Tuberculum Sellae/Planum Meningiomas

Tuberculum Sellae/Planum Meningiomas


Keywords: tuberculum sellae meningiomas, planum sphenoidale meningiomas, endoscopic skull base surgery, minimally invasive surgery, supraorbital approach


Luigi Maria Cavallo, Norberto Andaluz, Alberto Di Somma, Domenico Solari, Paolo Cappabianca



Abstract


Planum sphenoidale and tuberculum sellae meningiomas require special surgical attention due to their close proximity to important neurovascular and endocrine structures. Surgical treatment of these anterior cranial base neoplasms has resembled the dramatic advances in neurosurgery over the past century. Being the open transcranial surgical approaches, the well-defined routes for such kind of pathologies, and the recent interest for minimally invasive techniques, has opened a new chapter in the surgical treatment options. The improvement of intraoperative visualization together with refined instrumentation, allowed the evolution of microneurosurgical techniques, and among those, the supraorbital keyhole approach has been used and validated over the last few years for the surgical management of such kind of tumors. On the other hand, recently, expanded endonasal approaches have been developed with the aim of reducing brain retraction and optic chiasm manipulation and improving ophthalmological outcomes by approaching the tumors with a below-to-above trajectory.


Based on these concepts, this chapter will discuss the advantages and limitations of the endoscopic endonasal and supraorbital routes offering an opposite perspective to access the tuberculum sellae and planum sphenoidale meningiomas.


15.1 Introduction


Meningiomas of the anterior cranial fossa are challenging lesions due their mostly close relationship to neurovascular structures and the difficulty of approaching them easily.


In particular tuberculum sellae, comprising 3 to 10% of all intracranial meningiomas, arise from the limbus sphenoidale, chiasmatic sulcus, and tuberculum sellae. They typically present slowly progressive visual deterioration and other symptoms, including seizures, endocrine, or behavioral symptoms as related to tumor size and the eventual perilesional edema. Accordingly, indications for treatment relate exclusively to mass effect and associated symptoms.


Planum sphenoidale meningiomas, accounting for 8 to 18% of intracranial meningiomas together with the olfactory groove, are based at the anterior skull base, in the midline, i.e., at the area of the frontosphenoidal suture. These lesions usually are diagnosed at later stages of the growth, as larger masses, with frontal lobe compression-related symptoms (apraxia, executive dysfunction, behavioral changes) or seizures; larger tumors may present also with optic nerve compression. 1


In these terms, it is worth reminding that tuberculum sellae meningiomas displace the optic apparatus superiorly and laterally, whereas planum sphenoidale, as well as, olfactory groove meningiomas displace the optic apparatus posteriorly. This represents a very important factor to be recognized during the operative planning for dural-based tumors in this region.


Given the benign nature of such neoplasm, the goal of surgery is complete removal of the tumor, dural attachment, and eventual “infected” bone. Major aims of the resection of these tumors can decompress the optic nerves and prevent further deterioration, or, eventually, reverse damage, 2,​ 3 but subtotal resection followed by radiation therapy may also be reasonable depending on the age of the patient and tumor location.


Open transcranial surgical approaches have been well-defined for such kind of pathologies, and surgical outcome has been improving over the last decades. 4


In most recent years, the improvement of intraoperative visualization, together with refined instrumentation, allowed the evolution of microneurosurgical techniques. Among those, the supraorbital eyebrow approach is a minimally invasive keyhole technique that is currently used to access lesions located at the anterior skull base. 5,​ 6,​ 7,​ 8,​ 9,​ 10


