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Falcine and parasagittal meningiomasDR PRAVEEN K TRIPATHI

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There is today nothing in the whole realm of surgery more gratifying than the successful removal of a meningioma with subsequent perfect functional recovery…Parasagittal meningiomas most interesting and characterstic of all intracranial meningiomas..

—Harvey Cushing29 August

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History 1743, Lorenz Heister, performed the first documented attempt of

surgical treatment of a meningioma- applied a caustic of lime to the tumor of a 34-year-old Prussian soldier

1835, the first meningioma was successfully resected by Zanobi Pecchioli.

Cushing in 1922, suggested the term ‘Parasagittal’ for meningiomas along the superior sagittal sinus (SSS).

Olivecrona was the first to distinguish these meningiomas according to the site of attachment along the SSS 29 August

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4INTRODUCTION

Meningiomas are the most common primary brain and central nervous system tumor (incidence rate, 6.29 per 100,000 persons).

convexity (19% to 34%)

parasagittal locations

(18% to 25%)

sphenoid wing and middle

cranial fossa (17% to 25%)

anterior skull base (10%)

posterior fossa (9% to 15%)

cerebellar convexity

(5%)

clivus (<1%).

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5PATHOLOGY

Meningioma’s cell of origin is believed to be the arachnoid cap cell.

The arachnoid villi protrude into the venous sinuses. The venous endothelium is in contact with all or a

portion of the arachnoid villi. In the latter case, these cells are referred to as arachnoid

cap cells. The rest of the granulation is covered by a fibrous

capsule. Nearly 50% invade the sinus, 50% get secondary

attachment to the falx and 25% are bilateral. Falcine meningioma arises from the falx cerebri or

inferior sagittal sinus and may rarely invade the SSS.

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6PATHOPHYSIOLOGY

raised intracranial pressure,

disruption of cortical electrophysiology or

direct mass effect on adjacent neural

structures.

Clinical symptoms from meningiomas

develop as a result of

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7DEFINITIONS

Falcine Meningiomas Falcine meningioma, as defined by Cushing, arises from the falx, is completely concealed

by overlying cortex, and typically does not involve the superior sagittal sinus

Parasagittal Meningiomas Cushing and Eisenhardt defined a parasagittal meningioma as one that fills the

parasagittal angle, with no brain tissue between the tumor and the superior sagittal sinus. Other investigators, such as Olivecrona, Elsberg, and Merrem, grouped all parasagittal

meningiomas with falcine meningiomas

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8DEFINITIONS

Anatomic differentiation of convexity, parasagittal and falcine meningiomas. A, Convexity meningiomas have no affiliation with the SSS and are separated from the SSS by intervening brain tissue that presents to the surface (arrow). B, Parasagittal meningiomas fill the angle between the convexity and falcine meningioma. They are at least attached to one wall (arrow) of the SSS and brain tissue at the angle is displaced laterally or deep. C, Falcine meningiomas primarily arise from the falx and are cloaked from the surface by convexity brain tissue (arrow).

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9CLASSIFICATION OF FALX MENINGIOMA

Falcine meningiomas can be divided into anterior, middle and posterior types, depending on their origin on the falx. The anterior third extends from the crista galli to the coronal suture, The middle third from the coronal suture to the lambdoid suture, The posterior third from the lambdoid suture to the torcula.

Yasargil classified falcine meningiomas as outer and inner types. Outer falcine meningiomas arise from the main body of the falx in the frontal (anterior or

posterior), central parietal, or occipital regions. Inner falcine meningiomas arise in conjunction with the inferior sagittal sinus.

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10CLINICAL FEATURES- ANTERIOR-THIRD MENINGIOMAS

Parasagittal and Falx meningiomas are considered together, as they have a similar clinical presentation.

Anterior-third meningiomas, located between the crista galli and the coronal suture, have a more insidious onset and often attain a large size before diagnosis.

Headache is the predominant symptom and may be present for years followed by gradually progressive impairment of memory, intelligence and personality changes.

Generalised epilepsy is a presenting symptom in 25–30% of patients. Ataxia, tremor and ipsilateral facial pain may, occasionally, accompany a large

meningioma in this location and thus may be misdiagnosed as a posterior fossa tumour.

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Tumours in the middle-third, from the coronal suture to the lamboid suture, classically present with contralateral focal motor or sensory epilepsy followed by progressive weakness of the contralateral lower limb.

