General
- Tend to grow predominantly into one cerebral hemisphere
- But are often bilateral,
- Some 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.
- Parasagittal meningiomas are discussed in Chapter 15.
Definition
- A meningioma arising from the falx cerebri that is completely concealed by the overlying cortex.
Numbers
- Account for 8.5% of intracranial meningiomas.
- Histologically
- Transitional variant is the most common histological subtype encountered.
- M:F(1:2.1) is similar to that for meningiomas overall.
- Average age at presentation is 55 years
- Close to 13% of meningiomas are huge at the time of diagnosis.
Classification
- Based on point of origin along the falx
- Between the crista galli and the coronal suture
- Located in a relatively silent area of the brain
- Clinical features
- Patients typically have an insidious onset of mental decline
- Tumors may grow very large before being discovered
- Raised ICP
- Headache
- Blurred vision secondary to papilledema
- Seizures
- Usually generalized but occasionally associated with speech arrest
- Multiple cognitive impairments, including amnesia
- Between the coronal and lambdoidal sutures
- This region borders the supplementary motor area and the primary sensorimotor cortex for the foot and leg
- Most common site out of the 3
- Clinical features
- Focal motor or sensory seizures are often the first symptom of these tumors.
- If lesion on the dominant side → speech arrest (due to SMA region compression)
- Progressive hemiparesis
- Mental decline
- Between the lambdoidal suture and the torcula.
- Clinical features
- Headaches
- Raised 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.
- Located sufficiently far posteriorly, these tumors may involve the junction of the falx with the tentorium and may reach the tentorial incisura. → see falcotentorial meningioma chapter
A) Anterior 1/3 falx meningiomas
B) Middle 1/3
C) Posterior 1/3
Pathology
- Unlike parasagittal meningiomas, which tend to have bridging veins running deep to them
- Some falcine meningiomas extend deep into the hemispheres with compression of the pericallosal arteries and the corpus callosum and have bridging veins running over them.
- The majority of cases upon opening of the dura the tumour is not visible, instead one can see the convexity brain overlying it.
- Can be unilateral or bilateral with varying proportions of tumour bulk on respective sides.
Clinical Presentation
- Foot drop
- Apoplexy
- Rare
- Due to
- Intraparenchymal hematomas,
- Subdural hematomas,
- SAH
- Spontaneous haemorrhage in a previously asymptomatic falcine meningioma has been described after the use of low dose aspirin over a prolonged period
Management
Surgery
General
- Given that these tumours tend to grow ‘into the brain’, it may, in some unilateral cases, be advantageous to approach them from the contralateral side to avoid excessive brain retraction and manipulations, disturb the overlying bridging veins and gain early control of the falcine blood supply.
- Patients with tumours adjacent to the supplementary motor cortex may suffer transient postoperative hemiparesis and mutism.
- Gross total resection of tumour is the single most important predictor of an improved surgical outcome.
- For complete surgical removal, when indicated, resection of the falcine origin is recommended, but preservation of important dural venous channels needs to be ensured, especially if the SSS is also compromised.
- Surgery of a falx meningioma is composed of four essential consecutive steps
- Devascularization
- Detachment
- Debulking
- Dissection
- In large tumours
- Attempts at en bloc resection may lead to cerebral damage,
- Debulking will be necessary to decrease the tumour volume and allow access to the falx for devascularization.
Preoperative
- MRI + C
- Helps to delineate the
- Tumour's relationship with the venous sinuses,
- Tumour interface with the cerebral cortex,
- Presence of significant blood supply
- Presence of atypical imaging features or cerebral oedema,
- Which might predict
- Increased tumour aggressivity
- Increased incidence of neurological deficits postoperatively.
- Tumoral or adjacent dural enhancement.
- Valid predictor of the degree of dural involvement in the region of the sinus and adjacent falx.
Operative Procedure
Adjunct
- Continuous monitoring of neural function in patients under general anaesthesia using somatosensory evoked potentials has augmented our ability to assess the health of “at risk” brain adjacent to the tumour.
- Intraoperative
- Ultrasonography
- Is used to identify the anterior, posterior, and lateral margins of the tumor below the cortical surface.
- Navigation
- May be used for the same purpose
- But lacks real-time feedback.
