Endovideomonitoring in Transsphenoidal Surgery of Pituitary Neoplasms

V.Yu. Cherebillo, V.R. Gofman, A.V. Polezhaev, V.A. Manukovsky

Chair of Neurosurgery, Medicomilitary Academy, Saint Petersburg, Russia

 

Introduction

Striving for total selective removal of adenoma and a smaller rate of intraoperative damage of the cavernous sinuses, optic nerves and sella diaphragm has led to use of endoscopic devices, applied earlier only in transsphenoidal interventions for diseases of accessory sinuses [1, 4, 6, 9].

Obtained results are indicative of such main advantages of the method, as a panoramic view of the sphenoid sinus cavity, precise differentiation of neoplastic and intact tissue of the pituitary body, early diagnosis and elimination of liquorrhea. Rigid and fiber endoscopes, having different diameters and angular views, are used at various stages of an operation both in combination with a surgery microscope and without it. In contrast to a limited tubular examination with a microscope, an optic system of an endoscope with a lateral and retrograde view of 0-120o allows to examine supra- and retrosellar structures, to identify extrasellar areas of a tumor and to perform radical removal of adenoma with maximum preservation of intact adenohypophyseal tissue [3, 5, 8].

Today endoscopic systems are used widely. Endoscopic videomonitoring in a transseptal transsphenoidal approach to the pituitary gland is not only possible, but also expedient, as this method permits to visualize main anatomic landmarks of the sphenoid sinus in a panoramic examination of its cavity and to ensure optimum access to the saddle fundus and structures [2, 7, 8].

Materials and Methods

During the last decades Clinics of Neurosurgery and Otorhinolaryngology of the Medicomilitary Academy gained a rather profound experience in surgery of pituitary adenomas, using a transnasosphenoidal approach. It was applied in 614 patients, operated during the last 7-8 years. The mean age was equal to 37. The male/female ratio was 1:1.8. Chromophobic, acidophilic and basophilic adenomas were watched in 68%, 29% and 3% of cases respectively. Adenocarcinomas were present in 0.8%.

According to hormonal activity all adenomas were divided into prolactinomas (20.1%); somatotroph (24.8%), corticotroph (9.1%), gonadothroph (0.9%), thyrotroph (0.2%) and nonfunctioning (44.9%) adenomas.

The tumor growth was as follows: suprasellar - 42%, parasellar - 11%, retrosellar -3%, antesellar - 2%, infrasellar - 21% and total -11%. Besides, there were endosellar adenomas (3%) and microadenomas (7%).

Vision impairment was present in 74% of patients; hormonal disorders were watched in 68% of cases (hypersecretion - 55% and hypopituitary disorders - 13%). General cerebral symptoms and oculomotor disturbances were typical of 76% and 6% of patients respectively.

Indications for Surgical Treatment of PituitaryAdenomas

There are absolute and particular indications for surgical treatment of different pituitary adenomas.

Absolute indications are irrespective of a degree, to which hormonal activity of tumors is marked, and include:

  1. Vision acuity reduction and narrowing of visual field margins, caused by an extrasellar growth of tumor and compression of the chiasm and optic nerves.
  2. An impaired function of oculomotor nerves, caused by a parasellar growth of tumor.
  3. Impaired liquor discharge, hydrocephalus and intracranial hypertension, caused by impression of tumor into the 3rd ventricle fundus.
  4. Hemorrhage into a tumor.
  5. Nasal liquorrhea, caused by destruction of the saddle fundus and its diaphragm by tumor.
  6. A prolonged growth of tumor in spite of conservative treatment, including radiation therapy.

Particular indications are dependent on clinical manifestations of secreting pituitary adenomas; they are as follows:

  1. For corticotroph adenoma:
    . Cushing's disease irrespective of a tumor size.
    B. Nelson's syndrome irrespective of a tumor size.
  2. For somatotroph adenoma - acromegaly (as an operation of choice or the first stage; ineffective radiation therapy).
  3. For prolactinoma - ineffective therapy with bromcriptine or other drugs of this group against a background of:
    - marked impotency
    - infertility (in desired pregnancy)
    - insensibility or intolerance to drugs of the bromcriptine group.
  4. For thyrotroph adenoma - progressive thyrotoxicosis (in ineffective conservative treatment).
  5. For gonadotroph adenoma - marked impotency or infertility (in desired pregnancy).

An Approach Choice

In our opinion, there are only three absolute indications for choosing a transcranial approach:

A transsphenoidal access should be an approach of choice in all the rest cases.

