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 » Introduction
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 » Surgical Techniques
 » Tips and Tricks
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Table of Contents    
NI FEATURE: CENTS (CONCEPTS, ERGONOMICS, NUANCES, THERBLIGS, SHORTCOMINGS) - COMMENTARY
Year : 2016  |  Volume : 64  |  Issue : 4  |  Page : 724-736

Endoscopic pituitary surgery: Techniques, tips and tricks, nuances, and complication avoidance


Department of Neurosurgery and Gamma Knife, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi, India

Date of Web Publication5-Jul-2016

Correspondence Address:
Dr. Bhawani Shanker Sharma
Department of Neurosurgery and Gamma Knife, Neurosciences Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.185352

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 » Abstract 

Endoscopic pituitary surgery is useful in all micro- and macro-pituitary adenomas including those with suprasellar and cavernous sinus extension. The endoscope provides a panoramic close-up, a multi-angled view with excellent illumination and magnification, permitting complete excision of the tumor with preservation of normal pituitary. However, surgeons need to learn altogether different skills unique to endoscopy and the learning curve is steep. The learning curve can be shortened by proper selection of cases, gradual transition from the microscopic to the endoscopic approach, adequate sphenoethmoidal recess widening, identification of important landmarks during each stage of surgery, and use of neuronavigation. Results and long term outcomes can be improved with bimanual dynamic dissection and sequential tumor excision, preservation of normal pituitary, avoidance of arachnoidal tear and use of extended approach for tumors with large suprasellar extension. The gradual transition from microscopic to endoscopic approach, adherence to step by step technique and learning 'tips and tricks' of the endoscopic pituitary surgery reduce complications.


Keywords: Endonasal; endoscopy; pituitary adenoma; surgical technique; trans-sphenoidal surgery


How to cite this article:
Sharma BS, Sawarkar DP, Suri A. Endoscopic pituitary surgery: Techniques, tips and tricks, nuances, and complication avoidance. Neurol India 2016;64:724-36

How to cite this URL:
Sharma BS, Sawarkar DP, Suri A. Endoscopic pituitary surgery: Techniques, tips and tricks, nuances, and complication avoidance. Neurol India [serial online] 2016 [cited 2019 May 25];64:724-36. Available from: http://www.neurologyindia.com/text.asp?2016/64/4/724/185352



 » Introduction Top


The surgical management of pituitary tumors has evolved over time from the transcranial to endonasal transsphenoidal approaches. The latter approach is possible by using either a microscope or an endoscope.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12] When an endoscope is used as the sole visualizing tool in place of the microscope during endonasal transsphenoidal surgery, the procedure is termed as the endoscopic pituitary surgery (EPS).

EPS is an advancement over the microsurgical technique and has emerged as a better alternative to the microscopic transnasal transsphenoidal (TNTS) technique.[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16] With experience, there is an improvement in endocrinal remission, extent of tumor resection, and preoperative visual deficits. There is reduction in postoperative hypopituitarism due to preservation of the normal pituitary gland. In addition, there is reduction in the duration of surgery, postoperative visual deterioration, mucosal trauma causing postoperative discomfort, hospital stay, and cerebrospinal fluid (CSF) leak.[2],[6],[9],[10],[11],[13],[15],[16]

EPS has the following advantages: (1) Better illumination and superior visualization as the light source is close to the target.[2],[3],[4],[5],[7],[8],[9],[10],[11],[13],[17],[18] (2) Wide angle view and visualization of the opticocarotid recess (OCRs) as well as carotid and optic protuberances.[3],[4],[5],[7],[8],[10],[12],[13],[15],[16],[17],[18] (3) Angled endoscopes expand the range of visualization including visualization of corners and hidden angles permitting complete removal of the tumor.[3],[4],[5],[7],[8],[9],[10],[12],[13],[15],[16],[17],[18] (4) A high image resolution [2],[3],[4],[5],[7],[8],[9],[10] permitting more accurate differentiation between the diaphragm sellae and the arachnoid, and between the normal and neoplastic tissue enabling preservation of normal pituitary.[2],[3],[12],[13],[18] (5) Avoidance of nasal speculum and packing causes less postoperative discomfort and an early return to work.[2],[3],[7],[8],[9],[10],[11],[12],[13],[15],[16],[19],[20]