The supraorbital route has been a frequently employed surgical resource for the treatment of anterior cranial base meningiomas. 11 Several iterations occurred since its introduction. The most remarkable includes Dandy’s “hypophyseal” approach, with a skin incision concealed behind the hairline. Dandy’s frontolateral pterional approach was refined with the microsurgical techniques of Yasargil et al 12 in 1975, with drilling of the sphenoid ridge, constituting what has become perhaps the most popular approach in neurosurgery, i.e., the pterional. The landmark description of the supraorbital approach, which sparked an increasing interest in its application was that of Jane in 1982. Ever since this report, and based on the speed, versatility and results reported with the supraorbital/subfrontal route, a series of modifications followed, ranging from larger approaches popularized in the 80s with the explosion of skull base techniques (i.e., the orbitocranial approach of Al-Mefty 13), to minimally invasive techniques, as popularized by Perneczky through the keyhole concept. 14,​ 15 With increasing experience in skull base and keyhole techniques, the supraorbital route epitomized the reconciliation of both concepts, benefiting from the tenets of minimal, efficacious access of keyhole approaches, and those of maximal, effective, atraumatic to the brain exposures from skull base. In consequence, a series of modifications that serves as targetable options for approach followed, i.e., the supraorbital eyebrow incision approach, the mini-supraorbital keyhole craniotomy, the transciliary approach, the eyelid approach, and the endoscope-assisted supraorbital approach and its variants.


Recently, expanded endonasal approaches have been developed in an attempt of reducing brain retraction and optic chiasm manipulation and improving ophthalmological outcomes by approaching the tumors from an anteromedial and inferior trajectory. 16,​ 17,​ 18,​ 19,​ 20,​ 21,​ 22,​ 23,​ 24,​ 25,​ 26,​ 27,​ 28,​ 29,​ 30,​ 31,​ 32,​ 33,​ 34,​ 35,​ 36,​ 37 Despite initial discussion about the possibility of accessing the anterior skull base, and eventually dealing with lesions involving this area via the nose, the pure endoscopic endonasal approach extended to the suprasellar area and anterior cranial fossa has proved to be both effective and safe. 38


In regards to the management of planum sphenoidale and tuberculum sellae meningiomas, the advantages of the endonasal approaches are early devascularization of the tumor, removal of all involved bone, lack of brain retraction, and easier dissection of the tumor from the optic nerves and chiasm which are not surgically manipulated. Furthermore, improved visualization of the medial portion of the optic canal can be obtained. However, major drawbacks are, difficult skull base reconstruction, leading to an increased risk for cerebrospinal fluid (CSF) and possible loss of olfaction and other nasal complications. Since the endonasal is a midline pathway, it may limit the access to the lateral extent of the meningioma. 39,​ 40,​ 41,​ 42,​ 43,​ 44,​ 45 For such reason, transcranial approaches are more suitable for tumors that extend lateral to the carotid artery or optic nerve as well as those that may encase the vasculature, providing a wider view of the lateral extent of the tumor. This chapter will focus on the management of tuberculum sellae and planum sphenoidale meningiomas via the endoscopic endonasal and supraorbital approaches which are someway complementary routes, thus overcoming their respective limitations.


15.2 Preoperative Definition of Lesion Features


Preoperative workup includes MRI and CT with two-dimensional reconstructions to assess the relationship of the tumor with the optic nerves and paranasal sinuses, visual acuity and visual field exams, and a vascular anatomy study to establish the relationship of the internal carotid arteries and its branches with the tumor. Our choice of vascular study is CT-angiography. Hence, preoperative evaluation of tumor position, extent, and relationship with critical neurovascular structures is mandatory (▶ Fig. 15.1). Additionally, careful evaluation of the relationship of the tumor with the optic canals and patterns of optic nerve compression are paramount to deciding the best approach route.



9783132412866_c015_f001.tif


Fig. 15.1 (a) Three-dimensional volume-rendered reconstruction as seen from an endonasal perspective, (b) sagittal fluid-attenuated inversion recovery (FLAIR) MRI scans showing a tuberculum-planum sphenoidale meningioma. The tumor as well as the main neurovascular structures surrounding it have been highlighted with different color. (c) The tumor, as seen via the endonasal pathway, can be appreciated after removing the sphenoid bone. (d) The neurovascular structures after virtual tumor removal can be seen as well. These imaging has been obtained using the BrainLAB navigation system (BrainLab Curve, Feldkirchen, Germany).