Positioning the Patient
- Place the tumour uppermost in the operative exposure,
- Midline of the skull positioned in the true vertical plane.
- Anterior and middle 1/3 falcine meningiomas
- Slouch or semi sitting 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.
- Lateral position, usually with the tumour side down
- Posterior 1/3 falcine meningiomas
- Prone position
- Three-quarter prone
- Park bench position
Skin incision
- Ant 1/3: coronal incision
- Posterior 2/3: horseshoe incision
- Make sure skin incision is carried well across the midline
- So that SSS may be exposed over the length of the bone flap, not only on the side of the tumour but also 2 to 3 cm to the opposite side, to provide access to the contralateral dura as well as the entire superior sagittal sinus.
Craniotomy
- Bone flap
- Large enough to access
- Tumour AND
- Adjacent cortical surfaces to provide sufficient exposure for an elective cortical resection should it be necessary
- For tumours in those areas anterior to the sensorimotor region, therefore, the bone flap should extend somewhat further anteriorly. Conversely, for those tumors posterior to the sensorimotor area, the bone flap should expose an adequate cortical surface posterior to the tumor.
- Once the bone flap has been elevated and any bleeding from the epidural space and superior sagittal sinus is controlled, dural tack-up sutures are placed.
- Dura flap should be opened up to the margin of the SSS and retracted medially over the sinus with stay sutures.
- When the tumour is large or located near the superior sagittal sinus, the interhemispheric fissure may be splayed and the tumour immediately visible.
- It is helpful, regardless, to use ultrasonography once again to be certain that adequate exposure of the tumour has been achieved.
Tumour removal
- Work medially between tumour and falx
- Coagulation and sectioning of the tumour's attachment to the falx.
- Find arachnoid plane laterally between tumour and brain
- Gentle sharp dissection of the arachnoid plane identifies the tumour's pseudo capsule
- Careful attention must be given to the bridging veins, especially the vein of Trollard in middle third falx meningiomas.
- Retraction against the falx
- To minimize retraction of already compromised brain.
- The arachnoid plane is gently developed with bipolar forceps and microdissection, and cottonoid pledgets are inserted into the interface between tumour and brain tissue.
- Debulk the tumour
- The surface of the tumor capsule is coagulated before its incision, and intratumoral debulking with the use of the ultrasonic aspirator is begun
- Care is taken not to violate the capsule.
- The deepest midline aspect of the tumour is frequently supplied by branches of the ipsilateral pericallosal artery
- Extra care should be exercised during tumor resection in this area.
- Tumour extending to the contralateral medial hemisphere is removed though the falx.
- When the tumor has been significantly reduced in bulk, the surgeon approaches the midline and identifies the medial aspect of the tumor in its relation to the normal falx anterior and posterior to the tumor.
- If the tumor’s attachment to the falx is fairly broad at the margin of the superior sagittal sinus,
- It is often wise to consider amputating the tumor at a point ~1 cm from the falx and then to confront resection of the tumor’s midline attachment to the superior sagittal sinus after the bulk of the tumor has been removed.
- This maneuver prevents significant bleeding from the superior sagittal sinus while a major portion of the tumor still remains within the cerebral substance.
- The infiltrated falx may be coagulated and the falx, and the sinus if occluded, can be removed en bloc and the proximal and distal limbs of the sinus closed with Prolene 2–0 suture (Ethicon, Inc., Somerville, NJ).
- If the sinus is partially infiltrated, we remove the falx just below the sinus, avoiding resection of tumor in the sinus wall.
- The falx should be resected beyond the site of tumor attachment. The inferior sagittal sinus can be safely divided provided that the superior sagittal sinus is patent.
- Tumors of the anterior and middle third of the sinus
- Can remove the infiltrated falx and infiltrated wall of the sinus, with reconstruction of the sinus wall with a dural flap, bovine pericardium, pericranium, or synthetic dural replacement. Vascular clips are applied to isolate the compromised wall, and the suture is done with Prolene (Ethicon) as quickly and carefully as possible to avoid venous thrombosis.
- Tumours of the posterior 1/3 of sinus
- The vein of Galen and the straight sinus should be preserved at all costs.