Disadvantages of EPS include (1) Endoscope provides a two dimensional (2D) vision.[3],[6],[7],[8],[10],[15],[20],[21] (2) Spatial distortion of the periphery of the image occurs.[8] (3) It has limited zoom and focus capability.[12] (4) The 3–4 handed technique requires two surgeons.[3],[8],[11],[12],[15],[20] (5) The operating time is longer in the initial phase of the learning curve.[3],[4],[7],[8],[10],[11],[15],[16],[20]

The authors have operated more than 350 cases and have demonstrated the EPS technique in many live operative workshops in different centers in India. The endoscopic endonasal transsphenoidal approach is increasingly being used and is gaining wide acceptance as the first-line treatment for most pituitary adenomas at many centers in India. It is worthwhile to describe our technique, surgical nuances, lessons learned, and “tips and tricks” which may help to shorten the steep learning curve, help in avoiding complications, and improve the results and long-term outcomes.


 » Transition from Microscope to Endoscope Top


Microscopic surgery is considered like eating with fork and knife while endoscopy is like eating with one chopstick in each hand.[4] EPS needs altogether different skills and hand–eye coordination, and one needs to really learn it.[4],[8],[22]

Endoscope gives a two dimensional image which causes difficulty in depth perception.[3],[6],[7],[8],[12],[20] This can be compensated by the pseudo-depth perception from the dynamic in and out movement of the endoscope in relation to instruments and fixed anatomical landmarks.[8],[10],[11],[12] A steep learning curve exists during the change from microscopic to endoscopic surgery.[2],[4],[10],[11],[23] This sudden change from the microscopic to the endoscopic view may be difficult and discouraging.[6],[11] Hence, a slow transition and a stepwise, progressive learning reduces the steep learning curve, complications, and brings confidence in the ability of the neurosurgeon to tackle complications.[4],[8],[11],[15],[23],[24],[25]

It is advisable to change the approach from the microscope to the endoscope in the following sequence: (1) Initially change from the conventional microscopic sublabial to endonasal approach; (2) perform endoscopic anterior sphenoidotomy by teaming up with the rhinologist; (3) perform endonasal endoscopic approach after the sellar stage with self-retaining trans-sphenoidal retractor in place; (4) perform pure endoscopic approach after the sellar stage without placing the retractor; and finally, (5) all nasal, sphenoidal, and sellar stages are performed endoscopically.[4],[6],[8]

The frustrating experiences in first 50 cases that occur because of difficulties encountered in the initial phases of the procedure can be overcome by adequate knowledge of the endoscopic equipment, a detailed understanding of the endoscopic perception of the anatomy, and by learning endoscopic skills.[5],[15],[25],[26] It is advisable to follow the endoscopic technique step by step by strictly adhering to the basic principles, teaming up with the rhinologist, gaining knowledge regarding the tips and tricks, learning from watching videos of experts, assisting experts, practicing in the laboratory on models and by attending cadaveric workshops, courses, conferences and fellowship programs at regular intervals.[5],[8],[16],[20],[24]

For smooth transition, attention should be given to the following -

  • Patient Selection
  • Preoperative Planning
  • Endoscope and equipment
  • Preparation and position
  • Operating room set up
  • Preliminary Endoscopic Exploration.


Patient Selection

For the beginner, a proper case selection is of paramount importance.[8] In the beginning, patients with a nonfunctioning adenoma confined to the sella in a well-pneumatized sphenoid sinus are the best cases. Patients with conchal/presellar sphenoid pneumatization, acromegaly/Cushing's disease (where the nasal mucosa is fragile and hypertrophied)/recurrent tumors/tumors with a dumbbell suprasellar extension/giant tumors are difficult to approach in the initial stages of one's experience and should be taken up for endoscopic surgery only after gaining sufficient experience.[8]

