Endoscopic Endonasal Trans-sphenoidal Approach: Minimally Invasive Surgery for Pituitary Adenomas

The protocol here illustrated follows the guidelines of the human research ethics committee at the University Hospital of Lausanne.

NOTE: The procedure explained here is focused on the classical approach performed for pituitary adenomas.

1. Preoperative Protocol

1. Systematically perform a pre-operative craniofacial CT-Scan and MRI, along with the endocrinological and ophthalmological assessments.

2. Positioning and Anesthesia

1. Induce general anesthesia and perform orotracheal intubation.
2. Place the patient in the supine position after general anesthesia and orotracheal intubation.
3. Position the head in a head holder and secure the band for the magnetic neuro-navigation around the head.
4. Raise the head of the table to 20 ° to improve venous drainage and slightly rotate the head about 30 ° towards the neurosurgeon, while performing a contralateral head tilt.
   NOTE: The degree of extension or flexion of the patient's head depends upon the surgical target: slightly flexed (15 – 20 °)¹⁷ for the sella turcica approach, neutral for anterior skull base surgery, and flexed up to 45 ° for lower clival lesions.
5. Sterilize the face with an alcohol-free chlorexidine solution. Clean the nasal fossae with an antiseptic solution before wicking with cotton pads impregnated with diluted Xylocaine 1% with adrenaline (1:1,000,000).
   NOTE: In addition to the local anesthesia and vasoconstriction, this wicking also provides a lateral retraction of the middle turbinate to enable the endoscopic approach. An adjustable holding arm may be fixed to the operating table to be used at specific phases of the surgical procedure (particularly during the sellar phase). However, some surgeons prefer not to fix the endoscope to have a more dynamic view of the surgical field. In these cases, they either leave the endoscope to the assistant to enable work with both hands or they hold the endoscope themselves.
6. Clean the right abdominal quadrants and drape the abdomen while leaving a small window in the right peri-umbilical region as it represents a possible site of fat graft harvesting in the case of an intra-operative cerebrospinal fluid (CSF) fistula.
   NOTE: Anesthesiologists should take special care for deep morphinic analgesia and control the mean blood pressure during the nasal phase of the procedure, to reduce the bleeding due to the rich innervation of the nasal mucosa.

3. Surgery

NOTE: The choice of the side of the nasal fossa to be used primarily is determined by the nasal anatomy (septal deviation, mega-turbinate, polyps, previous surgeries, etc.), lateral extensions of the tumor (contralateral approach to a lateral extension), and the size of the tumor (binostril approach for large tumors). In the majority of pituitary adenomas, a unilateral approach is sufficient to achieve a good exposure of the tumor and its extensions.