ON, optic nerve; PS, planum sphenoidale; S, sella; T, tumor; ICA, internal carotid artery; Pg, pituitary gland; Ch, optic chiasm;


*pituitary stalk; **anterior cerebral-communicating artery complex; +, tuberculum sellae.


Preoperative tumor embolization in this region is not recommended due to the risk of ischemic injury to the optic apparatus. Careful study of the anterior skull base and paranasal sinuses anatomy is mandatory. Patterns of hyperostosis, pneumatization of the paranasal sinuses in anticipation to planning for the approach and consideration for repair techniques is recommended.


Especially for the endonasal route, the configuration of the sphenoid sinus should be evaluated as well as the conformation of the tuberculum sellae, namely the suprasellar notch. 46 This preoperative analysis is crucial to tailor the bony opening to gain access to the suprasellar area. Particularly, it has to be stressed that acute angle of the suprasellar notch (type I, i.e., angle <118°) is the most troublesome to deal with during an endoscopic endonasal transtuberculum transplanum approach. 46 Lastly, image guidance protocols, mandatory for neuronavigation systems, may be helpful in selected cases, i.e., in the presence of a conchal-type sphenoid sinus, certain cases of recurrences with a previous history of transsphenoidal surgery, and patients with large lesions involving the para-suprasellar areas. It has to be highlighted that neuronavigation system is useful for surgical planning as it helps in determine the position of the tumor in relation with the key neurovascular structures surrounding it.


On the other hand, when selecting a supraorbital eyebrow approach, care should be taken to the size and lateral extent of the frontal sinus that dictates the placement of the supraorbital craniotomy. A large lateral extension of the frontal sinus may discourage one from using the supraorbital approach, but in general, this is only an issue in a minority of cases.


The location and extent of the tumor also dictates the likelihood of success with a supraorbital approach and the potential need for a larger alternative craniotomy. Axial and coronal MRI sequences should be closely studied to determine the lateral extent of the lesion. The use of image-based frameless stereotaxy is helpful and allows the surgeon to assess the available surgical trajectory prior to making the skin incision.


15.3 Surgical Indications


Which lesions of the planum sphenoidale and/or the tuberculum sellae should be resected transcranially and which should be approached from below, i.e., transphenoidally, remains yet a debate. 3,​ 45,​ 47 Surgeon’s technical experience and appropriate patient selection yields excellent extent of resection and reduced complications. 3 The ideal surgical approach should provide enough exposure of the tumor, including its dural attachment, to interrupt its blood supply as early as possible in the procedure. In addition, brain retraction and manipulation of critical neurovascular structures should be minimized in order to avoid procedure-related morbidity. Finally, in choosing the optimal surgical approach, the anatomic limits of each surgical route must be carefully considered.


Generally, the decision to approach these tumors by endonasal, supraorbital, or other wider craniotomies should be based on tumor features, extension, growth pattern, size, and, last but not least, the extent of the surgeon’s experience with both transcranial and transnasal cranial base surgery (▶ Table 15.1).






















Table 15.1 Main factors influencing endonasal or supraorbital approach selection for tuberculum sellae and planum sphenoidale meningiomas

Factors influencing approach selection


Supraorbital eyebrow


Endoscopic endonasal transtuberculum transplanum


Lateral tumor extension


Midline lesion


Conchal type of sphenoid sinus


Sellar type of sphenoid sinus


Encasement of neurovascular structures


Intrasellar tumor extension


15.3.1 Indications for the Endoscopic Endonasal Approach


Key considerations for endoscopic endonasal surgery of anterior cranial base meningiomas include sphenoid sinus and tuberculum sellae (also called suprasellar notch) anatomy, 46 as well as parasellar extension of the tumor or encasement of neurovascular structures. Although involvement of the optic canals was initially thought to be a limitation for endoscopic endonasal surgery, adequate and safe opening of the optic canals with resection of the intracanalicular part of the meningiomas has been demonstrated. Hence, it has to be outlined that endonasal approach would be difficult in case of conchal sella, “kissing” internal carotid arteries, too-lateral extension, main vessel encasement, large size, or asymmetric shape.


