Modern pituitary surgery using a transsphenoidal approach is relatively noninvasive, as it utilizes the nasal passages and regular sinus anatomy to reach the sella. Successful treatment requires the surgeon to navigate to the sella and visualize the lesion through a relatively narrow corridor with minimal damage to the surrounding tissues (sinonasal anatomy, nonadenomatous pituitary), while removing the tumor as completely as possible. Thus, a profound knowledge of the nasal anatomy and its variations is crucial.
Imaging
Imaging consists of MRI with a focus on sellar pathologies, including T1 sequences in three planes (axial, coronal, sagittal) with and without contrast enhancement. Additionally, dynamic contrast sequences should be obtained in cases of microadenomas. Individual anatomy has to be analyzed in every case, including size and location of the sphenoid sinus, its septations, the carotid arteries, and the attachment of the nasal septum to the anterior wall of the sphenoid sinus.
Particularly for less experienced transsphenoidal surgeons, intraoperative fluoroscopy and/or neuronavigation may be helpful and can prevent a too superiorly located approach toward the sphenoid plane and the risk of cerebrospinal fluid (CSF) leakage. CT and/or image guidance is especially helpful in cases of recurrence. ▶Fig. 7.1, ▶Fig. 7.2, ▶Fig. 7.3, ▶Fig. 7.4, ▶Fig. 7.5, ▶Fig. 7.6, ▶Fig. 7.7, ▶Fig. 7.8, ▶Fig. 7.9, ▶Fig. 7.10, ▶Fig. 7.11, ▶Fig. 7.12, and ▶Fig. 7.13).
Fig. 7.1 (a, b) Positioning and draping. A patient undergoing microsurgical, endonasal transsphenoidal surgery is positioned strictly supine. It is recommended not to turn the head, which is placed in a horseshoe (or equivalent) and reclined slightly to achieve a vertical approach to the sella. The plane of the table is tilted to raise the level of the patient’s head above her/his heart, in order to reduce venous bleeding. The surgeon’s position is straight behind the patient, as for most cranial procedures.In our department, draping (with a nontransparent drape) leaves only the nose uncovered. Different draping methods are possible, many of which leave the patient’s face cleaned and at least partly uncovered (usual in ENT rhinosurgery, which allows intraoperative access to the eyes).Fig. 7.2 (a, b) Nasal inspection and lateralization of the middle turbinate. View of the patient in the supine position; the surgeon stands behind the patient’s head. Right-handed surgeons usually use the right nostril for the endonasal transsphenoidal approach. As anatomical variations within the nose might mean that the other nostril should be chosen, initial inspection of both nostrils is suggested.After inspection of the nasal cavity, the middle turbinate is identified as the landmark and is lateralized in order to gain space within the nose. The speculum can be used to mobilize and push the turbinate laterally. In the endonasal approach, the anterior sphenoid wall is directly exposed without any incision into the septal mucosa. To make sure that the orientation is correct, fluoroscopy, image guidance, or orientation via nasal anatomy can be used. The choanae can be visualized as the most inferior structure and guide the surgeon’s way more cranially to the anterior sphenoid wall and to the sphenoid ostium.Fig. 7.3 (a, b) Identification of the sphenoid ostium. The orientation of the nasal speculum should not exceed a 20° angle to the bony palate. At the level of the middle turbinate, the sphenoid ostium (marked with an arrow) can be found and inspected. After definitive identification of the right sphenoid ostium, the mucosal dissection is carried on from the ostium in a caudal direction, including coagulation of the septal mucosal membrane and identification of the cartilage and vomer.If CSF leakage was observed during surgery, a lumbar drain is placed at the level of L4/L5 immediately after surgery and kept in place for 3 to 5 days. A daily drainage of 120-mL CSF is recommended.Fig. 7.4 (a, b) Mobilization of the nasal septum. As the septum is now mobilized from its mucosal layer, the speculum is used to crack the posterior bone of the nasal septum to the contralateral side. This reveals the vomer, shaped like a ship’s keel. Further, the contralateral sphenoid ostium becomes visible.Fig. 7.5 (a, b) Partial removal of the vomer—opening the sphenoid sinus. After identification of the vomer and both sphenoid ostia, a Kerrison punch is used to combine the sphenoid ostia and remove the superior part of the vomer. Now the more lateral section of the anterior sphenoid wall is opened in a downward direction, using a Kerrison punch. After disconnection of the bony anterior sphenoid wall, the vomer is removed using Blakesley grasping forceps and kept for later reconstruction.Fig. 7.6 (a, b) Lateral extension of the sphenoid opening. The approach has to be extended more laterally (arrows) by further resection of the anterior sphenoid