Surgical Management of Parasellar Meningiomas

Introduction

Meningiomas are the second most common tumor in the parasellar region, less frequent than only pituitary adenomas. While most often histopathologically benign, their development in close apposition to critical neurovascular structures can render their surgical management challenging, highlighted by risk to these neurovascular structures and by difficulty obtaining complete resection with correspondingly frequent tumor recurrence. This chapter will review salient management considerations including strategies for surgical resection of parasellar meningiomas. Particular attention will be paid to use of the frontotemporal approach, which remains one of the most commonly employed surgical approaches for these tumors.

Definition and Clinical Presentation

For the purposes of this chapter, we will define parasellar meningiomas as those tumors centered on dura overlying the tuberculum sella or anterior clinoid ( Fig. 33.1 ). Patients with these tumors most frequently present with vision loss, though clinoidal tumors may also manifest with diplopia due to their more lateral location and propensity to displace the oculomotor nerve or invade the cavernous sinus. ^, Occasionally either tumor may present with endocrine dysfunction secondary to compression of the pituitary stalk and/or gland. Admittedly, tuberculum sella and clinoidal tumors can be quite different to manage surgically, namely the propensity of clinoidal tumors to engulf adjacent neurovascular structures necessitates more operative finesse in order to remove them without incurring morbidity ( Fig. 33.2 ). However, despite these differences, the boney exposure and basic principles of resection of either tumor remain the same. While an open surgical approach is often favored for lateral projecting anterior clinoid meningiomas, some of these cases are increasingly being considered for transorbital approaches. For tuberculum sellar meningiomas there are several reasonable open and endoscopic surgical approaches, and while we focus mainly on the open lateral approach in this chapter, surgeon expertise should guide approach decision-making.

Diagnostic Evaluation

Patients with a suspected parasellar meningioma should undergo contrasted magnetic resonance imaging. This allows for evaluation of several important tumor characteristics that may impact operative planning, namely whether or not the tumor extends into the optic canal or cavernous sinus, and to what degree the carotid artery and/or its branches may be encased by the tumor. ^, Computed tomography can also be helpful in identifying adjacent bony hyperostosis and/or erosion, intratumoral calcification, and anterior clinoidal variants such as pneumatization or bony connection to the middle clinoid.

All patients should be considered for preoperative ophthalmologic evaluation, including visual acuity and field testing, as this may help guide the laterality of the surgical approach, as discussed later in the chapter. Lastly, endocrinologic evaluation is important to identify any preoperative endocrine dysfunction that could influence perioperative management.