Introduction

A primary falx meningioma, as defined by Cushing and Eisenhardt, is a meningioma arising from the falx cerebri that is completely concealed by the overlying cortex.1 Falcine meningiomas tend to grow predominantly into one cerebral hemisphere but are often bilateral, and in some patients extend to the inferior edge of the sagittal sinus.

Falcine meningiomas and parasagittal meningiomas with falcine extension may arise at any point along the anterior to posterior midline and have similar clinical presentations. Although similar clinically, technical considerations differ between these tumor locations. Para-sagittal meningiomas are discussed in Chapter 15.

Whether considering their clinical presentation or surgical treatment, it is useful and customary to categorize falx meningiomas based on their point of origin along the falx cerebri ( Fig. 17.1 ). Thus, anterior falx meningiomas arise between the crista galli and the coronal suture, those of the middle third between the coronal and lamb-doidal sutures, and those of the posterior third between the lambdoidal suture and the torcula.

Epidemiology

Falcine meningiomas account for 8.5% of intracranial meningiomas. The transitional variant is the most common histological subtype encountered.2 The ratio of male to female incidence (1:2.1) is similar to that for meningiomas overall. The average age at presentation is 55 years.2

Clinical Presentation

Falcine meningiomas arising anterior to the coronal suture compromise relatively silent areas of the brain, and patients typically have an insidious onset of mental decline. These tumors may grow very large before being discovered ( Fig. 17.2A,B ). Symptoms of increased intracranial pressure, including headache and blurred vision secondary to papilledema, are not uncommon. Seizures, usually generalized but occasionally associated with speech arrest, although infrequent, may be seen.3 Multiple cognitive impairments, including amnesia,4,5 have been described in patients harboring falx meningiomas.

The middle third of the falx is the most common site of origin of falx meningiomas ( Fig. 17.3 ). This region borders the supplementary motor area and the primary sensorimotor cortex for the foot and leg.6 Focal motor or sensory seizures are often the first symptom of these tumors. Large tumors of the middle third can present with progressive hemiparesis as well as with mental decline.7 In addition, with lesions on the dominant side, the seizures may be heralded by speech arrest, a syndrome that derives from compromise of the dominant supplementary motor area.

Finally, falcine meningiomas arising in the posterior third generally present with headaches and signs and symptoms of increased intracranial pressure (ICP). Homonymous hemianopsic visual field defects of varying degrees of completeness, with or without macular sparing, indicate compromise of the visual cortex. Visual hallucinations may be present. If located sufficiently far posteriorly, these tumors may involve the junction of the falx with the tentorium ( Fig. 17.4 ) and may reach the tentorial incisura. Falcotentorial meningiomas are specifically addressed in Chapter 19.

Rarely, falcine meningiomas may present with apoplexy due to intraparenchymal hematomas, subdural hematomas, and subarachnoid hemorrhage.8–10 Spontaneous hemorrhage in a previously asymptomatic falcine meningioma has been described after the use of low-dose aspirin over a prolonged period.9

Differential Diagnosis

There are several tumors that may mimic a falcine meningioma. Osteochondromas, chondrosarcomas, solitary fibrous tumor of the meninges, epidermoid tumors, and metastasis are the most frequently reported.11–14

Current Treatment

Preoperative Diagnosis and Management

MRI with and without gadolinium helps to delineate the tumor’s relationship with the venous sinuses, the tumor interface with the cerebral cortex, the presence of significant blood supply, and the presence of atypical imaging features or cerebral edema, which might predict increased tumor aggressivity or an increased incidence of neurological deficits postoperatively. These imaging data can be integrated into neuronavigation protocols to be utilized in the operating room. Gadolinium-enhanced MRI allows demonstration of tumoral or adjacent dural enhancement. The radiological appearance affords a valid predictor of the degree of dural involvement in the region of the sinus and adjacent falx.

Operative Procedure

Gross total resection of tumor is the single most important predictor of an improved surgical outcome.2

Surgery of a falx meningioma is composed of four essential consecutive steps; devascularization, detachment, debulking, and dissection.17 In large tumors, attempts at en bloc resection may lead to cerebral damage, and debulking will be necessary to decrease the tumor volume and allow access to the falx for devascularization.

Positioning the Patient

The key to positioning the patient who has a falcine meningioma is to place the tumor uppermost in the operative exposure, with the midline of the skull positioned in the true vertical plane. For those tumors in the anterior and middle falx, we prefer to position the patient in the slouch or semisitting position. This position requires the use of a central venous catheter and Doppler monitoring so that any air embolus can be recognized and effectively managed. Some authors prefer the lateral position, usually with the tumor side down, for meningiomas of the middle third. For those tumors located in the posterior portion, we prefer the prone position, whereas others prefer the three-quarter prone or park bench position.

Related posts:

16 Parasagittal Meningiomas 20 Falcotentorial Meningiomas 27 Cerebellar Convexity Meningiomas 26 Sphenoorbital Meningiomas 33 Meningiomas of the Third Ventricle and Pineal Region 30 Meningiomas of the Temporal Bone

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