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

Podsumowanie

The aim of this paper is to describe the different steps of the endoscopic endonasal approach to the sella turcica.

Streszczenie

Endoscopic endonasal trans-sphenoidal surgery has become the gold standard for the surgical treatment of pituitary adenomas and many other pituitary lesions. Refinements in surgical techniques, technological advancements, and incorporation of neuronavigation have rendered this surgery minimally invasive. The complication rates of this surgery are very low while excellent results are consistently obtained through this approach.

This paper focuses on the step-by-step surgical approach to pituitary adenomas, which is based on personal experience, and details the results obtained with this minimally invasive surgery.

Wprowadzenie

The introduction of endoscopic techniques to the skull base surgery has markedly improved the outcomes of skull base surgery when used in itself or as an adjunct to standard microsurgical approaches. The endoscopic endonasal approach was initially introduced to treat sellar lesions¹, but during the last two decades the applications of this technique have expanded thanks to significant technological improvements and increased surgical experience. The endoscopic approach is now also used for lesions of the anterior and antero-lateral skull base through extended midline and paramedian approaches. Approaches from the anterior skull base to the odontoid are now safely performed in many specialized centers with satisfying results^2,3,4,5.

In fact, the endoscope allows a direct visualization of the lesion through a natural access without crossing important neuro-vascular structures. Multiple reviews have sustained the safety and relative advantages of endoscopic procedures over traditional microscope-based approaches and affirmed that the major outcomes, such as the extent of tumor resection and the changes in hormonal levels, were not different between the two approaches. However neurological complications, operative time and hospitalization length, as well as patients' postoperative discomfort, were significantly lower with the endoscopic approach⁶. According to a provocative publication, even a less experienced surgeon may achieve a similar outcome with a fully endoscopic technique as a very experienced surgeon using a microscopic technique in a cohort of non-functioning pituitary adenomas⁷.

The endoscopic endonasal trans-sphenoidal approach is actually widely recommended for sellar lesions, even in the case of cavernous sinus invasion or suprasellar extension. If the suprasellar extension is very important, a fully-endoscopic two-staged procedure may be performed, while waiting for the natural descent of the residue⁸. If the diaphragm is very tight ("waist sign"), a transcranial approach may be performed to address the suprasellar component⁹. Concerning the invasion of the cavernous sinus, the endoscopic technique seems to be superior to microscopic techniques for Knosp grade 2 and 3 non-functioning pituitary adenomas¹⁰, and the endoscopic endonasal inspection may help in detecting the invasion of the cavernous sinus¹¹.

Factors which might hinder an endoscopic radical excision are: tumors extending above and lateral to the supraclinoid internal artery or the presence of "kissing carotids", an asymmetric subfrontal extension, tumors reaching the foramen of Monro, or fibrous tumors invading the surrounding cerebral parenchyma⁹. In these complicated cases, a combined transcranial approach may be proposed to the patient. Also the pneumatization of the sphenoid sinus is an important factor in determining the feasibility of the surgery because conchal type sinuses render the endoscopic approach more challenging¹².

Through their personal experience of approximately 500 endoscopic endonasal approaches for pituitary adenomas, the authors here describe the different stages of the approach for pituitary tumors. The surgery may be divided into three main steps: the nasal, the sphenoidal, and the sellar phase. They are performed through a fully endoscopic procedure. The cohort here described included patients with micro or macro-adenomas with a variable extension to the cavernous sinus, to the sphenoid sinus, or the suprasellar space. Both functioning and non-functioning adenomas were included.

A fully endoscopic procedure may be also performed for a variety of other lesions such as craniopharyngiomas, pituitary metastases, clival chordomas, or petro-clival meningiomas. However, these pathologies often required wider approaches and the description of these variants goes beyond the aim of this paper.

Indication

The procedure described here is for pituitary adenomas (functioning or non-functioning). A suprasellar extension was not a contraindication for the procedure, nor were the extension or invasion of the cavernous sinus. The pneumatization of the sphenoidal sinus and the orientation of the septa of the sphenoidal sinus were analyzed at the pre-op CT-scan. Also the orientation of the optic nerve and the internal carotid artery were important factors to plan the surgical strategy.

This surgical technique can also be useful for others tumors located in the sellar region like craniopharyngiomas¹³, symptomatic Rathke's cleft cysts, pituitary metastases¹⁴, or lymphomas¹⁵. Also, other lesions may be approached through the endoscopic approach, such as meningiomas of the sellar diaphragm or the sphenoidal planum, meningiomas of the petro-clival region and clival chordomas^5,16, and epidermoid or dermoid cysts of the prepontine cistern. In these cases, however, a wider approach is necessary.

Protokół

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.

Wyniki

Since 2009, our pituitary program has evolved to a point where a fully endoscopic endonasal approach has been used to treat pituitary tumors with excellent postoperative results. From 2009 to 2016, the two senior surgeons (RTD and MM) operated on 473 patients with pituitary adenomas through a full endoscopic technique. The histology is detailed in Table 1: most of these cases were non-functioning pituitary adenomas (57%) (Figure 1), followed ...

Dyskusje

For the majority of pituitary tumors, surgery remains the first-line treatment in case of symptomatic patients^19,20. Only for prolactin (PRL)-secreting adenomas, the first-line of treatment is dopamine agonists and surgery is chosen secondarily when medical treatment fails²¹.

Since the introduction of the endoscope in the field of skull base surgery in the early 1990's^22,

Materiały

Name	Company	Catalog Number	Comments
The StealthStation surgical navigation system	Medtronic	ENT Fusion Software 9733652
4-mm 18cm 0° rigid endoscope	Karl Storz	28132AA
4-mm 18cm 30° rigid endoscope	Karl Storz	28132BVA
4-mm 18cm 45° rigid endoscope	Karl Storz	28132FVA
Suction Tube	Karl Storz	28164XA
Coagulation Cannulas	Karl Storz	28164MXB
Bipolar Forceps	Karl Storz	28164BDB
Kerrison Bone Punches	Karl Storz	28164MKA
Kerrison Bone Punches	Karl Storz	28164MKB
Kerrison Bone Punches	Karl Storz	28164MKC
Ring Curettes	Karl Storz	28164RN
Ring Curettes	Karl Storz	28164RO
Ring Curettes	Karl Storz	28164RI
Ring Curettes	Karl Storz	28164RG
Ring Curettes	Karl Storz	28164GLL
Ring Curettes	Karl Storz	28164GLR
de DIVITIS-CAPPABIANCA Scalpels	Karl Storz	28164M
Forceps	Karl Storz	28164TD
High-speed drill	Midas Rex Medtronic	1898430
Hemostatic agent	Floseal, Baxter	1503350
Fibrin sealant	Tisseel, Baxter	600065
CT Lightspeed	GE medical systems, Milwaukee, WI, USA
Carestream Vue PACS	Carestream Health, Rochester, NY, USA
3-Tesla Siemens Tim Trio scanner	Siemens AG, Erlangen, Germany