Meningioma growth may be related to hormonal status due to the presence of estrogen and progesterone receptors. The tumor may become clinically evident during pregnancy or in the luteal phase of the menstrual cycle.²³ The expression of progesterone receptors alone in a meningioma could be related to a favorable behavior. Absence of both progesterone and estrogen receptors or the presence of estrogen receptors alone correlates with aggressive clinical behavior, progression, and recurrence after complete surgical resection.²⁴ Despite the presence of these receptors, drug therapies targeting hormonal status have not been particularly successful.

Immunohistochemistry

In most cases, immunohistochemical staining is not needed for the diagnosis of meningiomas but may be useful in distinguishing certain tumor types from them. Meningiomas present focal positive staining with epithelial membrane antigen (EMA). This feature could be absent in World Health Organization (WHO) grade II and III variants. Nearly all subtypes exhibit vimentin diffuse positivity, but this is not pathognomonic of this tumor. They show variable positivity staining with S-100 protein and cytokeratin markers. The secretory variant of meningioma could have positive staining for carcinoembryonic antigen (CEA). This method could be helpful distinguishing meningiomas from schwannomas in small biopsies from difficult locations; immunoreactivity for S-100 protein is focal and generally low for meningiomas and strong and diffuse for schwannomas. EMA is commonly absent in schwannomas.

Classification

Histological subtypes are classified according to the most recent WHO grading system published in 2007 ²⁵ (Box 36.1). In the 2000 WHO classification of meningiomas, brain invasion was associated with aggressive behavior and increased probability of recurrence, but was not included as a diagnostic criterion for grade II or grade III tumor.³ Perry and associates demonstrated that brain invasion indicated a greater likelihood of recurrence and felt that it should be considered one of the diagnostic features of grade II meningioma.²⁶ Following these findings, brain invasion by a meningioma is now an independent criterion for WHO grade II. Subtype classification does not appear to influence prognosis unless atypia or malignancy is evident.

Grade I

Grade I (benign meningiomas) is defined as the absence of criteria for grades II and III. The subtypes include meningothelial, fibroblastic, transitional, angiomatous, microcystic, secretory, lymphoplasmocyte-rich, metaplastic, and psammomatous variables. This subclassification into nine different subtypes has no prognostic significance but is useful in recognizing unusual histological patterns as meningiomas.

Grade II

Grade II (atypical meningiomas) implies the presence of 4 or more mitotic cells per 10 high-power fields or three or more of the following features: increased cellularity, high nuclear/cytoplasm ratio, geographic necrosis, prominent nucleoli, sheet-like growth, or brain invasion. There are also two morphological subtypes that are by their nature atypical:

Clear cell type is distinguished by lobulated or sheet-like proliferations of polygonal cells with clear, abundant glycogen cytoplasm (periodic acid–Schiff positive [PAS+]). This type is associated with a higher incidence of recurrence, frequently affects young patients, and commonly arises in spinal or cerebellopontine locations.²⁷

Chordoid type is marked by the presence of cords of eosinophilic, epithelial-like, and vacuolated cells in a prominent myxoid background, similar to the appearance of chordomas. It is associated with chronic inflammation cell pattern, dysgammaglobulinemia, and microcytic anemia (features observed in Castelman’s disease).²⁸ This variant also presents a high rate of recurrence after subtotal resection.²⁹

Grade III

Grade III (anaplastic malignant meningiomas) is characterized by the presence of 20 or more mitoses per 10 high-power fields or obviously malignant cytological characteristics such as tumor cells resembling carcinoma, sarcoma, or melanoma. Again, certain types are typical:

Rhabdoid variant is characterized by rhabdoid-like cells with prominent eosinophilic cytoplasm, prominent nucleolus, and eccentric nuclei. This histological presentation has been associated with increased risk of recurrence and distant metastases.

Papillary type is composed of relatively uniform meningoendothelial cells disposed in a perivascular pseudopapillary pattern, resembling the perivascular pseudorosettes of ependymomas. It has aggressive behavior and a propensity to recur and metastasize. This histological pattern has a higher incidence of presentation in children and young adults.

Metastases

It is extremely uncommon for meningiomas to metastasize outside the nervous system. If metastasis occurs, it is generally associated with anaplastic or malignant patterns. The most common sites of metastasis include lungs, lymph nodes, liver, bones, and heart. Histologically benign meningiomas may also metastasize.

