal technique used at Peking Union Medical College Hospital (PUMCH). This protocol is routinely used in the surgical center for removal of pituitary adenoma and is designed to be simple and clear so the beginner can mastered it quickly. This protocol may help to generalize the transsphenoidal approach. Extensive transsphenoidal approach is beyond the scope of this article.
We report 4 116 cases using a transsphenoidal approach that have been done in the surgical center of PUMCH during the past 30 years for removal of pituitary adenoma. There were 1 496 males and 2 620 females. The patients' ages ranged from 7 years to 79 years (mean 36.7 years). There were 1 176 pituitary growth hormone adenomas, 1248 prolactinomas, 1024 non-functional pituitary adenomas, 512 pituitary adrenocorticotropic hormone adenomas and 156 other types of pituitary adenomas. The total cases included 1456 microadenomas, 2235 macroadenomas and 425 extra-macroadenomas.
We had used each variation of the transsphenoidal approach at PUMCH during different periods. A sublabial transseptal approach was used as the standard approach before 2002. Later, we used a transnasal approach as the standard approach except for an extensive transsphenoidal approach. At the beginning of a transnasal approach, an endonasal rhinoseptoplastic, transnasal septal displacement, or transnasal endoscopic approach was used according to the personal habit of the surgeon. Currently, we prefer the submucosal tunnel via an anterior mucosal incision as the standard method for a transnasal transsphenoidal approach. According to surgical results and complications, we developed a set of unified protocols using the transsphenoidal approach in the surgical center for pituitary adenoma at PUMCH.
We systematically reviewed the routine protocol for the transsphenoidal approach used in the surgical center for pituitary adenoma access at PUMCH. The operation could be divided into several parts, including positioning and preparation, surgical exposure, tumor removal and control of CSF leakage. Each part has its key technical points. Each key-point of the technique was concluded from clinical experiences including surgical results and complications.
According to surgical procedure, the whole technique of the transsphenoidal approach, from positioning and preparation, surgical exposure, tumor removal, to control of CSF leakage, is formulated objectively step by step in details. We will also discuss the reasons to performing this protocol of transsphenoidal approach.
Positioning and preparation
In our center, the patient is comfortably supine, with the upper half body elevated 20 degrees to 30 degrees and the head extended slightly (Figure 1A). The major surgeon stands at the right side of the patient, looking up into the nasopharynx. We position the microscope at a comfortable height and direction for the surgeon (Figure 1B).
The head is supported on a soft gel donut, which permits subtle adjustment of the head position to obtain an optimal field of view during the operation. Some surgeons prefer to immobilize the head using the Mayfield headrest with skeletal fixation; this is only used in situations of intraoperative navigation in our center. The lateral fluoroscope is not routinely positioned, except for a complicated sphenoidal sinus or for a patient with a history of septal or transsphenoidal surgery.
The retropharynx is packed with soft gauze to prevent blood from pooling. The perinasal skin is prepared with antiseptic solution and we irrigate the nasal cavity with Povidone Iodine, and administer a prophylactic antibiotic. The right thigh is prepared for harvesting of a fat graft. A routine stress-dose steroid coverage is provided with 100 mg of hydrocortisone, unless the patient has Cushing’s disease.
Using a long hand-held nasal speculum and the operative microscope under low power, we pack the nasal cavity and sphenoethoidal recess with cotton pieces, which are infiltrated with epinephrine and normal saline (1 mg/10 ml). Two minutes later, the cotton pieces would be taken out (Figure 2A).
In this approach, we prefer the submucosal tunnel via an anterior mucosal incision. An anterior hemitransfixion incision about 1.5 cm is performed in the mucosa near the conjunction of nasal skin and muscosa (Figure 2B) and extended back to the sphenoid rostrum through a submucosal tunnel (Figure 2C). During this step, the orientation in the sagittal plane can be confirmed using the trajectory provided by the middle turbinate or the location of the sphenoid ostia. The sphenoid ostia should be located in the anterior one-third of the ecarteur. As the septum is deviated, the contralateral mucosa over the rostrum is elevated and retracted. A self-retaining speculum is then placed with the leaves of the speculum on either side of the small remnant of the fractured bony septum (Figure 2D).