Surgical Technique

All interventions were performed with application of multicomponent anesthesia with tracheal intubation. The Polystar-2 universal rentgenologic C-arm system (Germany) was positioned so that lateral views of the skull and chiasm-sellar region could be taken (Fig.1).

A patient was placed on an operating table, whose head end was elevated about 30o. A surgeon stood on the right at the level of his thorax.

Endolumbar administration of oxygen (20 ml) was carried out before operation in an extrasellar growth for verifying neoplasm's upper pole and ensuring optimum safety of intraoperative manipulations (Fig.2).

Infiltration anesthesia (10-15 ml of 0.5% novocain solution) was followed by hydropreparation of soft tissues of the nasal septum on the left. A vertical incision of the mucous membrane was performed in the area of the septum of the left nasal vestibule (1-2 mm backward from a free border of the septum cartilage). The incision ran from the nasal cavity bottom up to a place of junction of the septum and lateral cartilage. Septal mucosa was separated from the cartilage and periosteum by blunt dissection. A vertical incision of the cartilage was made with involvement of the conralateral side, whose mucosa was then separated by blunt dissection as well. Temporal packing (for 1-2 min) of the nasal cavity with gauze turundae, soaked with 3% hydrogen peroxide solution, was used.

Illumination of an operative field and a straight view, ensured by a binocular optic-fiber magnifier at the stage of resection of the cartilage and a greater part of bone segments of the septum, were sufficient for good visualization of necessary anatomic structures in the majority of cases. Endovideomonitoring started after resection of septal bones with Luk's forceps. Lower segments of the perpendicular plate of the ethmoid bone, upper segments of the vomer, separated and retracted nasal mucosa were visualized at this stage of an operation quite well. In case of bleeding from septal bones or mucosa of posterior segments of the nasal cavity, its source could be visualized without any difficulty. It allowed to provide effective hemostasis. Subsequent removal of lower segments of the perpendicular plate of the ethmoid bone and the vomer's upper segments was performed with the help of Luk's forceps and a chisel in the direction of the sphenoid sinus; rostrum sphenoidale was mobilized and removed (Fig.3).

Use of endovideomonitoring in approaching the anterior wall of the sphenoid sinus was justified, as it permitted to determine localization of rostrum sphenoidale more precisely. Simultaneous lateral fluoroscopy of the skull was aimed at precise choice of a place of trepanizing an anterior wall of the sphenoid sinus. There was no necessity of rigid fixation of an endoscope in an operative wound during resection of the nasal septum.

As a rule, a cavity of the sphenoid sinus turned out to be open after resection of rostrum sphenoidale. However, an opening on the anterior wall of the sinus (3-5 mm) was insufficient for further manipulations. A butt end of the endoscope, introduced through this narrow opening, became flooded with blood. It demanded its repeated extraction from the operative wound and cleaning. As a result, there was considerable increase in operation duration.

Opening of the sphenoid sinus was performed with the help of Luk's forceps or the chisel. Then it was widened with Hajek's forceps and/or the chisel. The endoscope was inserted into the sinus cavity for providing its panoramic view. The most important landmarks of the sinus were determined; the saddle fundus and projection of its median line were verified (Fig.4).

The first important endoscopic landmark was a medial wall of the sphenoid sinus (intersinus septum), visualized after sphenoidotomy in the majority of cases. It was absent only in 2-4% of our cases. The sinus septum looked like a bone plate, whose both sides were covered by mucosa, lining the sphenoid sinus cavity.

It should be noted, that a form, localization and thickness of the septum varied. Usually it ran along a midline (or nearly it) from the anterior wall of the sphenoid sinus up to the saddle, dividing the sinus cavity into two halves. However, the septum deviated from its initial position and ran to this or that side in almost 45% of cases. Thus, the sphenoid sinus consisted of two unequal parts, one of which was much bigger in some cases. Such anatomic localization of the septum resulted in the following: it ended at convexities of the ICA and optic nerves. Additional septa were watched in 20%. They divided the sphenoid sinus into 2-3 segments partially or completely (Fig.5).

Removal of the median intersinus septum was performed in the majority of cases for good visualization of the sinus cavity. In case of its considerable deviation from a midline and localization out of the fundus projection, only initial segments of this septum were resected. Additional septa of the sinus were removed, when they passed via the area of the saddle fundus in a place of supposed trephination and hampered orientation in the sinus cavity.

