gms | German Medical Science

ESBS 2005: Skull Base Surgery: An Interdisciplinary Challenge
7th Congress of the European Skull Base Society held in association with
the 13th Congress of the German Society of Skull Base Surgery

18. - 21.05.2005, Fulda, Germany

Application of extended transbasal approach to pituitary adenomas

Meeting Contribution

  • W. Bonicki - Nervous System Cancer Department, Cancer Center, Warsaw, Poland
  • R. Michalik - Nervous System Cancer Department, Cancer Center, Warsaw, Poland
  • R. Krajewski - Head and Neck Cancer Department, Cancer Center, Warsaw, Poland
  • J. Kunicki - Nervous System Cancer Department, Cancer Center, Warsaw, Poland
  • P Poppe - Nervous System Cancer Department, Cancer Center, Warsaw, Poland

ESBS 2005: Skull Base Surgery: An Interdisciplinary Challenge. 7th Congress of the European Skull Base Society held in association with the 13th Congress of the German Society of Skull Base Surgery. Fulda, 18.-21.05.2005. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc05esbs46

DOI: 10.3205/05esbs46, URN: urn:nbn:de:0183-05esbs464

Published: January 27, 2009

© 2009 Bonicki et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Abstract

Although transsphenoidal approach is the standard and the method of choice for almost all patients with pituitary adenomas, in some cases the extensions and size of tumour make the transsphenoidal approach insufficient. We have applied in such cases an extended transbasal approach for better visualisation of the tumour and better control of the adjacent structures. Between 1998 and 2004 615 patients with pituitary adenomas were operated upon by our team. 520 patients underwent transsphenoidal procedure whereas 82 with extensive suprasellar and lateral growth of the tumour were treated with extended transbasal approach. 13 patients were treated with other skull base approaches. Mortality in the group of patients operated upon with extended transbasal approach was 3,6% and all these events occurred in first two years. Total removal of the tumour was achieved in 79% of procedures and subtotal in 19%. Cerebrospinal fluid leak was observed in 6% of cases. Transnasal transsphenoidal approach can be used for removal of the majority of pituitary adenomas. Extended transbasal approach is very useful in selected cases, offering an excellent view into parasellar area and minimizing the brain retraction.

Keywords: pituitary adenoma, transbasal approach, skull base techniques


Text

Introduction

Microsurgical transsphenoidal approach has been established as the standard surgical treatment for pituitary adenomas, including giant ones. There is, however, a number of patients with extremely large tumours, and/or with tumours growing into areas that are very difficult to reach via transsphenoidal approach, patients with recurrent adenoma after an intracranial operation, where the transsphenoidal procedure is insufficient to safely separate the tumour [1], [5], [6], [7], [8]. The adenomas that extend up to 2.5 cm above the level of the sellar tuberculum are called the giant adenomas and in selected cases of this group one of many types of craniotomies is usually recommended.

It is generally accepted that appropriate surgical treatment for pituitary adenomas should be complete resection. The goal of an operation in the patients with giant tumours is to remove its suprasellar and intrasellar parts without damage of the visual paths, brain. Ideally, it should be achieved via a single surgical approach. Giant pituitary adenomas, even though not malignant, are particularly aggressive, invade the bone and also adjacent structures, the dura and the walls of the cavernous sinuses. Total, histologically radical removal of such adenomas seems to be impossible, and only a gross total or subtotal removal are usually achieved, even if postoperative imaging shows no residual tumor mass.

Standard transcranial approaches to pituitary adenomas include variants of unilateral subfrontal and fronto-temporal/pterional craniotomies. From this angle of surgical approach the working space between optic nerve, optic tract and carotid artery or below and behind the carotid artery, or anteriorly to the optic nerve is markedly limited and usually allows for intracapsular tumour removal only. Similar removal can be achieved via transsphenoidal approach. Application of skull base surgery techniques allows to eliminate some of limitations of standard intracranial approaches and to improve extent of intracranial tumor removal [4], [5], [7], [8], [9].

Materials and methods

Over a period of 7 years, from 1998 through 2004 extended transbasal subfrontal approach was used in 82 out of 615 patients with pituitary adenoma treated by our team. In the majority of cases (520 – 84,6%) the transsphenoidal approach was advised. The group of 82 (13,3%) patients presented in this analysis required midline anterior subcranial approach due to superior, anterior and lateral extensions of the adenoma. In 13 patients with only lateral tumour extensions, lateral and anterolateral craniotomy approaches were used. There were 79 cases of non-functional adenomas and 3 cases of acromegaly. All the patients presented with visual symptoms. Neurosurgeon, ophthalmologist, endocrinologist, and radiologists participated in a complete preoperative evaluation of every patient and in follow-up review. Subcranial approach was advised when adenoma extensions were difficult to reach via transsphenoidal approach (Figure 1 [Fig. 1]).

Bicoronal skin incision and small craniotomy comprising lowermost parts of the frontal bone down to frontonasal suture and involving medial parts of both orbital rims were done. Olfactory nerves were separated and frontal lobes elevated gently to reach suprasellar area. If tumour had significant extension into sphenoid sinus and posterior ethmoids, planum sphenoidale was removed. Defects in the dura were closed with fascia lata and periosteal flap. The completeness of tumour resection was assessed on the basis of both operative report and postoperative MRI imaging. The number of transbasal procedures per year decreased from 23 (29,5% of all operations for pituitary adenomas) in 1998 down to 3 (2,5%) in 2004.