Preoperative Planning

Preoperative magnetic resonance imaging and computed tomography should be assessed meticulously for the assessment of size of the nasal airway (deviated nasal septum [DNS], concha bullosa); anatomy of the paranasal sinuses (extent of pneumatization, intra/inter-sphenoid septa, etc.) and sella (anatomical variations, kissing carotids, and bone dehiscence); consistency of the tumor (which is likely to be firm if it is hypointense on T2 weighted image); and, its extension and involvement of the surrounding structures, especially the encasement of vessels, the location of the shifted normal pituitary gland [by observation of the enhancing posterior pituitary], the evidence of pituitary apoplexy, pre- and post-fixed chiasma, and deviation of the pituitary stalk.[10],[27] Image guidance is useful in the beginning of one's career, while encountering a presellar or conchal type of sphenoid sinus, in redo cases, in the presence of kissing carotids and when extended trans-sphenoidal procedures are being performed for dumbbell/giant tumors.[1],[8],[9],[23],[28],[29] The need for the vascularised nasoseptal Hadad flap should be analyzed before surgery and planned accordingly.[7],[10],[23],[30],[31] In recurrent cases, the mucosa over the previously removed site is not suitable for the flap as it is friable and is without a vascular pedicle. However, the nasoseptal flap can be used again (recycled) if it has already been used during the previous surgery. It can be easily dissected from the recipient's bone but its dissection from the ICA and ON is not advocated. A uninostril approach through a capacious nostril may be chosen in a adenoma confined to the sella in the presence of a DNS. Lateralized unilateral microadenomas and cavernous sinus lesions are best approached through the contralateral nostril.[8]

Endoscope and Equipment

In general, we used the 0° endoscope, 18 cm scope (Karl Storz, Germany) for the nasal and sphenoidal stages. For the sellar stage, a 30 cm scope may be used. The 30° and 45° scope are used at the end of surgery for inspection of the tumor cavity and removal of tumor remnants. A four-millimeter scope provides better illumination and resolution. Use of the external sheath reduces the operative time.[9] It permits irrigation and cleansing of the lens. Therefore, the in and out movements of the endoscope through the nasal cavity are considerably less.[9] Instruments should be held in a precision grip, should be straight (not bayonet shaped) and should be slightly curved at the tip.[8] A suction coagulator is very useful rendering the operation clean, and rapid.

Preparation and Position

Oxymetazoline nasal drops are instilled the night before surgery, and then again, in the morning before shifting the patient to the operation room. The patient is positioned supine in the reverse Trendelenburg position, with hips and knee flexed, and the trunk elevated 20° in the “beach chair position” to allow for an easy access to the middle turbinate (MT).[14] The patient's head is kept neutral, rested on a horseshoe head holder, or fixed with a three pin headrest when neuronavigation is used. The chin-forehead line or the bridge of the nose is maintained horizontally parallel to the floor, with the head turned 15° towards the surgeon and 15° tilted towards the contralateral shoulder (with the left ear towards the left shoulder).[3],[5],[14] The endotracheal tube is fixed to the left side of lower jaw and throat packing is done. A nasogastric tube is placed to aspirate blood and secretions prior to the extubation of the patient. It is advisable to use propofol infusion to reduce bleeding, keep the blood pressure around 90 mmHg, and the pulse around 60/min. Lumbar drain may be inserted in patients having a large tumor with a considerable suprasellar extension. For antisepsis, betadine-soaked cotton patties are inserted in bilateral nasal cavities after positioning of the patient.

Operating Room Setup

The monitor screen is set up behind the patient's head, and if available, another screen is set up in front of an assistant [Figure 1]. A right-handed surgeon stands on the right side of the patient. In 3/4 handed technique, in the nasal stage, the surgeon holds the scope without or with the irrigation and suction endoscope handle (Thumfart) in the left hand and the dissecting instruments (drill, suction, curette, etc.) in the right hand. The endoscopic holder or the position of the Mayo stand is adjusted so as to provide rest to the elbow of the assistant surgeon [Figure 2]. The assistant surgeon manipulates another suction in the nasal stage. He may also manipulate endoscope (after the sphenoidotomy) in relation to the instruments and works in synchrony with the main surgeon.[6],[16],[22] All cables (light, camera, and irrigation) are tied together to the shaft of the scope and rested on the table on the left side of the patient away from the surgical field. Visual obscuration due to staining/soiling of the lens tip by blood, bone dust, fluid or tissue can be cleared by cleaning the debris with wet sponge, antifog-savlon, baby shampoo or betadine.[6],[20] Glue and hemostatic agents (FloSeal hemostatic agent, etc) should be available for usage, if required, during surgery.[32]
Figure 1: Operation room setup showing the position of patient, main surgeon, assistant surgeon, scrub nurse, monitor, equipment for image guidance and anesthesia equipment