After the self-retaining speculum is in place, you can enter the sphenoid by fracturing the anterior wall with an osteotome and removal by grasping it with forceps. The bone is removed until it exposes the tuberculum sellae anteriorly, the clivus posteriorly and the eminence of carotid artery bilaterally. In the most cases, adjustment of the head position or the projection of the microscope will permit us to observe all of the above anatomic landmarkers.
We routinely exenterate the entire mucosa from the sphenoid, which will minimize the risk of a postoperative mucocele (Figure 2E). After incising the mucosa, the face of the sella can often be visualized (Figure 2F). Thinned bone can sometimes be outfractured using a small bone curet. The sphenoid may be incompletely pneumatized, especially in children, which will require drilling a channel to achieve an open pathway to the sella. You should apply intra operative navigation if the later condition is encountered.
Correlating the preoperative sagittal MRI with intraoperative anatomic landmarks is useful to plan the dural opening. We prefer an X-shaped dural opening with bipolar cauterization of the dural leaflets (Figure 2G). Before making the dural incision, we pierce it with a spinal needle to help ensure that the proposed incision is not over the carotid canal or an ectatic carotid artery.11-15
With a large macroadenoma, tumor will be seen immediately upon opening the dura (Figure 2H). Enter the tumor inferiorly using ring curets, and the tumor fragments are removed piecemeal using cup forceps. The tumor is removed inferiorly back to the dorsum, and then out laterally to either cavernous sinus. Continue dissection superiorly, up the lateral walls, until the attenuated diaphragm prolapses into the field. The normal pituitary is usually flattened posteriorly against the diaphragm or dorsum (Figure 2I). It can be recognized by its more yellow color and firmer consistency, and should be left intact if possible. Adenomas are usually soft and reddish gray, although growth hormone-secreting tumors can be almost white.
When exploring for a microadenoma, you can usually see the normal gland upon opening the dura. If you have visualized the tumor on the preoperative MRI, it can be approached by dissecting through the gland in the appropriate direction with a blunt probe, and then be removed with a small ring curet.
Hemostasis must be meticulous (Figure 2J), since the accumulation of even a small postoperative hematoma can be problematic in a confined space. Usually, packing with Surgicel will suffice. Bleeding from a large tumor will often cease as the tumor is completely removed. For difficult cases in which significant residual cavernous sinus or suprasellar tumor remains, an intrasphenoidal drainage tube should be required.
Control of cerebrospinal fluid leakage
Careful dissection and curettage will minimize the risk of a CSF leak, but intraoperative leakage may be inevitable. In the most cases, CSF leaks from the superior dural margin. Packing the tumor bed with autologous fat is usually sufficient to control the leak. Biological glue and collagen sponge have been used to buttress the fat in place. The patients should stay in bed for 5-14 days. We do not routinely place lumbar drainage for a CSF leak. Recently we use lyophilized dura and iodoform gauze to repair CSF leakage. In this procedure, normal dura mater beyond the place of CSF leakage should be exposed. We then buttress lyophilized dura in place by iodoform gauze. In 5 days to 10 days after the operation, the iodoform gauze is taken out with a neural endoscope, and we find the CSF leakage to be quite well healed. Lumbar drainage and lying in bed are not required. We do not routinely pack the sphenoid sinus but would do so if the repair was tenuous.16,17
The septum can be returned to the midline and mucosa returned to its position. The nostril is packed using oiled gauze. The packing is removed on the first postoperative morning (Figure 2L).
Although the operative technique of transsphenoidal approach is not standardized and the transsphenoidal approach has a number of iterations, the unified protocol for transsphenoidal approach to pituitary adenoma, formulated in the surgical center of PUMCH, is clear and simple. Each step plays an important role in the operation. Ignoring even a little step may lead to disaster.
Careful positioning of the patient is critical. Poor positioning could cause problems during the operation. The operative site is above the level of right atrium, which facilitates venous drainage of the sella and sphenoid sinus, therefore reduces bleeding. Venous air embolism is not a major concern.