wall, using different punches. Extending the approach laterally often leads to bleeding from sphenopalatine artery branches, which can be easily controlled by bipolar coagulation.Fig. 7.7 (a, b) Superior extension of the sphenoid opening. Using standard curettes, the lateral and superior extension of the approach can be verified and extended, if necessary. This palpation secures a sufficient exposure cranially and allows identification of the tuberculum sellae in lesions with suprasellar extension.Fig. 7.8 (a, b) Removal of the sellar floor. After removal of the sphenoid mucosa, the complete floor of the sella is visualized and the bony floor can be resected with punches. Note that the opening should be tailored to the size of the adenoma. The lateral opening of the sellar floor should extend to the cavernous sinus, which can be identified by both its blueish color and often a dural ridge. The carotid artery is located just laterally. Cranially, it is recommended to leave a small bony rim to cover the dural reflection to avoid CSF leakage.Fig. 7.9 (a, b) Opening the endosteum (dura) and removal of the adenoma. Following bipolar coagulation, the endosteum/sellar dura is opened in a cruciate fashion. Care is taken not to incise too cranially, as this may open the dural duplication anterior to the pituitary gland (CSF leakage!). Usually, the adenoma prolapses through the incision as a sign of elevated intrasellar pressure. Pulsation of the brain will push the grayish adenoma tissue toward the opening. Blunt curettes are used to dissect the tumor and anterograde movement of the instruments toward sellar structures is applied, instead of pulling in the direction of the surgeon. It is recommended to start the dissection of the adenoma inferiorly and then proceed laterally. In infiltrative tumors, the noninfiltrated side is dissected first, as opening of the cavernous sinus causes venous bleeding. To reach the more cranial portions of adenomas, various maneuvers have been applied (compression of jugular veins or saline injections to the subarachnoid space). In our experience, gentle manipulation of the adenoma and diligent dissection in tissue planes is sufficient. Sometimes, a pseudocapsule can be helpful.Fig. 7.10 (a, b) Hemostasis. Hemostasis can be achieved through bipolar coagulation if needed. Blood oozing from the cavernous sinus is easily stopped with small pieces of Gelfoam, placed laterally on each side of the sella. Temporary compression with cottonoids and/or elevation of the head may be required.Fig. 7.11 (a, b) Reconstruction of the sellar floor—closure. Methods of reconstruction and closure of the sellar floor are still a matter of debate and range from no specific closure (in the absence of CSF leakage intraoperatively) to routine use of subcutaneous fat from the abdomen or fascia lata. As the latter adds to the overall risk of morbidity of the procedure, we use Gelfoam and fibrin sealant-coated collagen fleece (arrow), which is stuck to the diaphragm to prevent CSF leakage. For closure of the dura and the sellar floor, the coated collagen fleece and autologous bone (double arrow), harvested during opening, is applied. Most importantly, the piece of bone is interlocked with the bone of the sellar floor to achieve a robust buttress and keep the applied materials in place.Fig. 7.12 (a, b) Repositioning of the nasal septum and the middle turbinate. After removal of the speculum, the septum is repositioned medially and inspected meticulously. Iatrogenic damage to the septum may occur, although it is very rare, and needs to be readapted with absorbable sutures. Finally, the middle turbinate is repositioned in order to prevent an artificial recess with accumulation of blood and mucosal exudate.Fig. 7.13 (a, b) Placement of tamponades—finish line. Finally, two tubed tamponades can be used for gentle nasal packing to prevent blood oozing from the nasal mucosa. These are placed using the speculum and remain for approximately 24 hours.
Checklist
Use fluoroscopy or image guidance in anatomical variants and recurrent tumor surgery.
Inspect both nostrils to identify anatomical variations and pathological obstructions.
To find the sphenoid ostium, work your way up from the choana to the anterior wall of the sphenoid sinus.
Aim to remove the anterior sphenoid wall (or a sphenoid septum) in one piece—and retain harvested bone for closure.
Make sure your sphenoid opening does not extend too far cranially—use curettes to check cranial (and lateral) extension.
Perform hemostasis before opening the dura.
Cavernous sinus bleeding can easily be controlled using Gelfoam and head elevation.
Reconstruction of the sellar floor should be done meticulously to prevent CSF leakage.
Repositioning of the middle turbinate and the nasal septum is mandatory.
In case of intraoperative CSF leakage, use lumbar CSF drainage for 3 to 5 days.
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