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Figure 2: Endoscope holder used as an arm support both by the main surgeon (a) and the assistant (b) at different stages of surgery

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Preliminary Endoscopic Exploration

Check the orientation of the endoscopic camera by craniocaudal and side-to-side movements. First, a diagnostic endoscopy is performed to study for any variation in the nasal anatomy [Figure 3]. This includes three passes.[33] During the first pass, the endoscope is passed in the floor of the nasal cavity to the nasopharynx in the inferior meatus. The structures seen are the nasopharynx,  Eustachian tube More Details opening, choana, and nasolacrimal duct opening [Figure 4]. During the second pass, the endoscope is passed between the middle turbinate (MT) and the nasal septum, i.e., medial to MT. The structures seen include the superior turbinate (ST), superior meatus, sphenoethmoidal recess (SER), and sphenoid sinus opening. This is followed by the third pass in which endoscope is passed in the middle meatus, i.e., lateral to the MT. The structures seen are the uncinate process, bulla ethmoidalis, hiatus semilunaris, and ground lamella.
Figure 3: Endoscopic view of the nasal cavity (a) and the artistic impression (b), showing the middle turbinate, inferior turbinate, and septum. MT - Middle turbinate, IT - Inferior turbinate

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Figure 4: Endoscopic panoramic view (a), and the artistic impression (b), showing important endoscopic landmarks such as the nasopharynx, Eustachian tube opening, choana, middle turbinate, sphenoethmoidal recess, and septum. MT - Middle turbinate, ET - Eustachian tube, NP - Nasopharynx, SER - Sphenoethmoidal recess

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 » Surgical Techniques Top


Various modifications are available such as a uninostril versus a binostril approach; a two- versus a four-handed technique; nil, partial, or complete resection of MT; and, different types of repair of the sellar floor. In general, the four-handed technique is preferred.[7],[8],[9],[10],[18] One must be aware of all the modifications in techniques so as to tailor surgery according to the requirements of the situation in a particular case.

The surgical technique includes four stages, namely, the nasal stage, the sphenoidal stage, the sellar stage and the reconstruction stage.[10] Recognition of important landmarks during each of these stages is the key to a safe exposure.[3],[6],[7],[10],[17],[18]

A. Nasal stage

The endoscope is inserted in line with the floor of the nasal cavity, parallel to the MT at an angle of 25° inferiorly to initially visualize the choana.[10],[11] The inferior turbinate (IT), which points towards the eustachian tube, is identified and lateralized. The choana is the anatomic reference point.[9],[19] Then, the endoscope is steered in between the septum and the IT, as well as between the septum and the MT in the SER. The inferior margin of the MT leads to clival indentation, which is about 1 cm, below the level of sellar floor. This is quite a consistent surgical landmark.[3],[4],[5] Super selective packing of 2–4 cotton patties (that are soaked in five ampules of adrenaline 1:1000 diluted in 30 ml of 1% xylocaine and gently squeezed to ease out the excess fluid) is performed between the MT and the nasal septum from the anteroinferior to the posterosuperior direction from the choana and left in situ for 5–10 min, to widen the space.[6] This is an important step and helps in creating adequate space by facilitating decongestion of the nasal mucosa.[6],[8],[9],[10] Once this space is created, fresh cotton patties are again pushed back into the SER and left for 2–5 min.[5],[10] Investment of 10–15 min at this stage gives dividends in rest of the operation. This maneuver may have to be repeated 2–3 times to widen the SER. The MT is lateralized with the shaft (not tip) of freer dissector over a cotton patty or it is fractured and lateralized [Figure 5].[3],[5],[9],[18]
Figure 5: Endoscopic view (a) and the artistic impression (b) showing the technique of lateralization of the middle turbinate using the shaft of the Freer dissector over cotton patty. MT - Middle turbinate

