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Complication Avoidance in Endonasal Endoscopic Pituitary Surgery
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.287665
Keywords: Complication avoidance, endoscopic pituitary surgery, tips and tricksKey Message: Endoscopic pituitary surgery is the best approach to remove pituitary tumors. Adequate training with stepwise shifting from microscopic to endoscopic approach is the best way to avoid complications. Thorough knowledge of anatomy is also must for good outcomes.
Pituitary adenoma is one of the most commonly diagnosed benign intracranial neoplasms.[1] They cause symptoms by a) compression of the surrounding structures like optic apparatus, b) compromising normal pituitary function leading to hypopituitarism or c) excess hormone secretion resulting in Cushing's disease or acromegaly. The treatment of choice for pituitary adenomas is surgical removal, except in the case of prolactinomas where medical management is the first line of treatment. The goals of pituitary tumor surgery are to -
These goals can be achieved by complete excision of the tumor with preservation of the normal pituitary gland. The endoscopic approach to pituitary surgery has been the most successful method of managing such cases and has transformed the field of pituitary surgery for the better in past two decades.[2] The endoscope provides the surgeon better visualization by illumination and magnification, and a panoramic wide close up view.[3] It also provides multi-angled view to look around corners allowing removal of hidden tumor under direct vision as in microscopic technique. Endoscope permits a better distinction between the tumor and normal pituitary gland allowing total excision of the tumor and preservation of the normal pituitary with improvement in preexisting visual deficits, the extent of tumor removal, endocrine remission in functioning tumors, post-operative hypopituitarism.[4],[5] Better distinction between diaphragm and arachnoid helps in prevention of postoperative CSF leak. Endoscopic approach has higher total tumor resection, endocrine remission, visual recovery, and less complications (morbidity of <6% and mortality of <1%) as compared to microscopic approach.[6] It has been shown to be safe and effective way of tumor resection in the elderly as well.[7] A recent systematic review and network meta-analysis concluded that endoscopic transsphenoidal surgery is a far more proper surgery method than microsurgery and recommended it to be the first choice as it appeared to be the more tolerable and safer than microscopic transsphenoidal tumor excision.[2] The endoscope provides a 2D and requires different hand-eye coordination and dexterity. Hence, a steep learning curve exists during which complications are likely to occur. Complications of endoscopic pituitary surgery can be divided into nasal, neurosurgical, vascular and conversion to microscopic surgery, and are summarized in [Table 1].
Complications can occur in the learning curve period. With the increasing experience in endoscopic technique, there is a reduction in nasal mucosal trauma, postoperative visual deterioration, postoperative nasal discomfort, CSF leak, duration of surgery and hospital stay. These complications can be avoided by properly structured training, anticipating common pitfalls and following a systematic stepwise approach as described in the subsequent sections.
A sudden change from microscopic to endoscopic technique is difficult. Hence, a gradual and progressive shift is recommended.[8] We advocate stepwise shifts. First, from sublabial to endonasal microscopic, then to endoscope assisted a retractor, then to endoscopic without retractor up to sellar stage, and finally all stages are done with endoscopic technique. Frustration in first 20-30 cases can be avoided by proper knowledge of the endoscopic equipment, detailed understanding the endoscopic endoscopic perception of anatomy and learning endoscopic skills. With the increase in the number of practicing neurosurgeons, along with a renewed emphasis on limited working hours for residents, time tested methods of apprenticeship have proven to be less effective in the dissemination of the requisite skills required for endoscopic training. Several simulators and virtual reality-based techniques of hand eye coordination, dexterity and handling endoscopic instruments in a laboratory on models and cadavers[9] are now available at several neurosurgery departments which replicate the surgical experience and enhance the learning of endoscopic techniques for the trainees.[10],[11] Observing or assisting experts and periodic update of knowledge by attending seminars and cadaver training courses and fellowships are the key prerequisites before embarking on an independent endoscopic pituitary surgery.