Decision Making

The treatment of meningiomas depends on their natural growth rate, radiological characteristics, and location; the patient’s clinical status; and an assessment balancing the potential morbidity of conservative versus invasive treatment. With the advent of better imaging techniques, more meningiomas are being incidentally discovered. Issues in decision making concerning proper management become particularly important.

In order to integrate these variables some treatment algorithms have been developed. Dr. Takeshi Kawase and his group (Adachi and associates ³⁰) in 2006 presented a set of rules for treating cranial base meningiomas. They give a score to each tumor based on predetermined risk characteristics:

Attachment/size (0-2)

Arterial involvement (0-2)

Relation to brainstem (0-2)

Cranial nerve involvement (0-2)

A higher score number (risk factor) implies a lower chance of complete resection.

Dr. Joung Lee ³¹ and his group at the Cleveland Clinic designed the “CLASS” algorithm for the treatment of all meningiomas. This algorithm compares negative features (comorbidity, location, and age) against benefits (size and symptoms) and assigns a score:

Comorbidity (−2 to 0)

Location (−2 to 0)

Age (−2 to 0)

Size (0 to 2)

Symptoms and signs (0 to 2)

Patients with a score of +1 or higher had a 1.9% rate of poor outcome; those with a score of 0 to 1 had a 4% rate of poor outcome; and of those with a score of −2 or less, 15% had a poor outcome. Therefore, more negative features are related to an increased chance of having an undesirable postoperative outcome.

Even with these grading systems, the final management strategy for meningiomas should be based on the patient’s age, general medical condition, and wishes for treatment.

Conservative Treatment

Around two thirds of asymptomatic meningiomas do not continue to grow and may be observed at appropriate time intervals. Absolute growth rates of meningiomas vary between 0.03 and 2.62 cm³ per year. Several studies following the behavior of asymptomatic meningiomas showed minimal growth during the follow-up period. In a retrospective study of tumor growth rate in 37 patients, 9 of the 37 (24.3%) showed tumor growth during a mean follow-up period of 4.2 years. Annual growth rates were calculated as the difference in tumor volume between the initial and latest imaging, divided by the time interval (years) between these determinations, with tumor growth defined as an annual increase in tumor volume more 1 cm³ per year. In this study they associate the age of patients and the volume of the tumor at its initial diagnosis with growth rate increased. They concluded that young patients and those with large tumors should be carefully observed.³² Nakamura and colleagues³³ studied 41 patients with asymptomatic meningiomas, reporting a majority (66%) of growth rates less than 1 cm³ per year. They also correlated growth rate with patient age but did not consider initial tumor size as a predictive factor for tumor growth. Yano and Kuratsu in their study of surgical indications for asymptomatic meningiomas reported 37% of tumor growth during a period of observation of 3.9 years and only 6.4% becoming symptomatic.³⁴ Some authors recommend the surgical resection of meningiomas when the tumor growth rate is greater than 1 cm³ per year.^32,³³ Radiological features such as partial or complete calcification is related to slow growth rate or absence of it, so these tumors may be kept only under observation. Meningiomas that remain asymptomatic but show displacement and compression of delicate structures as spinal cord, optic nerve, chiasm, and brainstem, or with considerable surrounding edema, should be considered for early treatment. Observation alone, with periodic neurological and MRI evaluation follow-up, first at 3 months, second at 6 months, and then every year, is reasonable for asymptomatic or minimal symptomatic elderly patients with fewer than 10 to 15 years of remaining life expectancy.

Surgical Treatment

General Surgical Planning

Preoperative Embolization

The main goal of this procedure is to decrease intraoperative blood loss in meningiomas with high vascular supply. The superselective catheterization makes this procedure safer and allows for controlling the aggressiveness of embolization. The proximal occlusion of the tumor-feeding arteries only reduces the blood supply temporarily and collateral flow quickly develops. The time between embolization and surgery is controversial. The possibility of necrosis induced by vascular occlusion and therefore the softening of tumoral tissue should be compared to the increase of collateral supply development on time. The optimal interval could be between 3 and 9 days. Complications such as painful trismus, facial pain, scalp necrosis, ischemic stroke, and intratumoral hemorrhage could occur but are infrequent.