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B. Sphenoid stage

The sphenoid ostium (SO) is identified posterior and inferior to the root of the ST in the lateral rostral corner of sphenoid rostrum [Figure 6]. In 30% of the cases, the ostium may not be visible.[2] In such cases, visualization of the air bubbles associated with mucosal secretions or gentle probing in the region may locate it [Figure 7].[2],[6],[9],[10] If these measures also fail to locate the sphenoidal ostium, then the bluish thin area 1.5 cm above the choanal roof called the sphenoidal fontanelle can be perforated to enter the sphenoid sinus.[19] The mucosa over the rostrum of sphenoid sinus is coagulated [Figure 8].[5],[9] The nasal septum is gently pressed, fractured and pushed to the other side [Figure 9]. Submucosal dissection along the contralateral side of the sphenoidal rostrum to visualize the sphenoidal ostium (SO) contralateral to the side of approach gives the classical “owl eye appearance” [Figure 10]. The SO is enlarged medially and inferiorly and a “V”-shaped, wide anterior sphenoidotomy is performed [Figure 11].[10],[18] The vomer is drilled and the rostrum of the sphenoid sinus is removed [Figure 12].[10] Posterior one-third of the nasal septum is removed by a backbiter to facilitate a binostril approach [10],[17] [Figure 13]. The limits of the sphenoidotomy include: Cranially, the superior limit of SO providing adequate visualization of the planum sphenoidale, the optico-carotid recesses and the optic protuberances; caudally, the pterygo-sphenoid synchondrosis/vidian canal at 5 and 7 O' clock position. It is necessary to create a 5–6 mm space below the sellar floor for free manipulation of the instruments. The lateral limit is the crest marking the the junction of the sphenoid and ethmoid sinuses with visualization of the carotid artery (CA) protuberance.[10],[18] The operative space can be increased by removing the posterior ethmoids and communicating it with the sphenoidal cavity. The scope is then kept in this additional space created by the ethmoidectomy called the “cavity and half” technique.[22] After the sphenoidotomy, the midline is identified by visualizing the remaining segment of the rostrum (vomer) inferiorly and the middle of the two carotid bulges. After the sphenoidotomy, the endoscope may be mounted on a holder;[9] or, the second surgeon holds the endoscope and acts as a navigator (co-pilot) with the main dissecting surgeon (pilot) providing the 3D perception.[6] The pilot and co-pilot work in synchrony.[7]
Figure 6: (a) Endoscopic view after lateralization of the middle turbinate and superior turbinate and the artistic impression (b), showing a widened sphenoethmoidal recess with sphenoid ostium. ST - Superior turbinate, MT - Middle turbinate, SO - Sphenoid ostium, SER - Sphenoethmoidal recess

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Figure 7: (a) Normal sphenoid ostium.Identified by (b) visualization of an air bubble with secretions or (c) by gentle probing of the mucosa at about 1.5 cm above the choana. (d) Opened the ostium after the probing

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Figure 8: (a) Endoscopic view and (b) artistic impression of mucosal coagulation with suction coagulator. ST – Superior turbinate, MT - Middle turbinate, SO - Sphenoid ostium

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Figure 9: (a) Endoscopic view and the artistic impression (b) showing disarticulation of the posterior bony nasal septum from the rostrum of sphenoid to the opposite side. Subsequent submucosal dissection reveals the opposite side sphenoidal ostium. SO - Sphenoid ostium

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Figure 10: (a) Endoscopic view and the artistic impression (b), showing both the sphenoidal ostium and rostrum ('Owl eye' appearance). SO - Sphenoid ostium

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Figure 11:(a) Endoscopic view and the artistic impression (b) of the “V” shaped shoulder sphenoidal osteotomy, where the sphenoidal ostium is enlarged inferiorly and medially. ST - Superior turbinate, MT - Middle turbinate, SO - Sphenoidal ostium

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Figure 12: (a) Breaking of the sphenoidal rostrum with a bone punch along with the artistic impression (b). ST - Superior turbinate, MT - Middle turbinate, SO - Sphenoidal ostium

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Figure 13: (a) The posterior septectomy using backbiter and the artistic impression (b). MT - Middle turbinate

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C. Sellar stage

The sphenoidal mucosa located only on the anterior wall of the sella and the floor is coagulated with a bipolar and excised (and not stripped, to avoid bleeding).[3],[4],[5] Anatomical landmarks are identified in the aerial panoramic view and mimic a “fetal face” [Figure 14].[3],[5],[9],[10]
Figure 14: Endoscopic view (a) and the artistic impression (b), of the “Fetal face” like appearance after a wide sphenoidotomy. At the center, is the sella; rostrally at 12 O'clock position, is the tuberculum sellae; caudally at 6 O'clock position, is the clival indentation; laterally at 10 and 2 O'clock positions, is the optic protuberance and at 5 and 7 O' clock positions, are the carotid protuberances. The cavernous sinuses are located bilaterally at 3 and 9 O' clock postions. S - Sella, OP - Optic protuberance, CP - Carotid protuberance, m'OCR - Medial opticocarotid recess, l'OCR - Lateral opticocarotid recess, CL - Clivus, CLR - Clival recess