An ideal case for a beginner would be a non-functioning pituitary macroadenoma confined to the sella in an adult patient with well-pneumatized sphenoid sinus. A gradual progression to functional pituitary adenomas with fragile or hypertrophied nasal mucosa, and then to more complex cases like the ones with large suprasellar extension, cavernous sinus invasion, dumb-bell tumors, recurrent tumors, giant adenomas is advisable. Tackling such cases becomes easier with increasing experience and results also improve in the favor of patients.[12]
A thorough and detailed knowledge of the relevant anatomy of nasal cavity, sella and adjacent structures from the endoscopic perspective is essential. A careful assessment of the preoperative imaging should be done. Computed tomography reveals anatomical variations such as deviated nasal septum, turbinate hypertrophy, sinusitis, concha bullosa, extent of pneumatization of the sphenoid sinus, location and number of the sphenoid septum, intercarotid distance, bone dehiscence/enlargement/erosion, and the extent of destruction of the sellar floor.[13],[14] Magnetic resonance imaging shows the extent of the tumor, invasion of the cavernous sinus, encasement of the carotids, displacement and location of the normal pituitary gland, pre and post fixed chiasm, evidence of pituitary apoplexy and the presence of hydrocephalus. Consistency or firmness of the tumor can be gauged on T2 weighted and fluid attenuated inversion recovery (FLAIR) images. Rare anatomical variations, such as kissing carotids should be actively looked for and picked up before taking up the patient for surgery to avoid any inadvertent injury during surgery. A thorough analysis of the tumor and its relations to surrounding structures should be done.[15] The site and side of microadenomas (whether anterior or posteriorly placed; on the right or left side of the sella) should be carefully assessed. Anatomical and tumor characteristics which predict difficult tumor removal include an absence of pneumatization of the sella, fibrotic and solid tumors with large suprasellar extension, dumb-bell tumors with a narrow neck, encasement of the carotids or its branches, anterior cranial fossa extension, brain invasion with perilesional edema, cavernous sinus invasion, significant lateral extension of the tumor and small diaphragm sella. Such extensions of tumors result in poor outcome following an endoscopic endonasal surgery alone and might indicate the need for an additional transcranial approach in order to achieve a good outcome.[16],[17]
Preoperative workup should include a complete hormone profile, and documentation of visual acuity and visual fields. Preoperative nasal swab culture to rule out colonization/infection by sinister organisms may be done. Broader spectrum antibiotic is used for 24 hours in the perioperative period. Inclusion of an antibiotic in the fluid used for irrigation during surgery may help in reducing the incidence of post-operative infection. Preparation of nasal mucosa is done by instilling oxymetazoline nasal drops one day before surgery and on the morning of surgery.
The procedure is performed under general anesthesia with propofol being the preferred maintenance agent in order to reduce intraoperative bleeding.[18] Mean blood pressure is kept around 90 mm Hg and pulse around 60 beats/minute. A surgical pack is placed in the throat to avoid aspiration of any collected blood or secretions. The patient is positioned supine with hip and knee flexed and the trunk is elevated by 20 degrees. The head is turned 15 degrees towards the surgeon and 15 degrees' lateral flexion is done towards the opposite shoulder. Chin forehead line is maintained parallel to the floor. Proper positioning avoids some unwarranted complications like excessive bleeding. A betadine-soaked cotton patty should be inserted first in the nasal cavity for antisepsis.[16],[7] The operating room should be ergonomically setup to ensure maximum surgeon comfort and ease. The viewing screen should be behind the patient head, in front of the surgeon at the level of his/her eyes. The endoscope is held in the left hand, while the other instruments are held in the right hand. One can avoid getting into trouble and ensure the smooth progress of surgery by following this set up every time.