Neuronavigation

The principle of image guidance in neurosurgery is based on three-dimensional (3D) volumetric information obtained from preoperative CT, angiographic CT, and MRI images. The data are processed by graphic station software that provides high-resolution images in axial, coronal, and sagittal planes. This triplanar reconstruction can be rotated, segmented, and colored in real time. It is also possible to see through surfaces by turning them transparent, allowing the visualization in different depths. The image modality can be changed and adapted to each surgical step. CT is best for bone landmarks in the approach, angiographic CT is useful for vascular-bone relationships, and MRI is better to demonstrate soft tissue components and tumor removal.

The possibility of brain shift during tumor debulking may make the preoperative MRI no longer accurate. This can be solved with an intraoperative MRI. However, brain shift has a minimal impact in meningioma surgery because meningiomas are commonly attached to rigid structures such as dura or skull bone.

General Microsurgical Technique

Whenever possible, the dural origin of the tumor is primarily coagulated using the bipolar forceps to reduce tumor vascularization. After tumor capsule coagulation, internal debulking is performed by use of suction or ultrasonic aspirator. The cleavage plane between the tumor capsule and the underlying arachnoidal sheet must be identified, preserved, and followed as far as possible. The thinned tumor capsule is pulled toward the center of decompression and cottonoid pads are placed in the brain-tumor interface in order to protect the brain parenchyma from possible surgical trauma. Only confirmed feeding arteries are coagulated and divided. In large tumors portions of completely dissected and devascularized capsule can be removed to provide better visualization of deeper structures. These sequential steps of internal debulking, extracapsular dissection, and removal of dissected-devascularized capsule are repeated until the meningioma is totally removed. Whenever feasible all affected dura and bone surrounding the tumor are removed, preserving adjacent neurovascular structures. When total resection implies a significant risk of morbidity, subtotal removal must be considered, with further observation followed by reoperation or radiotherapy (RT) when the tumor is noted to be growing or causing new symptoms.

General Recurrence Rate

In 1957 Simpson ³⁵ classified meningioma resection as follows: grade I, complete removal, including resection of dura and bone; grade II, complete tumor removal with coagulation of dural attachment; grade III, complete tumor removal without resection or coagulation of dural attachments; grade IV, subtotal removal; and grade V, decompression. This classification remains useful for evaluating recurrences. In Simpson’s series, grade I through grade IV tumors had recurrence rates of 9%, 19%, 29%, and 40%, respectively, at a follow-up period of 10 years.

Considerations by Location

Surgical Technique

Positioning

The patient is positioned in a way that the center of the tumor will be the highest point in the surgical field. The supine position is used for meningiomas located anterior to the coronal suture. Lateral or prone positions are reserved for tumors located behind the coronal suture or in the occipital convexity. The head is fixed with a three-point head rest. The patient’s trunk and head are elevated 20 degrees.

Approach

Depending on the location and size of the lesion a linear or horseshoe incision is done with preservation of scalp vascularity. The scalp incision should extend at least 2 cm away from the craniotomy; this should allow extending the dura resection around 2 cm beyond the meningioma border. The pericranium is dissected from the skull and prepared for later grafting. Bur holes are placed around the tumor, and the dura is separated from the overlying bone with a blunt dissector. The bone flap is cut with a high-speed craniotome. Bleeding from bone edges is controlled with bone wax. The infiltrated dura or identified tumor-feeding vessels are coagulated.

Tumor Resection

The microscope may help for part of this resection but is usually not necessary. The dura is open at the tumor margin with minimal exposure of brain. Dural feeder vessels are coagulated and cut under direct visualization. The tumor is debulked and the capsule generally dissected from surrounding brain with care taken to avoid damage to vessels. The resected dura is replaced with pericranium or an artificial substitute.

Postoperative Care

Generally the patient is extubated before arriving to the intensive care unit (ICU). The patient spends the first 24 hours in the ICU and the next day is encouraged to ambulate.

Operative Results

In a series of convexity meningiomas Black and co-workers ³⁶ reported no surgical fatality and no significant difference in morbidity between age groups younger and older than 65 years. The overall morbidity rate was 5.5%. The 5- and 10-year survival rate was 90% with overall recurrence rate of 4.3%. The 5-year recurrence rate for WHO grade I tumors was zero, for grade II 27.2%, and for grade III was 50%. In their series 15 patients (9%) underwent radiation therapy.