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The boundaries of the sella are confirmed by navigation. The medium sized 3–4 mm coarse diamond burr is used to drill the sellar floor. Gentle drilling with a diamond burr under low speed is done to thin the sellar floor to an egg shell thickness, which is then dissected and broken with a fine spade dissector [Figure 15] or a Kerrison number 1 punch without actually taking a bite. By pressing the sellar dura gently, an estimate of lateral bone removal can be made. The anterior wall of the sella and its floor is removed millimeter by millimeter circumferentially till four blue lines (both the superiorly and inferiorly located inter-cavernous sinuses and the laterally located cavernous sinuses) are seen [Figure 16].[3],[9],[10],[17] An extended approach with removal of the tuberculum sellae, planum sphenoidale, and the medial optico-carotid recess with or without transdiaphragmatic dural opening is required for firm tumors with dumbbell configuration and a narrow waist.[1], 18, [34],[35],[36]
Figure 15: After drilling of the sella at the center and exposure of the sellar dura, dissection between the sellar bone and the sellar dura is done with a fine curved tip before attempting the widening of sella, as shown in figure (a) and in the artistic impression (b). OP - Optic protuberance, CP - Carotid protuberance

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Figure 16: Extension of the sellar bone removal is performed until four blue lines are seen

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1. Opening of the dura

The dura may be opened in many ways; these include placing a vertical linear incision with crossed extensions, a cruciate incision,[6],[10],[37] or two lateral vertical cuts joined by a transverse cut.[38] We prefer to open the dura transversely in the center, and then extending the incision laterally on both the sides, stopping a few millimeters before the bony margins and then extending the opening caudally and obliquely toward 5 and 8 O'clock position with the scissors, thus creating an inferior flap [Figure 17].[18] Only the dura is cut (not the tumor capsule), and dissected from the tumor and reflected.
Figure 17: Method of dural opening (a) the diagrammatic representation (b) Dural opening

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2. Tumor removal

  1. Extracapsular tumor removalExtracapsular tumor excision: For the extracapsular dissection of the suprasellar tumor, it is imperative to remove the bone overlying the medial optico-carotid recess. This is done by opening the outer layer of the dura in the lower part first and then making a U-shaped upward flap. Only the outer layer of dura is cut and reflected upwards or excised completely. Dissection with a ball dissector keeps the inner layer intact. This is followed by the all around dissection of the capsule to remove the tumor in a single piece.[39],[40]
  2. Piecemeal tumor removalThe tumor should first be mobilized free in piecemeal manner [Figure 18] and then taken in a holding forceps or suction [Figure 19].[5] First, the basal and posterior part of the tumor is removed from the opening in the inferior flap in a posterior trajectory toward the clivus-dorsum sellae junction in a caudal to rostral direction.[9],[10] During this time, the superior dural flap supports the superior or anterior part of the tumor, like a retractor, preventing the premature arachnoidal bulge. Next, the lateral portion of the tumor is removed with the upward angled curettes. Lastly, the superior portion of the tumor is removed after making an upward oblique cut in the dura at 10 and 2 O'clock position. Tumor decompression is done with a bimanual dissection-curette in the right hand and the suction in the left hand; or, utilizing the double suction method, where the left suction retracts the dura up, and the right suction sucks the tumor.[3],[18] This results in progressive descent of the suprasellar tumor, which is then continuously removed concentrically. The normal pituitary gland is identified as a thinned out, pinkish, firm tissue plastered to the diaphragma sella and is preserved [Figure 20].[1],[3] While approaching the cavernous sinus medial wall extension of the tumor, the space between the posterior clinoid and the carotid siphon (the reverse S contour) represents an ideal entry point for the removal of tumor from the posterior segment of the cavernous sinus.[18] Bleeding from the cavernous sinuses is controlled with surgicel, gelfoam, or FloSeal.[10],[32]