These tumours are detected at an early stage because of focal epilepsy. Bilateral tumours may, occasionally, give rise to bilateral disturbances

and, rarely, paraplegia that may be wrongly attributed to spinal pathology

CLINICAL FEATURES- MIDDLE-THIRD

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Tumours in the posterior-third between the lambdoid suture and the torcular herophili may present with

Features of raised intracranial pressure alone. The only characteristic sign, a homonymous field defect, either

quadrantanopic or hemianopic, may not be noticed by the patient.

Epilepsy is uncommon.

CLINICAL FEATURES- POSTERIOR-THIRD

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13IMAGING

CT best reveals the chronic effects of slowly growing mass lesions on bone remodelling. Calcification in the tumour (seen in 25%) and hyperostosis of overlying skull may be

seen. MR imaging reveals a number of characteristics highly suggestive of meningioma. These include a tumour which is

o Dural-based and isointense with grey matter, o Demonstrates prominent and homogeneous enhancement (95%), o Frequent cerebrospinal fluid/vascular cleft(s) and often an enhancing dural tail (60%).

However, approximately 10–15% of meningiomas have an atypical appearance on MR images, mimicking metastases or malignant gliomas. 29 August

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14IMAGING

CT scan showing a middle-third falx meningioma29 August

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CT scan showing a large anterior-third falx meningioma 29 August 2016

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CT scan of the brain showing a large posterior-third falx meningioma

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3.3a. Pre-contrast Axial T1 Wtd MRI 3.3b. Axial T1 Wtd MRI (C+) 3.3c. Coronal T1 Wtd MRI (C+)

60 year-old lady had MRI of the brain following a seizure.

A dural-based intensely enhancing (arrows) meningioma arising from the right side of the falx.

Diagnosis: Falcine Meningioma

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IMAGING

Parasagittal meningiomas may pose a difficult surgical challenge since venous patency and collateral anastomoses have to be clearly defined for correct surgical planning.

Contrast-enhanced magnetic resonance venography (CE-MRV) provides additional and more reliable information concerning venous infiltration and the presence of collateral anastomoses compared with phase contrast (PC) sequences

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Tumours in the mid and posterior-third may be investigated by angiography, mainly to assess the status of the SSS and the distribution of the cortical veins.

Middle PSMs depress the pericallosal arteries and the anterior tumours displace these vessels posteriorly and downwards.

The anterior cerebral artery may be displaced to the same side and bilateral tumours often cause spreading of the pericallosal and callosomarginal arteries in opposite directions and outline the extent of the tumour

IMAGING

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20DECISION MAKING

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Their natural growth rate,

Radiological characteristics,

Location;

The patient’s clinical status

Assessment balancing the potential morbidity of conservative versus invasive treatment.

The treatment of meningiomas depends on

21DECISION MAKING- “CLASS” algorithm

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Dr. Joung Lee 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.

22DECISION MAKING - CONSERVATIVE TREATMENT

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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. Some authors recommend the surgical resection of meningiomas when the tumor growth rate is greater than 1

cm3 per year. 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.

23INCIDENTAL MENINGIOMAS

Currently, incidentally discovered meningiomas represent 10% to 20% of all meningiomas Because they exhibit no growth or slow linear growth, the majority of asymptomatic,

incidental meningiomas may be observed without surgical intervention. Specific imaging and patient characteristics associated with more rapid meningioma

growth rates have been identified. The likelihood of tumor growth is higher in young patients and tumors larger than 3 cm . Tumors that lack calcification and are hyperintense on T2-weighted MR-imaging are also

more likely to display an aggressive growth pattern. For each clinical situation, the decision to recommend surgery should be evaluated on an

individual basis, incorporating patient comorbidities, age, observed growth rate, and image-based predictive factors for growth.

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24INCIDENTAL MENINGIOMAS

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25INCIDENTAL MENINGIOMAS

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26INCIDENTAL MENINGIOMAS

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27Indications

The clearest indication for surgery is the development of neurologic symptoms attributable to the tumor.

Rarely, tumors may present with significant hyperostosis or skin ulceration, necessitating surgical intervention for cosmesis and/or reducing the risk of infections.

Meningiomas associated with significant peritumoral edema may also carry an increased epileptogenic potential and represent an indication for early removal, even if tumors are relatively small in size.

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Contraindications

Contraindications:Small tumors with no edema, asymptomatic tumors, and tumors in

unfit or elderly patients (older than 70 years) should be considered relative contraindications

Tumors closely associated with the sensorimotor cortex may cause symptoms even when relatively small and should be strongly considered for surgery rather than observation or conservative management. 29 August

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29Preoperative Evaluation

Preoperative evaluation minimizes the risk of perioperative morbidity and mortality, allows an appropriate estimation of the risks of surgery.