Adjustment of the head position or the projection of the microscope permits us to correct the operative trajectory according to anatomic landmarks exposed during operation. The procedure is extremely suitable for inexperienced surgeons attempting a transsphenoidal approach.
It should be understood that the relative projective angle between the microscope and patient determines the field of view under the microscope. We define the relative angle between the projective direction of the microscope and the body side of the patient as the projective angle. The field of view under microscope is adjusted to the anterior (sellar tuberculum) when there is less projective angle or more head extension. With a larger projective angle or less head extension, the field of view is turned to the posterior (clivus). Laterally tilting the projection of the microscope from right to left, the field of view is adjusted to the left. Alteratively, the field of view can be turned to the right. Adjustment of the head position leads to similar effects.
Even with diminished bleeding, routine packing of the oropharynx is necessary, for we could not correctly estimate the bleeding volume before the operation. Packing the nasal cavity and sphenoethoidal recess with cotton pieces is an important step, which is easily ignored. During this manipulation, we could determine the position and direction of the middle nasal concha and sphenoethmoidal recess. Careful packing can push away the middle and superior nasal concha and provide a wider operative corridor and epinephrine is used to reduce bleeding of the nasal mucosa.
Correct midline orientation is provided by the location of the keel of the rostrum. A midline approach is crucial to prevent inadvertent damage to perisellar structures, especially the cavernous sinus, carotid artery, and optic canal.18-20 It is very important to identify the correct anatomic landmarks including the middle turbinate, the sphenoid ostia and the keel of the rostrum. Those would help us to recognize the correct midline and establish our orientation in the sagittal plane.
Even in those patients with small nostrils, an endonasal approach could provide adequate direct visualization. The sublabial approach was only used in an extensive transsphenoidal approach to offer a wider field of view.
Knowledge of the bony anatomy of the sphenoid is useful in maintaining the correct orientation. This anatomy can be determined from preoperative CT or MR scanning. Septations within the sphenoid are individual and variable, but correct midline orientation can be maintained by correlating their intraoperative position with preoperative imaging studies.
If the sella is partially empty, plan the dural opening sufficiently inferiorly on the face of the sella to allow entrance into tissue, not into the suprasellar cistern. With larger tumors, this is less important, although entry into the anterior recess of the suprasellar cistern along the superior margin of the sella may still cause CSF leakage. You can sometimes identify cystic fluid or CSF through the dura as a bluish tint. The dural face of a small sella, explored for a microadenoma, may contain venous channels or the intercavernous (circular) sinus. It is worth planning the dural opening to allow cauterization of these channels if possible, since the search for a microadenoma requires absolute hemostasis.
It is usually safer to divide the tumor bluntly by curettage rather than biting it away with cup forceps, as undue traction on a tenacious tumor may damage surrounding structures. Removal of large tumors can be difficult if the tumor does not deliver itself or is of fibrous consistency. Delivery of the suprasellar tumor can sometimes be achieved by breath holding. A staged resection can sometimes be beneficial for situations in which the suprasellar remnant does not descend during the initial procedure, since CSF pulsation over time may slowly force it into the sella where it can be resected in a second procedure. A side-angled curet introduced into the suprasellar space in an attempt to sweep down residual suprasellar tumor is dangerous. Tumors are sometimes very firm and vascular, and these can be difficult both to remove and to separate from the compressed normal gland.
By using lyophilized dura and iodoform gauze to repair CSF leakage, problems with CSF leakage have become less important in our center. We seldom harvest autologous fat and we do not require lumbar drainage and an extended period of bed rest.
The routine protocol for transsphenoidal approach to pituitary adenoma, which we use in the surgical center at PUMCH, is clear and simple. In the surgical center of PUMCH, new surgeons can master the protocol within three months. With the protocol, transsphenoidal surgery is safe and effective in the management of pituitary adenoma, with acceptably low risks.21 Although it needs to be emphasize that each step plays an important role in the operation and even a little deviation may lead to disaster.
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