The second important landmark in the sphenoid sinus was convexity of the saddle fundus. A panoramic view of the sphenoid sinus after resection of the intersinus septum allowed to watch and to identify it rather easily. This structure looked like a round or oval eminence and was localized in the posterior one third of the sinus upper wall. The saddle fundus was limited by planum sphenoidale from above, which could be visualized in all cases; there was no dependence on a type of pneumatization of the sphenoid sinus. Convexities of ICA, optic canals and opto-carotid recesses were localized on both sides. The lower part of the fundus continued with excavation, corresponding to Blumenbach's clivus, in the area of the sinus posterior wall (Fig.4).

The cavity of Blumenbach's clivus was localized just under convexity of the saddle fundus and served a posterior wall of the sphenoid sinus. Its size depended on a type of the sinus structure. The greatest (1.2 mm on the average) and smallest (0.5 mm on the average) depth of this cavity corresponded to sellar and presellar types of pneumatization. The convexity of the saddle fundus was marked to the smallest degree in a presellar type. This convexity had clear contours and was marked to the utmost in a sellar type of pneumatization.

The next endoscopic landmark was twin convexities of internal carotid arteries, which could not be seen only in 5% of cases. When a butt end of the endoscope was placed at the level of sphenoidotomy, a panoramic examination of the sinus allowed to visualize these structures in the majority of cases. An average distance between a place of trephination of the sinus anterior wall and the saddle fundus was 16.9 mm. Such a position of the endoscope allowed to carry out full-value examination of the sinus cavity and to determine an axis of its subsequent route.

The endoscope introduction and placement of its butt end at a distance of 4-5 mm from the saddle fundus made it possible to examine ICA convexities in detail. It should be noted, that ICA convexities differed, depending on a type of the sphenoid sinus pneumatization. They were marked poorly in a presellar type; thus, their identification was less frequent.

Optic canals formed twin convexities in a cavity of the sphenoid sinus and were visualized in the majority of cases. We failed to identify them in 2.5% of patients. Convexities of optic canals were visualized in the upper part of the lateral wall of the sphenoid sinus. They were localized on both sides of the saddle fundus above ICA convexities. The canal convexities looked like two symmetrical toruli. A depth of their penetration into the sinus cavity was dependent on a pneumatization type. A length of convexities of optic canals varied from 4.9 up to 11.1 mm (7.1 mm on the average).

Convexities of ICA and optic canal formed an opto-carotid recess in an upper lateral angle of the sphenoid sinus. It looked like an excavation between an upper part of the ICA presellar segment and a lateral part of the optic canal convexity. It was limited by the saddle fundus medially.

Maxillary branches of the trigeminal nerve formed twin convexities in the cavity of the sphenoid sinus in 77% of cases. A convexity size was conditioned by a type of pneumatization of the sphenoid sinus.

It was found out, that a sellar type of pneumatization was the most convenient type both for performing an approach and carrying out endovideomonitoring. It allowed to use extensive sphenoidotomy (a height of 15 mm). A maximum angle of operative activity (19o on the average) was achieved in application of the endoscope with a diameter of 4.0-5.8 mm and placing the optic system and microinstruments above each other in a vertical plane.

A presellar type of pneumatization was less favorable, as a vertical size of trephination defect was reliably smaller (10 mm on the average). It reduced an angle of operative activity up to 16o. Thus, it made orientation in adjacent structures and manipulations of a surgeon more difficult.

In this situation it was expedient to widen a sphenoid opening for obtaining the maximum bone defect. It was done with spoons for bones, Luk's and Hajek's forceps. The endoscope was introduced into the sinus cavity after performing sphenoidotomy (15x20 mm in a sellar type of the sinus pneumatization) and verifying a position of instruments with the help of lateral fluoroscopy. These manipulations were a necessary condition for getting a panoramic view of the sinus cavity, as well as for unimpeded coaxial insertion of other instruments into it.

However, it should be emphasized, that sphenoidotomy with a height of more than 8 mm could not be performed in 7-8% of cases. It was caused by an extremely small size of the sinus anterior wall. It was possible to identify main landmarks during examination of the sinus cavity, but coaxial insertion of microinstruments and the endoscope was technically unfeasible. A panoramic examination of the sinus, fundus and the saddle was carried out after taking the instruments out of an operative wound. Thus, it was a staged endoscopic control.