There are three important tumor characteristics -significantly impact the objective and approach to resection of these tumors.

These include the (1)Involvement of the SSS and development of collateral veins, (2)The extent and type of bone involvement, and (3)The presence of edema and brain invasion in adjacent eloquent cortices

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30Preoperative Evaluation

The evaluation of SSS patency, invasion and the development of collateral venous pathways are performed with contrast-enhanced MR-venography (CE-MRV).

DSA is still performed if tumor embolization is considered or if arterial supply to the tumor needs to be better defined

These may reveal significantly dilated scalp veins and diploic veins in addition to engorged cortical venous collaterals.

These supplementary collateral venous pathways play a critical role in venous drainage, especially in the setting of parasagittal meningiomas causing occlusion of the middle or posterior third of the superior sagittal sinus.

When possible, surgical approaches should avoid transgression of these structures with tailored scalp incisions and bone flaps.

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31SUPERIOR SAGITTAL SINUS INVOLVEMENT

Clinical classification of parasagittal meningiomas. Parasagittal meningiomas may be classified based on their relationship with the superior sagittal sinus (SSS). A, Type I meningiomas are attached only to the outer surface of the SSS. B, Type II meningiomas invade the SSS but the lumen remains patent. C, Type III meningiomas invade the SSS and cause its occlusion.

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32Sindou Grading system for meningioma invasion of the superior sagittal sinus-2006

coronal section through superior sagittal sinus (SSS). Type I = attachment to lateral wall of sinus; Type II = invasion of lateral recess; Type III = invasion of lateral wall; Type IV = invasion of lateral wall and roof; Type V = total sinus occlusion, contralateral wall spared; Type VI = total sinus occlusion, invasion of all walls

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33Preoperative evaluation

BONY CHANGES Bony changes associated with meningiomas can be caused by hyperostotic changes or direct bone invasion

by tumor. Hyperostotic changes are generally considered a benign form of inductive ossification caused by tumoral

increases in alkaline phosphatase production.

TUMOR AND BRAIN CHARACTERISTICS Postcontrast MR imaging often reveals trailing linear enhancing structure along its dural attachment referred

to as the “dural tail.” The dural tail is not specific to the diagnosis of meningioma, but its management continues to be a point of

controversy. Although evidence suggests that most of the dural tail is an imaging correlate of dilated meningeal vessels

and dural congestion, many still advocate extensive resection of the dural tail believing that it can contain tumor.

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34Preoperative evaluation

Identification of a T2-weighted hyperintense arachnoid cleft between tumor and brain is often indicative of a distinct anatomic plane.

Absence of an arachnoid cleft in combination with significant peritumoral edema may be indicative of pial vessel parasitization and/or brain invasion.

Addressing brain invasion is a key aspect in the operative management of parasagittal meningiomas.

If extrapial resection is not possible in an area of eloquence, a small amount of tumor may be left attached to the cortical surface and observed postoperatively.

For tumors near eloquent areas with variable representation, such as Broca’s and Wernicke’s area, fMR imaging or awake surgery with mapping is valuable in elucidating their anatomic relationship and determining risks of resection.

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35EMBOLIZATION

It can be used to reduce intraoperative blood loss, which can potentially reduce surgical complications and improve overall outcome.

The surgeon must balance the use of embolization against its known complications (6%), including ischemic stroke, hemorrhage, and acute cerebral edema.

Rarely found it necessary to embolize parasagittal meningiomas of any size, because the source of tumor bleeding is readily apparent at the working surface and can be controlled with meticulous hemostasis.

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36When to perform?

Timing of parasagittal meningioma resection is influenced by the extent of SSS involvement.

Because acute surgical obstruction of the patent SSS can cause significant cerebral edema and venous infarction, A tumor causing partial obstruction may be followed closely to observe for the development

of complete occlusion, allowing that the intracranial component of the tumor does not greatly increase in size, cause symptoms, or encroach on large adjacent superficial anastomosing veins.

Alternatively, an asymptomatic meningioma without evidence of invasion into the SSS may require intervention at the earliest sign of growth so that a complete resection can be performed without entering the SSS. 29 August

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37Guidelines

Unfortunately no class I guideline exist.

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38Technique Of Parasagittal Meningioma Resection

The technique of parasagittal meningioma resection is based on the following principles:

1. A bicoronal incision is preferred because it allows maximal vascularity to the skin, especially if subsequent craniotomies are performed.