1. Nasal phase
   1. Introduce the 0 ° short rigid endoscope (18 cm length, 4 mm diameter) into the right nostril to identify the inferior and middle turbinates laterally and the nasal septum medially. Prefer the left nostril approach in case of septal deviations, anomalies of the turbinates, or for specific tumor extensions that are detected in pre-operative imaging.
   2. Place the endoscope tube either at the superior or inferior aspect of the nostril to provide enough space to other instruments entering the nasal cavity.
   3. Gently retract laterally the middle and superior turbinates with a blunt spatula to achieve a wide access to the ipsilateral sphenoid ostium. Take care to support the superior and middle turbinates through their entire length with the spatula to avoid fractures during the retraction maneuver.
2. Sphenoidal phase
   1. Coagulate the nasal mucosa in a vertical linear fashion for about 10-15 mm with a monopolar between the sphenoid osteum and the choana, to avoid bleeding from the nasoseptal arteries (branches of the sphenopalatine arteries running at the superior margin of the choana).
   2. Open the coagulated nasal mucosa with a blunt spatula vertically until a bony contact, corresponding to the vomer, is felt.
   3. Follow the vomer anteriorly until its junction with the nasal cartilaginous septum and push it to the left side to expose the contralateral sphenoid ostium, while taking care to remain in the submucosal plane.
   4. Expose and remove the sphenoid rostrum with bone forceps and a rongeur extending the resection from one ostium to the other. This opening of the sphenoid sinus allows exposure of the exocranial skull base surface.
   5. Gently remove the sphenoid mucosa if it interferes with the sellar opening.
   6. Remove the sphenoid septum (often multiple septa are present) with rongeurs to provide a wide exposure of the sella turcica.
   7. Carefully analyze the pre-operative magnetic resonance imaging (MRI) and/or CT scan for the number and direction of these septations; this is crucial to recognize the relevant anatomy. Some of these septations may insert directly onto the carotid prominences and therefore should be identified as important landmarks during this phase of the surgery (Figure 1, Figure 2, Figure 3, Figure 4).
      NOTE: The CT-scan was performed using a 64-detector row-based system. Three-dimensional reconstruction was processed using a series of thin-slice data. The MRI protocol was performed on a 3-Tesla imager. The protocol included a sagittal T1-weighted gradient-echo sequence (MPRAGE) with and without contrast injection, 160 contiguous slices, 1-mm isotropic voxel, repetition time (TR) 2,300 ms, echo time (TE) 2.98 ms, field of view 256 mm as a basis for segmentation, and 3D T2 sequence.
3. Sellar phase
   1. Identify the sella turcica anterior and superior to the clival recess in the midline.
      NOTE: In large and/or invasive pituitary tumors, the sellar floor may be very thin or completely eroded. The sellar floor is limited anteriorly by the depression that corresponds to the tuberculum sellae and laterally by the carotid prominences (C3 to C5 segments) and by the optico-carotid recesses.
   2. After identification of the carotid prominences laterally, open the sellar floor with a 5-mm large bone cutter to tailor or hinge a bone flap that may be repositioned at the end of the surgery. At this point, enlarge the sellar osteotomy laterally or anteriorly with bone rongeurs, according to the surgical target.
      NOTE: Some surgeons may prefer to open the sellar floor with a diamond drill and to enlarge the bone opening secondarily with a small bone rongeur. This procedure may be faster and it is generally used with extended approaches. However, the bone cannot be repositioned at the end of the procedure and attention should be paid to drill in the midline to avoid injuries to the carotid artery. Use neuronavigation to guide the procedure.
   3. Open the sellar dura with a micro-blade in the midline for a macroadenoma or laterally in cases of lateralized microadenomas. If needed, extend this dural opening laterally and take care to avoid any injury to the carotid arteries.
   4. Limit the risk of arachnoid breaches in the anterior recess by performing a small anterior opening of the dura and push up the dura with the suction tip to provide sufficient access to the sellar contents.
   5. Remove the tumor tissue with annular angled curettes, forceps, and suction tips.
   6. After an intra-sellar saline wash-out, use the 30 ° angled endoscope to inspect the intrasellar space and check for any remnant, particularly towards the cavernous sinuses.
   7. Ask for a Valsalva maneuver at the end of the resection procedure to detect a CSF leak before the closure step.
4. Closure
   1. Do not place any hemostatic material within the sella if not absolutely required, to enable a more accurate interpretation of the postoperative MRI.
   2. Obtain hemostasis within the pituitary sella with patient saline irrigation and slight pressure with cotton pads.
   3. Reconstruct the durotomy with a patch of bio-absorbable artificial dural substitute that is placed extradurally and reinforce it with a thin layer of surgical adhesive (e.g., bioglue).
   4. Replace the bone flap and secure it with surgical adhesive.
      NOTE: In cases where the sellar floor is drilled, the disarticulated rostrum or a piece of cartilage coming from the posterior part of the nasal septum may be used to close the bone defect. Other options of the use of synthetic materials (e.g., Porex plates) have also been described.
   5. Do not leave artificial material in the sphenoid sinus to avoid any chronic inflammatory reaction.
   6. Pay attention to the hemostasis of the nasal mucosa, particularly in the region of the nasoseptal branches of the sphenopalatine arteries on both sides, to prevent postoperative epistaxis.
   7. Gently replace the superior and middle turbinates in their original position with a blunt spatula.
   8. If a CSF leak has been observed during the procedure, pack the sella with a small fat graft. Do not use nasal packing unless strictly necessary.

4. Postoperative management

1. Provide adequate hormonal substitution in the perioperative period. Use intravenous hydrocortisone during the first 24 h (100 mg per day) and then provide an oral substitution (variable from case to case but at least 30 mg per day during the hospitalization).
2. Twice a day, check blood and urinary osmolality and electrolytes, along with the urinary density. Monitor the urinary output constantly. Perform a hormonal check-up to evaluate the anterior pituitary function at day 4 postoperatively.
3. Keep amoxicillin/clavulanate at 1.2 g twice a day till day 5 postoperatively. Provide standard analgesic treatment while combining acetaminophen and NSAIDS and provide tramadol for refractory pain.
4. Constantly clean nasal fossa with saline solution to limit the risk of postoperative crostous rhinitis.
5. Explain to the patient the importance of avoiding Valsalva maneuvers to allow a correct healing of the operative site during the first postoperative weeks.
6. Perform an MRI in the early postoperative period only if the resection is suspected to be subtotal, if the intraoperative aspect is atypical for pituitary adenomas, or if complications are suspected. After standard procedures, perform the cerebral MRI at 3 months postoperatively.
7. Perform a first evaluation 3 months postoperatively and organize follow-ups in collaboration with the endocrinology unit and schedule them according to the pathology and the extent of resection.