A zero degree as well as an angled 30 degree endoscope of varying thickness (2.7 mm-children, 4 mm-adults) and length (18 cm-nasal stage, 30 cm-sellar stage) along with a high definition camera and viewing screen are necessary.[12],[19] Image guidance is useful for beginners and in patients with abnormal sphenoid anatomy, kissing carotids, dumb-bell or recurrent tumors, and in extended procedures. The use of an external sheath permits irrigation and cleaning of the lens along with avoidance of frequent in and out movement of the endoscope. Other instruments include long and straight (non-bayoneted) instruments including sickle shaped or an endoscopic retractable knife (Cappabianca), straight and angled scissors, Blakesley Thru-Cut Forcep, cottle dissector back biting forceps and pituitary curettes. Image guidance (navigation), suction coagulator, curved suction, coblator, microdebrider, unipolar and bipolar (Kassam) cautery and a high-powered drill are the other requirements. Glue for skull base repair and hemostatic agents like FLOSEAL™® (Baxter) for stopping cavernous sinus bleeding should be available. The orientation of the endoscope, with all the buttons facing the screen, should be checked every time the scope is taken inside the nasal cavity. A three-dimensional endoscope for depth perception is now available in some setups, though its advantage is yet to be proven.[18],[20],[21]
Gentle handling of nasal mucosa and involvement of an otolaryngologist are the best ways to avoid nasal complications. An aerial view and a sequential diagnostic examination along the three turbinates are first performed to identify the anatomical landmarks such as the nasopharynx, choana, opening of the Eustachian tube More Detailss and the nasolacrimal duct, sphenoid ostia, uncinate process, hiatus semilunaris and bulla ethmoidalis. Any variation in the nasal anatomy is observed.[13],[14] Packing the space between the middle turbinate and nasal septum with cotton patties soaked with a solution of adrenaline mixed with xylocaine facilitates decongestion of the mucosa as well as creates space for manipulation. This process may have to be repeated 2-3 times to create adequate space. A similar process is repeated in the contralateral nasal cavity. Investment of 10-15 minutes in selective packing and widening sphenoethmoid recess helps in smooth conduction of further steps of surgery. Inferior margin of middle turbinate leads to clival indentation 1 cm below the level of sellar floor and is a consistent landmark. Inferior turbinates are lateralized and the middle turbinate is lateralized or out fractured. Care must be taken not to damage the mucosa as this can cause postoperative scarring and crusting. All the cables should be neatly tied together to avoid obstructing the operational field. The scope should always follow the instruments by about 1 cm into the nasal cavity for adequate visualization and both should be moved in a coordinated manner. They should not collide or cross each other. The path to sella should be kept as straight as possible. The scope should not touch the nasal walls to prevent frequent soiling of the lens, and it should always be kept at an 11 o'clock position. Two surgeons with 3 or 4 hand technique working in synchrony as pilot-copilot is preferred. The assistant periodically cleans the lens tip using Savlon solution and provides irrigation using warm saline to defog the lens.[12],[22],[23],[24],[25] Bleeding from the mucosa should be controlled using infiltration or coagulation at a low setting.[12],[13],[14],[15],[16],[17],[22],[23],[24],[25] Mucosal coagulation in the upper part of the nasal cavity should be avoided to prevent anosmia.[26] Nasal septum should be removed judiciously to avoid post-operative saddle nose deformity. Posterior septal artery (branch of sphenopalatine artery), located superolateral to the choana at the inferolateral margin of the sphenoethmoidal recess near the inferior margin of middle terminate, may be a source of intraoperative bleeding or postoperative epistaxis.[26] This artery may be coagulated when access is made between middle turbinate and nasal septum for anterior sphenoidotomy.[26] In extended endonasal approaches, a vascularized nasoseptal flap based on this artery may be harvested and kept ready at the outset for later use in sellar reconstruction.[27],[28],[29] Sphenoid ostia are identified medial to the root of the superior turbinate [Figure 1]. It may not be visible easily in some cases. A careful inspection may reveal air bubbles coming through the secretions. Probing at the expected location (1.5 cm above the roof of the choana) in the sphenoethmoid recess or fontanelle may be done to enter the sphenoid sinus.
Surgeon should be familiar with both the uninostril and binostril approach so that either can be used as per the requirements of a particular case.[30],[31] Neuronavigation can be useful in the initial cases for easy localization of sphenoid ostia and guiding the correct trajectory to the sella.[32],[33] Recent advances such as the self-expanding retractor (Easytrac) for trans-septal approach to the pituitary have the potential to avoid most of the complications involved in the nasal stage, giving straightforward and easy access to the sella.[34]
The sphenoid ostia are enlarged medially and caudally to avoid opening up of the skull base. Posterior septostomy is performed. Vomer is removed en mass and preserved for possible use in sellar floor reconstruction later on. Adequate sphenoidotomy and rectangular opening of the anterior sphenoid wall is done for wide exposure of the sella.[16],[17],[22],[23],[24],[25] Wide sphenodotomy is done to remove coffin effect [Figure 2]. Limits of sphnoidotomy are superior margin of the sphenoid ostium cranially, crest marking junction of sphenoid with ethmoid laterally, pterigo-sphenoid synchondrosis/palato-vaginal canal for vidian nerve at 5 and 7 O' clock position caudally. Space of more than two suction tips below the sellar floor permits easy instrument manipulation. Sphenoid mucosa is coagulated and removed in a limited fashion wherever absolutely necessary. Sphenoid septum is drilled with diamond burr right up to the sellar floor. For “cavity and half” technique, superior turbinate is excised, bulla ethmoidalis is removed and posterior ethmoid is communicated with sphenoid cavity. Endoscope is parked in the additional space created in posterior ethmoids.