2. A pericranial flap is reflected separately.

3. Multiple bur holes are made in close approximation to one another at the periphery of the tumor.

4. Bur holes straddling the superior sagittal sinus allow safe separation of the dura from the bone.

5. Microsurgical separation of the tumor capsule from surrounding cortex is performed while preserving the vessels overlying the normal cortex. 29 August

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39Surgical principles in the resection of falcine meningioma

The surgical principles in the resection of falcine meningiomas include the following:

1. Microsurgical interhemispheric exposure is achieved.2. For a unilateral tumor, early devascularization along the falx is preferred.3. For larger tumors, central enucleation allows subsequent microsurgical

separation of the tumor capsule from surrounding arachnoidal areas.4. Liberal use of cottonoid pledgets along the dissection plane helps avoid

surrounding cerebral cortex injury and protects the pericallosal arteries in the inferior margin of the dissection. 29 August

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40Simpson Grading System 1957

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To further minimize the recurrence of meningiomas, an additional dural margin of about 2 cm around the tumor is removed (Grade 0 removal). – Al Mefty etal 1993

41Modified Shinshu Grade or Okudera-Kobayashi Grade 1992

GRADE DESCRIPTION

I Complete microscopic removal of tumor and dural attachment with any abnormal bone

II Complete microscopic removal of tumor with diathermy coagulation of its dural attachment

IIIA Complete microscopic removal of intradural and extradural tumor without resection or coagulation of its dural attachment

IIIB Complete microscopic removal of intradural tumor without resection or coagulation of its dural attachment or of any extradural extensions

IVA Intentional subtotal removal to preserve cranial nerves or blood vessels with complete microscopic removal of dural attachment

IVB Partial removal, leaving tumor of <10% in volume

V Partial removal, leaving tumor of >10% in volume, or decompression with or without biopsy 29 August 2016

42Positioning

Anterior third tumors A supine position with the head and neck in a neutral or gently flexed position will permit direct access to the tumor.

Middle third tumors A supine semisitting position with slight head and neck flexion will often allow direct access to the tumor.

Or Lateral with their head elevated so that the scalp over the tumor is at the highest point in the field.

Parasagittal tumors located along the posterior third of the sss A prone position with the head and neck in neutral or slightly extended position can provide direct tumor access.

Or Another positioning option for tumors in this location includes placing the patient three quarters prone with the tumor

below the midline, allowing for the brain to fall away with minimal retraction 29 August

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43Positioning

Parasagittal meningioma. Positions and incisions for operation.

The approximate center of the tumor is the highest point. 

(A) Anterior third of sagittal sinus. 

(B) Middle third of sagittal sinus.

(C) Posterior third of sagittal sinus.

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44Incision

Parasagittal meningiomas of the anterior third of SSS are exposed via a bicoronal incision. Meningiomas of the middle and posterior third of the sss can be exposed through a bicoronal, S-

shaped or a U-shaped incision. Bicoronal or S-shaped incisions are centered over the tumor mass in the anteroposterior plane and

should permit exposure of the uninvolved side of the sss. U-shaped incisions for parasagittal tumors should extend at least 2 cm past the midline to provide

exposure to the uninvolved side of the sss. U-shaped incisions should have a wide base that is 1.5 times the length of the pedunculated flap

to ensure adequate perfusion to the distal portions. During incision, it is important to attempt to maintain larg anastamotic collaterals that may have

developed within the scalp and diploe to prevent venous congestion, brain swelling, and/or infarction

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45SSS involvement- choices

There are three choices.

1. Ligate the sinus. This option carries the risk of venous infarction and can be performed only in the anterior third.

2. Leave the portion of the tumor attached to the sinus in place, with the understanding that this will most likely grow and possibly cause slow occlusion of the sinus with the formation of collateral venous channels, allowing easier resection in the future.

3. Resect the portion of the sinus involved and then repair the sinus primarily or with a patch. Decisions regarding the sinus, however, should be individualized for each case according to

several factors: the patient’s age and symptoms, patency of the sinus, location of the tumor, and cortical venous collateral system.

A truly occluded sinus can be totally excised at any point. 29 August 2016

46SSS involvement

Type I tumors can be peeled from their attachment to the dura overlying the SSS

After this is accomplished, the external layer of dura is cauterized to achieve a Simpson grade II resection.

If type II tumor, perform a Simpson grade III resection. Type III tumors allow for ligation and resection of the SSS. Because

immediately adjacent veins that enter the SSS just anterior or posterior to the obstruction represent important collaterals, it is imperative that these vessels not be compromised in an attempt for greater resection.