It should be noted, that quality of visual examination of the sphenoid sinus cavity was dependent on intensity of bleeding from adjacent anatomic structures in general, and its mucous membrane in particular. Accumulation of blood in the cavity of the Bumenbach's clivus and lower parts of convexity of the saddle fundus hampered visualization and demanded non-stop aspiration of clots with a microscopic suction unit. When a mucous membrane was almost intact and bleeding was minimum, quality of endoscopic visualization was very high. If mucosa, lining the sinus internal surface, was damaged considerably, quick accumulation of blood in the sinus cavity and, as a result, a dirty optic system made examination of an operative field to be a real problem. Total removal of mucosa in case of its damage and bleeding allowed to reduce an effect of this unfavorable factor on an operation course. Its removal with microforceps ensured a "dry" operative field in the majority of cases and allowed to choose a place of trephination of the saddle fundus without any difficulty.

Sometimes endoscopic examination after sphenoidotomy was indicative of opening only of the right or left half of the sinus. A surgeon, lacking due experience or qualification, can think by mistake, that he has performed a full-value approach; it will result in loss of orientation and surgical errors. As for our research, detailed endoscopic examination of the sinus half allowed to visualize convexities of ICA, optic and V2 canals, opto-carotid recesses only on one side. Convexities of the saddle fundus, planum sphenoidale and the cavity of Blumenbach's clivus were visualized partially. It was impossible to reveal a median plane, passing through the saddle fundus, on the basis of these landmarks. The endoscope permitted to determine peculiarities of localization of the intersinus septum more precisely, to estimate dimensions of an opened segment of the sinus and presence of additional septa or crests.

The most important thing in making an approach and using endoscopic landmarks in the sphenoid sinus was to choose a correct place of a puncture and subsequent trephination of the saddle fundus. At first, a thin puncture needle was inserted into an operative wound. Lateral fluoroscopy was used for control of placing its sharp end near the saddle fundus, so that an axis of its route was directed at an upper point of the saddle dorsum. After achieving an optimum position of the needle in a sagittal plane, the endoscope was introduced coaxially into the sinus cavity. It was done with the purpose of verification of accuracy of the instrument position. In case of necessity the needle position could be corrected under simultaneous fluoroscopic and endoscopic control.

The thin needle, used for the saddle puncture, was replaced by a thick one. Obtained defect was widened with Kerrison microforceps up to an approximate size of 10x10 mm. Anatomic landmarks, limiting the saddle fundus defect, were as follows: on the sides - margins of both cavernous sinuses, on above - a place, where the saddle diaphragm joined its tubercle (1-2 mm below planum sphenoidale), on below - anterior parts of the clivus cavity. Manipulations with microforceps were performed under continuous endoscopic control, as magnification of 8-10 times was a necessary condition for identifying cavernous sinuses and other important anatomic structures. Introduction of the forceps' heel under a bone plate of the saddle fundus and careful staged widening of a trephination window by nipping off the bone under visual control was an effective method of creation extensive defect of the fundus and further adequate examination of the saddle contents (Fig.6).

After trephination dura was incised, using Y- or X-shaped incisions and a microscalpel. Then the rigid endoscope was fixed in an operative wound with a special holder, whose design permitted to place it in a desirable position and to carry out continuous endovideomonitoring. In case of necessity the endoscope position could be changed very quickly and without any technical difficulties.

Examination of tissues, prolapsing into the dura incision, allowed to diagnose a tumor in 96% of cases. Neoplastic tissue looked like nodes with distinct borders against a background of intact pituitary tissue, which as a rule was reddish-brown. As for nodes, they were yellowish-pink and had a harder structure (Fig.7).

We failed to visualize neoplasm during examination of an anterior surface of the pituitary body in 3-4% of cases. As a rule, it was typical of microadenomas, localized in posterior segments of the saddle. In this case, adenohypophysis was dissected with a microscalpel for examination of its deeper-lying segments. It resulted in revealing soft neoplastic tissue.

Yellowish-brown cystic fluid was aspirated at a stage of the saddle puncture in 15% of cases. A panoramic visual examination of the sinus after dura dissection revealed a cyst cavity. Introduction of the endoscope's butt end into this cavity demonstrated a small quantity of residual fluid. It was aspirated with a suction unit under endoscopic control.

Magnification of 8-10 times, obtained in application of the endoscope, allowed to differentiate between intact and pathologic tissues of the pituitary body practically in all cases.

After approaching the saddle and tumor cryodestruction of neoplastic tissue was carried out. Navigation of an active tip of a cryoprobe into pathologic tissue was assisted by application of an endoscope and an image converter see (Fig.8), (Fig.9). It permitted to reduce bleeding.