Results

Total macroscopic tumour removal was obtained in 65 patients (79,3%) according to surgical report, but postoperative MRI showed no remnant of the adenoma in only 17 cases (20,1%) and 9 out of these 17 patients had no recurrence in follow-up ranging from 3–7 years. 36 patients required second stage transsphenoidal procedure that was performed from 4 months to 5 years after first surgery. No patient has required repeated craniotomy. In all cases of subtotal or partial tumour removal the adenoma remnants were observed in lateral or postero-lateral part of one or both cavernous sinuses. In 3 acromegaly cases macroscopic total removal proved impossible and endocrinological cure was not achieved.

During the first 2 years of the series, there were 3 postoperative deaths (3,6% perioperative death rate), as a result of intracranial haematoma observed in 6 patients of the group (7,6%). CSF leak occurred in 5 patients (6,3%) operated in the years 1998–2000. 2 patients were successfully reoperated. In the remaining 3 patients lumbar drainage was used for 7 days with good result. Meningitis complicated the postoperative course in 2 cases (2,5%). Diabetes insipidus occurred postoperatively in 52 patients (65,8%) and persisted in 23 (29,1%).

Improvement of the mild and moderate preoperative visual impairment was observed in 33 patients (75%). No change was observed in 8 (18,9%) and the deterioration in 2 (4,6%) patients. The results in patients with severe visual impairment were 21 (55,3%), 10 (26,3%) and 4 (10,5%) respectively.

The loss of useful smell sensation was observed in all patients, including those in whom olfactory tracts were preserved.

Discussion

The extended transbasal subfrontal approach differs significantly from traditional antero-lateral surgical approaches to the sallar region of the base in that it allows a wide inferior access with tumour, optic chiasm and hypothalamus exposure with minimal brain retraction. The space between optic nerves is the widest window into the suprasellar area. Drilling away planum sphenoidale and tuberculum sellae provides additional working space and access to sphenoid sinus.

The question arises as to whether a less extensive transsphenoidal operation could have achieved a similar result. There are numerous publications on both techniques but randomized assessment is impossible due to selection bias. Transsphenoidal procedures with extensions into cavernous sinuses via posterior ethmoidectomy, into anterior cranial fossa with removal of the planum sphenoidale and with improved techniques of postoperative CSF leak prevention are used in more and more advanced pituitary adenomas. Our practice reflects this tendency, with decreasing number of patients advised an extensive skull base approach.

Number of complications in presented group of patients is relatively high. This reflects both advanced local disease and systemic effects of giant pituitary tumors that combined together pose major surgical risks. Each patient advised transbasal subfrontal approach must be informed about risk of postoperative loss of smell even if the techniques of olfaction preservation are used [2], [3], [10].

Our observations have shown two learning curves. First was the reduction of complications. The second was the reduction of indications for craniotomies in general, with simultaneous expansion of indications for transsphenoidal approach.

Important factor in all extended transbasal subfrontal procedures was the plasty of the sellar diaphragm with fragment of temporal fascia or fascia lata sutured into defect. It proved beneficial in the patients reoperated later on via transsphenoidal route. The fascia was then found as a firm barrier facilitating procedure and preventing CSF leak and intracranial hemorrhage. No intracranial tumor regrowth was observed in all patients after the transbasal subfrontal approach. Recurrent tumors were intrasellar and/or intracavernous, amenable to further surgery or radiotherapy.

Conclusions

1.
Extended transbasal subfrontal approach to supra and intrasellar area provides the largest exposure of this area and facilitates tumour removal with minimal trauma of the brain.
2.
This approach is indicated when transsphenoidal approach is deemed insufficient to remove large suprasellar part of pituitary adenoma with anterior and lateral extensions.
3.
In patients with significant optic nerve compression anterior subfrontal exposure allows the safest tumour removal around optic nerves and chiasm with preservation of ICA branches.
4.
Extended transbasal subfrontal approach produced loss of smell sensation in all operated patients.
5.
With growing experience in transsphenoidal surgery and with earlier diagnosis of pituitary tumors, skull base approaches are used less frequently but can be useful in selected patients.

References

1.
Bonicki W, Michalik R, Krajewski R, Kukwa A, Ozieblo A. Skull base surgery techniques in the treatment of pituitary adenomas. Neurol Neurochir Pol. 2002;36(6):1121-30.
2.
Ciolkowski M, Michalik R, Ciszek B. Arteries to the proximal part of the olfactory tract. Folia Morphol. 2004; 63(4):455-8.
3.
Honeybul S, Neil-Dwyer D, Lang DA, Evans BT. Extended transbasal approach with preservation of olfaction: ananatomical study. Br J Oral Maxillofac Surg. 2001;39(2):149-57.
4.
Kawakami K, Yamanouchi Y, Kawamura Y, Matsumura H. Operative approach to the frontal skull base: extensive transbasal approach. Neurosurgery. 1991;28(5):720-4.
5.
Lang DA, Honeybul S, Neil-Dwyer G, Evans BT, Weller RO, Gill J. The extended transbasal approach: clinical applications and complications. Acta Neurochirurgica. 1999;141(6):579-85.
6.
Pia HW, Grote E, Hilderbrandt G. Giant pituitary adenomas. Neurosurg Rev. 1985;8:207-20.
7.
Raveh J, Turk JB, Ladrach K, Seiler R, Godoy N, Chen J, Paladino J, Virag M, Leibinger K. Extended anterior subcranial approach for skull base tumours: long-term results. J Neurosurg. 1995;82(6):1002-10.
8.
Sekhar LN, Nanda A, Sen CN, Snyderman CN, Janecka IP. The extended frontal approach to tumours of the anterior, middle, and posterior skull base. J Neurosurg. 1992;76(2):198-206.
9.
Shillito J Jr. Craniopharyngiomas: the subfrontal approach, or none at all? Clin Neurosurg. 1980;27:188-205.
10.
Spetzler RF, Herman JM, Beals S, Joganic E, Milligan J. Preservation of olfaction in anterior craniofacial approaches. J Neurosurg. 1993;79(1):48-52.