Paramedian septum often leads to the carotid artery or the optic nerve and should be removed carefully. This should be done only when necessary. Midline is identified after sphenoidotomy by the remains of the rostrum cranially, vomer inferiorly and staying between the carotid bulges on either side. Repeated irrigation with warm saline stops bleeding from the mucosa and keeps the surgical field clear. Internal carotid injury is rare but most feared and catastrophic complication of endoscopic endonasal approach, and its incidence is inversely related to the surgeon's experience. The narrow corridor and limited space available for maneuvering of instruments make this even more devastating. It is grossly under reported with the incidence ranging from 0-4% in various reports. Puncture or laceration of cavernous segment of the ICA is the most commonly injured segment. It can be prevented by careful preoperative evaluation and looking for any bone dehiscence (in about 25% cases), septations, kissing carotids, vessel encasement by tumor in preoperative MRI/CT. Doppler or neuronavigation may be used for intraoperative identification of carotids. Immediate recognition of an intraoperative carotid injury is necessary. A large bore suction should be immediately introduced to keep the surgical field clear. The head end of the patient should be raised along with carotid artery compression in the neck. Apply immediate tamponade using gelfoam and cotton patties. Foley's bulb is inflated in the tumor cavity as a last resort. Immediate angiogram should be performed to identify the site of injury and any pseudoaneurysm which might have formed. This may be tackled with an endovascular procedure[35],[36] (coiling/flow diverter/carotid stenting).
A small hole is made in the center of the sellar floor. Dry drilling with diamond burr acts as a hemostatic agent and stops bleeding from the bone. A drill is moved in small bursts like a paint brush and is removed out of the surgical field only when it has stopped rotating completely. Sellar floor is removed circumferentially till four blue lines (superior and inferior intercavernous sinus and cavernous sinus on both sides laterally) are seen. The dura is coagulated and cut from 3-9 o'clock position. The opening is extended caudally and obliquely to 5 and 8 o'clock position, thus creating an inferior flap. Linear incision in the superior part is avoided as there may be an arachnoid bulge anterior to the tumor which may cause CSF leak.[22],[23],[24],[25] A cruciate incision may cause the anterior part of the tumor to bulge, thus obscuring the posterior part of the tumor [Figure 3].
1. Macroadenoma – Once the dura is cut, the dural flaps are dissected off the tumor capsule. Superior half of the intact dura holds the superior and anterior part of the tumor in place, thus preventing premature arachnoid bulge. Tumor should be gradually mobilized free and removed in piecemeal manner. It should not be pulled towards the scope to avoid frequent soiling of the lens. Basal and posterior part of the tumor is removed first, followed by the lateral and the superior portion is tackled in the last.[16],[22],[23],[24],[25] The suprasellar part of the tumor gradually descends and is removed concentrically. Failure of diaphragm to descend or asymmetric bulge indicates residual tumor, while uniform bulge and pulsating diaphragm is a robust indicator of complete tumor removal. The space between the posterior clinoid and carotid siphon is the ideal location for removal of tumor from the posterior segment of the cavernous sinus.[16],[22],[23],[24],[25] The normal pituitary should always be predicted in preoperative MRI. It is identified by its pink color, firm consistency and presence of vasculature compared to the tumor and is preserved. It has striated appearance. In macroadenoma, thinned out residual pituitary tissue appears as an apron plastered on the under surface of the diaphragm. The endoscope should be taken deep into the sella, close to the target for a detailed and magnified view (flash light effect). It helps to distinguish between tumor and normal pituitary and between diaphragm and arachnoid. Utmost care should be taken to prevent arachnoid tear and CSF leak. The diaphragm can be pushed carefully with a cotton patty to remove any hidden tumor. Angled endoscope is used to examine the tumor cavity and remove any tumor remnants. The last piece of the tumor is often located at insertion site of pituitary stalk. The most common sites found to retain tumor are angle between optic nerve and carotid artery at medial optico-carotid recess (mOCR) and under the anterior lip of dura at the level of superior intercavernous sinus. In large suprasellar tumors, removal of planum, tuberculum sellae and MOCR permits retraction of dura up with suction allowing removal of the suprasellar tumor extension under vision. An extended endonasal approach may be required in cases with large suprasellar extension, dumbbell shaped tumors with narrow neck, anterior extension in the anterior cranial fossa and parasellar extension of the tumor.[37],[38],[39],[40],[41] 2. Microadenoma – A limited sellar opening is done based upon the preoperative assessment of the site and side of the microadenoma. Tumor is identified as yellowish colored, slightly firm lesion separate from the normal pituitary tissue. An extracapsular dissection is done to avoid leaving behind any remnant.[42] A thin shell of normal pituitary is shaved along the tumor cavity to enhance chances of a complete cure in cases of functional adenomas.
