Introduction

Although meningiomas represent the most common primary tumor histology after the age of 35 in adults, most of them grow slowly and take many years to produce clinical symptoms.1,2 Tuberculum sellae meningiomas (TSMs) represent a small percentage of surgical case series and arise from the region of the chiasmatic sulcus and tuberculum, usually with a point of origin at the junction of the optic canal and lateral aspect of the chiasmatic sulcus.

Decision making is usually rather straightforward for TSMs. Patients generally present with symptoms related to compression of the optic apparatus. As a result, observation is usually an undesirable option, and tumoristatic therapies, such as stereotactic radiosurgery, three-dimensional (3-D)-conformal radiotherapy, and intensity-modulated radiotherapy, do not decompress the optic apparatus and are similarly unsuitable in most situations.2–4 Thus, the current thinking regarding the management of TSMs generally focuses on which surgical approach best achieves optic decompression with the best morbidity and success profile.

In this chapter, we review the clinical presentation of TSMs and discuss the available surgical approaches utilized in contemporary practice. We provide our insights and experiences regarding the bifrontal–extended frontal approach to TSMs, which is our approach of choice. We review existing modern series regarding surgical outcomes for TSM.

Clinical Features

The intimate relationship between TSMs and the optic apparatus characterizes the clinical picture, surgical decision making, and risk–benefit profile of patients with TSM. Most patients with TSM present with visual loss.5–7 This may be unilateral or more commonly bilateral with a chiasmatic syndrome (bitemporal visual field loss). The optic nerves are usually displaced laterally and superiorly and the optic chiasm superiorly or posteriorly. Frequently there is extension down the medial aspect of one or both optic canals, best seen on fat-suppressed coronal and axial thin-sliced magnetic resonance imaging (MRI).

With very large tumors, a frontal lobe syndrome may become evident, with mental status changes, including changes in personality or behavior, loss of motivation, depressed mood, apathy, and changes in short-term memory.5 As with other meningiomas, TSMs are more frequent in women than in men, typically presenting in the fifth or sixth decades of life. Physical findings include those consistent with chronic compression of the optic apparatus with reduced visual acuity, an enlarged blind spot, impaired visual fields, and optic atrophy in chronic cases. These findings may be asymmetric.

Imaging Characteristics

Most TSMs are assessed by MRI5,8 ( Fig. 22.1 ). Classically, these tumors are distinguished from other midline anterior fossa meningiomas by their general trajectory of growth, which is frequently superior and posterior toward the optic apparatus ( Fig. 22.2 ).8 Because of their location adjacent to the skull base and orbits, fat suppression techniques should be used to identify tumor extension down the medial aspect of the optic canal, as already mentioned. Thin slices, with little or no interslice spacing, are necessary when postcontrast MR images are obtained. Sade and Lee analyzed the incidence of optic canal involvement on a series of 29 patients9 and found that radiographic evidence of canal involvement was present in 23 of 29 patients (79%) and was lateralized in 19 of 23 (83%).

Cerebral angiography is usually unnecessary, except for the largest of tumors, where a roadmap for the course of the displaced vessels is desirable. Given that the typical blood supply of these tumors arises from pial, posterior ethmoid, and unnamed meningeal vessels arising from the cavernous segment of the carotid artery in the largest tumors, significant preoperative embolization is rarely possible.10 Magnetic resonance angiography can also demonstrate the course of displaced vessels. Magnetic resonance venography has little role in the assessment of these tumors preoperatively or in the choice of surgical approach.

Approach Selection

As already stated, surgical resection is the only reasonable treatment option for most patients with TSM because visual loss is usually present, making any therapy that does not relieve this mass effect on the optic apparatus an undesirable option in most cases. Further, the proximity of these tumors to the optic apparatus usually eliminates radiosurgery as a treatment option for these tumors.4

Thus, clinical decision making in TSM usually involves which approach to use. A brief summary of approach options for large and small TSMs is provided in Table 22.1 . In large part, given the lack of definitive comparative data, this decision stems from an individual surgeon’s comfort with these approaches, especially with the endonasal approaches. However, with larger tumors, it is important to systematically study the preoperative images because specific pathoanatomical characteristics can make a specific approach more or less favorable for a given tumor’s anatomy.

1. 
   

   Optic canal invasion:

   
   
   
   
   • 
     

     TSMs usually invade the optic canal in its me-dial aspect. Although the medial optic canal can be opened endonasally to address this tumor through the sphenoid sinus, opening the medial optic canal in its length and successfully closing this defect is challenging; thus the presence of medial optic canal invasion is a contraindication to the endonasal approach in all but experienced hands. The presence of tumor lateral to the optic nerve is presently a contraindication to the endonasal approach in all hands.

     
     
   • 
     

     Bioptic canal involvement is usually easier to address via the bifrontal approach ( Fig. 22.3 ), however the anterolateral approaches (pterional/orbitozygomatic) are also able to deal with this situation in most cases.

   
   
2. 
   

   Optic chiasm location:

   
   
   
   
   • 
     

     The chiasm is typically displaced superiorly or posteriorly by these tumors. The location of the tumor in relation to the optic nerve can significantly change the relative simplicity of the transcranial or transsphenoidal approaches. For example, a superiorly displaced, somewhat prefixed chiasm can have a relatively small intraoptic triangle to work through transcranially, especially toward the end of the resection, but might be a straightforward surgery approached transsphenoidally. Alternately, the presence of a significant portion of tumor superior to the chiasm may be better approached transcranially.

   
   
3. 
   

   Vascular encasement:

   
   
   
   
   • 
     

     Significant involvement of the internal carotid, anterior cerebral, or anterior communicating arteries largely contraindicates the endonasal approaches.

Outcomes

Over the past decade, several surgeons have published their results with the use of the microsurgical transcranial and the extended endonasal approaches for removal of these lesions.1,5–7,9,11–32 These studies are summarized in Table 22.2 . In addition, we provide a summary of the published literature regarding extent of resection, and visual outcomes for the transcranial and transsphenoidal approaches, for studies published since 2000. The 95% confidence intervals (95% CI) in this table were calculated using a random effects iterative least squares meta-analysis method with weighting performed using the inverse variance method as published by DerSimonian and Laird.33–36 In short, this method provides a pooled portion that analyzes between center heterogeneity and generates a pooled proportion (in this case, the rate of gross total resection [GTR], visual worsening, or improvement) for these approaches that considers the effect of between-center differences in surgical technique, or personal philosophies when generating an estimate of pooled rates.

As demonstrated in Table 22.2 , GTR was achieved in 88 to 92% (95% CI) of cases operated via the transcranial approaches. Visual worsening was reported in 12 to 17% of these cases, whereas visual improvement was noted in 57 to 63%. Significantly fewer data are available for TSMs operated via the extended endonasal approaches; however, we estimate a pooled rate of 55 to 78% (95% CI) of GTR with these surgeries, with stable or improved vision in 91 to 100% of cases. Taken together, these data imply a more conservative approach by surgeons performing the endonasal approach, with marginally better visual outcomes traded for fewer complete resections. However, more data are clearly needed to further elaborate this issue, especially given the limited experience with the endonasal approach to treat TSMs.

In the following discussion, we focus on a few studies that address issues outside the simple rates of success represented in a pooled rate of the literature.

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