Freezing, exposure and defreezing lasted about 10, 30-60 and 25 seconds respectively. A zone of cryonecrosis was dependent on a period of freezing. It corresponded to tumor dimensions, varying from 7 up to 15 mm in diameter. Trice-repeated successive freezing and defreezing was applied for achieving 100% necrosis of a calculated volume of neoplastic tissue. It was found out, that there was no visual change of tissue after destruction; it had the same color; no bleeding from tumor or its considerable reduction were watched. Then destructed tissue was removed with the help of an ultrasonic disintegrator and microsurgical technique. If a tumor was more than 1.5 cm in diameter, its cryodestruction was fragmentary with subsequent removal of destructed tissues.

Removal of neoplastic tissue was performed with microforceps, a microscopic suction unit, hypophyseal curettes of a different size, an ultrasonic disintegrator. Endoscopic control and staged lateral fluoroscopy were applied (Fig.10), (Fig.11).

Endosellar structures and peculiarities of relationship between a tumor and adenohypophysis were visualized rather well in removal of a neoplastic node in 31 cases (77.5%). When infra- and endosellar fragments were removed, endovideomonitoring and fluoroscopy allowed to examine suprasellar neoplastic segments and to perform their stage-by-stage removal. Direct visual control of neoplastic tissue, grasped by microforceps or aspirated by a suction unit, made it possible to avoid damage of intact tissue of the pituitary body, traction of adjacent nerves and vessels in the majority of interventions. Due to double control a surgeon had exact visual information on position of microinstruments in relation to the saddle median line and a depth of their introduction into its cavity. It was very important for preserving integrity of the diaphragm and other eloquent anatomic structures.

Endoscopic visualization, permitting differentiation between neoplastic and intact tissue and estimation of a character of relationships between adenoma and adjacent structures, is a valuable source of information for a neurosurgeon, who uses it for determination of tactics of tumor removal and an operation volume. Such advantages of endoscopy, as good illumination, a phenomenon of endomicroscopy and presence of a lateral view, make it possible to estimate adenoma borders intraoperatively and to determine localization and dimensions of neoplastic fragments, which still demand removal. Striving for greater efficacy of an operation and prevention of relapses in the future, a surgeon tries to remove residues of adenoma to the maximum. However, attempts to increase a volume of operation result in a higher risk of damage of anatomic structures, adjacent to adenoma or characterized by tumor invasion.

Efficacy of intervention and hemostasis was estimated after adenoma removal (Fig.12). A turunda, soaked with hydrogen peroxide and inserted into the sphenoid sinus for 2-3 minutes, was a sufficient means of hemostasis after tumor removal. Sometimes staged endovideomonitoring allowed to detect continuous bleeding from the saddle depth. This situation demanded repeated tamponade of the sinus with the above turunda; caprofer was used less frequently. An operation was completed only when endoscopic examination did not reveal tumor residues and efficacy of hemostasis was confirmed.

Powder of kanamycinum or cephalosporine of the 2nd-4th generation (1.0 g) was administered into the sphenoid sinus for prevention of infectious complications. Anterior tamponade according to Voyachek and applying four-tailed bandage were the last steps of intervention.

Results

The results of operations were estimated on the basis of such conventional criteria, as postoperative CT examination of the chiasm-sellar region and arresting of hormonal changes in blood. Radical, subtotal and partial removal of tumors was performed in 87%, 11% and 2% of cases respectively. The relapse rate in the whole group was 12%. It should be noted, that there was a gradual decrease of this rate from 18% in the group of patients, operated without intraoperative endovideomonitoring, up to 7% in the group, where endoscopes were applied. Comparison of the first and second groups revealed higher regress of visual disturbances (64% and 87%) and hormonal disorders (74% and 88%). Besides, endovideomonitoring resulted in considerable regress of intra- and postoperative complications (see the Table, given below).

Table

 

Amount of Intra- and Postoperative Complications (%)

A Type of Complications

Before Use of Endovideomonitoring (n=316)

After Use of Endovideomonitoring (n=298)

Intraoperative nasal liquorrhea

12.3

3.1

Damage of cavernous sinuses

2.1

0.7

Damage of a carotid artery

0.9

-

Postoperative paresis of oculomotor nerves

2.7

0.1

Damage of optic nerves

3.6

-

Hemorrhage into neoplastic tissue

4.5

-

Damage of planum sphenoidale, subarachnoid hemorrhage

2.3

-

Meningitis

3.2

-

Conclusion

Intraoperative monitoring permits to perform operations under constant visual control, to increase their efficacy and to decrease a number of complications. Improvement of surgical technique and high professionalism of a surgeon ensure a "functional" character of intervention even in big tumors by arresting both visual and hormonal disorders.

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