1 Meningiomas: A Personal Perspective

A meningioma is, in many ways, the soul of neurosurgery. The progress in meningioma treatment mirrors advances in neurosurgery, while advancements in neurosurgery are put to maximum use to improve the treatment of meningiomas. 1

The last 20 years confirmed the statement above. Many advances have taken place, in both the treatment and the biological understanding of meningiomas. I (OA) commend Dr. DeMonte and Dr. McDermott for their outstanding effort embodying these new advances in this current edition of Meningiomas.

Over the past two decades and especially in the last several years, the biology and natural history of meningiomas have become better understood. The reader is referred to Chapters 2 through 9 for a detailed summary of these advances. Unlike the decade before, however, the last decade has been overwhelmed with reports on radiosurgery’s role in the treatment of meningiomas, reports declaring a “change in paradigm” in the treatment of meningiomas and implying the need to alter time-tested surgical goals and attitudes. Some authors have called for the primary treatment of meningiomas by radiosurgery,2–5 whereas others have evolved their surgical role into a decompressive, partial removal to be followed by radiosurgery.6–10 These changes have taken place without data on the long-term outcome of such approaches or recognition of the profound effect of failure on both longevity and quality of life.

Durante’s success in the total resection of an olfactory groove meningioma in 1885 began paving the way for treatment of meningiomas.11 The goal of treatment cannot be more eloquently stated than the words of Cushing: “There is to-day nothing in the whole realm of surgery more gratifying than the successful removal of a meningioma with subsequent perfect functional recovery.”12 Meningiomas, as a benign tumor, are amenable to surgical cure. This should be the aim of their management. Complete removal of a meningioma, Simpson grade I, offers a cure in more than 90% of cases.13,14 That extent of surgical removal directly influences the recurrence rate has been repeatedly confirmed. A subtotal removal, Simpson grade IV is doomed to recur when the patient is followed longer than 15 years.15 Sixty percent of patients who experience recurrence after subtotal removal die from the tumor, with the majority of deaths occurring within 10 years.16

Radiation therapy administered to treat residual meningioma has failed in its purported goal of long-term control; 75% of patients thus treated experience recurrence, and 56% of these patients endure neurological complications related to radiation.14 Recent long-term reports on radiosurgery not only raise the concern of increasing failure but also address the aggressive tumor growth that occurs after the failure of radiosurgery.17 The 15-year patient actuarial survival rate after gamma knife surgery for meningioma is only 53%, and 68% of the deaths in these patients are caused by the tumor.18 We are seeing increasing numbers of patients who have been treated in various centers around the world with subtotal removal and radiosurgery who are now desperate; they have undergone multiple surgeries and radiosurgery, only for the tumor to grow faster and transform to a higher pathological grade. The result is a long course of accumulated morbidity, agony, and expense for palliative management, while the chance for a cure is lost because of the failure to attempt or to achieve total surgical removal the first time. One must admit that not every meningioma can be removed totally, and the surgeon is forced in some cases to accept residual tumor, but it should be the surgeon’s goal to attempt a total removal with zeal while preserving or improving the patient’s neurological function. We believe cranial base approaches facilitate the achievement of these goals. If these approaches are associated with higher morbidity in an early experience, then the technique should be refined, but not abandoned. Today’s neurosurgeons are fortunate to be armed with microneurosurgical techniques and skull base approaches in their quest for cure of meningiomas.

In pursuing safe and total removal of meningiomas, which not only provides elimination of the tumor but also contributes to the preservation and improvement of neurological function and the high quality of life that accompanies it, I (OA) have found the following points particularly important.

Bony Invasion by Meningioma

Meningiomas frequently invade adjacent bone, manifested by the radiological appearance of hyperostosis. We have documented pathologically the almost universal presence of meningioma in the Haversian canals of this hyperostotic bone19 ( Fig. 1.1 ). The floor of the middle fossa is an area frequently involved. We believe that removal of the hyper-ostotic bone provides a more complete resection and leads to a lower rate of recurrence ( Fig. 1.2 ). Conservative resection of the bone is typically the cause of the high rate of delayed recurrence after presumed total tumor removal, such as is seen in olfactory groove meningiomas.20 This hyperostotic bony invasion is particularly well known in parasagittal and sphenoid wing meningiomas, which are two sites historically associated with a higher rate of recurrence. We believe their treatment requires the complete removal of the hyperostotic bone.21

Pathological Anatomy and Intraarachnoidal Dissection

We believe that the site of origin must be the basis for classification of meningiomas, as established by Cushing24 and supported by others.1,25,26 It is critical to the understanding of the pathological anatomy of tumoral displacement, encasement, and adherence to the neurovascular structures; thus, it has a profound influence on the surgical intervention and its outcome. The presence of multiple arachnoid layers facilitates the safe dissection of neurovascular structures despite their encasement by tumor. In other words, surgery in basal meningiomas is intraarachnoidal surgery.27 The success comes in the presence of a double arachnoid plane that facilitates the resection of the tumor while preserving the neurovascular structures and their finest details, including perforating arteries, veins, and nerve rootlets. Clinoidal meningiomas present striking evidence supporting this concept. We have distinguished three categories of these tumors, groups I, II, and III, each with a marked influence on the surgical difficulties, ability to achieve total removal, and outcome. These groups relate to the presence of an interfacing arachnoid membrane between the tumor and the cerebral vessels. The presence or absence of this arachnoid membrane depends on the origin of the tumor and its relation to the short intradural carotid artery segment that lies outside the carotid cistern28 ( Figs. 1.4, 1.5, 1.6, and 1.7 ). This same principle not only applies in the classification of tumors of the petroclival area but also has a profound effect on the degree of removal, the rate of complications, and the surgical approach for these tumors ( Figs. 1.8, 1.9, and 1.10 ).

Related posts:

2 Meningioma Surgery During the Twentieth Century 5 Pathology of Meningiomas 12 Risk Evaluation and Anesthesia for Intracranial and Spinal Meningiomas 27 Cerebellar Convexity Meningiomas 33 Meningiomas of the Third Ventricle and Pineal Region 39 Current Surgical Techniques in the Treatment of Spinal Meningiomas

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