- Tributaries of the internal cerebral veins and the basal vein of Rosenthal are responsible for drainage of the midbrain structures. → Inadvertent compromise of these structures may lead to severe compromise of neurological function and death.
- Subtotal resection should be achieved to preserve neurological function.
- In those cases, additional resection of the falx and/or incision of the tentorium may be performed to allow complete resection (Simpson grade 1 and 2) in almost 85% of patients.19–24
- For tumors placed posteriorly and in the inferior portion of the falx, the occipital interhemispheric approach should be tailored to the dural origin and extent of the tumor as depicted from preoperative MRI.
- Managing SSS
- In the treatment of tumors anterior to the coronal suture
- The surgeon can be relatively aggressive with excision of the lateral walls of the superior sagittal sinus and tumor-involved falx because the whole dural venous sinus can be ligated in this area, with minimal neurological complications, even if it is patent.
- If the sinus is occluded and the falx is infiltrated, then the involved sinus and subjacent infiltrated falx are excised in one piece.
- In treating lesions posterior to the coronal suture,
- The patent SSS cannot be removed safely, and excision of lateral wall infiltrated with falcine parasagittal meningioma is difficult and complex.
- In the past, the lateral sinus wall was sutured successively as the tumor was excised.
Closure
- Following a watertight dural closure, the bone flap is replaced and held firmly in position with miniplates.
- In cases where bony resection is needed, either autologous bone grafts or premanufactured prostheses could be utilized.
- According to Barajas et al, large falcine meningiomas may be successfully removed using a contralateral interhemispheric approach.
- This provides an excellent way of directly dealing with large, deep interhemispheric feeding vessels unsuitable for embolization.
Trigeminocardiac Reflex
- Mechanical stimulation of the falx may induce a trigeminocardiac reflex (TGR), which could lead to bradycardia and even cardiac asystole.
- Attentive monitoring of the patient’s blood pressure and heart rate and clear communication with the surgeon are necessary.
Radiosurgery
- Either
- Primary
- Adjuvant treatment
- Indicated for
- Especially in elderly patients,
- Patients with severe comorbidities,
- Residual meningiomas
- Recurrent atypical meningiomas
- Patients who refused surgery.
- Is an effective treatment option for
- Malignant meningiomas
- Recurrent meningiomas
Surgical Outcome and Prognosis
- The rate of recurrence of falx meningiomas significantly increases in cases of subtotal resection of tumour.
- Aggressive surgical treatment, although of increased risk at times, significantly reduces the risk of recurrence.26
- Cushing and Eisenhardt reported a 57% mortality in their series of seven patients.
- Chung et al
- Characteristic
- 22 men and 46 women
- Between 1990 and 2004
- Location
- 22 anterior third of the falx,
- 20 middle third,
- 15 posterior third.
- Total removal (Simpson grade I or II) was achieved in 58 of the 68 patients (85%).
- Six of the 10 patients with subtotal resection had their residual tumour treated with radiosurgery and had no evidence of recurrences.
- Reasons for subtotal removal were typically related to the need for venous preservation.
- Two patients with a total removal and four patients with a subtotal resection had evidence of recurrence/progression.
- All underwent reoperation.
- A good outcome was seen in 59 of 68 patients.
- Six patients had temporary neurological deficits and two had new deficits (one contralateral leg weakness, one with severe visual loss).
- One patient (1.4%) who was herniating on arrival had emergent surgery but unfortunately died.
- Nowak and Marchel n=87
- Surgically treated for parasagittal and falcine meningiomas
- There were no tumour recurrences following radical resection of the tumour and invaded part of the sinus,
- Two postoperative deaths due to hemodynamic complications were observed.
- In the other 12 patients, meningiomas were removed but sinus infiltration was left in place
- The postoperative period was uneventful
- The rate of clinically important regrowth in this group of patients was 25% in long-term follow-up.
- Huge meningiomas
- Negatively affect
- Extent of resection,
- Recurrence rate,
- Postoperative outcome,
- Operative morbidity
- Mortality rates
- Survival time
Differential Diagnosis
- Osteochondromas
- Chondrosarcomas
- Solitary fibrous tumor of the meninges
- Epidermoid tumours
- Metastasis
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