Complications

Neurological deficits arise from vascular injury or brain edema from manipulation or retraction.

Parasagittal Meningiomas

These meningiomas represent about 16.8% of meningiomas and are classified in relation to their location along the superior sagittal sinus (SSS) and its invasion. The anterior third extends from the crista galli to the coronal suture, the middle third from the coronal to the lambdoid sutures, and the posterior third from the lambdoid suture to the torcular. Sindou and associates have classified sinus involvement as follows:

Type I: Attachment to outer surface of the sinus wall

Type II: Fragment inside the lateral recess

Type III: Invasion of the ipsilateral wall

Type IV: Invasion of the lateral wall and roof

Types V and VI: Complete sinus occlusion, with or without one wall free, respectively ³⁷

To achieve a Simpson grade I or II radical resection, the infiltrated SSS should be removed with the tumor. They represent about 16.8% to 25.6% of all intracranial meningiomas.³⁸

Clinical Presentation

Anterior third meningiomas usually cause headache, progressive mental deterioration, seizures, and possibly papilledema secondary to increased intracranial pressure. Motor or sensory focal seizures in the contralateral extremity are often seen in patients with meningiomas of the middle third. Tumors in the posterior third can produce homonymous hemianopia. Meningiomas arising from the anterior or posterior third have a more silent growth.

Evaluation

MR venography is not adequate to judge sinus patency, and angiography is the best study for surgical planning. However, the best test of patency may only be at surgery with tentative entry of the sinus. On angiography the arterial phase can predict the difficulty of dissection between the capsule and cortex when a pial vascular supply is identified. The late venous phase is important for evaluating sinus infiltration and the presence of collateral veins. Angiography may also allow embolization in vascular meningiomas. Navigation is very helpful in locating the tumor.

Pathology

The histological pattern in a reported series of 106 was 79.6% for WHO grade I tumors, 14.8% for grade II, and 3.7% for grade III meningiomas.³⁹

Treatment

Observation is acceptable in asymptomatic elderly patients or with tumor less than 3 cm in diameter. The SSS total or partial invasion can be treated by radical resection of the sinus with or without venous reconstruction. Resecting the SSS is associated with an increased risk of intraoperative and postoperative hemorrhage, sinus occlusion, corticovenous thrombosis, and venous infarction leading to brain edema. A less aggressive surgical approach, with satisfactory long-term effect and fewer complications, is to resect the tumor up to the sinus wall and leave the sinus intact.³⁶ Residual tumor can be followed up and treated with radiosurgery at recurrence. Radiosurgery as first-line treatment can offer good results for tumors smaller than 3 cm.

Surgical Technique

Positioning

The supine position is used for meningiomas located in the anterior or middle third of the SSS. For middle third tumors, a useful position is to “hang” the head so the tumor side is down. The prone position is reserved for tumors located in the posterior third of the SSS.

Approach

At our center the skin and bone flaps are marked out with the assistance of neuronavigation. The craniotomy is done in two steps; elevating a bone flap on the tumor side 1 cm away from the SSS, then separating the dura from the overlying SSS and elevating the second bone flap on the contralateral side across the midline. Hemostasis of the SSS superior wall or major dural vessels is done with an oxycellulose packing or bipolar coagulation. Epidural bleeding is controlled with hitching sutures between dura and adjacent bone.

Microsurgical Resection

The dura is opened around the tumor under magnification, taking care not to compromise the afferent veins to the SSS. The tumor is dissected from the brain parenchyma using microsurgical techniques with careful preservation of the arachnoidal plane. Any tumor on the SSS wall is removed and the sinus wall is cauterized. The SSS is not opened or reconstructed.

Operative Results

In Black and co-workers’³⁶ series the anterior third of the SSS was involved in 12.8% of tumors, the middle third in 69.2%, and the posterior third in 17.9%. In 63.2% of patients there was total tumor resection, Simpson grades I and II. In 14 patients (36.8%) residual tumor was found on postoperative imaging, and 13.2% of those had tumor progression. Recurrence-free survival rate was 94.7% at 5 years.

Complications

Intraoperative bleeding can be reduced with the elevation of the patient head and compressive packing with absorbable hemostats. Brain swelling can be prevented with the preservation of the cortical vessels and avoiding brain retraction.