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For type I tumors, the tumor is peeled from the dura of the SSS and this area of attachment is cauterized (Simpson grade II resection). Areas of dural attachment can be resected (bold line) up to within a few millimeters of the SSS.For type II tumors, a layer of tumor residual invading the wall of the SSS is cauterized and left in situ. Areas of dural attachment can be resected (bold line) up to within a few millimeters of the SSS. Tumor within the sinus is not treated (Simpson grade III resection). For type III tumors, the occluded SSS is ligated and resected (bold line), along with involved convexity and/or falcine dura (arrowheads)( Simpson grade I resection).

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48MATERIALS USED TO REPAIR SSS

The main materials used to repair vessels are The autogenous great saphenous vein, Neck superficial veins, and Artificial blood vessels such as Dacron and polytetrefluoroethylene, which

are suitable for the larger diameter of arterial system, whereas silicone tubing is suitable for dural venous sinuses and veins. 

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49surgery

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Surgical approach to parasagittal meningiomas. A, After pericranial graft harvest, two burr holes are placed on the opposite side of the superior sagittal sinus (SSS), approximately 1.5 cm off the midline and one burr hole is placed on the convexity ipsilateral to the tumor. B, The dura is opened and reflected contralaterally. Care is taken to avoid cortical veins that may cross to bridge with the SSS. Extracapsular dissection and intratumoral debulking is performed until the tumor is removed. C, After the principal mass is removed, areas of dural attachment to the convexity and/ or falx are examined and extent of SSS involvement ascertained.

50surgery

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Parasagittal meningioma with a patent posterior third of the sagittal sinus and hyperostosis invading the skull. The hyperostotic, invaded bone is divided into pieces before it is removed.The tumor is debulked with an ultrasonic aspirator, and the capsule is separated from the cerebral cortex. The pial plane is maintained, and utmost attention is paid to preserving the cortical veins. The tumor capsule is then amputated along the sinus, and a piece of tumor invading the sinus is left.

51Complications

New neurological deficits (approximately 2%) Wound infection (5%) Cerebrospinal fluid leak (1%) Postoperative hematoma (5%) Seizure (1%) Air embolism (1%) and significant blood loss. Permanent neurologic deficit and worsening of functional status (approximate 10%)

occurs as a result of postoperative brain swelling and/or venous infarction, likely from acute occlusion of important collateral vessels

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SSS INVOLVEMENT

Surgical microscopic radicality was unexpectedly difficult to achieve.

Gammaknife radiosurgery was a useful adjunct but only in patients with tumors of low proliferative index.

It should probably be used as part of the initial surgical management.

As expected, treatment results for these patients seem to have improved during the last decades but recurrence and malignancy remained a problem, which is not always solved by repeated radiosurgery.29 August

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retrospectively evaluated surgical experience from June 2004 to January 2010. Seventy patients harboring falcine meningiomas were included and submitted for surgical resection.

The patients were divided into three main groups: anterior third 32 patients (Group A), middle third 15 patients (Group B), 23 patients in the posterior third of falx (Group C).

Group A meningiomas had a better outcome due to the position they were in, the tumor and surrounding structures.

In the middle and posterior third, resection of sagittal sinus is a factor of a bad outcome, due to cerebral infartion.

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56Venous preservation–guided resection: a changing paradigm in parasagittal meningioma surgery

CONCLUSION: Analysis of the data obtained in the 67

patients confirmed good outcome and long-term tumor control following a surgical strategy aimed to preserve venous outflow.

These findings and the results of the authors’ analysis of the literature emphasize that the goal of radical tumor resection should be balanced by an awareness of the increased surgical risk attendant on aggressive management of the SSS and bridging veins. 29 August

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57PROGNOSIS -PARASAGITTAL AND FALX MENINGIOMA

Rate of recurrence of parasagittal and falx meningioma significantly increases in cases of non-radical resection of tumour.

Aggressive surgical treatment presents several hazards and carries an increased risk of unsatisfactory outcome; the risk of recurrence, however, is significantly decreased.

Recurrence rates after Total resection of meningiomas involving the sagittal sinus wall range from 5 to 9%; Those after sub-total resection accompanied by sinus wall excision range from 16 to 17%; After sub-total resection of the tumour is approximately 29%; And after partial resection of the tumour it is approximately 39%.

If a conservative and less aggressive approach is adopted, then the patient has to be informed regarding the prognosis and may be given the option of adjuvant radiosurgery.

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