3. Inspection of the tumor cavity

An angled endoscope is introduced into the sella to examine the tumor remnants.[9],[10] At the end of the procedure, the diaphragma sellae is pushed up with cotton patties and the hidden tumor remnants are removed using curved suction/curette from the recesses under direct vision using a 30° scope.[10] An angled scope is stationed at 6 O'clock position and the instruments are passed above the scope at 12 O'clock position. The 30° scope visualizes the area located opposite to the light cable (the cable hangs inferiorly while operating on the anterosuperior part of the tumor). Finally, inspection of the sella in a clockwise fashion starting at 6 O' clock position using a 30° endoscope is performed.[8] In the case of the 30° scope, one needs to rotate the scope for examining the cavernous sinus. At the same time, the assistant is asked to rotate the camera to maintain orientation by keeping the buttons of the camera facing the screen. Failure of descent of the diaphragma sellae indicates the presence of retained tumor in the suprasellar space; while if there are pulsations visible in the diaphragma, it is a robust finding of near total tumor removal [Figure 21].[18] The capsule of the normal pituitary gland may be present all around the lesion especially in a microadenoma and this may require its incision and dissection. In a functioning microadenoma, a thin shell of normal pituitary gland is shaved along the tumor cavity to enhance the chances of “cure.” Even 10% of preserved pituitary tissue may be enough for a normal functioning. The endoscope needs to be taken inside the sella, closer to the target, for a detailed study (for utilizing its flashlight effect and magnification), and then is withdrawn slightly to facilitate tumor removal under vision in a dynamic fashion.[17],[18] The last piece of tumor is often located at the insertion site of the pituitary stalk.[3],[9],[18] The most common sites where the tumor has been found to be retained are the angle between optic nerve and carotid artery at the medial optico-carotid recess and under the anterior lip of dura at the level of anterior intercavernous sinus.[9],[18]
Figure 18: (a) Bimanual dissection of the tumor and the artistic impression (b), where posterior part of the tumor is first dissected and made free with a ring curette

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Figure 19: Freed tumor is grasped with a biopsy forceps and gently removed without pulling on it as shown in the endoscopic image (a) and its artistic impression (b)

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Figure 20: The interface between the tumor and the normal pituitary gland is seen. The pituitary gland is seen as a pinkish tissue plastered to the diaphragm

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Figure 21: (a) Endoscopic view and the artistic impression, (b) showing the arachnoidal bulge after complete removal of the tumor

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D. Reconstruction

After tumor removal, the Valsalva maneuver is performed to check for cerebrospinal fluid leak.[10],[15] The tumor cavity is filled with fat (except in a microadenoma), even if there is no cerebrospinal fluid leak, to prevent an empty sella syndrome and postoperative cerebrospinal fluid leak from the delayed rupture of the arachnoid either during extubation or in the postoperative period [Figure 22].[3],[6],[10] In case of cerebrospinal fluid leak, the sella may be repaired in the “gasket seal” fashion [14],[41] or by utilizing the “bath plug” technique.[42] A multilayered repair with fat, fascia, and glue may be used.[9],[10],[43],[44] One should make sure that the fat graft is pulsating. An overzealous sellar packing should be avoided.[7],[9] The bone piece recovered from the septum/rostrum may be used to provide a firm support to the fat graft. Glue is used to hold the tissues together. The MT is medialized back to its normal position to keep the maxillary drainage patent [Figure 23].[9],[37] No nasal packs are used.[7] Examples of total excision of the pituitary tumor by a uninostril and binostril four-handed technique are shown in [Figure 24] and [Figure 25], respectively.
Figure 22: Endoscopic view (a) and the artistic impression (b) of the sellar packing with fat

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Figure 23: Medialization of the middle turbinate at the end of surgery. MT - Middle turbinate, IT - Inferior turbinate

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Figure 24: Uninostril approach. (a) Sagittal and (b) axial magnetic resonance imaging showing the pituitary macroadenoma. (c) The right side uninostril approach with the intact mucosa of the left side. (d) Tumor removal. Postoperative (e) sagittal and (f) coronal magnetic resonance imaging scan showing total excision of the tumor

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Figure 25: Axial (a), sagittal (b), and coronal (c) view of magnetic resonance imaging scan of pituitary macroadenoma. Postoperative follow-up images (d-f) showing total excision of the tumor