Falx Meningiomas

These meningiomas arise from the falx cerebri and tend to grow and compress the medial surface of the cerebral hemispheres. They can be classified according to involvement of the falx in longitudeal dimension. Like parasagittal meningiomas, they can be divided into anterior, middle, or posterior types. The classification proposed by Yasargil ⁴⁰ separated them into outer falx meningiomas, which arise from the body of the falx, and inner falx meningiomas that arise adjacent to the inferior sagittal sinus (ISS). Falcine meningiomas represent 8.5% of all intracranial meningiomas.⁴¹

Evaluation

About 60% of falx meningiomas present the dural tail sign.⁴¹ MRVA or angiographies are useful to determine the displacement or involvement of the anterior cerebral artery (ACA). The venous phase shows the SSS of ISS invasion and the localization of venous drainage.

Under magnification the dura is opened on the side of the larger component of the tumor or the side of the nondominant hemisphere. The dura is reflected and attached to the soft tissue. The medial aspect of the hemisphere is retracted to identify the SSS and the limits of the lesion. Afferent veins to the SSS should be respected. If it is possible, the falx is divided 1 cm away from the tumor limits to disrupt the blood supply. The internal debulking is performed to facilitate the capsule mobilization. Following the extra-arachnoidal plane the tumor is dissected from the brain parenchyma, taking care to preserve the ACA and its branches.

Operative Results

In the series of 68 patients presented by Chung and colleagues,⁴¹ 85.2% had total resection with no evident recurrence and 92.6% achieved a good outcome (no neurological deficit or complications). SRS was performed as a postoperative adjunctive treatment in six patients.

Complications

Unilateral dural opening is preferred if it is possible to avoid bilateral infraction of bridging veins. If major arteries are encased in the tumoral tissue a subtotal resection followed by radiation therapy must be considered. In case of extreme bilateral edema the bone flap should not be repositioned after tumor resection.

Olfactory Groove Meningiomas

Olfactory groove meningiomas (OGM) arise in the midline of the anterior fossa, from the apophysis crista galli to the planum sphenoidal. Usually bilateral, they grow over the cribriform plate and frontosphenoidal suture. The invasion of the ethmoid bone and the paranasal sinuses makes a complete resection difficult and increases the chance for recurrence. Small meningiomas displace laterally the olfactory nerves and large tumors push them together with the optic chiasm into a posteroinferior direction. Blood supply of this tumor usually comes from ethmoidal branches of the ophthalmic artery, the anterior branch of the middle meningeal artery (MMA), and meningeal branches of the internal carotid artery (ICA). They represent 10% of all intracranial meningiomas.

Clinical Presentation

Common symptoms usually appear when the tumor is considerably large. Anosmia, headaches, seizures, and changes in personality are frequent. Visual deficits are almost always present, even with small tumors, generally as diminution of the acuity and restriction of the inferior field.

Surgery is indicated in almost every case due to the size of the tumor at the time of diagnosis. Preoperative embolization is rarely indicated for the potential risk of occluding the ophthalmic artery and the consequent blindness. If major arteries are involved in the tumor mass, subtotal resection is recommended follow by RT or SRS in selected cases. Small, asymptomatic and commonly incidentally diagnosed meningiomas can be observed or treated with RT/SRS.

Surgical Technique

The frontotemporal (pterional) approach is preferred for small and medium-sized tumors and bifrontal craniotomy is recommended for large lesions.

Positioning

An external lumbar cerebrospinal fluid (CSF) drainage is placed to prevent or reduce brain retraction. For a frontotemporal approach the patient is placed in the supine position. The patient’s trunk and head are elevated 20 degrees.The head is turned to the contralateral shoulder, 30 degrees for more anterior lesions and 20 degrees for posterior tumors. The head is flexed, taking the chin to the ipsilateral clavicle and then slightly hyperextended so that the maxillary eminence reaches the highest point in the surgical field. For the bifrontal approach the patient is also placed in a supine position but with the head in a neutral position and minimally extended inferiorly.