Generally, the most amenable lesions to be selected for endoscopic endonasal management are those that are mostly midline, maintain their arachnoid plane intact as evidenced by a lack of peritumoral edema, do not encase neurovascular structures.


15.3.2 Indications for the Supraorbital Approach


The supraorbital approach is an effective window for the surgical management of planum sphenoidale and tuberculum sellae meningiomas. In cases where tuberculum sellae meningioma has a large extension over the planum sphenoidale with large dural implant in the coronal plane, the supraorbital route offers greater microsurgical control on the tumor borders. On the contrary, meningiomas entering the sellar region and growing below the optic chiasm may be difficult to manage from a transcranial perspective. However, in cases where the tumor extends lateral to one or both of the optic nerves or lateral to the supraclinoid carotid arteries, the supraorbital approach is generally preferred. Regarding optic canal decompression, the supraorbital approach allows both optic nerves to be decompressed from above (superiorly) whereas the endonasal approach allows both optic nerves to be decompressed inferomedially. Thus, tumor location relative to the optic nerves and canals should dictate whether an endonasal or transcranial approach is best suited to allow effective optic nerve decompression.


15.4 Surgical Techniques


15.4.1 Endoscopic Endonasal Approach


For endoscopic endonasal transtuberculum transplanum approach, the patient is placed supine and head is slightly extended in order to optimize the access to the anterior cranial base. The face is turned 5 to 10° toward the surgeon. After induction of general anesthesia, if required, frameless neuronavigation is registered by using CT and/or MRI. Routine nasal mucosal preparation is used: cottonoids, soaked with diluted adrenaline and lidocaine, are inserted in both nostrils between the middle turbinate and the nasal septum and left in place for about 5 minutes. Further, suitable donor sites (fascia lata and/or periumbelical fat) are prepped and draped in order to allow material harvesting.


The nasal phase of the surgical procedure begins with middle turbinate laterally displaced on one side and unilateral middle turbinectomy with removal of the posterior ethmoidal cells, generally performed in the same cavity where the Hadad-Bassagasteguy nasoseptal flap will be raised. As already highlighted elsewhere, 48,​ 49 elevation of the flap is realized at the end of the procedure, in order to reduce the nasal bleeding during surgery and eventually avoid the ischemia of the flap due to the twisting of its pedicle and, at the same time, increase the adhesive property of the same flap that is lifted from the septum and immediately placed on the osteo-dural defect.


Afterwards, the posterior aspect of the nasal septum is removed minding to not extend anteriorly to the head of the contralateral middle turbinate.


A wide sphenoidotomy is performed with complete removal of the rostrum and flattening of the floor of the sphenoid and intrasinus septae also to aid the placement of the nasoseptal flap at the end of tumor removal.


A high-speed drill with a round diamond bit is used to remove bone over the anterosuperior sella, just below the superior intercavernous sinus, extending up to the tuberculum, lateral to the medial opticocarotid recesses and anteriorly along the planum up to the anterior extent of the tumor attachment.


Therefore, bone removal over the uninvolved pituitary gland is minimized unless the tumor extends into the sella. If optic canal invasion has been identified on preoperative imaging, the medial optic canals should be drilled away to reach the anterior extent of the tumor within the canals (▶ Fig. 15.2).



9783132412866_c015_f002.tif


Fig. 15.2 (a) Preoperative axial and (b) sagittal MRI scans showing a tuberculum sellae extending into the right optic canal. (c) The tumor has been removed via an endoscopic endonasal transtuberculum transplanum approach. The optic canal on the right side has been opened thus showing the meningioma below the optic nerve and above the ophthalmic artery. (d) The optic nerve sheath has been opened up to the annulus of Zinn.


ON, optic nerve


*tumor; **optic nerve sheath.

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Jul 31, 2019 | Posted by in NEUROSURGERY | Comments Off on Tuberculum Sellae/Planum Meningiomas
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