After tumor resection, Valsalva maneuver is performed to check for any CSF leak. If an arachnoid tear is detected, care should be taken to prevent its further enlargement. Size of the tear dictates the type and the extent of repair. A small tear should be immediately sealed using glue or covered with gel foam to prevent blood seeping into the sub-arachnoid space and its resultant vasospasm. The tumor cavity is filled with fat (even if no CSF leak occurs) to prevent empty sella syndrome and to prevent postoperative CSF leak from arachnoid bulge and rupture into the empty cavity during or after extubation. A single large piece of fat is better than using multiple small pieces.[43],[44] On the contrary, care should be taken not to over pack the cavity, which may itself cause mass effect and compression over the chiasm and pituitary stalk. A practical way to prevent over packing is that the graft must be pulsating. Sellar floor may be reconstructed using bone piece. No foreign material should be left in the sphenoid sinus cavity. Intact residual mucosa keeps the sphenoid sinus as a physiological air-filled cavity. If the sphenoid sinus is packed with fat, all the mucosa should be removed to prevent mucocele formation. A large arachnoid tear or a dural defect warrants a multilayered repair using fat graft, inlay fascia lata, outlay fascia and glue, bone piece followed by fat graft and vascularized nasososeptal flap along with surgicel and gelfoam. This should be followed by a rigid buttress of nasal tampons or an inflated Foley's catheter bulb.[45],[46] The middle turbinates are medialized back to their normal position to keep maxillary ostia patent.[34]
Patient should be shifted to the intensive care unit in the postoperative period, where a close watch on the neurological status, fluid intake/output and electrolyte status is kept. In case of any visual decline, nasal packs are removed immediately. It prompts the surgeon to review the operative steps for any possible surgically correctable cause for the same. Post-operative CT scan should be done routinely to look for any hematoma in the operative cavity or residual tumor apoplexy. If any of these is found and the patient is symptomatic, an immediate re-exploration is warranted, either via transphenoidal or transcranial approach.[47],[48] Post-operative lumbar drain is inserted with an instruction to drain around 5 ml/hr of CSF in cases where CSF leak occurs even after repair. If the CSF leak persists even after 72 hours of lumbar drain insertion, patient should taken up for repacking of the sella. The reported mortality after endoscopic endonasal pituitary surgery is less than 1%.[47],[48],[49]
Steps that can avoid complications and need of conversion to microscopic include:
Nasal complications can be avoided by:
ICA injury can be avoided by proper analysis of preoperative CT/MRI and use of neuronavigation and doppler. Neurosurgical complications can be prevented by-
A step-wise progressive learning brings confidence and ability to tackle complications. Complications, as and when they happen, should be detected early and managed systematically. Multimodality management is advocated.[50]
In conclusion, majority of complications can be avoided by the involvement of a rhinologist, two surgeons – 3/4 hand technique, use of neuronavigation, bimanual dissection and maximum tumor removal with preservation of normal pituitary and integrity of arachnoid. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]
[Table 1]
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