Approach

In the frontotemporal (pterional) approach, the skin incision is begun 1 cm anterior to the tragus at the level of the zygomatic arch and is extended superiorly, then curving anteriorly from the superior temporal line to the midline, just behind the hairline, and extended behind. The scalp flap is reflected anteriorly with sharp dissection against the galea. The superficial and deep fascia of the temporalis muscle are incised 1 cm posterior and parallel to the course of the frontal branches of the facial nerve and retracted anteriorly with the skin flap. The temporalis muscle is incised posterior to the superficial temporal artery and lifted anteriorly and inferiorly using fish hooks to expose the roof and the lateral rim of the orbit. At the supraorbital ridge the supraorbital nerve and vessel run through the supraorbital foramen, and care must be taken to preserve them. The pericranium is dissected behind and incised as posteriorly as possible and then is reflected anteriorly over the scalp flap. A keyhole is placed behind the suture between the frontal bone and the frontal process of the zygomatic bone. Bur holes are made in the floor of the middle fossa and if it is necessary posterior to the superior orbital rim. The bone flap is done with a craniotome. The superior arch of the orbit may be removed for a wide exposure in large tumors. In the bifrontal approach the skin is cut posteriorly to the frontal hairline from zygoma to zygoma. The craniotomy is performed through bur holes placed on each side of the SSS with a high-speed drill. Approximately 1 cm of bone is left posteriorly to the orbital rim.

Microsurgical Resection

For the frontotemporal approach the dura is opened in a C-shape fashion with an anterior base along the sphenoid ridge. It is folded and anchored with sutures. Under magnification the sylvian fissure is dissected allowing the visualization and opening of the optic carotid and carotid oculomotor cisterns. The arachnoid membrane between the optic nerve and frontal lobe is incised and opened to allow the retraction of the frontal lobe and dissection from the tumor capsule. The internal debulking is performed with an ultrasonic aspirator or laser. Following this step the tumor capsule can be easily disected from the underlying brain. The blood supply is occluded along the base and the tumor capsule. With microdissection the tumor is removed. The dura attachment in the anterior fossa base is coagulated, the crista galli cuted and drilled. After hemostasis control the dural defect is closed in a watertight fashion with the vascularized pericranial flap, avoiding tension on the brain and allowing tenting to the bone flap to occlude dead space. If the frontal sinus is exposed it must be cranialized by removing its posterior wall. The frontonasal ostia are occluded with muscle and bone.

For the bifrontal approach the dura is opened in both sides of the SSS. The sinus is ligated or sutured and divided on its anterior third. The falx cerebri is cuted and with gentle retraction the tumor is exposed. Microsurgical tumor removal steps are followed as usual. The posterior surface of the tumor can be closely related to the ACA; care must be taken to avoid its injury. The frontotemporal artery is frequently attached to or encased in the tumor and should be released but can be sacrificed without consequence. After the tumor removal, the involved dura must be resected and coagulated. Hyperostotic bone should be drilled until normal bone is identified assessing the ethmoidal sinus in order to remove all invaded cavities. The dura defect must be closed in a watertight fashion to avoid CSF leakage.

Postoperative Care

External lumbar drainage may be left for 5 postoperative days. For patients with preoperative visual deficits a neuro-ophthalmological evaluation should be performed.

Operative Results

In Obeid and Al-Mefty’s⁴² series of 13 benign OGMs gross total resection was achieved in 93.3% of patients. Vision remained stable in six patients and improved in eight with no recurrence in a median follow-up period of 3.7 years. They reviewed the recurrence rate for OGMs reported in the literature and found that it ranged from 5% to 41%, and concluded that radical tumor resection, including the dural attachment and any involved bone during the initial surgery, is the best way to reduce the chances of recurrence.⁴²

Complications

A vascularized pericranial flap is crucial for a proper reconstruction of the anterior cranial fossa; it must cover the frontal and ethmoid sinuses and be closed in a watertight fashion. The placement of an external lumbar drainage tube is mandatory to avoid brain retraction during surgery and help to prevent CSF rhinorrhea in the postoperative period. To prevent thrombophlebitis and pulmonary embolism, pneumatic compression thigh-high air boots should be used intra- and postoperatively. Bilateral subfrontal craniotomy with sectioning of the falx may improve the surgical field, allowing preservation of olfaction.