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 » Tips and Tricks Top


  • While introducing the scope, one must take advantage of the elasticity of the alar cartilage and therefore, lift and retract the ala of nose cranially, deforming the right nostril and station the scope at 11 O'clock position
  • The instruments should be slowly introduced taking advantage of the rigidity of the floor. They should be glided gently alongside the nasal septum below the endoscope through the lower part of the nostril
  • The scope should be introduced slowly, like passing through a tube without touching its walls, to avoid soiling of the lens
  • Insertion of instruments by endoscopic-guided visualization, and keeping the suction at a low setting, avoids injury to the mucosa
  • The bleeding from the mucosa should be controlled by infiltration/coagulation
  • In and out movements inside the nasal cavity should be performed to judge the depth of the operative field and to establish surgical landmarks for orientation and depth perception [8]
  • Proper orientation should be checked for at all times, especially after each insertion and exit of the endoscope from the nasal cavity, and the buttons of the endoscope should be facing the screen
  • Quick movements in proximity to the surgical target should be avoided [8]
  • The distance between the tip of instruments and the scope is kept at about 1 cm and both are advanced simultaneously. They should not touch each other or cross over
  • The presence of the crescentic rim (semilunar sign) in the endoscopic image on the screen may occur due to impingement of the scope tip on any of the nasal structures. The endoscope should be moved 180° away from the current position to avoid injury to that structure [45]
  • Vapors due to humidity and temperature difference may cause fogging of the lens, which can be cleared by irrigation with warm saline [20]
  • Avoid mucosal coagulation in the upper nasal septum to maintain olfaction
  • Sphenoidotomy should be adequately widened to remove the coffin effect
  • Drill is first be taken close to the target. When the tip is seen on the screen, it is turned on and the target touched. The drill should be used in bursts with paint-brush like movements
  • Remove the drill only when it has completely stopped its revolutions
  • While drilling, keep the endoscope away and zoom out to avoid soiling of its lens
  • Dry drilling with a diamond burr stops bleeding from the bone
  • Increased bleeding may be observed due to the 'blocked choana' effect, so blood should be sucked away from the choana during surgery, to keep the operative field clean and dry
  • Repeated warm saline (40°) irrigation stops bleeding from the sphenoidal sinus mucosa and also keeps the field clean [11],[45]
  • Do not coagulate on or near the sella as bone may be deficient in that region. Intersphenoidal septum is drilled flush with the sellar floor [6]
  • The paramedian septum often leads to the carotid artery, so it should be removed only when mandatory [Figure 26][3],[6],[10]
  • Make the trajectory as straight as possible during the passage of the scope and instruments, and move the scope in relation to the instruments [3],[4],[5]
  • Near the venous sinuses, the Kerrison's punch tip is used obliquely rather than at 90° to avoid injury and bleeding from the sinuses [3],[4],[5]
  • Superiorly, the arachnoid may bulge down to the diaphragma sellae in front of the thinned out pituitary gland, and one should be cautious while opening the dura superiorly as there is a significant risk of cerebrospinal fluid leak
  • There should be no blind dissection. Do not hold/pull the tissue if you do not see the tip of the instrument
  • Do not move the tumor towards the scope as it may soil the lens. The tumor should be moved away from the scope in a side-to-side manner to visualize the structures located on the deeper side
  • Use “flashlight effect” to visualize the arachnoid and prevent its tear [18]
  • Create a zero view while using an angled telescope before introducing it into the nasal cavity [45]
  • Postoperative cerebrospinal fluid leak is best treated with immediate repacking.
Figure 26: Different type of sphenoidal septum (a) midline sphenoid septum attached to the central part of sella; (b) paramedian septum; (c) another paramedian septum with its attachment ending close to the location of the carotid artery on the right side. (d) Artistic impression of different types of sphenoidal septa

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 » Complications and Their Avoidance Top


These can be divided into two major categories: (1) Nonendocrinal; and, (2) endocrinal complications [Table 1].[2],[14],[15],[23],[26],[46]
Table 1: Complications and their avoidance

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In conclusion, gradual transition from an operative microscope to an endoscope; and, a proper learning of the tips and tricks reduces the complications of endoscopic pituitary surgery.

Acknowledgment

We extend our gratitude to Mr. Ramchandra B. Pokale, Chief Artist, Department of Community Medicine, All India Institute of Medical Sciences, New Delhi, for his valuable help in making an artistic impression of the endoscopic images.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26]
 
 
    Tables

  [Table 1]

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