Tuberculum Sellae Meningiomas

Tuberculum sellae meningiomas (TSMs) arise from the dura of the tuberculum sellae, diaphragma sellae, chiasmatic sulcus, and limbus sphenoidale. Usually bilateral, they grow from the midline over one side. They can invade the suprasellar region as other meningiomas with different dural origins. TSM can be distinguished from OGM by the displacement of the optic nerves and chiasm. TSMs elevate the chiasm and optic nerves superolaterally, but OGMs displace the chiasm downward and posteriorly as they grow. TSMs represent 5% to 10% of all intracranial meningiomas.⁴³

Clinical Presentation

The most frequent presentation of a TSM is optic atrophy with bitemporal hemianopia. The asymmetrical visual loss usually begins in an insidious way and progresses slowly. Other occasional symptoms include headache, mental status deterioration, seizures, anosmia, hyperprolactinemia due to pituitary stalk posterior displacement and compression, and hydrocephalus in cases of third ventricle compression.

Evaluation

Classical radiology presentation, CT images in coronal plane can show hyperostosis of the tuberculum sellae and chiasmatic sulcus. MRVA images provide information about ACA or ICA encasement or displacement often seen in these tumors. Ophthalmological evaluation must be considered.

Treatment

Surgery with total tumor resection must be considered as the first-line treatment before causing optic nerve and ICA involvement. TSMs are usually fed from the posterior ethmoidal artery, a branch of the ophthalmic artery. Preoperative embolization is not indicated for the potential risk of occluding the ophthalmic artery. In TSM encasing major arteries or the cavernous sinus subtotal resection followed by RT or stereotactic radiotherapy (SRT) should be considered. RT or SRT as the initial single therapeutic option is not usually indicated.

Surgical Technique

Bifrontal, frontotemporal, frontolateral, and the expanded endonasal approaches should be considered for these meningiomas.

Positioning

Bifrontal and frontotemporal pterional positioning and approach were described under surgical technique for OGM treatment. The frontolateral approach provides a more medial view of the clinoid and suprasellar region. The patient is placed in a supine position with the trunk and head elevated 20 degrees. The head is turned 10 to 20 degrees to the contralateral shoulder and slightly extended. The frontal lobes spontaneously fall downward because of gravity and allow less retraction to expose the anterior fossa.

Approach

The skin incision is made as in a pterional approach. The craniotomy is performed through a single bur hole at the orbital rim of the frontal bone behind the anterior temporal line. The inner table of the supraorbital ridge is drilled to make the frontal base flat and allow a better visualization of the anterior fossa. If the frontal sinus is opened during the craniotomy the mucosa must be removed completely and coagulated. Before removing the posterior wall, the frontonasal ostia are occluded with muscle and bone.

Microsurgical Resection

The dura is opened in a C-shape fashion with an anterior base along the supraorbital ridge. Under the microscope, the sylvian fissure is opened with a microsurgical technique. For frontolateral and frontotemporal (pterional) approaches the optic carotid and carotid oculomotor cisterns are identified and opened to release CSF and to achieve a better retraction of the frontal lobe. The tumor is identified medial to the ipsilateral optic nerve. Devascularization of the tumor is accomplished by coagulating the dural feeders and detachment from the dura base. The capsule is open to allow internal debulking. With delicate maneuvers the TSM is dissected from the frontal parenchyma until the optic chiasm and the contralateral optic nerve are visible. Small arteries arising from the medial wall of the ICA provide blood supply to the chiasm and optic nerves; their injury must be avoided—in fact, no vessels coming directly off the ICA should be coagulated. The posterior surface of the tumor can displace the pituitary stalk; care should be taken when this area is dissected. If the tumor grows into the optic canal below the optic nerve, the optic canal is unroofed with a high-speed drill. After the tumor is removed the dura attachment is resected and coagulated. Bone invasion is drilled away.

Postoperative Care

Diabetes insipidus and hypopituitarism should be considered as possible postoperative complications. For patients with preoperative visual deficits a neuro-ophthalmological evaluation should be considered.

Expanded Endonasal Approach

Provide access to the anterior skull base extending from the crista galli to the foramen magnum;⁴⁴ all 12 cranial nerves and the carotid and vertebrobasilar arteries can be seen through the nose. This approach should be considered only for small TSMs measuring less than 4 cm owing to the limited lateral explosion. Tumors arising lateral to the optic nerve or beyond the midline of the superior orbit are best approached via craniotomy if the objective of surgery is total removal.⁴⁴ Neuronavigation is commonly used.